Motorcycle Repair/fuel problems


I'm having trouble with my carbs overflowing with fuel. Just bought bike. It has a aftermarket fuel pump that puts 4psi to the carbs.  I have also noticed that the fuel pump is off til you hit the starter then it never stops pumping. Tried running with pump removed and it seems to run fine. So I'm not sure what to do next. Replace pump with oem or? Please help me figure out what's going on.

Chris, giving me the make/model/year of your bike would have been very helpful.....

Motorcycle carbs don't need fuel pressure to the bowls more than a pound or so. If you can't turn the pressure down and it runs with the pump off then leave it as it is, I guess. The pump seems to be overwhelming the float valves, unless they are just dirty from sitting for a long time or there was contamination in the tank. If the bike ran okay without fuel pressure then the float valves must be okay, just unable to contend with excess fuel pressure. It sounds like the a/m pump was hard wired into the 12v lines, instead of being run through a relay.

Depending upon where the fuel load is in relationship to the carburetors, the pump might not be needed until the fuel load drops below the level of the carburetor float bowls... then it will need one.

If the bike had a pump from the factory, then they did it for a reason. OEM parts are always the best choice, but many older bikes have discontinued part numbers. The pump relays are generally supposed to run when the switch is turned ON for a few seconds to prime the carburetors, then stop until it sees impulses from the engine that indicate that it is running, then the pump resumes operation.

Bill Silver

Motorcycle Repair

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Bill Silver


Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.


I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

VJMC (Vintage Japanese Motorcycle Club) of North America

VJMC newsletter, as editor for two years and as contributing editor currently.

3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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