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Author Topic: How is your carb jetted for K&N and megaphone?  (Read 1593 times)

mypvtidho

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How is your carb jetted for K&N and megaphone?
« on: March 07, 2013, 01:16:39 AM »
If you are running the K&N cone filter and the megaphone muffler with the stock VM28 MICARB, what jets are you running and what notch on the jet needle?
PLEASE ONLY REPLY IF YOU ARE RUNNING THE ABOVE EQUIPMENT.

jedaks

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Re: How is your carb jetted for K&N and megaphone?
« Reply #1 on: March 07, 2013, 12:48:40 PM »
I have used a K&N on a Mikcarb, and I do run a Goldstar straight-through. If that is any help to you....

First, you need some way to support the back of the carby so the rubber inlet tube isn't supporting the weight..you will get air leaks which will mess up your jetting and add confusion. The cone filter lets in lots of air so you need richer jetting to compensate or you WILL ruin a piston, which WILL put molten shards of metal all through your engine. I have experience with that. :'(

Before I knew better, I ran a cone filter and free flow muffler with the stock jets of 25 pilot jet, P0 needle jet, clip on the 4th groove and a 120 main jet. That was too lean. An engine rebuild taught me the lesson the hard way.

I live at sea level so the jetting I use is a P2 needle jet, the needle clip in the lowest groove and a 127.5 main jet. The pilot jet is 27.5 That is appropriate for my situation. However I now use an Ace Canister, which I think is better than a cone filter. The carburetor is drawing from a supply of still air.

Anyway, I hope this is of some help to you.
« Last Edit: March 07, 2013, 12:51:36 PM by jedaks »

mypvtidho

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Re: How is your carb jetted for K&N and megaphone?
« Reply #2 on: March 07, 2013, 10:25:04 PM »
Yep. Thanks. I was looking for a comparison.
I also am at sea level, am using a 30 pilot, 135 main, and A5DH7 needle (bottom groove) on unknown needle jet.
Still having issues at around 1/8 throttle. All other areas runs good.

ace.cafe

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Re: How is your carb jetted for K&N and megaphone?
« Reply #3 on: March 07, 2013, 11:02:52 PM »
Your main jet is too rich. Try a 130.
Problems at 1/8 throttle position are often related to the throttle slide or the needle jet needing to be richer, or both. This is a transition zone from the pilot circuit to the needle jet circuit, and the transition is helped by the throttle slide cutaway.
For sea level, a P2 needle jet is commonly needed.
The carb comes with a 4.0 slide. People sometimes need a 2.5 or a 3.0 throttle slide if the richer needle jet doesn't solve the problem. But the richer needle jet is needed anyway. The stock O8 needle jet is too lean for sea level operation with a free-flow system on the bike.

The needle jet is Mikarb-specific, and cannot use a Mikuni brand needle jet. You have to get it from NField Gear or Hitchcocks. The throttle slide can use a Mikuni brand slide from a VM28 with the proper cutaway specified.

These items are the most expensive parts in the Mikarb, and that's why the stock ones are often left in the carb, and why it is hard to tune unless you put the right ones in.

I would buy the P2 needle jet, and see if you can tune the problem away with that. If the problem persists, then you can get the throttle slide with the richer cutaway.
« Last Edit: March 08, 2013, 03:43:27 PM by ace.cafe »
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greekxj

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Re: How is your carb jetted for K&N and megaphone?
« Reply #4 on: March 08, 2013, 01:56:14 PM »
I have the K+N also with a wide open Goldstar and 28 mm carb. I have a 130 main, 30 pilot, P2 needle jet, needle on bottom notch(stock slide btw), 1.5 out on the air screw if a remember right. Its been a while but that's what i got if i remember correctly. It took me a while to get it set but the thing that really helped alot was the P2 needle jet. Forget the stock one, and i even went to the P0 first with no luck. Runs great now though

REVirginia

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Re: How is your carb jetted for K&N and megaphone?
« Reply #5 on: August 25, 2013, 04:07:40 AM »
Wondering if anyone will see this... Great thread. So today I installed the Goldie style system from Hitchcock to my 2009 AVL. No header leak noted. Sounds great, good acceleration after some brief initial lag, but now getting backfire on decelerating. I had long ago performed the filter mod with the K&n filter into the Hitchcock chrome traditional filter housing. This housing's base is absent, so it's possibly pulling in turbulent air. I had no issues previously with stock exhaust. I'm guessing I'm running much more lean now with a less restrictive header pipe and the filter arrangement.
Realizing I need to rejet, what is the forums opinion? I don't know what stock is on my bike specifically. I'm in VA, so elevation about 150', though like to get into mts for drive, which can get to > 3000ft. Any thoughts about what I might try?
Thanks in advance!

Sean

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Re: How is your carb jetted for K&N and megaphone?
« Reply #6 on: August 25, 2013, 05:06:56 PM »
If you're not exceeding 3000' in altitude, you'll probably be ok keeping the same settings you have for at home.  As for your crab settings, you didn't even mention what you have currently so it's kind of hard to give you any direction.

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REVirginia

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Re: How is your carb jetted for K&N and megaphone?
« Reply #7 on: September 02, 2013, 05:33:34 PM »
Sorry Scottie. I'm still stock with the Ucal BS29 main 110, pilot 15. I did add one shim to raise the needle with no difference. I'm going to call around tomorrow for a 120 main and start there. Taking carb off today.
Thanks

guss,guss

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Re: How is your carb jetted for K&N and megaphone?
« Reply #8 on: September 21, 2013, 10:54:38 PM »
now i am worried about my bullet.
 I'm still a newbie . i bought my 99 just last June. the guy said he put  a new exhaust on it and it turned blue. he knows less than i do. i checked the timing and it was retarded allot. i advanced it till i felt good about it.
 but after reading this?
 the exhaust is a shorty megaphone, i think that's what you call it, and it has a k&n flat round filter like a pancake. it also has a piece of radiator hose holding the carb on . i have one of those high dollar rebuild kits from japan and a replacement mounting tube but haven't done anything with it cause i was going to read up on mikcarb rebuild and and try it my self. but in the meantime i don't want to burn up a piston.
 so any advise on making sure i don't burn it up for now till i learn the ways of carb rebuild and tuning.
i think i am, therefore, i must be.

ace.cafe

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Re: How is your carb jetted for K&N and megaphone?
« Reply #9 on: September 22, 2013, 12:11:06 AM »
now i am worried about my bullet.
 I'm still a newbie . i bought my 99 just last June. the guy said he put  a new exhaust on it and it turned blue. he knows less than i do. i checked the timing and it was retarded allot. i advanced it till i felt good about it.
 but after reading this?
 the exhaust is a shorty megaphone, i think that's what you call it, and it has a k&n flat round filter like a pancake. it also has a piece of radiator hose holding the carb on . i have one of those high dollar rebuild kits from japan and a replacement mounting tube but haven't done anything with it cause i was going to read up on mikcarb rebuild and and try it my self. but in the meantime i don't want to burn up a piston.
 so any advise on making sure i don't burn it up for now till i learn the ways of carb rebuild and tuning.

There's really not much to "rebuild". Just jet it right and run with it.
A good starting point for elevations near sea level is 27.5 pilot and P2 needle jet and 127.5 main jet. Leave the radiator hose connector to the inlet manifold stub. That's a good connector.
Put the air bleed screw about 1.5 turns out from the bottom, and set the idle speed screw to a good idle speed that isn't too slow. Don't try to idle so low that it might stall. Get a good steady idle, not too slow, and do it when the engine is warmed up. It should need to have the choke(enrichment lever) on when cold starting, and then move it to off as soon as the bike will idle on its own.
You'll need to do a little individual tweaking with the air bleed and idle speed screw to suit your own bike. They are all a little bit different.
Make sure that there are no leaks in the exhaust or intake.
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guss,guss

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Re: How is your carb jetted for K&N and megaphone?
« Reply #10 on: September 22, 2013, 02:40:48 AM »
thanks, i will do some reading before i take it apart and clean it and put it back with the new parts.
 as for now, i never need to use the enrich lever to start it. should i adjust something right away before i ride anymore or do you mean cold start as in ambient temps below 50 f ?
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ace.cafe

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Re: How is your carb jetted for K&N and megaphone?
« Reply #11 on: September 22, 2013, 11:17:41 AM »
thanks, i will do some reading before i take it apart and clean it and put it back with the new parts.
 as for now, i never need to use the enrich lever to start it. should i adjust something right away before i ride anymore or do you mean cold start as in ambient temps below 50 f ?

The clarify, the enrichement lever is "on" when the lever is down, and "off" when the lever is up. It's not uncommon for people to have this backwards, and be riding around with the enrichment lever "on" all the time, while the carb is jetted too lean. More common than you might expect. That's why I mentioned it.
If you never need it to start the bike, I would speculate that the bike is jetted rich in the pilot, or you are riding with the enrichment lever "on".

However, all the jets have numbers on them, so you can find out what's in there when you take the carb off and remove the existing jets. That's your first step.
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guss,guss

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Re: How is your carb jetted for K&N and megaphone?
« Reply #12 on: September 22, 2013, 02:25:28 PM »
ok.  i dont know whats in there now. i see the new kit has main #110 and pilot #25. the enrichment lever is always horizontal, off, with the pluger down. before i order bigger pilot and main jets i should have a look at whts in there now.
 if i have been starting it without the help of enrichment it may have some big honkin jets in there already.
 about checking for leaks. i read to spray wd40 around the intake gasket...
 but for exhaust, the "silencer" is clamped tight , other than that and no holes  in the pipes what is there to look for?
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ace.cafe

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Re: How is your carb jetted for K&N and megaphone?
« Reply #13 on: September 23, 2013, 12:59:52 PM »
ok.  i dont know whats in there now. i see the new kit has main #110 and pilot #25. the enrichment lever is always horizontal, off, with the pluger down. before i order bigger pilot and main jets i should have a look at whts in there now.
 if i have been starting it without the help of enrichment it may have some big honkin jets in there already.
 about checking for leaks. i read to spray wd40 around the intake gasket...
 but for exhaust, the "silencer" is clamped tight , other than that and no holes  in the pipes what is there to look for?

I don't know what your elevation above sea level is, but for anywhere near sea level, the jets in "the kit" are totally useless. If you tell us your elevation, we might recommend some, and if you are near sea level, the jets that I recommended in the previous post will work as a good starting point.

The most common place for exhaust leaks is at the joint of the head and exhaust header. It is a "push fit" and commonly leaks. Look for signs of black carbon residue around that location to identify if significant leaks are there, or you can try to hold your hand about an inch off the metal at that joint while it's running, to see if you can feel any air jets coming out from that area. If you do, we can recommend fixes for that. Many Bullets do have problems in that area, so it wouldn't be unusual to find an exhaust leak there.
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guss,guss

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Re: How is your carb jetted for K&N and megaphone?
« Reply #14 on: September 24, 2013, 12:20:09 AM »
 i appreciate all the help.
 i am 880 ft elevation. and now that i look at the header i do see a small amount of carbon on the pipe around the port.
 i was planning to wrap the pipe with fiberglass, add a heat fin, and replace the El cheap o muffler that is pitted with a new El cheap o muffler that will look good for a year or two. i think that how old the one on there is. so adding a heat fin will require pulling the pipe away anyway i may as well put it back right. so I'm all ears.
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ace.cafe

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Re: How is your carb jetted for K&N and megaphone?
« Reply #15 on: September 24, 2013, 12:35:09 AM »
i appreciate all the help.
 i am 880 ft elevation. and now that i look at the header i do see a small amount of carbon on the pipe around the port.
 i was planning to wrap the pipe with fiberglass, add a heat fin, and replace the El cheap o muffler that is pitted with a new El cheap o muffler that will look good for a year or two. i think that how old the one on there is. so adding a heat fin will require pulling the pipe away anyway i may as well put it back right. so I'm all ears.

I am at the same elevation as you, and have the same year Bullet as you, and the jetting I previously recommended will work for you.

Regarding the exhaust leak, you can put some clear silicone sealer on the outside of the header pipe when you push it into the head to re-install the header after you have taken it off. Let it cure overnight before using the bike. It will last probably a whole riding season, and you can do it again over the winter, or if it blows out and needs re-doing.
If there is a loose enough fit, you can cut a piece of beer can with some snips that is the right size to wrap around the header just once, with close-butted ends, and that will take up the space around the header and seal it up. I have done this with very good success, and it never blows out, and can be re-used when you take out the exhaust system in the future.
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guss,guss

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Re: How is your carb jetted for K&N and megaphone?
« Reply #16 on: September 24, 2013, 01:04:12 AM »
 excellent. i have some more tinkering projects on my list.
 keeps me out of the pool halls.
 
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guss,guss

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Re: How is your carb jetted for K&N and megaphone?
« Reply #17 on: October 03, 2013, 12:35:32 AM »
well, if any of you gearheads are still out there, i didn't jump ship and swim back to japan.  i wanted to go ahead and those jets before i take it apart. i just got the parts from our friends here in the states but they sent the wrong main jet.
 but i did take care of that exhaust leak and wrapped the pipe with fiberglass.
 i didn't put the heat fin on because i thought i wouldn't be able to slide it down the pipe past the wrap to check for leaks.
 does any one think the wrap could cause the head to run hot? i mean the heat has to go somewhere. if the wrap keeps it from radiating from the pipe then the pipe itself will retain more and its inside the exhaust port.
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ace.cafe

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Re: How is your carb jetted for K&N and megaphone?
« Reply #18 on: October 03, 2013, 01:54:50 AM »
well, if any of you gearheads are still out there, i didn't jump ship and swim back to japan.  i wanted to go ahead and those jets before i take it apart. i just got the parts from our friends here in the states but they sent the wrong main jet.
 but i did take care of that exhaust leak and wrapped the pipe with fiberglass.
 i didn't put the heat fin on because i thought i wouldn't be able to slide it down the pipe past the wrap to check for leaks.
 does any one think the wrap could cause the head to run hot? i mean the heat has to go somewhere. if the wrap keeps it from radiating from the pipe then the pipe itself will retain more and its inside the exhaust port.
I haven't wrapped any pipes myself, but it's good to keep the heat in the exhaust pipe. It keeps the exhaust stream well heated and expanded, and that keeps the exhaust speeds higher for better extraction effects during scavenging. Don't worry about it heating up the head. The head gets the full exhaust temperature as the exhaust gases go out the exhaust port anyway. The finned thing doesn't do anything except possibly reduce the bluing of the pipe a little, maybe. It's just an appearance doo-dad that some people like, and it doesn't do any harm.
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guss,guss

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Re: How is your carb jetted for K&N and megaphone?
« Reply #19 on: October 07, 2013, 11:40:05 PM »
OK. i got all the right jets. took it apart yesterday and put it back. i think i did pretty good. it did have the stock ones in there. the only problem i had was the new enrichment plunger would not go down into its place. just wouldn't go. i didn't want to force it. i tried several times. so i used the old one.
 when i got it to run and idle for a few minutes i had to set the pilot air screw at one half turn out to make it rev up without stumbling.
 i did not get to take it out for a ride. i was planning to replace the throttle cable but the new one is too short. i got it awhile back from one of those places in India and the add said it was suitable for all four speed bullets. the old cable  only has a few strands left.  i just pulled on the free end to rev it up.
 but i notice when i reach to adjust the idle stop screw i feel puffs of air from the oil catch tank under the battery. is that normal?
 thanks, ace, for the advise on the exhaust. but i think i blew out my nice little silicone job at the port. as i was revving the engine i happened to look at the pipe and it was blowing away from the head. startled me at first, thought i had created a monster. then after i thought it out i think in the future if i run the bike without the tank on i should go ahead and bolt that stabilizer from the head to the frame back up.
 
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