turboglenn

i have the tak s stage, and it has a 18 mm carb with a #85 & 95 main jet selection...i have the 85 in and the needle in the 2nd clip from the bottom

seems like this carb doesn't like being up ina wheelie very well and starts to drown out, i lowered the float level 1mm , but not much improvement. it also pops loudly from the intake when it's cold and i blip the throttle, but goes away when warm...

I have the stock pipe , and was almost thinking about putting the stock carb back in w/ a diff main jet.

any thoughts on this, or can the 18mm be made useable for street stunting w/o the overflooding and whatnot.

fab5fiddy

that thing should run flawless with very minimal tuning. not sure what an s stage is but i have a tak 88 with stock head over here and 18mm keihin that runs as good as fuel injection. 85 main, clip in the middle. 50mph wheelies for thousands of feet without a single glitch. a pop in the exhaust is a lean condition, but the engine must be at normal temperature before tuning.

turboglenn

that's the same kit fab, stock head........ it's only giving me trouble in the very slow first gear hanging past BP wheelies, the carb is just doing an exagerated version of what the stock one does where you just have to keep it pinned to clear it out. I guess i'm being a little picky but the stock carb was soo tiny it leaked and still ran good

it only "pops" when it's cold and the throttle is opened quick (lean gasping) but i was nervouse cause it's a loud a$$ pop.... and teh "o" mark on the cam gear sits justa hair above the 9 o'clock mark on the head. or way below if i move it a tooth. so i've just left it as close to correct looking as i can get it

and it doesn't say anywhere if this kit needs higher octane fuel...it's 11.5:1 CR but then again that's not abnormal for todays high perf 4 - stroke.

fab5fiddy

like i said before, ours doesnt make a single glitch. even at 12. might want to re check that cam timing. is the stumble at a low or high rpm?

turboglenn

it just stumbles whenever the carb's beent tipped back too long, i double checked cam timing , valve learance and all last night. everything is cool. I think i'm gonna lower the float a little, see what happens, other than that there is no problems.

i'm gonna be giving you a call prolly today about a clutch fab.

fab5fiddy

yeah try the float. def, gimme a call

COWFIDDY

are you talking about at 12, or just while wheelie for a little ways? if it cuts out after wheelie for a while then you need to adjust float height lower. it gets to rich cuz the fuel is pooring into the carb intake. most of those kits run lean in florida sealevel, ive had to re-jet 4 of them, so a poping while cold is pretty normal for those kits.

turboglenn

i'm walking a few city blocks in first gear, going way past BP then coasting it back into BP, after a block it's pretty loaded up ....it's gotta be the float level.

but as long as that "popping" is normal when cold i'm not worried. i should just get off my **** and throw the wideband in it and jet it right on..i was just a bit curious if this was normal, as this is the first time i've overbored a fiddy.

fab i'll call ya after i get back from the hospital and picking up my womans car from the window shop. prolly bout 2 PM CST,

imprezawd

I im'd Fab as well. I am having similar probs too with my 18mm carb. They have always had problems with tuning this carb right. I am surprised that Fab has his running so well. I am going to lower the clip one more and see what that does.

imprezawd

My setup has run ok but it either bogs right off of idle or it misses at high rpm? What is this. I have the 85 main and the clip in the middle. I have to turn the air screw almost all the way out! Do I need a different pilot? Thanks for the help. I would love to get this carb to run well.
Thanks
Richie

turboglenn

i'm going back to the middle clip, i was 2nd clip from top and it's abit too llean, but when i'm in the middle i'm a little rich. i think the only answer for me is to go to a slightly smaller mainjet and run the needle higher(lower clip slot)

Z50NATIONALS

fabs runs right cause he knows how it works, and how to make it work.
you have to mess with them for a while to get them right
this is made even more difficult when you dont understand what your doing

turboglenn

i understand carbs, i just don't like them..hahha

i spent so many years of my life developing and programming electronic fuel injection that carb's just are cave-man-ish IMO. mines running better now, i'm back to middle clip, #85 MJ, and lowered float height 1mm again. mY wideband is still showing in excess of 10:1 A/F ratio in the top end, so i'm gonna have to buy some jets off fab after the comp is over. (but it's at least back to running as good as stock on this 18mm carb)

i bought a rev box off fab and it actually helped w/ the spitting and popping in the top end and then i discovered a lot of the "popping" was teh BBK putting the lil 50 motor on it's rev limiter in a hurry.

lemme know how yours is doing, also try unbolting your spark arestor and riding around...the extra backpressure is loading mine up pretty good, runs way better w/ the tip just unbolted...hahahah....seems ghetto though

imprezawd

i am gonna go with a 92 main now and see what happens? I already have the spark arester cut out so that should do it. It was popping so loud today it was crazy. I just installed the 92 main and gotta wait for this rain to go away to tune this up>? U think a smaller jet would help not a bigger jet? I really dont think im hitting the rev limiter. I can hold it thier for a sec or 2 and then it revs just a bit higher buts its popping or missing or something loud and nasty. thanks for the help

turboglenn

hmmmm..... lemme know how you come out on the 92 jet, i was thinkin about it but got mine runnin good.

imprezawd

92 no good. 85 main with clip in the middle position. Thats the only way it would run strong, But it still feels like it hits the rev limiter to early??

turboglenn

i ended up raising the needle above the middle by one clip position, and mine is finally good to go, i had to go for a long cruise at about half throttle before i got an accurate reading from the plug while working on the clip position
i know what ya mean about the feel of revving too quick though, i think that's just 88cc's working a gearbox meant for only 50cc's

Z50NATIONALS

cavemanish heheheheh
i have also played with e.f.i. and d.f.i. most of the time we would pull them off and went to smooth bores or flat slide carbs.
nowadays they are more tunable if you got the cash for the comp and the program and all the other goodies you need to tune them. dont need nadda to tune a carb screwdriver and some jets and a brain.
good to hear you got it sorted out

HurricaneF2

read this befre you waste anymore time
http://www.motocross.com/motoprof/mo...1/carb101.html

Z50NATIONALS

good read there hurricane