4k stumble!!!! Im stumped!!!

[65fury]

WARNING LONG WRITE

Well im still having a horrible 4k stumble, regardless of gear im in anything over 1/4 past 4k and it falls on its face and stumbles its way to 6k where it pulls hard. I have stock needles, but the PO drilled the slides.

Ive tried shimming the needles with .4mm shims and .8mm shims and even stacked them. The bike stumbles regardless of shims or not, but it does run a bit better with the .4mm shim over no shim. I even ran a 150 main and between the 165 and 150 mains my top end pulls harder with the 165s, but my 4k stumbloe is still there. Ive pulled the plugs constanlty after every change and they have always looked tan.. only a few times did they look more whitish.

I put all new solid core sparkplug wires and ngk caps, sparkplugs are fairly new NGK also, the wire and caps made the bike sound a lil crisper and rev a tad quicker but did nothing for my 4k stumble, also chokig it during the stumble doesnt help or even change how it runs.

It acts like its running rich but if i remove teh shims it runs even worse and at the lower 3k rpms to, without shims at 3k it pops and studders cruising, and anything over 1/4 throttle at 3k itll stumble and sounds like its running on 3cyl, so i left the .4mm shim in and that cleared that issue.

Im outa ideas??? ive syncd the carbs and it still runs like crap, I dont know what to do?? the bike ran great before i cleaned the carbs(pulled and cleaned them twice now) my floats are set 16mm below tick mark on bowl(wet level) all sparkplugs look the same.

Ive also tried smaller PAJ2's to slow the slides down form opening so quick, (used 160s) and that made the bike run worse, Ive run with vboost open and closed(cant run it normal since the controler is on the fritz) with all the different shims and settings and regardless of what i do i always have teh 4k stumble!!! My midrange just wont clear up!! This is driving me nuts, im suppose to be on vacation taking a rode trip to CO and TX, but my bike wont run right any ideas????

Jason

 

[maxcruiser]

Not sure if this is a singular problem or not, but 4k is when the needle jets should start to react. Yours sounds like it is reacting to quickly creating the stumble.

You mentioned that po drilled the slides, do you know why he did this? Usually, it is done as part of a stage 7 conversion. So begs to ask the question, is all other components in the carbs stock, like the diaphram springs, stock air box, etc...

Mike

 

[65fury]

Not sure if this is a singular problem or not, but 4k is when the needle jets should start to react. Yours sounds like it is reacting to quickly creating the stumble.

You mentioned that po drilled the slides, do you know why he did this? Usually, it is done as part of a stage 7 conversion. So begs to ask the question, is all other components in the carbs stock, like the diaphram springs, stock air box, etc...

Mike

I dont know the PO of the bike, i bought it from his buddy, but no other parts were changed in the carbs, stock needles all jets were stock except there were 165 mains. Stock airbox and when i bought the bike it had supertrapp slipons. I dont know what the guy did before to get the bike to run so good but i apparently cant:bang head:

The bike was totally stock except for the supertrapps and the 165 mains, drilled slides and i noticed the carb floats were all set rich. I put in 160s for the PAJ2s to try and slow the slides down, but it seemed to make it run worse:confused2:

Jason

 

[m-cman]

Sounds like he put a Dynojet kit in the bike. They have you drill the slides also in their basic kit not just the stage 7. Also the main jet numbers may not relate as the jets in the Dynojet kit are numbered differently. I would get some stock jets from Sean (probably 150's if you still have the Supertrapps - stock are 152.5), epoxy the holes in the slide, verify the slide springs are stock (not cut) and see how that works. You can also try without filling the slide holes as that normally just gives quicker throttle response as does the cut springs. I can't believe you have Mikuni 165 jets as that would be super rich.

Be advised I have installed Dynojet kits on several bikes BUT not on either of my Maxes. I am assuming they are generally the same on all bikes. My first Max had Dale Walker needle shims, K&N air filter, Jardine slip-ons and the "Y" removed. Everything else was stock. It ran great. My current Max is completely stock except for Kerker slip-ons and K&N filter. It also runs great (when the carbs are clean!). I am planning on going to 150 main jets though as it is a little rich.

 

[65fury]

Well i dont know if he did a jet kit or just felt like playing with the carbs but the 165s in the carbs were mikuni, i tried 150 mikunis but my top end didnt pull as hard so put the 165s back in and my top end still runs and pulls great, im runnning a full kerker 4-2-1. Slide springs are stock (8-9inches long i believe, kits usually have 6inch ones) I dont know why the 165 mains work so well in my bike since my airbox is stock with the y still on, but they do:biglaugh: I just cant figure out my mid range:ummm:

Jason

Sounds like he put a Dynojet kit in the bike. They have you drill the slides also in their basic kit not just the stage 7. Also the main jet numbers may not relate as the jets in the Dynojet kit are numbered differently. I would get some stock jets from Sean (probably 150's if you still have the Supertrapps - stock are 152.5), epoxy the holes in the slide, verify the slide springs are stock (not cut) and see how that works. You can also try without filling the slide holes as that normally just gives quicker throttle response as does the cut springs. I can't believe you have Mikuni 165 jets as that would be super rich.

Be advised I have installed Dynojet kits on several bikes BUT not on either of my Maxes. I am assuming they are generally the same on all bikes. My first Max had Dale Walker needle shims, K&N air filter, Jardine slip-ons and the "Y" removed. Everything else was stock. It ran great. My current Max is completely stock except for Kerker slip-ons and K&N filter. It also runs great (when the carbs are clean!). I am planning on going to 150 main jets though as it is a little rich.

 

[m-cman]

Sorry, my error. I thought you had the Supertrapp slip-ons. However, I do think 165's are still too large but I will defer to the carb gurus.... :ummm:

 

[65fury]

No worries, yeah i thought they were too big too, but after swapping them out and putting the 150s in my top end didnt feel very powerful, and i still had my 4k stumble so i figured i try the 165s again since i hadnt run them with the kerker yet and i found my top end to feel much stronger:biglaugh: altho my mids didnt change:bang head:

jason

Sorry, my error. I thought you had the Supertrapp slip-ons. However, I do think 165's are still too large but I will defer to the carb gurus.... :ummm:

 

[Woody]

replace the O rings . around the emulsion tube in each carb.
thats what stopped my 4 grand spit and sputter. this will cost under 20 bucks.
and get the factory ones. don't just size up an O ring and hope it works.
i've been there,done that. use the oem ones.

 

[one2dmax]

I wonder if it is too rich? If you have them put larger mains in the PAJ2 area. Dynojet would be 190 and we use 177.5 mikuni's. I wonder if it isn't something other then carbs??

Sean

 

[gamorg02]

sounds similar to mine, but i had a morley kit. only fix was stg7 needles, but my cruise was also a bit off.

 

[65fury]

I wonder if it is too rich? If you have them put larger mains in the PAJ2 area. Dynojet would be 190 and we use 177.5 mikuni's. I wonder if it isn't something other then carbs??

Sean

It feels and sounds like its running lean, when i do the hard pull when studdering and then kill it and a pull a plug its tan... but its got the symptoms of being lean, its got this higher pitched popping like its a 2 stroke dirtbike and runs like its only firing on 3cyl. If i just whack it at 4k it has a slight hesitation then stumbles. if i SLLLOOOWWWLLLYYYY roll into 4k i can almost not get it to stumble. Im actually gunna do both Sean, i got some 150s im gunna put in just to see what happens and the local bike shop has more mains so im gunna get a few more to play with.


jason

 

[maleko89]

Did you test your coils?

 

[65fury]

Did you test your coils?

No... how do i do that? oh and i stopped st teh local bike shop that ive been going to for parts and ideas and they hooked there sync gauge up for free and even resynced the carbs(they were all off.. but i dot know why cause i used my two vacuum gauges and got them all perfect...????)so it ran better but my mid range still flubbed, with the vboost closed it ran better than with it open. Mark your the man:worthy:, its gotta be running a rich, so im gunna pull my .4mm shim and see if that helps and if i still stumble i got some 155 mains to swap in and ill have the shop sync them again.


Jason

 

[maleko89]

Test primary windings by unplugging 2-pin connector for each igntion coil. Should be 3-3.5 Ohms. Test secondary side by measuring from plug boot to ground. Should be about 19 KOhms. Test P/U coil too....should be two pin connector on left side near battery if you have late model bike. Colors are orange and black and should be about 110 Ohms.

 

[65fury]

okay so i pulled the shim sto see if that would help the stumble and it didnt seem tomake much of a difference so i just put some 155 mains in(i woulda used 152.5s but the shop doesnt stock those so hopefully these work, gunna take it down and get it syncd and repor tback. also ill check my coild as suggested. Thanks

jason

 

[65fury]

Okay so i made a little bit of progress today, after spending some time at my local bike shop they let me use there good sync tool and i syncd my carbs after installing 155 mains. Even after the 155s the bike still had the 4k stumble, then we put softer and slightly shorter slide springs in and the bike ran even worse, so then we used my stock springs and added a smaller spring(one that fits inside my spring) and the bike ran a bit better, still stumbles in the mids but doesnt stumble as bad. So i guess my slides are opening to fast.

Do stck slides have any holes in them? if so how big should they be? im thinking of epoxying or jb welding my holes and then drilling the right size hole and seeing if that helps.

jason

 

[Rhoy Carter]

I would think you are still too big on ur mains

 

[65fury]

I would think you are still too big on ur mains

155s??? thats only a hair larger than stock(152.5s) and the bike originally had 165s in it and it ripped!!! all i can say from everything ive done and experienced so far is changing the mains hasnt changed my mids ive kept the midrange stumble regardless of main size from 150s to 165s to 155s my mids havent changed. Until now that is, i still have some popping and studder in my mids but it has more smooth spots in that part of my power band now that i added another spring inside my stock slide spring.

I ran the bike without the Faux tank cover and my midrange still was great but my top end ripped real good, then i put the cover back on and my mids didnt really change but my top end 6k and up pulled but didnt start pulling real hard till after 6k, before without the tank cover it started pulling hard around 5700rpms.

jason

 

[Rand-5107]

Hey. If your in oakdale, cal. I'm in Modesto. P.M. Me a phone # . I don't know how much help I'll be but misery loves company. Have you thought about a dyno with an air fuel ratio meter ?

 

[65fury]

Hey. If your in oakdale, cal. I'm in Modesto. P.M. Me a phone # . I don't know how much help I'll be but misery loves company. Have you thought about a dyno with an air fuel ratio meter ?

Id love to dyno it, but I only know of one dyno and i cant afford to go dyno tuning it right now, unless you got a dyno at home:biglaugh: im stuck using the old fashion dyno "seat of your pants" and listen to any odd noises:rofl_200:


jason