Total Motorcycle Community Forums

I don't know if I would say a carb rebuild is out of your skill level. Depending on the carb, it's not really that hard, it just sounds harder than it really is. If you are careful, take your time, and even take pictures of where the parts go before you completely take them apart, it can be a fairly straight forward job.

If the gas cap vent is not the problem, you might want to check your float valves. In the carbs, there is a float in the bottom that will raise and lower depending on the amount of fuel in the float bowl. If this float is not working right, it can cause all sorts of problem that range from not enough fuel being in the bowl, to too much fuel being in it and causing it to run rich or for gas to just run out. It could be possible that the float valve is gummed up and not allowing fuel to flow in fast enough. After running for a fuel minutes, the fuel gets depleted and it won't run right.

It could also be a bad ignition coil. Ignition coils can be fine while they are cold, but really weak as they get hot. As Buzzz pointed out, plugs can do this too, as well as the wires. If your plugs and wires haven't been replaced in a while, do it, it's a cheap thing and should be done once in a while. You can check the resistance of your coils with an ohmmeter. I would do it when they are cold, then run the bike for a while to heat it up and get it to fail, then check the resistance on the coils again to see if there has been a change.

It could take a while just trying to do it yourself, but I don't think that you would be incapable of solving it yourself as long as you try things and post questions here. Someone can always offer advice or a procedure to follow to test things.

Rule out the simple things first though. If you get some clear fuel lines to replace the old ones, you can see if fuel is flowing to the carbs.

Also, you can buy some seafoam to put in the gas tank to see if that helps clean things out.

thespirit wrote:If the gas cap vent is not the problem, you might want to check your float valves. In the carbs, there is a float in the bottom that will raise and lower depending on the amount of fuel in the float bowl. If this float is not working right, it can cause all sorts of problem that range from not enough fuel being in the bowl, to too much fuel being in it and causing it to run rich or for gas to just run out. It could be possible that the float valve is gummed up and not allowing fuel to flow in fast enough. After running for a fuel minutes, the fuel gets depleted and it won't run right.

The spark plugs are new. And expensive apparently.
Ill call about fuel lines right agter this.

Its just strange, to me, that when the problem surfaces I am able to keep it running by giving it enough gas to keep the revs up.

Lastly, what is seafoam?
Thanks for all te info. I really hope this isnt being bothersom to keep asking questions as i go.

ok, i went and bought sea foam, put a few ounces in. I also opened up 3 of the 4 carburetor valves. The 4th one was hard to reach for now.

I called the service place i usually go to and the manager said some people have been having problems with the new ethanol fuel. More prone to getting water in the system.
I let them drain... and drain... and drain. How big are the bowls in the carburetors? On the first one i used a container to cath and it just kept comming. I got propbably 1/8-1/4 of a cup before i decided to close the valve back up. Similar thing with the 2nd carburetor.
Is this normal? I dont think i had the fuel falve set to free flow, it is pointing down like im pretty sure it always is.

I started up the bike and let it run just sitting there. Sure enough in about 3-5 mins it started falling slowly and eventually the engine just stopped.

I am tempted to take the carburetors off and have a peak but dont have the time yet.
Any thought?

If it is a problem with the float is the solution just a matter of taking apart the carburetors and cleaning some gunk out of the insides?

Was your "fuel valve" (petcock) set to off? The ones I'm familiar with have three positions: On, Off, and Res. You want "Off" to stop the flow, it should be pointing sideways. It's possible you have a vacuum actuated petcock, I'm not familiar with those ones.

Carbs aren't that bad to clean, there is some disassembly required. If you're mechanically inclined it's do-able; if you're not, I'd leave it to a professional.

I think i have a vacumb petcock. It has 3, res primary and one other, but no off. The third selection is basiacally just a free flow.

Im good with my hands, i like working with bolts and nuts and what not.
I think that im not good at things that have to do with precise measuring. Dont have a tourq wrench, or spacers etc. If putting it back together is simply the reverse of taking it apart i should be fine.
If i have time tomorrow, ill see if i cant take them apart. How long should it take?

to properly clean a carb bank takes a full day. It can be done in under an hour...

I just posted the right pictures so I'll do a quick and dirty how to clean post.


Here is your carb, top is top, bottom is bottom.

Remove the float (this is the bottom part) by carefully taking out the screws... careful you're going to spill gas all over!



This is the airbox side of the carb, spray some brake clean or carb clean into all the little holes and blast it out with compressed air. Repeat several times.



This is the cylinder side, brake clean, compressed air all over. Repeat several times



This is the float bowl - holds the gas, remove it.



Once you've removed the float you will be greeted with something like this, but there will be a float in place (little plastic bit that works like a toilet bowl float to stop gas from coming in).

Take a small flat head screw driver and go down the hole labeled IJ. This is your idlejet. Turn it all the way out, spray brake clean into the jet (small piece of copper) and blast it out with compressed air several times. I like to let mine soak in brake clean for a couple minutes.

Spray brake clean into the hole it came out of - compressed air again.

Replace the jet - screw it in all the way.

Flathead screw driver and remove the part labelled MJ - this is the mainjet. Same process as the idlejet. Repeat several times.

Then spray brake clean into the mainjet hole and work the throttle up and down several times, then compressed air again.

Do this several times.

Reinstall the mainjet. Then you can bolt the carb back together and test it.

You may need to repeat a couple of times.

I forgot to mention two things

1) Do not break apart the carb bank. Keep all 4 carbs attached together.

2) Do one carb at a time, take your time, and make sure everything is put back where it came from securely.

Seems easy enough.