Hey Guys I thought my mk3 was running a little rich so I changed the main jets from the 230 with the needles set on the top notch ( leanest ). The carbs are pretty new and have the 106 needle jets. It ran very well and pulled like a train at full throttle. The reason I changed jets was when I checked the plugs they both were burning a little black and the exhaust smelled rich to me. It,s definitely not oil on the plugs, the motor is a solid no oil burner. I went to 220 jets and tried them and noticed that when on a restart with a very warm engine I would have to use the choke for a short distance to keep the engine from trying to die out. And it seems like it doesn,t pull quite as hard at full throttle. I reset the needle to the second notch and that did help with restarts but still have to use a little choke. I,am not much above sea level ( 1000 feet or so ). What jets do most of you guys use. I,am thinking about going back to the 230 jets with the needle at the top notch. What,s your opinion??
main jets
- Thread starter hershey
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Cdo's are only supposed to need choke when cold, though new lean burn gasoline may shove cause need of choke more often. Sound like a tad lean set up. You might fudge the mix to richer perfection by float level fine tuning. Your current best idle screw setting may be a clue already.
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hershey
The needle jets are they new or old. You may have worn out needle jets. The main jet only comes into play from 3/4 to full throttle. Do a full throttle plug chop on a slight uphill grade and pull over and check the plugs. Set then forget the mains. The needle jet gets oval rubbing with the needle from mileage. Depending on how much slop the slides are in with the main body this will compound the wear pattern on the needle jets. The technical information has lots of info for you to ponder over.
Cheers.
CNN
The needle jets are they new or old. You may have worn out needle jets. The main jet only comes into play from 3/4 to full throttle. Do a full throttle plug chop on a slight uphill grade and pull over and check the plugs. Set then forget the mains. The needle jet gets oval rubbing with the needle from mileage. Depending on how much slop the slides are in with the main body this will compound the wear pattern on the needle jets. The technical information has lots of info for you to ponder over.
Cheers.
CNN
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hersay wrote;
Are you saying that you changed the needles to the leanest position as well as changing the main jet, or was that where the needles were set originally?
IF you have altered the needles to the leanest position, as the main jet apparently has little or no effect at tickover, I'd revert the needles to the original position and that should make it run as before, at lower throttle openings.
If you haven't moved the needles, disregard this post!
Are you saying that you changed the needles to the leanest position as well as changing the main jet, or was that where the needles were set originally?
IF you have altered the needles to the leanest position, as the main jet apparently has little or no effect at tickover, I'd revert the needles to the original position and that should make it run as before, at lower throttle openings.
If you haven't moved the needles, disregard this post!
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hersay wrote;
It might be just the way you've written it and I'm not trying to insult you, but if the circlip on the needle is in the uppermost slot (??top notch), that equals the leanest setting for the needle.
The richest setting for the needle is when the circlip is on the lowest groove/slot on the needle, which raises the needle and allows more fuel to pass.
It might be just the way you've written it and I'm not trying to insult you, but if the circlip on the needle is in the uppermost slot (??top notch), that equals the leanest setting for the needle.
The richest setting for the needle is when the circlip is on the lowest groove/slot on the needle, which raises the needle and allows more fuel to pass.
That,s correct top notch lean bottom notch rich. With the 230 jets the needles were set on the top notch ( lean ). When I changed to 220 jets I left the needle set on the top notch ( Lean ) but on restart with very warm engine I had to use the choke for a short distance, so I moved the needles to the second notch ( richer ) and the engine did run better on restarts but not as good as the 230 jets with the needles on the top notch ( lean ). I know that the main jet isn,t suppose to have much to do with engine performance up to about 3/4 throttle but with my bike they do. More ridding will be needed to determine whether or not to go back to the 230 jets and the needles set on the top notch. I know that each bike has a different personality. I was just curious what size jets the majority were running in their bikes and if any 220 jets were used. Thanks for your input and interest !! HersheyReggie said:
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Hey hershey,
If it was pulling well and not 4 stroking at high revs on WOT then the main is probably OK.
A plug chop needs to be done at SUSTAINED high revs ( 6000 FOR A COUPLE OF SECONDS AT LEAST) with a little load.
As pulling the clutch in and hitting the kill switch at a 100 miles an hour is not much fun, you need to find an
up hill stretch of road, and do a chop in second or third gear. That tells you about the Main jet.
WOT at 4000 revs tells you nothing because the engine needs to be revving, to coincide with the throttle opening.
Three quarter throttle at 4500/5000 ish, will indicate needle setting.
By changing the Main jet things shouldn't alter at start up or earlier throttle openings other than sustained wot.
A bit Rich is not a bad thing.
Do all your testing either, with the Air filter on, or off.
Unless you are a particularly hard rider,(sustained high revs), the main jet is not a big deal, a little rich, a little lean...,
but the needle / needle jet is used all the time.
Only change one thing at a time.
Just remember,... It's all good fun.
AC.
PV may be right here, go back to original settings and try another plug range.
If it was pulling well and not 4 stroking at high revs on WOT then the main is probably OK.
A plug chop needs to be done at SUSTAINED high revs ( 6000 FOR A COUPLE OF SECONDS AT LEAST) with a little load.
As pulling the clutch in and hitting the kill switch at a 100 miles an hour is not much fun, you need to find an
up hill stretch of road, and do a chop in second or third gear. That tells you about the Main jet.
WOT at 4000 revs tells you nothing because the engine needs to be revving, to coincide with the throttle opening.
Three quarter throttle at 4500/5000 ish, will indicate needle setting.
By changing the Main jet things shouldn't alter at start up or earlier throttle openings other than sustained wot.
A bit Rich is not a bad thing.
Do all your testing either, with the Air filter on, or off.
Unless you are a particularly hard rider,(sustained high revs), the main jet is not a big deal, a little rich, a little lean...,
but the needle / needle jet is used all the time.
Only change one thing at a time.
Just remember,... It's all good fun.
AC.
PV may be right here, go back to original settings and try another plug range.
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