what carb to run

[ban1]

ok had some other posts on here trying to figure out jetting.

have 01 shee with cool head and the old owner just told me it has 18cc domes,bills pipes vitos supperstock pistons carbon flex reedsuni pod filters and it is ported (dont know how much) had 34mm kehin flat slides and couldnt get rid of low end bog. so got new 28mm makuni flat slides and bilt an air box to mount the pod filters in (some people told me it might be sucking to much air) now has bog on top end,

tried jetting with 27.5 pilots and 300 mains wich made it better got just past 3/4 throttle before bog so i drilled an old jet out to 1/16 and it got even better but still just above 3/4 throuttle it would bog out.i then drilled jets out to 5/64 naw can get almost to foll throttle before it bogs.

tried to get bigger jets today and the biggest ones they had were 520 and they arent as big as the ones i drilled out. have the needle in the second clip from bottem.

also at about 1/4 throttle just putting around it sounds like its fluttering,noy running smooth.

the 34mm kehins had diala jets with 135 mains and 40 pilots but it had a bad bog when you stabed the throttle and it kinda fluttered at 1/4 throttle also. i did a compresion check and have 140lbs in both cylinders.

so my question is wich carbs should i run and what jets i am at 2500 ft

 

 

 

thanks ken

[Yaxy]

Ken, Lets start with the low end.

 

The 28 FS Carbs are very sensitive on the bottom end. The air screw on the side of the carb plays a major part in your throttle response. You mentioned that you have a 27.5 pilot. Now lets assume your carbs are clean in in sync (both the throttle cables and then the idle screws). For starters turn the air screws all the way in. Now put along in like 2nd or 3rd gear at low RPM and apply WOT. If the bike just bogs and wants to stall your pilot jet is to small, go up to a 30 and try again. If quad accelerates you know you are in the range with the pilot jet. Turn air screw out 1 turn and try again and you should be fine.

 

Your needle sounds good

 

On top end I still think you need to go to a larger main.

 

Here in NY at about 1000' above see levle I run

 

20 pilots on both shees ( I have run as low as 15's on the one), a 270 main on one quad and 340 on the other with airboxes and lids on, as mentioned on my other post.

 

Chris

[ban1]

raeding other guys mods and what they are running for jets doesnt it seem like me needing bigger than 520 jets is a bit much for the mods i have and still needing to go bigger yet.

[ban1]

i will try that for the bottem end and see what happens thanks fir the input.

 

 

ken

[Yaxy]

ken,

 

Do you mean 320? There is no way you should be running a 520 jet. Sleds with twice the displacement at much cooler temps don't approach that. If anything try a 340 or 350. If that is still to lean you have problems elsewhere.

 

Chris

[Bansh-eman]

there is no such thing as sucking too much air , as long as you can get enough fuel to matchg it your motor is only going to allow so much air/fuel mixture to enter the motor.. assuming your not running lean, you can never get too much air.

 

 

with stock carbs at sea lvl your bike should be running around a 320 main... so you shouldnt be far from this as a starting point..

[ban1]

like i said above i drilled the jets out to 5/64th and still need to go bigger and im at 2500ft.

there has got to be something wrong some where that i would need to run that big of jets but dont know what it could be.

when i was running the 34mm carbs i ran 125 mains and had the dial a jets opened all the way and it kindof acted like it was a little lean the last time out so i stoped riding it and rode my blaster.

 

 

 

 

 

 

ken

[jmd0346]

Ken, Lets start with the low end.

 

The 28 FS Carbs are very sensitive on the bottom end. The air screw on the side of the carb plays a major part in your throttle response. You mentioned that you have a 27.5 pilot. Now lets assume your carbs are clean in in sync (both the throttle cables and then the idle screws). For starters turn the air screws all the way in. Now put along in like 2nd or 3rd gear at low RPM and apply WOT. If the bike just bogs and wants to stall your pilot jet is to small, go up to a 30 and try again. If quad accelerates you know you are in the range with the pilot jet. Turn air screw out 1 turn and try again and you should be fine.

 

Your needle sounds good

 

On top end I still think you need to go to a larger main.

 

Here in NY at about 1000' above see levle I run

 

20 pilots on both shees ( I have run as low as 15's on the one), a 270 main on one quad and 340 on the other with airboxes and lids on, as mentioned on my other post.

 

Chris

 

 

 

 

 

Going slow then going WOT will not give you a reading on your pilot jet. WOT is controlled by the needle, needle jet and main jet circuit.

[Handyman]

like i said above i drilled the jets out to 5/64th and still need to go bigger and im at 2500ft.

there has got to be something wrong some where that i would need to run that big of jets but dont know what it could be.

when i was running the 34mm carbs i ran 125 mains and had the dial a jets opened all the way and it kindof acted like it was a little lean the last time out so i stoped riding it and rode my blaster.

ken

 

Too big of jets will cause a bog on top, been there done that. I have 35mm carbs and run 142mains and 45 pilots and that's for 4500 ft above sea level for my 421cc cheetah powervalve motor. I think you were jetted too lean so yeah your assumtion was right you were way lean. From what I can tell(assuming you are on a mostly stock motor) you had too big of carbs not feeding enough fuel and then you down sized to smaller carbs and went way too rich on jetting. I may be way off on my assumtions on this so can you post a list of your engine/exhuast mods so we can try to help you better??

[ban1]

the mods are at the top of page. and needing biger jets doesnt sound right to me neither but every time i go bigger jets it runs better on top end. dont want to run it lean.

thinking i might put the 34s back on and jet the pilots down a bit and see what happens. atleast with those carbs it ran great on top end with the 140 mains in it.

 

 

 

 

ken

[Handyman]

the mods are at the top of page. and needing biger jets doesnt sound right to me neither but every time i go bigger jets it runs better on top end. dont want to run it lean.

thinking i might put the 34s back on and jet the pilots down a bit and see what happens. atleast with those carbs it ran great on top end with the 140 mains in it.

ken

 

Mods are similar to my '99. For my 26mm carbs on my 99 I run a 27.5 pilot and a 310 main for 200ft above sea level and a 340 main for 4500ft above sea level. You might want to try to range anywhere from a 310-140 main and see what happens for your 28mm carbs. If you swithc back to the 34's I'd jet it at 145 mian and a 42-45 pilot with the clip in the 3rd or 4th position and I'd adjust the air screws a little with each jet change to see where it runs the best at.