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Discussion Starter · #1 · (Edited)
So I wanted to use a oem fuel pump on the bike I’m playing with. I have several oem pumps. All good when I put them in zip lock bags and set them on the shelf. My cut tank allows me to see the pump assembly clearly.
I put enough fuel in the tank to cover the filter pickup but left the rest of the pump assembly up out of the fuel. I was looking in the tank to see if the return line was aerating the fuel.
what I saw was fuel streaming out of the top of the pump as if the fp nipple was cracked. Spraying fairly hard. So damn it. Have to take it apart. When I took it apart the nipple was NOT cracked. I replaced it with another oem pump I had on the shelf. You guessed it. This pump was spraying out the top from somewhere too ! Ok out it came. No cracks at the nipple or anywhere. So, I put a third oem pump I had on the shelf in. This pump was spraying fuel out the top too. This time I could clearly see it was coming out from where the metal body meets the plastic top with the nipple. My finger is pointing at the spot.
85BFAE96-991A-40A6-A933-DCFA145C77ED.jpeg


Kzscott suggested a oring dried out.

interestingly enough, the bike started with all three pumps and fuel with pressure was being returned through the port check valve.

conclusion: used pumps that have been sitting, even wrapped in a plastic bag could leak bad, as all three of my do. And in a stock tank you cannot see down in there. I ordered up a walbro gss 242.

cmg
 

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It would have been interesting to know it this also reduce the RPM at around 6-7,000k
 

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Discussion Starter · #3 ·
It would have been interesting to know it this also reduce the RPM at around 6-7,000k
I agree.
I wonder if it’s just a used pump sitting or is it why
there is that 6-7k issue you pointed out.
I made mention of this so one could be cautious
of used pumps.
the Walbro was less than $85us.

cmg
 

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Are you running an A model style pump/rail set up or B?
 

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theres a good chance this issue would fix itself soaking with some regular fuel. always good to store bikes with a full tank to avoid issues. sometimes hard with spare parts.
 
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