Pump Around Carb

Tagged: fuel yz125 yz125cc yamaha filter gas vent pump around carb carburetor Keihin PWK Mikuni

This topic has 7 replies, 4 voices, and was last updated 10 years, 10 months ago by Sanford Mitz.

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- October 2, 2015 at 9:38 pm #55075
  
  Paul Mendoza
  Participant
- October 3, 2015 at 12:34 pm #55078
  
  William Martin
  Participant
  
  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.
  - October 3, 2015 at 5:46 pm #55089
    
    Paul Mendoza
    Participant
    
    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?
    - October 4, 2015 at 10:27 am #55101
      
      William Martin
      Participant
      
      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.
      
      Bill
- October 4, 2015 at 2:54 pm #55112
  
  John Mulvihill
  Participant
  
  Hi
  
  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.
  
  John
- October 21, 2015 at 10:37 am #55680
  
  Paul Mendoza
  Participant
  
  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.
- October 25, 2015 at 8:34 am #55808
  
  Sanford Mitz
  Participant
  
  For future reference, use the flat end of a small drill bit.
  
  They will wiggle right in to place.
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