95' 600 Carb Overflow...won't stop!!

I have a 95' 600 and I can't get the carb to quit overflowing. It's driving me nuts! When I bought the bike it ran well with the stock carb but it would just start leaking gas from the overflow at random times. I adjusted the float, made sure it wasn't hanging up and all that stuff. It would work fine in a bench test and then when you get a couple miles down the road it would just start leaking again. Well now I scrapped it and put an xrs only mikuni flat slide on. This carb is doing the exact same thing now! I have taken the bowl off and adjusted the float level on this one too but no luck. It uses a split float setup so I think if one float sticks the other should shut off the fuel. There is no pattern as to when this is happening. It may go for miles without leaking and then just decide to dump half my fuel out! The bike just got a completely new top end when I changed out the carb too. I'm not really sure what is going on and I just wondered if anybody else may know....thanks.

Check your tank breather hose. When its blocked it builds up pressure and forces the fuel out.

more likely than not it's a float needle/seat issue...ether sum junk in the seat preventing the needle from stop'n the fuel flow...possibly the needle or seat is worn...and an outside chance the float level is too high.

remove bowl, inspect/clean and/or replace any worn parts...also make sure ur gas is free of junk float'n around. :worthy:

:lol:

My guess is that the issue is not with either carb. You have debris in the gas tank, petcock, or fuel line and it's getting stuck in the float valve keeping it open. Clean everything and I bet the issue goes away. About the only other thing it could be is something pressurizing the tank.

I had a similar issue on my XR500R. The bike didn't have a fuel filter so I put one on and re-cleaned the carb. No further issues.

I'm off this weekend so I'll have to take a couple of minutes and pull the fuel lines and petcock apart and see what is going on. I will keep you guys posted.

My guess is that the issue is not with either carb. You have debris in the gas tank, petcock, or fuel line and it's getting stuck in the float valve keeping it open. Clean everything and I bet the issue goes away. About the only other thing it could be is something pressurizing the tank.

I'd follow this advise OP.:worthy:

I checked the fuel cap on my ims tank as I was on the way out the door going to work. It can't be building any pressure because there is nothing obstructing the vent line. I flushed the tank out and replaced the fuel line when I bought the bike but I guess maybe there could be some debris left in the petcock??.. It's just weird how it comes and goes like it does. I was riding last night and it wouldn't stop leaking so I turned the gas off until it started to choke down and then I cut it back on again. That seems like a float issue but what are the odds of that happening with 2 different carbs??!!

I checked the fuel cap on my ims tank as I was on the way out the door going to work. It can't be building any pressure because there is nothing obstructing the vent line. I flushed the tank out and replaced the fuel line when I bought the bike but I guess maybe there could be some debris left in the petcock??.. It's just weird how it comes and goes like it does. I was riding last night and it wouldn't stop leaking so I turned the gas off until it started to choke down and then I cut it back on again. That seems like a float issue but what are the odds of that happening with 2 different carbs??!!

There has to be something holding the float needles open, or they are worn.

Can't fathom why you are looking at the Petcock. Why would that cause carbs to overflow. (Whoops ..ok,, you're checking for junk) As has been said it'll be the Needle jet up above the Floats thats causing the problem. Have to say though that even with a worn out needle jet I have never had fuel pouring out of the overflow tubes when a bike is running. I have a 500 with the issue. Only if I were to leave the Petcock turned on with the engine off will fuel come out the overflow tubes and not immediately either..Generally takes two or so minutes before it'll start pouring out. Is this Mikuni new new or new used...??

Agree Martin ..somethings wrong with either the pin which holds the floats or the Needle jet. Pin may be binding or something along those lines.

Yeah the mikuni is brand spanking new. I just need to pull it back off the bike again and take another look I guess.

Be pretty unusual for a brand new Mikuni to be leaking gas however I suppose if it;s been sitting round the Warehouse to long with no gas in it I expect the needle jet could possibly get stuck wide open..When you get it apart the Needle jet will be above the floats behind the little metal tang that contacts it's tip. Pull it out of there..not sure on how thats done on new Mikuni flatslides as I only own an older one. Anyway make sure the small pin on the end of the Needle jet moves in and out. It's a pretty fine fit in there so any sort of binding will cause the thing to jam open thus allowing the gas to continue pouring into the carb when it should not be.

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