cb350f terrible fuel mileage

[stowaway117]

hey gents, lets talk fuel mileage. im about to tear into my carbs but i wanted to see if anyone could offer insight on anything else it could be; my 350f purrs like a kitten, but sucks gas like nothing ive ever seen. im talking 50 miles to a tank!!!! top end is freshly rebuilt, timing is dead on, coils are new. plugs are new. valves are adjusted properly and my local machine shop did a resurface and valve job last winter. im running pod filters and rejetted the carbs to accompany the pods, but i really dont think that should be affecting my fuel consumption so much. im thinking ive got a loose jet somewhere or the floats are way off, even though i checked and double checked them in the beginning of spring. i pulled all the plugs and all showed wet thick carbon deposits, same with the piston heads. if i cant find anything wrong im gonna drop a few jet sizes and see if it helps. any other ideas? thanks guys. cheers.

 

[Bert Jan]

If plugs are wet and black you're running waaay to rich. How many sizes did you go up? Wich filters are on? Rule of thumb is 10% bigger mains. So if its a 80, go to 88. Could be you need a 86 or even 84, could also be you need 90/92.

If your jets are the push-in type, renew the o-rings holding them in place.

 

[Bert Jan]

If youve got the cv carbs on, be sure the slides are in the right way. Left and right are interchangable and will give bad consumption numbers

Edit, see its a 350f so no cv's...

 

[SONICJK]

My guess would be you have a leak. Or an overflow issue.
Its pretty difficult to get a 350cc bike to run rich enough to get 15 mpg's

 

[stowaway117]

correct, not cv's. i went from 75 to 80 on the mains, 35 to 40 on the secondarys. i have the carbs on the bench right now. o rings are good, floats are good, everything looks spot on. im wondering if my cam chain could be a link off after the rebuild... please no.

 

[carnivorous chicken]

hey gents, lets talk fuel mileage. im about to tear into my carbs but i wanted to see if anyone could offer insight on anything else it could be; my 350f purrs like a kitten, but sucks gas like nothing ive ever seen. im talking 50 miles to a tank!!!! top end is freshly rebuilt, timing is dead on, coils are new. plugs are new. valves are adjusted properly and my local machine shop did a resurface and valve job last winter. im running pod filters and rejetted the carbs to accompany the pods, but i really dont think that should be affecting my fuel consumption so much. im thinking ive got a loose jet somewhere or the floats are way off, even though i checked and double checked them in the beginning of spring. i pulled all the plugs and all showed wet thick carbon deposits, same with the piston heads. if i cant find anything wrong im gonna drop a few jet sizes and see if it helps. any other ideas? thanks guys. cheers.

With a stock tank you should get over 100 miles on a tank. With a stock set up (carbs, airbox), closer to 120. Gotta be a leak or overflow, can't see rejetting using that much more fuel. If you're not turning the petcock off when you stop (or if it's not working properly) and if you've got a stuck float valve or valves, gas is just going to pour out of the bottom of your carb, and if you've got tubes on there, it'll be directed to under your bike. Other leaks could be in fuel line, between carbs, and in the tank. I'd look for leaks first, then dig into carbs next.

 

[stowaway117]

nailed it. where my fuel line plugs into the carb rack the hose clamp had slipped off a little and it was leaking. i never noticed because i always shut the petcock off whenever i stop. thanks gents.

 

[carnivorous chicken]

Easy fix is always nice.

 

[scfire]

nailed it. where my fuel line plugs into the carb rack the hose clamp had slipped off a little and it was leaking. i never noticed because i always shut the petcock off whenever i stop. thanks gents.

Lucky you didnt go out in a BLAZE of glory