Got a new needle combo for my stock single 44mm waveblaster carb and as I pump up the mikuni pop off tester, the carb is still leaking air. It does pop off at 22psi which is right around what I'm shooting for but from what I understand, it should hold pressure until the needle pops. Since I just put a new needle combo in, what other parts within the carb would cause this to still leak?
Carb not holding pressure
- Thread starter SWLAmarshrunner
- Start date
Yes, wd40
DAG
Yes, my balls tickled from that landing
- Location
- Charlotte, NC
Schrader valve in your pump itself may be leaking. Any hose/barb connections could be leaking. Really could be anywhere but those are the most common if its not leaking around the needle itself. If it’s not that try dunking the carb in a bath of wd-40 and follow the bubbles.
- Location
- Charlotte NC
Are you blocking the return fitting to keep the air from just blowing through? Are you making sure you hold the needle open when you spray the wd-40 so the tip actually gets wet?
Vumad
Super Hero, with a cape!
- Location
- St. Pete, FL
I have the same problem, brand new mikuni needle/seats that have air bubbles coming up until popoff wet with wd. Tried the old ones which look fine and same thing.
So far I've tried new springs and arms, made it bubble slightly less. If I slightly bend a set of arms downward it cures it but then my popoff if not what I want it at.
So far I've tried new springs and arms, made it bubble slightly less. If I slightly bend a set of arms downward it cures it but then my popoff if not what I want it at.
Yes, genuine mikuni n&s. There are no leaks coming from the n&s. No bubbles, good pop off. Sounds like the leak is coming from the pump side of the carb. If I put my finger over the other barbs going into the fuel pump, I can feel a little pressure relieve when I take my finger off. So sounds like I may need to redo fuel pump also. All I had done so far is a n&s replacement only. I have the other parts but had only replaced the N&S at the time of testing since that was quick to change out and test. Will go ahead and finish rebuilding the rest of the carb.
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Vumad
Super Hero, with a cape!
- Location
- St. Pete, FL
If you have leaking from the fuel pump, then you should be able to spray wd40 on the fuel pump side and see bubbling. You don't always need to rebuild the fuel pump side. I frequently restore that side to working condition by just cleaning up the surfaces. The genuine mikuni O-rines hold up very well. SBT and other generic kits don't seal brand new. If money isn't an issue, then $100 for 2 fresh fuel pumps is worth the expense.
Find the leak before you start spending money. We use reusable zip ties on the tester hoses. The line itself will not seal adequately.