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Author Topic: slow acceleration to 1/4 throttle.......then WOW!!!  (Read 2581 times)

kfthompson

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slow acceleration to 1/4 throttle.......then WOW!!!
« on: August 01, 2013, 09:59:44 PM »
2008 military, bobbed out, stripped down. Did the performance thing, k&n, heat tube removal, shaker exhaust. Jetted carb-17.5 pilot, 120 main, needle on middle slot. this is the mikarb by the way the -old bs29. Sounds like a great setup, but i have an issue. From closed to quarter throttle, it accels slowly and at first I thought it was maybe the transmission or something, but when I go above quarter throttle it is a totally different bike.  It really roars! is the needle to low? mixture setting off?  help! i want it to roar from idle to top end.

Arizoni

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #1 on: August 01, 2013, 10:26:43 PM »
It might be running a little lean at idle.
Have you tried adjusting the idle mixture screw to a slightly richer condition?
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kfthompson

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #2 on: August 01, 2013, 10:52:49 PM »
In or out?

kfthompson

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #3 on: August 01, 2013, 10:54:20 PM »
Plus it idled fine

tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #4 on: August 01, 2013, 11:36:33 PM »
Plus it idled fine

            I have the same engine, same carb (did yours have the plastic collar permanently covering the needle height grooves?), hot tube removed, open muffler, 17.5 Pilot, same basic setup as yours. I'm using shims to raise & lower the needle because of the collar which I should have broken off a year ago, but didn't. So I can't say where my needle height is relative to yours. My mixture screw is approx 1 1/2 turns out & I think I'm still a hair lean (slow to return to idle). Mine kickstarts fine & runs fine in all gears at 3/4 (or a hair more) throttle (e.g. 50 in 4th & 5th). Never tries to die at stop signs.

              I can't do WOT tests yet. Only 766 miles on my '08 Classic.

               You don't mention how it is at WOT. Does it kickstart start cold with no enrichener?

                I think your easiest thing to try first (after you're sure the mixture screw is right) is raise your needle one shim (.002"). If that makes it better, but not Grrrate, then remove the shim & raise it one full groove & see what THAT does.

                 Oh, forgot to mention my Main Jet is still stock 110. I want at least 1,000 before I start cranking it & I'm already sure I'll have to go one larger right away. 110 is fine for now. I think there's a jet between 110 & 120. You may have gone too big too soon. Who knows? It's a tricky, time-consuming process.

               
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kfthompson

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #5 on: August 01, 2013, 11:55:11 PM »
no collar, just a round plastic ring at the bottom, does turning out enrich the mixture? WOT is where the beast lives, it does fine there.  i just want the lower idle area to match the rest of the pull. I take it easy in town, and put at night. The megaphone is kind of loud, i need to redo my packing. First time is not a charm.

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #6 on: August 01, 2013, 11:59:03 PM »
Out is leaner, in is richer.  It's an air bypass into the throat and no fuel actually passes through it.  Hence, out = more air (leaner) in = less air (richer).
Mikuni manual will tell you how to adjust the mixture:
http://www.mikunioz.com/tuning_manuals.htm
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barenekd

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #7 on: August 02, 2013, 12:45:53 AM »
Anything at or below 1/4 throttle is controlled by the idle mixture. Changing the needle or main jet isn't going to change that. Check all the little holes in the body for blockage, particular the one behind the mixture screw. Use one strand of electrical wire to stick through the holes. Do not hog them out!
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tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #8 on: August 02, 2013, 01:15:55 AM »
Out is leaner, in is richer.  It's an air bypass into the throat and no fuel actually passes through it.  Hence, out = more air (leaner) in = less air (richer).
Mikuni manual will tell you how to adjust the mixture:
http://www.mikunioz.com/tuning_manuals.htm

           Wrong! Not for the BS-29. CCW (out) is richer. CW (in) is leaner. It's a gas screw, not an air screw in the BS-29.

            The Mikuni site you've linked him to does not cover the BS-29 on the AVL engine. 
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tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #9 on: August 02, 2013, 01:25:35 AM »
no collar, just a round plastic ring at the bottom, does turning out enrich the mixture?

        No, you've misunderstood me. That's the mixrure screw. I was talking the needle that goes up & down with the slide.  There is no round plastic ring at the bottom of the slide needle. This is why tuning by mail is so hard.

         BS-29. Mixture screw: Screw IN you go LEAN.
                                          Screw OUT you go RICH.

 
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kfthompson

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #10 on: August 02, 2013, 02:09:02 AM »
mine has a round plastic ring at the bottom of the needle that fits into the hole the needle seats into. i didn't misunderstand you, i think it was the other way around. i simply added a question at the end of a statement. I know turning the ring doesn't affect mixture


kfthompson

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #11 on: August 02, 2013, 02:10:52 AM »
and thanks for verifying what i thought i already knew about the screw. Guess I just need to enrichen it up a bit.

tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #12 on: August 02, 2013, 02:23:40 AM »
mine has a round plastic ring at the bottom of the needle that fits into the hole the needle seats into.
            Yes. That's the MIXTURE screw.

 i didn't misunderstand you,
[/quote]

            Yes, you DID. Go back & reread my original post. I was asking about the SLIDE NEEDLE (the sentence where I mention the NEEDLE HEIGHT GROOVES). The needle height grooves are in the slide needle, not the mixture screw.

 i think it was the other way around. i simply added a question at the end of a statement. I know turning the ring doesn't affect mixture
[/quote]

            Of course not. It's just an O-Ring, a gasket.

   
« Last Edit: August 02, 2013, 02:28:43 AM by tooseevee »
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kfthompson

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #13 on: August 02, 2013, 03:28:27 AM »
Not really UNDERSTANDING ALL THE CAPS, but I am pretty sure its not an o-ring. its about a 1/4 inch thick, plastic and sits under the notches on the slide needle inside the slide. I am not making this up, there is a plastic ring (plastic not rubber like an o-ring) under the notches on the slide needle that seats inside the slide.  There is no disrespect meant in this post, just trying to clarify. I am talking about the inside of the slide, not the screw on the outside of the carb.

D the D

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #14 on: August 02, 2013, 03:44:16 AM »
           Wrong! Not for the BS-29. CCW (out) is richer. CW (in) is leaner. It's a gas screw, not an air screw in the BS-29.

            The Mikuni site you've linked him to does not cover the BS-29 on the AVL engine.

Ooops.  Yep, wrong carb.  Glad I don't have one of those. Threw one from my old Suzuki in the trash.
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tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #15 on: August 02, 2013, 12:39:24 PM »
Not really UNDERSTANDING ALL THE CAPS, but I am pretty sure its not an o-ring. its about a 1/4 inch thick, plastic and sits under the notches on the slide needle inside the slide. I am not making this up, there is a plastic ring (plastic not rubber like an o-ring) under the notches on the slide needle that seats inside the slide.  There is no disrespect meant in this post, just trying to clarify. I am talking about the inside of the slide, not the screw on the outside of the carb.

          Yes. Now we're on the same page.

           That's what I asked you in my original post & I quote from it now (go back & read it):

                  "Did yours have a plastic collar permanently covering the needle height grooves"?

             I think where I got thrown off was you said it was at the "bottom of the needle". To me it's at the top of the needle as the carb is held in its normal position.

              OK. Anyway. Where are you now? What are you trying next?

               In thinking about it over night, I think we may both still be running lean in the mixture screw setting along (I think our Pilot jet & needle heights are damn close). I'm going to try at least another 1/2 turn rich next, maybe even a full turn. On my last ride I was less than 2 turns out from bottomed.

               Our glitches are both similar: You have a flat spot right off throttle & I have a slightly slow to return to idle problem. Both indicate lean.

               Can't do anything today - pouring rain.   
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tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #16 on: August 02, 2013, 12:51:47 PM »
Ooops.  Yep, wrong carb.  Glad I don't have one of those. Threw one from my old Suzuki in the trash.

       Yes, it's an old design pulled out of the closet & used for those couple years by RE to pass Fed Emissions before the UCE EFI was ready. It's not the greatest carb, but once you've had it apart a dozen times tuning for changes in exhaust & intake & understand it, it's a perfectly serviceable carb for just regular riding. Plus it has the advantage of being a forgiving CV type that's not so touchy with changes in temp, humidity. The magic diaphragm smooths things out. It suits me just fine the way I ride now plus I like things I can take apart whenever I feel like it.
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D the D

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #17 on: August 02, 2013, 02:29:37 PM »
 tooseevee
Just about every carb has it's lovers and haters.  Many HD owners think the CV is the bomb.  I'm just too wed to Mikuni.  I didn't care much for the Carter on my Sportster either! ;-)
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tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #18 on: August 02, 2013, 04:32:57 PM »
tooseevee
Just about every carb has it's lovers and haters.  Many HD owners think the CV is the bomb.  I'm just too wed to Mikuni.  I didn't care much for the Carter on my Sportster either! ;-)

           CVs on harleys can help cover up other small problems (especially with kick onlys) like slightly out of whack valve timing or ignition timing or mixture. They're more forgiving & they also don't fart as often when you hit a pocket of cold air. 'Course they're all fuel injected now & I don't care.

            I've had S&S Super Es on three kick only harleys I built since the mid-'70s & I love them. Others hate them (like you've said).

             
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tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #19 on: August 03, 2013, 03:31:53 PM »
    General carburetor question for the experts:

     If the "sweet spot" for the mixture screw on the Mikuni BS-29 with a stock (15) Pilot Jet is 2 1/2 turns out, what does it become when you change to a 17.5 Pilot to rejet for removing all exhaust restrictions?

      Should the sweet spot now be closer to 3 turns out or fewer than 2 1/2 turns out? Seems to me it should be fewer turns out, right?

       Here's what I have & I can't seem to work it out:

         Bike kickstarts perfect & idles perfect. Runs perfect out on the road & around town, never dies, never farts. Purrs like a kitten at 50 in 4th OR in 5th (only 766 miles, ain't gonna go no faster yet). I have jumped it to 55 & 60 a few times & it's fine. Solid as a rock.

         Here's the ONLY problem I have & I can't work it out:

            It's slower than it ought to be returning to a dead idle. There's a 3 or 4 second delay (say at a stop sign) when it hangs onto a high idle, THEN it drops to the normal idle. It's reeaally aggravating.

            This would indicate that I'm still lean, but I've been out to 3 1/2 turns on the mixture & in to only 1 turn out & it makes no difference. Still returns to idle too slowly.

            I have no intake leak & no binding cable. It returned to idle perfectly as it should (quickly) prior to the hot tube removal & pilot jet change (the silencer is also pretty much wide open). 

             What should I try next? Ideas?  20 Pilot maybe?
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DanB

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #20 on: August 03, 2013, 04:25:33 PM »
1/4 throttle responsiveness.

I've had the same issue. Drop the needle one notch richer. That plastic washer will spin and then you can push it anyway you want. It moves once you free it up. Also, our UK brothers have shaved about .7mm off the bottom of the slide allowing a richer condition which may solve the slow to return to idle condition. I'm running a 17.5 pilot, 120 main now , richest notch, about 1/2 turn on the mixture screw.
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tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #21 on: August 03, 2013, 05:50:56 PM »
1/4 throttle responsiveness.

I've had the same issue. Drop the needle one notch richer. That plastic washer will spin and then you can push it anyway you want. It moves once you free it up. Also, our UK brothers have shaved about .7mm off the bottom of the slide allowing a richer condition which may solve the slow to return to idle condition. I'm running a 17.5 pilot, 120 main now , richest notch, about 1/2 turn on the mixture screw.

           Hey, Dan

                     Thanks for the quick answer. When I hit Send on my post I was going to go for a ride, but then it started raining again so I've been watching a round table discussion on Obamacare for an hour & a half. It's a huge mess of a stew & all the chefs are lunatics. Now I can go pull my carb & do something useful.

                      Anyway. What you say above is just about what I wanted to hear because futzing with the mixture screw wasn't getting me anywhere & it was curdling my mind logicwise.

                      But don't you mean raise the needle a notch richer, not drop the needle a notch richer?

                       Just askin'.  Also, could you discuss a little how shaving the bottom of the slide richens the mixture? I can't see it in my head.   
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High On Octane

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #22 on: August 03, 2013, 07:49:33 PM »
  ...........But don't you mean raise the needle a notch richer, not drop the needle a notch richer?
Just askin'.  Also, could you discuss a little how shaving the bottom of the slide richens the mixture? I can't see it in my head.   

A bigger cut-away on the slide leans out the mixture.  Most times, a larger cut-away is needed when drastically increasing the main jet size.  Also, lowering the needle will lean the mixture.  You will want to raise the needle, probably to the highest position from what you're describing.

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DanB

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #23 on: August 03, 2013, 08:37:08 PM »
Hope the rain stopped. It's beautiful by me and I'm out the door soon to ride!

I'm not a slide expert by any means, but Scottie said it.  By shaving the bottom our our BS29 slide, we reduce the size of the cutout thereby richening things up. The combo between slide and needle really effect that 1/8 to 1/4 throttle response I believe.

I always get by terms mixed up on the needle notches. Scottie's explanation is what I meant to say, but he's done a much better job.  ;D
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tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #24 on: August 03, 2013, 11:39:26 PM »
Hope the rain stopped. It's beautiful by me and I'm out the door soon to ride!

I'm not a slide expert by any means, but Scottie said it.  By shaving the bottom our our BS29 slide, we reduce the size of the cutout thereby richening things up. The combo between slide and needle really effect that 1/8 to 1/4 throttle response I believe.

I always get by terms mixed up on the needle notches. Scottie's explanation is what I meant to say, but he's done a much better job.  ;D

            Answering both you & Scottie:

               Couldn't get back to you before this. The twin granddaughters (12yo) stopped by.

                I see what you're saying now about increasing the cutout area on the slide. Hope I don't have to go there. Or drilling out the two holes in the bottom.

                Here's what I did before the girls arrived:

                 I pulled the carb & raised the needle 1 shim (.002") or 1/2 a notch. I set the mixture at one full turn out. Started 1 kick & sat there at a perfect idle.

                  Went for a ride. Didn't feel right. Stopped & came out a 1/2 turn on the mixture. Felt happier. Ran well around town under all RPMs AND out on the road at 50 in 4th & 60 in 5th. It's running really, really well again & going between buildings is eargasmic.

                  Came home & the idle drops to dead low in less than 1/2 the time than before PLUS the engine now reacts to the mixture screw way better than it did before. I came out almost another 1/2 turn & the idle increased. I dropped it again with the idle speed screw & left it 'til tomorrow. I think I just need to concentrate tomorrow on finding that perfect mixture screw position & I will be home free.

                   If not I can throw another shim in in 10 minutes & see what that does.

                   Thanks guys. I've really enjoyed the process of learning this Mikuni (& the whole bike) which I've been doing since December 2010 when I bought this never-sold, not running, dry as a bone, no electrics, all bulbs blown, orphan '08 Classic. I knew nothing from nothing about this bike. And I couldn't have done it without Pete Snidal & whining to all you guys ad nauseum.   

                PS: I have no problem leaving that damn collar on the needle alone & using shims. I think there are 3 in there now. If I move (or remove) the collar now, I'm back to square one in finding my correct needle height using the grooves again, and shims. (For those reading this who don't know - this hard plastic  collar on the needle of the BS-29 covers the 2 lower height grooves on mine. As I have freed up my intake & exhaust I've raised the needle progressively using .002" shims under the plastic collar. My needle is 3 shims (at least) higher now than it would be with an e-clip in the bottom groove). This carb was created to give an engine just barely enough fuel to run on, hence AVL Lean Burn.

                 Those carbs (BSs) were on bikes (Soozookies for one) & other small tools back in the '80s. Whose idea was that solid collar on the needle? Was it a Federal emissions thing? It must have been because the mixture screws were also plugged or capped in those days.

           

                 
« Last Edit: August 04, 2013, 12:00:33 AM by tooseevee »
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DanB

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #25 on: August 04, 2013, 12:27:58 AM »
Excellent!  Sounds like your very close. I find can't leave mine alone   :o

Enjoy 2CV
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D the D

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #26 on: August 04, 2013, 12:31:11 AM »
EPA required manufacturers make their carbs "tamper proof" starting in the mid to late 1970s.  I think bikes came after cars and were probably a Cali requirement first.  All bad things are a Cali requirement first.  :(
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tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #27 on: August 04, 2013, 03:29:16 PM »
Excellent!  Sounds like your very close. I find can't leave mine alone   :o


           Just to close out my part of this thread:

                  I rode 12 miles this morning with both around town & out on the road miles.

                   It could not BE any better. Raising the needle that one shim did it plus I stopped twice & tweaked the mixture screw, then again when I pulled back in the driveway 12 miles hot. I could not be any happier with this bike now. At 50 in 4th or 5th & at 60 in 5th it purrs so I'm not going to worry about the main jet until over 1,000 miles. It's got 785 now & I'll very seldom be over 45 the way I ride now so I'm not too worried about running lean at "high speed".

         Maybe tires next? ;>)

 
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kfthompson

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #28 on: August 04, 2013, 11:51:38 PM »
How many turns out on the mixture screw? How many did you start @?

tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #29 on: August 05, 2013, 02:12:01 AM »
How many turns out on the mixture screw? How many did you start @?

           I just went down & checked (just fer you  ;) ) & found it had settled in at just a bit more than one full turn out on the final tweaking (12 miles hot) in the driveway. It was at 1 1/2 turns out when I first left the driveway. The setting now seems reasonable with the larger pilot & the needle raised one shim higher than before.

           This doesn't mean yours will be the same. Depends on your needle height. 

           I need 250 more miles now & I can go ahead & work out my main jet size.
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kfthompson

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #30 on: August 05, 2013, 02:42:11 AM »
Thanks, mine is on the bottom notch. Just wanted a reference point.

tooseevee

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #31 on: August 05, 2013, 12:15:51 PM »
Thanks, mine is on the bottom notch. Just wanted a reference point.

            If you have your slide needle clip in the bottom groove already (richest) & you still can't solve your "0-1/8" throttle problem with the mixture screw, then you're going to have to raise your slide needle with shims (one at a time). Then road test & tweak your mixture screw with each change you make.

             These tiny little shims are available at any Jap bike dealer with a good stock of Mikuni parts.

              I thought you said your slide needle had the hard plastic collar on it covering the e-clip grooves. And also I don't remember - are your exhaust & intake systems wide open? No restrictions?   
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #32 on: August 07, 2013, 04:19:14 AM »
Looks like I'm going to have to pick up some shims tomorrow...

Thanks guys, this thread is great.  If I can figure out how to replace the pilot jet in my BS29 I'll be taking mine for its first test drive tomorrow after work.

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #33 on: August 07, 2013, 12:31:30 PM »
Looks like I'm going to have to pick up some shims tomorrow...

Thanks guys, this thread is great.  If I can figure out how to replace the pilot jet in my BS29 I'll be taking mine for its first test drive tomorrow after work.

           It's very simple to switch pilot jets with the carburetor removed.

           It's a little trickier with the carb left on the engine. You need a small mirror & a small, thin, regular slot screwdriver. The screwdriver must fit up into the tube the pilot hides in. You can't see the pilot jet slot with the carb on the engine. You can see the tube it's inside of with the mirror & then get the screwdriver in the slot by feel.

            If you (or anyone else) want an exploded diagram of the BS-29, I have one I can scan & post here. I just need time to rework the key to the parts. It's incorrect as printed.
« Last Edit: August 07, 2013, 12:33:52 PM by tooseevee »
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #34 on: August 07, 2013, 01:49:38 PM »
Thanks for the info and the offer of the diagram- I think I know what I need to do now.  I'll try and get the pilot in while it's mounted to the machine, but if I need to move the needle or add shims, I'll have to bring it inside somewhere clean and safe, right?

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #35 on: August 07, 2013, 03:02:47 PM »
Thanks for the info and the offer of the diagram- I think I know what I need to do now.  I'll try and get the pilot in while it's mounted to the machine, but if I need to move the needle or add shims, I'll have to bring it inside somewhere clean and safe, right?

           The first time I started the rejetting & needle height changing process I removed the carb totally because I wanted to learn about the whole thing & look at everything; the fuel line, the throttle cable mechanism etc.. I replaced the horrible stock fuel hose & gave it about an inch more slack.

           Now I can do everything without unhooking the fuel line OR the throttle cable. I just pull the carb from the manifold, turn the top slightly toward me & remove the two cap screws. Hold the cap as you remove the screws or the spring & the cap will end up on the floor.

            Now you can pull the slide out of the carb & take it wherever. The two tiny screws & hold-down for the needle are tricky the first time. Each successive time gets easier. A magnetic Phillips helps. I can't tell you how to do the needle hold-down & the tiny screws; only experience will do that. I felt like a monkey fucking a football the first time. Now? 5 minutes out & back in.

             Tilt the carb the other way & you can easily do the pilot & main jets (with a little neck twisting). I can do my pilot jet now totally by feel with the carb attached.

             Another hint: Lift the float & tape it up to the carb body with just a small piece
while you're doing all this so you don't accidentally bend something.

              Also note the tab on the neoprene slide diaphragm. I fits into its own slot on the carb body before the spring & cap go back on. This is what aligns the slide cutaway properly.

               The cap also has its own indexer; it's like a tiny open square on the edge of the cap that fits over a square lump on the carb body.  The cap won't sit down flat on the diaphragm unless it's indexed correctly on that lump.
« Last Edit: August 07, 2013, 03:16:32 PM by tooseevee »
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #36 on: August 07, 2013, 03:37:34 PM »
Quote
These tiny little shims are available at any Jap bike dealer with a good stock of Mikuni parts.

I ended up going to a True Value hardware store and found a number of very thin / small washers.  They work a treat!  I found them in the 'metric' section. 
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #37 on: August 07, 2013, 06:38:08 PM »
Super helpful- thanks again!

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #38 on: August 09, 2013, 04:11:32 AM »
 CV's are awesome ride a day carbys when set up decently. Very forgiving of seasonal atmosphere and altitude changes and very efficient at atomizing the fuel and mixing it with air.

 They can be modded for increased performance too.
http://www.indiancarsbikes.in/automotive-technology/crisp-punch-ported-throttle-slide-cv-carb-9399/
 
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #39 on: August 09, 2013, 12:23:29 PM »
CV's are awesome ride a day carbys when set up decently. Very forgiving of seasonal atmosphere and altitude changes and very efficient at atomizing the fuel and mixing it with air.

 They can be modded for increased performance too.
http://www.indiancarsbikes.in/automotive-technology/crisp-punch-ported-throttle-slide-cv-carb-9399/

            Yup. The little BS-29 is a fine little tool now that I completely understand it & have fondled all its innards.

             I took an almost 20 mile ride Wednesday on some nice RI blue highways. It was one of those rare Colorado/Wyoming type RI days. Clouds & sky like that day are very rare here. The RE is running the best it ever has with its now totally open exhaust, K&N cone, 17.5 pilot & its slide needle & mixture appear to finally be at the "pretty damn close" place. It's just running incredibly well & I'll say again - I love this damn bike! It's like my 50 mile an hour Hoveround ("Where would YOU go?") & I don't feel like a crippled up old dinosaur when I'm on it + Medicare (the taxpayers) didn't buy it for me.

            My main jet is still stock (runs fine at 50/55 in both 4th & 5th) & after I pass 1,000 miles (at 810 now) I'll start cranking her all the way once in a while. I'll no doubt have to increase one or two sizes.

            Thanks, Ice, for the reminder. I've had that slide porting article bookmarked since I first saw it mentioned here a few years ago. I'll think about it after I've ridden a season on the rejetted main. My problem with it is it's immediately permanent. There's no going back.   
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #40 on: August 09, 2013, 01:55:07 PM »
Ice, have you tried that slide punch technique?  I remember you posting it a year or two ago.  For now, I'm in tooseevee's boat where I like the idea of all my mods being reversible back to stock.  If I mess it up, I can build it back to the way it was intended.

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #41 on: August 09, 2013, 03:12:13 PM »
I've actually done this, and the response from the throttle is noticeable.  Not a 'stellar' increase in performance, but responsive is the best word to describe it.

I was worried about messing with the only slide I had, so I ended up contacting the author in the article to order an additional slide.  If I recall, it cost about 11 USD + about 25 in shipping from India.  So I have 2 slides. 

One thing to note is that I believe as a result of this mod (I say believe, as I changed a whole number of things and cant be certain the slide mod is the root cause), is that my starting procedure really changed.  After rejetting, and opening things up, I couldnt start the bike either cold or hot consistently.  Before all my mods, I was kicking it easy with just choke.  Not so after the mods.  It acted like it was missing air.  So now, I hold the throttle at about 1/8 open on kicking over (which should be a no-no), and I get zero kick back and 1st kick starts; hot or cold.  You may not experience the same thing as each bike has it's own personality.  It works for me. 

Would I do it again?  Yes I would...  I like the CV carb, but would like a little more performance out of it between 1/8 and 1/2 throttle.  When I wack it open, it goes nicely!
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #42 on: August 09, 2013, 05:17:29 PM »
Good to hear Dan,

I generally give a touch of throttle when kicking my current stock setup.  Not always necessary, but it definitely helps.  We'll see how it goes today.  I'm going to put in the 17.5 pilot and remove the hot pipe this afternoon.  I think I'll use the slide punch technique at a later date.  I want to get this thing set up real nice before changing things again.

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #43 on: August 09, 2013, 05:37:10 PM »
I've actually done this, and the response from the throttle is noticeable.  Not a 'stellar' increase in performance, but responsive is the best word to describe it.

I was worried about messing with the only slide I had, so I ended up contacting the author in the article to order an additional slide.  If I recall, it cost about 11 USD + about 25 in shipping from India.  So I have 2 slides. 

One thing to note is that I believe as a result of this mod (I say believe, as I changed a whole number of things and cant be certain the slide mod is the root cause), is that my starting procedure really changed.  After rejetting, and opening things up, I couldnt start the bike either cold or hot consistently.  Before all my mods, I was kicking it easy with just choke.  Not so after the mods.  It acted like it was missing air.  So now, I hold the throttle at about 1/8 open on kicking over (which should be a no-no), and I get zero kick back and 1st kick starts; hot or cold.  You may not experience the same thing as each bike has it's own personality.  It works for me. 

Would I do it again?  Yes I would...  I like the CV carb, but would like a little more performance out of it between 1/8 and 1/2 throttle.  When I wack it open, it goes nicely!

           Thanks for your above, Dan. Just for my future reference do you recall what size drill bit you used? I'll also get another slide before I do it. I should do that now. There can't too many of these things left.

            Mine is starting now in one or two kicks hot or cold with no enrichener & no throttle. Just turn the key on, kick it, it's running.

            I'll be interested to see what it does when it gets cold this Fall. 
« Last Edit: August 09, 2013, 05:40:03 PM by tooseevee »
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #44 on: August 10, 2013, 03:17:59 AM »
Quote
Just for my future reference do you recall what size drill bit you used?

If I recall, I used an 1/8 inch. Basically following the article. I did use a drill press to keep it as clean and straight as possible. I definitely recommend getting a 2nd slide; cheap insurance :) good luck 2CV!
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #45 on: August 14, 2013, 04:33:52 AM »
FYI that little white plastic collar on the CV needle... I got mine off no problem.  pushed down on it from the top with a small diameter wrench (bracing the needle's tip against the table).  Put it back on then based on a walkthrough I read on here.

Checked my plug today and it's white, so I decided to go to the richest notch (bottom notch = highest needle height = richest, right?)

I've been unable to keep a steady idle without using throttle when stopped.  When I messed with the mixture screw, leaning it out increased it to a healthy idle, but then my standard cruising throttle was severely lessened (excessive leanness?).  It was shocking to see the mixture screw affect this wide range of throttle, but I'm still not totally comprehending it.

One question:  To set idle on the CV carb, do I do it the same as I've read to do on other carbs? (reverse screw direction already taken into account).   in other words, do I get it hot, then mess with the screw til it's idling as high as it'll go, then reduce the throttle screw until it's fairly low but maintaining a healthy idle, then increase it again via the mixture screw?  (if it'll go any higher)?

thanks,

Chuck

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #46 on: August 14, 2013, 12:57:31 PM »
Not exactly.  When you're making your adjustments move the idle screw until the idles increases to it's "max" RPM in that range and then move the screw a 1/4-1/2 turn towards the rich side.  If you leave it at that "high idle" point you will be running too lean.

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #47 on: August 14, 2013, 03:38:52 PM »
Thanks, I'll give it a test ride tonight and try to get the idle speed all set.  Hoping this richest needle setting will be rich enough...

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #48 on: August 25, 2013, 04:02:58 PM »
Thanks to all for a great thread.
I'm a newbie to the carb dissection...thinking of undertaking the process, but I may not have to at this moment.  I'm running lean with a newly placed less restrictive filter/exhaust setup, getting slight hesitation from idle and some backfiring on deceleration. Great idle and acceleration otherwise.  Other members have suggested increasing pilot/main, which I may well have to do, but could I start with the needle and mixture screw first?  Iíve got AVL with BS29 stock.  I was going to play today.  In reference to the slide needle adjustment, raise to be RICH and lower to be LEAN. Correct?  Also, is that with the carb still attached?

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #49 on: August 25, 2013, 04:20:14 PM »
Yes, you could try that.

Mixture screw: clockwise lean; counter clockwise rich. Make sure the engine is nice a warm and set it up.

Needle:  the richest setting on the needle is the lowest slot as you look down the needle. This is how you raise the needle in the carb. 

Remember, the pilot jet, mixture screw and needle all work together between 0 and ~1/4 throttle. The main jet also plays a part and becomes more important as you work up the throttle. Most folks tend to start with the main jet first at WOT, then work their way down.
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #50 on: August 25, 2013, 04:41:13 PM »
If you pull the tank off you can get to the slide and needle without removing the carb.  That's my preference.  Others find it easier for them to leave the tank in place and remove the carb.  Really it's personal choice; 6 of one, half a dozen of the other.
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #51 on: August 25, 2013, 05:17:36 PM »
If you pull the tank off you can get to the slide and needle without removing the carb.  That's my preference.  Others find it easier for them to leave the tank in place and remove the carb.  Really it's personal choice; 6 of one, half a dozen of the other.

I definitely prefer to pull the tank.  Makes it a lot easier, plus Amals are notorious for warping when the flange bolts are over torqued, so I don't pull the carb off unless I'm doing a thorough cleaning.

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #52 on: August 26, 2013, 05:42:36 PM »
If you've never opened up the carb before I recommend removing it and doing it on the kitchen table... well lit, clean, and no risk of dropping tiny parts on the ground.  I tried to do stuff with it on the bike (first time ever) and it was WAAAAY easier to do it in the kitchen.  (at least for the needle settings).  Mixture screw and jets can be done with the carb on (and the tank on for that matter).

Still figuring out my own settings as we speak.  Either way, I can pretty much guarantee you'll need a 17.5 pilot, and a larger main too (most people end up using the 120 size main).  I'm on a 125 main right now but may be running a little rich.  Like I said, more experimentation is coming my way...

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #53 on: August 30, 2013, 03:29:46 PM »
Thanks all. I've played with the mixture screw, out 6 turns even and doesn't make a lick of difference. Will try a 17.5pilot to start.

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #54 on: September 11, 2013, 02:42:21 AM »
So I've taken this BS29 apart and learned it well. Amazing to understand what the posts are referring to. I put in a 120 main from the 110 and raised the slide needle one shim. Pilot stock at 15. The bike would hardly keep idle, poor throttle response and needed choke wide open to stay alive, but minimal backfire, only right before return to to idle. Mixture screw did little to make a difference of helping idle.
I changed 120 out to a 117.5 and raised the slide needle to highest point, with the white donut in place, plus shim(only has 3 notches). This resulted in less, mostly stable one or no pop backfire, but sluggish response to throttle overall and still idle wasn't super. So took slide needle back to middle, with the white donut in place and one shim. This resulted in great power and idle, but backfire increased again.
I don't have a baffle in the Goldie exhaust, and I was going to add a 17.5 pilot dice the 120 main seems too rich. Thoughts on this config?

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #55 on: September 11, 2013, 03:01:16 AM »
Sounds like you're making progress. The carb is fun to take apart, isn't it! I'm a constant tinkerer.

Anyway, I think your idle issue is related to the pilot jet, pilot circuit and / or the mixture screw. If the mixture screw was making no difference, then I'd suggest trying the 17.5. I tried a 15 pilot; it idles but was really anemic at any throttle point. At 17.5 and about 1/2 turn out, it idled nicely. That screw should make a difference.

Also, the crappy idle reminds me of an air leak in the air intake or the manifold forcing the whole system lean. I know it's another element, but its really important to make certain there is no air leak when tuning a carb. How to check?  Spray wd40 over the hoses while running and see if you hear any difference in the idle. That Indian rubber does wear out.

Also make sure the pilot circuit in the carb body is not blocked which could be another reason the mixture screw makes no difference.

I'd stay with the 120 until your able to get to wide open throttle and do a few plug chops. I change between 117.5 and 120 depending on temp as I seem to be right on the edge between them. Every bullet is a bit different.

Sorry for the long rambling post!  I'm too lazy to go back and edit it down.
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #56 on: September 11, 2013, 03:09:43 AM »
Thanks Dan. No worries; please ramble. Well, going on vacation for a week. Hate leaving a project sit, but will give time for the pilot to come in...and replacement baffle for that matter.
In the meantime...dropping it off for new 4x19 tires front back for that beefier look. But that's another thread on its own.
You all take care, keep the shiny side up, as they say.

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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #57 on: September 11, 2013, 03:24:42 AM »
Have a good vacation.  8)
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Re: slow acceleration to 1/4 throttle.......then WOW!!!
« Reply #58 on: September 13, 2013, 02:18:39 PM »
Congrats on the tuning!  I pulled mine apart again last night and shimmed up the needle.  I have a tiny brass washer between the white plastic collar thingie and the needle clip (which itself is at the bottom [richest] setting).

It's a monster now.  17.5 pilot, Needle position as noted above, and I think I still have the 122.5 main in there.  I'm loving it.  I think i need to lean out my mixture screw a bit to keep a steady idle.  Always a work in progress.  Always.

Cheers!   8)