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Author Topic: slow acceleration to 1/4 throttle.......then WOW!!!  (Read 2714 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?
Jim
2011 G5 Deluxe
1999 Miata 10th Anniversary

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.

               
2008 ACE Head AVL Classic
1977 Shovelhead Hardtail Bobber

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.

D the D

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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
'07 Iron Barrel Military (Deceased 14 September, 2013)
2014 Yamaha Bolt R Spec V-Twin
1975 XLCH

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. 
2008 ACE Head AVL Classic
1977 Shovelhead Hardtail Bobber

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.

 
2008 ACE Head AVL Classic
1977 Shovelhead Hardtail Bobber

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 »
2008 ACE Head AVL Classic
1977 Shovelhead Hardtail Bobber

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.
'07 Iron Barrel Military (Deceased 14 September, 2013)
2014 Yamaha Bolt R Spec V-Twin
1975 XLCH