ryansedy Posted June 1, 2009 Report Posted June 1, 2009 So today i finally rode my 421 cheetah cub for the first time, I noticed every once in awhile alittle fuel would come out on one side, out the overflow, When i put my jets in last night i kinda looked at the float but didnt really look at a way to adjust it....So how do you on a 38mm keihin carb? and where do i measure and whats the right height? Does anyone have any detailed pics? im at work now..... I thought jetting would be a bitch but it was actually really easy got it pretty close first time, is there that much of a difference when you change the mains between acouple sizes? it starts pretty much first kick, just wondering if i should even mess with it...but i want to stay on the safe side, plugs look good nice light brown.... Quote
lt1bird Posted June 2, 2009 Report Posted June 2, 2009 mine always leaks a bit.....even when I lowered the float level.... just vibration etc....get use to it..... Jetting.....be carful..... I started at 175 mains..... ran pretty good with those....a bit lazy/flat...no real power band hit... now im at 148 mains....runs much stronger and gets on the pipe now.....Still feels like I could go smaller on the mains... getting nervous to go smaller as I have a 535 and smaller than 148 seems a bit extream but the engine does seem to keep responding as I lower the main jets.... Im running race gas so I cannot do a plug chop or read the plugs correct. Plugs still look black with current jetting..... Quote
ryansedy Posted June 2, 2009 Author Report Posted June 2, 2009 I also started with 175 mains felt pretty good actually....i threw in the 180 mains havent got to ride it since ive been working 12 hr days, but started it and everything seemed good....im also running 110 octane at a 32:1 ratio.... Quote
lt1bird Posted June 2, 2009 Report Posted June 2, 2009 Ya, thats the hard part....if you keep going richer mine did not seem to care......it did get a litle bit of a rich studder before the power band but once it reved....it seem to run good but definatly seemed down on power....The leaner and lean I went to better and better it runs... This is my theory...... at 1/2 throttle if I hold the throttle in the same position and let it rev up it will rev then at 6k it revs quick and gets on the pipe and pulls hard.....This is my goal at WOT.......currently at wide open throttle it pulls good in the midrange then in the upper rpms it still pulls good but I do not get a big increase in rpm or a good power hit... Im thinking im still rich on the mains.... plugs are still black/very dark brown.... I am going to go down on the mains until I get a power hit....Ive lowered the main jets a bunch and it keeps running stronger and stronger.....seems like im very very close..... are you getting a good power hit or is it feel a little more smooth like a 4 stroke? Quote
ryansedy Posted June 2, 2009 Author Report Posted June 2, 2009 Well day before yesterday was the first i got to ride it with the new motor so, i was makin sure i had everything right else on the bike, however there was really no hesitation and it seemed to hit the powerband fairly quickly...i do remember tho when i held it at 1/2 throttle seemed like it took alittle to increase in rpms...im gonna wake up alittle early and try to ride it before work i work graveyard this week....ill let you know how it goes....im also running 58 pilots... Does yours start up without the choke? mine will but its also like 70 deg out...im sure 40 deg makes a big diffrence...it wont idle really for the first min but after that it does... Ill let you know how it goes.. Quote
lt1bird Posted June 2, 2009 Report Posted June 2, 2009 mine wants the choke unless its warm....when warm i do 1/4 throttle and kick.... the 58 pilots might be a bit large so it will start with no choke.... Quote
ryansedy Posted June 3, 2009 Author Report Posted June 3, 2009 So i went up to the 180 mains, this time when i held it half throttle it reved way faster, and hit the powerband alot harder it seemed...I think you are right on the pilots, but im just wondering cause it is so hot out today i didnt need the choke, but am gonna try one size smaller on the pilots... Its just weird tho cause there is no hesitation or bogg anywhere, and hit the powerband alot harder at WOT....I didnt think my mains would end up being this large?? I am running a 32:1 ratio and ive heard that you need 2 sizes larger mains, and pilots when you run it like that.... Tomm im going to try 56 pilot, and 185 mains, and see how that feels... Quote
ryansedy Posted June 3, 2009 Author Report Posted June 3, 2009 also lt1bird.....i kept turning in my idle screws, but it wouldnt idle...there almost turned in all the way...i had to adjust the cable up at the thumb throttle...is yours like that?? i did sinc em together, not with the vaccuum gauge but looking at the slides making sure they go up at the same time... Quote
lt1bird Posted June 3, 2009 Report Posted June 3, 2009 (edited) If your too rich at idle you will end up turning the idle/slide screws in a ton....Thats a good sign your rich....cut that pilot jet down and you will notice the idle will start going up.... The larger the mains the more fuel at idle as well...there is some interaction and big swings in mains does effect the idle...thats what ive seen.... Im having a hard time beliving that the main jets are that big.... you are doing WOT testing correct? Like I said....mine would run with 175 no problem.....pulled hard but real flat feeling like a four stroke..... It would not really scream like a 2 stroke until I started lowing the main jets down to 148.....this is a 535 power valve engine...no porting..... maybe some other folks could chime in..... If you had full drag pipes and a drag port then maybe larger jets would be needed.... What air cleaner are you running? Edited June 3, 2009 by lt1bird Quote
RagunCajun Posted June 3, 2009 Report Posted June 3, 2009 To answer your question give carb parts warehouse a call. They have very nice/helpful guys there who can answer your questions like that. They helped me with my new carbs and turns out the float height wasnt the problem i think. It's also a good place to order carb parts from. http://www.carbparts.com/index.html# Quote
wvbanshee1976 Posted June 3, 2009 Report Posted June 3, 2009 i no on my 38 mm carbs im running a 175 main jet and 55 pilot and i had to turn my air screw out 4 turns seems to be running the best at that Quote
ryansedy Posted June 4, 2009 Author Report Posted June 4, 2009 i no on my 38 mm carbs im running a 175 main jet and 55 pilot and i had to turn my air screw out 4 turns seems to be running the best at that you have stock drag ported cylinders? Quote
ryansedy Posted June 4, 2009 Author Report Posted June 4, 2009 i have the 8" k&n style air filters no box or anything... I put in 55 pilots this morning and now it wont idle without the choke for about the first two minutes...so i think im gettin pretty close on the pilots.. I also put in 170 mains havnt got to ride it yet ill try to tommorow tho... its just weird cause when i went from 175 to 180 mains, it seemed like it pulled harder....but ill try going smaller... my bike was dynoed at 100hp...well thats what the guy tells me anyways that i bought the motor from...to bad he cant rememeber the jet sizes with that dyno... Quote
lt1bird Posted June 4, 2009 Report Posted June 4, 2009 You said your air screws were out 4 turns.......your still too rich on the pilot if it will not idle...... keep going down on the pilots until it idles....then fine tune with the air screw and move the slide screws out.... Quote
ryansedy Posted June 4, 2009 Author Report Posted June 4, 2009 (edited) im still only 1 and 1/2 turns out on the air screws....i will adjust em though...see i didnt know thats what you were sopposed to do... Edited June 4, 2009 by ryansedy Quote
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