muscle jet stumble

[Onelegit]

g'day long time lurker first time poster and let me say what a great site and wonderful resource.anyway i need help with a carb problem.after fitting carbs with morleys jet kit and 2in1 2in1 hmf full exhaust i get a stumble just off idle to about 2000 rpm also when cruising at very small throttle openings to about 4000 rpm and crack it open i get a hesitation stumble. the bike idles good runs good to red line all gears.its drivin up the wall:bang head: carbs are 155 mikuni main 170paj stage 1 DJ needles second down from blunt end mixture screws 2 1/2 out. carbs are clean with no issues i can find. also i'm at sea level. i've tried to be as thorough as possible with symptoms and setup.carbs were birdopreys thanks. i hope you can help thanks in advance

 

[gamorg02]

do u have access to an a/f meter. the mixture screws may not be 100%. mine were from 3 - 5 turns out. also. u may want to try richening the needle slightly. is the stumble a lean or rich stumble?

 

[one2dmax]

I agree, may need to open up the mix screws a bit more. And if problem still persists you can try using a washer to shim the needle (washers are used to get a 1/2 position instead of the full clip position).

Sean

 

[Onelegit]

i think its a rich stumble as when i lowered the needle it got worse.

 

[Onelegit]

oh yeh no a\f meter.will changing paj2 smaller larger correct off idle issues.also any opinions on dj stage 1 needles as i have stock also.cheers

 

[gamorg02]

the stg1 and stock are very similar, but the stg1 gives much more tunability. Define "Lowered" the needle? did u move it more towards the blunt end or the pointed end?

 

[Onelegit]

the stg1 and stock are very similar, but the stg1 gives much more tunability. Define "Lowered" the needle? did u move it more towards the blunt end or the pointed end?

sorry i meant to say raised. moved clip to pointy end and symtoms got worse.i would'nt of thought needle to have as much an effect at just off idle and very small throttle openings.also i forgot to say slides have drilled standard springs.

 

[naughtyG]

So did you try moving the clip the other way? Did it improve things?

 

[Onelegit]

yes and it did improve but it still stumbles when just as you crack to take off slowly.needle is currently second clip from blunt end i might try it at the first clip position leanest setting.what toughts?

 

[gamorg02]

can't hurt. its worth a try.

how did u set your a/f screws?

 

[Onelegit]

can't hurt. its worth a try.

how did u set your a/f screws?

just by ear screw in till misses turn out till recovers + 1/2 turn .and been fiddlling with them in and out as you do trying to find a happy place. i cant seem to find the sweet spot .which is why i ask about paj2 what effect do'se it in regard to tuning.

 

[gamorg02]

not 100% sure on paj2, i'd ask one of the experts.

u happen to have someone who can get an a/f reading on the screws for you? i could never hear it right , but once i brought it to the dyno shop to set the a/f the idle really changed and it helped.

 

[one2dmax]

PAJ 2 effects a pretty wide range but we have mostly seen it in the mid area. I think fargo has done some recent testing to prove what it did for him.

Sean

 

[RagingMain]

PAJ 2 effects a pretty wide range but we have mostly seen it in the mid area. I think fargo has done some recent testing to prove what it did for him.

Sean

It affects all ranges, even the idle circuit.

 

[Onelegit]

no worrys thanks thank fellers i'll keep tinkering and i'll get it right eventually.it's good to able to pick your brains .the vmax has been around a long time and anything and everything that can be done to it has been done.most of it by sean morley judging by what i've read on here.sean morleys jet kit is very comprehensive.i just need to find the combination.im sure someone here has had the same problem and corrected it.

 

[Onelegit]

update i just swapped dj stage1 needles for stock units and its much better off idle and mid range. runs out of puff in the top end though leaning out.needs fattening up in the mains.what mains are you fellers running with simular set ups at sea level. cheers

 

[gamorg02]

i'm at 160s right now and it runs better now in like 50 deg weather so once it starts warming again come april i might goto 155s.

 

[Onelegit]

i'm at 160s right now and it runs better now in like 50 deg weather so once it starts warming again come april i might goto 155s.

yeh i've got 155s now think i'll go up 160s see how it go'es .im here in townsville australia its like florida weather i imagine hot and humid in summer not so bad know though

 

[gamorg02]

man i wouldn't go too much higher than what u have. esp if making the needle richer was worsening the problem.

 

[RagingMain]

Take it from me, do one step at a time. Trust me, dont aske me how I know this :bang head:
Go to 157.5s. One size makes a noticable difference