CB750K Help continued

[stevenolts]

I got it running but now it is pouring gas out of the overflow tubes. Not when turned off as before I cleaned the carbs but when running. The more throttle I give it the faster it pours out.

I posted about this last week / thank you for the comments.

I guess it was flooded last week when I posted because when I tried it today the bike fired up. I warmed it up and then slowly backed the choke off until completely closed as it warmed up. I adjusted the main idle knob under the carbs until it idled correctly. It will shut down and can be started back up. Fair throttle response for now until I can sink the carbs.

I just emptied the gas out last week and filled a gallon of fresh gas. Petcock is on the low fuel setting. Do you think maybe there is shit in the tank that clogged the carbs? I just bought an in line filter but have not installed yet.

[Bill1584]

It's been many years since my Suzuki GS750 days, so please forgive me if the following has no bearing on your carbs. If the carbs have fuel bowls, they will have a float and a needle valve to regulate flow. Excess flow would overflow through the tubes. If this is the case for your carbs, have you checked the floats and valves? Just a tiny bit of crud on the valve will cause it to stay slightly open. Also, your floats need to float in gasolene.... Again, I do not recall whether this even applies to the mikuni or mikuni style carbs of the day.

[stevenolts]

That is what I think is the problem and most likely caused by the tank being mixed around when emptying the stale gas. I just did a quick clean of the carbs since I had them off for another reason. The main problem was the overflow tubes leaked when the engine was shut off. I think now there is crud in there holding them open or a stuck or bad float.

[Bill1584]

Keep me posted please, and good luck! I have a feeling that sooner than later I will search out a metric 4-banger from the 70's. Knowledge is power. If I can make it safe and reliable to ride, then it would be fun to cat around on it sometimes.

[DMAGOLDRDR]

An easy task to perform to flush the needle valves is,,,

Fire the engine and as it is running shut the petcock off. Keep the engine running until it starts to die from fuel starvation. Then open the petcock and sometimes the rush of fuel into the bowls will wash out fine debris around the needle valves and seats.

Sometimes it works and sometimes it doesn't but it is easy to do.

[Bill1584]

An easy task to perform to flush the needle valves is,,,

Fire the engine and as it is running shut the petcock off. Keep the engine running until it starts to die from fuel starvation. Then open the petcock and sometimes the rush of fuel into the bowls will wash out fine debris around the needle valves and seats.

Sometimes it works and sometimes it doesn't but it is easy to do.

That is an excellent suggestion. My memory is not what it once was, but that reminds me: Alternatively, if you remove the air filter[s] and run the motor, you can rev it up a bit and quickly cup your hand over the air intake for each carb, one at a time. Listen for the motor to bog, and remove your hand. This will cause vacuum to rapidly suck most of the gas from the bowl and really swirling things around in there. All the fuel has to go rapidly through the valve, so it could knock the crud on through. Used to work with single barrel automotive carbs, too. Instant tuneup!

Note: If you leave the intake covered too long, you could also just flood that cylinder, so not too long. ALso, use a rag, not just your hand. That much fuel and you could backfire that cyl, which hurts like hell.

[Dirtstiff's F6B]

It's been many years since my Suzuki GS750 days, so please forgive me if the following has no bearing on your carbs. If the carbs have fuel bowls, they will have a float and a needle valve to regulate flow. Excess flow would overflow through the tubes. If this is the case for your carbs, have you checked the floats and valves? Just a tiny bit of crud on the valve will cause it to stay slightly open. Also, your floats need to float in gasolene.... Again, I do not recall whether this even applies to the mikuni or mikuni style carbs of the day.

+1