My kart is spraying fuel out of the vent tubes on the carb. I’m running a pump around setup on my 2002 YZ125. The carburetor is a Keihin PWK and the fuel pumps are Mikuni. When I first bought the kart, I opened up the carb and found the bowls stuffed with black foam. The foam was deteriorating so I removed it. I’ve found a troubleshooting guide here:
I’ve verified that everything is routed correctly and there are no kinks in any of the lines. All brand new fuel lines, fuel tank and fuel filter. Before I open up the fuel pumps, I wanted to post my photos here in case someone sees something obviously wrong. Should there be foam in the bowls? Thanks in advance!!
Did you replace the foam with new foam? It is in there for a reason, you know. Without the foam, there is nothing to stop the fuel sloshing around in the bowl, and you may see fuel coming out the vents under cornering g’s or bumps on the track.
Thanks for the quick reply! I replaced the foam with some folded up cotton fabric. I figured it wouldn’t deteriorate and would still soak up the gas. We have since removed the fabric from the bowls. The gas sprays out of the vent line even at idle. I’ve done some searches for the foam but didn’t find anything. Is it a specific type of foam? Who sells it?
It is fuel cell foam. Just do a search on that, possibly check with off-road racing shops, anyone that operates in a high-shake environment can provide a lead for you.
Worked on a similar set-up last week. No foam, but there was a horizontal baffle above the bowl to dampen fuel sloshing.
The problem that kart was having was in the return portion of the double pumper. It wasn’t pumping enough back to the tank until rebuilt and then it was fine.
Thank you everyone for the help!
The problem was infact the return pump. As we were rebuilding the fuel pump, we found a large piece of rubber debris inside, nearly blocking off the return side of the pump. We replace all the gaskets and darts. The darts were pretty difficult to replace. I ended up using a small pick that I rounded out with a file to make it as blunt as possible in order to push in the new darts. Even with the tool it was still difficult. I still had to lube them with oil and press down on the pick while I worked around the edges with a small flat head.
For future reference, use the flat end of a small drill bit.
They will wiggle right in to place.
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