GS300 carburetor problems

[Anonymous]

alright, let me start with some background on the problem. I recently purchased an 82 gs300 for my girlfriend. the bike ran when a picked it up. I changed the oil and spark plugs which improved things. then I ran the gas tank almost empty on a test ride (I had to switch to the reserve and then rode about 5 miles.) she ran good for the ride home but the next time I started her up the engine would idle well and rev up to about 1/4 throttle but wouldn't rev past that. I assumed the carbs might be dirty so I removed them from the bike removed the drains screws and the air jet, sprayed them with carb cleaner thouroughly. I know this isn't as good as total rebuild but I hoped it would help. I also drained the tank and checked the filter screen on the fuel cock. now the bike is re-assembled and starts very well but still will not rev past 1/4 throttle. when I opened the throttle to full and then killed the engine and checked the plugs they where black and sooty (note: this was done with no load on the engine). fuel mixture too rich? needless to say I am new to carb work so any suggestions or requests for more information are happily accepted and appreciated.
thanks for a great site. without your photos from the carb rebuild series I would have been totaly lost.

[satchmo]

I'm not sure if your carbs are different than mine, but if you sprayed cleaner in without taking the carbs apart, you may have messed up your o-rings inside the carbs on the main jet and the needle seat.

This would cause you to run rich, as fuel would seep through when you don't want it to.

I can't explain the 1/4 throttle thing though.

Satch

[Anonymous]

Hey thanks for the speedy reply. gofigure after I posted this I thought what the heck, I'm gonna go start that bike and see what happens. and sure enough she ran fine. I think one of the main jets must have been clogged somehow.

in response to the 1/4 throttle thing I've been doing alot of reading about carbs trying to figure this out and I learned that when idling the carbs run off of the pilot jet, however when the throttle is opened to about 1/4 enough suction is created to suck fuel through the main jet.

thanks again. I'll keep ya posted as I learn more since I assume this problem will probably resurface in the future.

[satchmo]

If your main jet was clogged than you might want to check the tank for rust, and put an inline filter in your fuel line, it'll catch those pesky particles that clam up your jets.

Satch