carbs overflow for no apparent reason

[Black wing]

i recently rebuilt the carbs in the bike and now they overflow for no reason. if i put the bike up on the centerstand and shut of the fuel the bike become more responsive untill it begins to starve, i turn on the fuel and the leak stops for however long i feel like letting it run. i get on drop it off the kick stand and begin driving it begins pouring it out the overflow as fast as the pump can trow it.

 

ive taken them appart again and hooked each carb to the fuel line manually and turned on the bike while pressing up on the float. the fuel flow stops as soon as the float presses on the valve. so the valves appear to be working.

 

ive taken all the floats out and submerged them in fuel and will check on them in a few hours to see it they are sinking but they dont apear to be. any ideas on why this leak is being so intermittent and limited to the right bank only but all 4 carbs are running super rich.

[raybear71]

Sounds like you need to set the floats just a tad lower.

[Black wing]

so just bend the little tab on the float up some?

[Snaggletooth]

Yep sounds like the bowl fuel level is to high.

 

As far as testing the floats for sinking, good luck. Probably not going to sink. They are a solid fiber body and are very bouyant. They can and will soak up fuel over time and that weight change will change the float level as it does.

 

I had several floats that were prone to saturation when I bought my '84. It had been stored for 9 years and the floats had deteriorated over time. The bodies were turning soft and where the brass tang attaches was breaking up.

 

Out of the four old floats taken right out of the working carbs I was getting four different readings off the scale. They won't be exactly the same but they should be real close.

 

I ended up drying them in the sun for a few days and then coating them with Airplane Dope to reseal the bodies. That did work. But the tangs coming loose was a problem.

 

I ended up buying all new floats and ended my problem.

 

When you look at the floats check for extreme softness and where the tang mounts into the body.

 

In the pics you can see where the soft spots were and the discoloration. The one pic is a side by side with a new float.

 

But, like I said, I'd lean more to the fuel bowl level before anything else. With all four carbs overflowing at the same time, pretty sure that's your problem.

[Black wing]

so how do i set them?

 

like what measurements am i looking for?

[jasonm.]

you cannot rebuld carbs w/o knowing your fuel LEVEL. This is done with a clear "drain" hose and the carb perfectly level... in a vise. It can take 10-30 minutes per carb or 5 trys to get the level correct in each carb. Yes, that tab is the key but the needles must be good and the floats also. FYI- a bad float does not completely sink. Rather they will have SOFT spots. Manual says, " with drain open fuel level should be 16mm below the casting mark" to the side of the DIAPHRAGM cover. Make sure no Air Bubbles are in the hose. The manual is great for this work. If it's wrong you must remove the bowl/cover an bend the tab. During your "rebuild", If you skipped all of the above...then you need to seperate the carbs into left and right banks....again. It took me a few times to get it correct. Parts Unlimited sells JUST needles...far cheaper than the needle seat assy. from Yamaha. Pushing on the float proves little. The actual pressure you are doing with your finger is 10 times what the float does. If original- Don't assume your floats and needles are perfect. I got my floats for approx. $15ea. from Partshark.

[Black wing]

ok so you put the carb together, shove the hose in the drain hose and fill the carb reading the level in the hose against the markings on the carb correct?

 

 

edit: ok so i did it the way i stated and i checked the floats for soft spots, they all seemed good i set the floats and put the carbs in they filled and the pump kicked out proped and no overflowing as of yet will see how they run tomorrow

 

edit 2: its been 2 days since i adjusted the floats and have put 520 km on it with no leaking so it seems to have done the trick

Edited August 7, 2012 by Black wing

[Black wing]

ok first sorry to double post but i needed to bump the tread

 

the problem is not quite fixed, im not sure why but everything will be fine for 200km or so and then it will leak for a few km then it goes right back to working. what would cause intermittent leaking, could the fuel pump be putting more pressure on the floats than its supposed to.

[Yammer Dan]

I know i've said it before but are they staying good and clean with the crap they are making us use for fuel. Sea-Foam??

[Black wing]

it has sea foam and i run ethanol free fuel