help with carby

[M2R]

hey im having problems with my carby, ok i kick the bike over starts fine but when i twist the throttle real fast it like makes a sound like its going to conk out even when im riding it dosent let me twist all the way

plzz help i have had the bike for ages and i cant fix it
thanks

 

[unit_mx]

Your twisting the throttle quicker than the engine can respond hence the flatspot , bog , and conk out. Do you twist the throttle that fast when your riding? If you do you either need a smaller carb or need to learn to use the throttle correctly.

As Cactus said:

It's simply the rider twisting the throttle quicker than the engine can respond ..... he's now opening it up twice as fast as he did before with the 1/2 turn throttle ..... I've said it stacks of times before ....... When you whack the throttle open too quickly you cause a sudden vacuum and air velocity drop ..... which means you also cop a sudden fuel delivery drop (aka BOGGGG !!!!!)

Since carbs rely totally on vacuum to maintain air velocity and suction on the jets ...... you can't tune it out either ... What you have to do is learn to open the throttle in 2 stages ... slow initially to get the motor starting to rev .... then fast once the revs are at the point where the engine can hack it ..... You have to re learn how much throttle your engine can tolerate from a certain rpm in a certain gear ..... After a while you'll get the knack of it with the quick turn throttle .......

I've actually seen and heard dick brains making a CRF250 bog , fart , cough and splutter like a sick dog ..... then after a while they learnt how to throttle it properly ..... then it revved crisp and clean like it was supposed to go ...

And:

If you're a throttle jockey and whack the throttle on and off quickly ...... the ONLY solution is to go to a smaller carb which maintains vacuum and velocity better ........

Check out what sized carb 65 to 70 HP Jawa 500 cc speedway solo racing engines run ... a 34 mm Delorto !!!!!!!!!!!! And they run that sized carb because they can't afford to have the engine bog , hesitate , cough or sputter when they pitch it sideways into turns at over 160 kph then feather the throttle to keep control of the bike ..... The rear wheel MUST be kept spinning all the time or the rear tyre bites , the bike high sides and throws the rider off ...... A big carb simply won't work with a quick turn throttle unless the rider slows his right hand down ..... The throttles are designed mainly so that you don't have to rotate your wrist so far to get to full throttle to make it easier to hang on and concentrate on controlling and steering the bike under max power ....

Description of JAWA Engine Type 884 and 888

Also ... check out the main jet run with METHANOL on a 500 (a # 230) ......... I read on Planet Minis where one guy was advising people to run a # 240 main in a Mikuni VM-26 on a YX 150 bored to 165 ....... and they call themselves tuning "experts"

VM26 snap crackle bog at 3/4 to full throttle - Planet Minis

Errrr ..... and when you go up above sea level ..... you usually go down in jet size .....

Rocky Mountain ATV Club

Rocky Mountain ATV Club

Don't twist it so suddenly , ease it on.

 

[M2R]

i dont twist it thats fast just fust

 

[M2R]

like i got an orion and i can give it to it and it dosnt do that

 

[M2R]

but if i ride with the chock on i can give it to it

 

[shreddin]

If its running fine with the choke on it sounds like your carb is running lean. The choke is just to richen up the mixture to aid cold starting. Try lowering the needle clip position or try a richer pilot jet.

 

[M2R]

fu*k i dont even no half the shit u just said lol

 

[M2R]

and can someone tell me what size carby is on the 125cc mso

 

[unit_mx]

It would be a 22mm mikuni copy , they reckon its a 25mm but its not.
Get a bigger main. Try a 102.5 Main jet , keep the same pilot jet. Fuel mixture at 2 1/2 turns out , idle screw at 3 1/2 turns out.

 

[mad man]

any who in terms you under stand, clean out your carby, clean the air filter and oil it correctly, check if it bogs still. Thats a starting point, after that lean it out a tad. Then go for the clip position or diff sized jetts, If it doesn't happen with the choke on i'd say you need to have the engine at the right revs before you give it to her, as cactus jack explaines.

john