2000 GTX mag carb not holding pressure

[Daniel2500]

Hi everyone!

Need some help with my carb rebuild. I could not find an answer in my forum searches. After rebuilding my carbs, the mag carb won’t hold pressure ( the other carb does perfectly). Pop off pressure is fine. I bought and used Mikuni BN46 I rebuild kit. The needle arm is flush with the carb body. What are my next steps to get this to hold pressure? New diaphragm? New needle and seat? Trying to get this running soon so my kids can ride before summer is over. Thanks in advance for your help/thoughts!

Daniel

 

[burtshaver2021]

Did you buy genuine Mikuni rebuild kit? A good place to get them is osdparts.com Follow Mikidymac’s carb rebuild thread to the letter. Will more than likely fix your issue. Be very careful when putting the grommets in for the Mylar check valves that you don’t poke through the grommets. I’ve heard pulling them through with dental floss works good

 

[JC-SUPERJET]

Probably needs a new Needle and Seat.

If the Needle Viton Tip is grooved, it's bad. Use a Magnifying Glass to check.

If the Needle Tip is not grooved, then the Valve Body O-Ring is leaking. Remove the Valve Body and install a new O-Ring. Can be Nitril Buna-N or Viton.

Then try Pop-Off Test again.

 

[burtshaver2021]

if the diaphragm doesn’t have a red button like in this picture then they will not always pass the 8 pounds of pressure in the inlet nipple test, i think it’s because the diaphragm isn’t up to specs and holds the needle valve open? Not 100 percent sure on that.