Yellow oily gas from 1 & 4 carbs

jwing

CB750 Member
Messages
10
Reaction score
1
Points
3
Location
Pennsylvania
I have a 1981 CB750k that I've recently put back together after disassembling for paint. I took it out for a short test ride, but it seemed to be very hesitant and sputtery when trying to open her up or accelerate. When i came back from the ride i noticed a small spot on the floor under the bike, as well as on the ends of the overflow hoses. Here is what i did leading up to this:

1. Re-assembled bike. Fresh oil change.
2. Cleaned the gas tank with screws/nuts and standard gasoline, drained it, added new gas and flushed it with that. Then added brand new ethanol-free gas.
3. Realized i had leaking fuel rail tube, sticky float(s) and a bad petcock, so i replaced petcock, new in-line fuel filter, replaced all fuel rail o-rings and unstuck the floats (no more leaks when opening the fuel supply :thumbsup:). I did, however, use an aftermarket petcock with a smaller (1/4" or so) outlet and 1/4" fuel hose (again, maybe this could be the cause of my hesitation throughout the rpm range?).

Any thoughts on my hesitation problem (I haven't made any carb tune changes from last year when the bike ran great)?
Any thoughts on the oily gas from the carbs?
 
Last edited:

amc49

CB750 Guru
Messages
3,476
Reaction score
20
Points
36
Location
Fort Worth TX.
I'd question the 'brand new' gas. Where did it come from?

If you have ethanol tank damage as in rust then you should know the plastic OEM petcock filter will let some of the smaller particles in the fuel get by, the filter does not filter that far down. You practically demand a paper fuel filter there but just try to find room for one.

You don't say what you did with the aircuts........
 
Top