I'm a member of a Formual SAE club at the university of Saskatchewan. We have recently been working on our test car trying to get it running. It has a F2 bike engine and F4 carbs (later 90's?)(normaly we run fuel injection, just had these around for the test car) The problem is the carbs seem to be pumping way too much fuel in, motor tries to start then floods right away. raw fuel filling up on top of throttle plates and seems to be coming in around the shaft that the (variable venturi?) rides on. our elec fuel pump puts out only 2.5 psi, we are running 100 octane racing gas, could this have melted some plastic parts in the carbs? floats? any ideas or issues we need to deal with to make this setup work? common problems like this? Any help at all is greatly appreciated!
Thanks!
Jesse



[Modified by Formularacer, 5:15 AM 10/17/2002]

 

hehe Ive been by the SAE shop quite a few times here at UF, however, just double check what your speed screws are set too.....i hope you already tried leaning the high and low?

 

Im a Mech student in Selkirk College in B.C. right now, and ive dealt with that prob alot.

most likely its the carb itself
overhauling it would be my first bet. try using a carb cleaner or break cleaner and spraying through all the jets and etc. it could be the float damaged (inside the carb, bottom of the carb where all the gasoline sits)

good luck

 

thanks for the tips, we'll probably have to tear in to them. Normally I'm a sb chevy guy so I don't know too much about motorbike carbs, is leaning out the high and low as simple as turning some screws or would it involve changing metering rods or jets or something like that? also, could the choke possibly be staying on somehow?
Thanks!
Jesse

 

Don't know how you have the motor and carbs mounted, but they'll need to be pretty close to their original orientation (in the bike) to work. If you've got 'em mounted wrong, the float will never close the float valve, and you'll pour gas all over.

 

It's probably the float needles sticking or worn out. Push the float pin out and have a look at the pointy end of the float valve, if they are damaged or worn in any way they will puke fuel like a.... fuel puking thing.

 

Ahh! exceltent point about the level, we'll have to chack that. I'll see if we can tear the carbs apart too to check the floats. Thanks a million!
Jesse

 

It sounds like my dirt bike's problem. It was always the floats and the needle valve. If that's the problem, All you gotta do is sand it back down to a nice sharp smooth point and there ya go!

Good luck anyways!