New mikuni fuel pump issues?

[Ameritude]

So here's my question. For all of those who have swapped new vm mikunis on to your sled, do you have any overflowing issues? If not, have you swapped in a new mikuni pump aswell? The problem im having, is that I put brand new vm38's and I can't get them to stop overflowing like crazy, at idle rpm <2000 it doesn't seem to, but with rpm it starts to flow. I know the floats are correct and I know the needles are seating (at low rpm). Last year I had the exact issue with some brand new vm36s and could not solve it so I swapped to the original carbs and it "seemed" to work. The solution I've found so far is to turn down the pulse line flow quite a lot (that is what my petcock controls) and it works. My theory is that the new mikuni pulse pump, which on the mikuni website, says it's pumping 35 l/hour is pumping to much and overpowering the needle and seat? Im at a loss however because the pump is made for the carbs I would think. Any suggestions would be helpful, I have the original pump and am probably going to swap it back to see if there's a difference, but I would rather use a brand new pump if I could.

[mswyka]

We have not experienced overflow on the 36s before, only the 32s on the 340s.  Whenever that has happened, we have put in new needles and seats and the problem goes away.

[Ameritude]

On new or used 32s?

[mswyka]

On new or used 32s?

All of our equipment is used.

Have you put a pressure gauge on your pump?

[Ameritude]

I have not yet

[Ameritude]

Figured it out! So when you buy new mikunis, make sure to buy some 1.5 needle and seats with em, unless yours say they already have them installed (whalbros and dennis kirk have the needle and seat sizes listed) the new mikunis that I got came with 3.3 seats! Great if I was running methanol lol. I swapped out the old carbs 1.5 seats and it did the trick. Anything bigger than 1.5 will be overpowered by the fuel pump and are made for gravity feed applications is what I've discovered.

[Ameritude]

We have not experienced overflow on the 36s before, only the 32s on the 340s.  Whenever that has happened, we have put in new needles and seats and the problem goes away.

If my solution is what you were referencing, than thankyou for the anwser, I shoulda listened better lol.

[mswyka]

We have not experienced overflow on the 36s before, only the 32s on the 340s.  Whenever that has happened, we have put in new needles and seats and the problem goes away.

If my solution is what you were referencing, than thankyou for the anwser, I shoulda listened better lol.

No, I didn't think about the needle size.  But we do mostly use 1.5s.  3.3 is really big.