Backfire
 

Hello all:

I'm new to the site and already have a question! My son has a Dune 150 that didn't get ridden much last year. When we tried to start it this year, we had fuel issues from bad gas. The needle valve was gummed-up, so I installed a new carb. It fired up, bur backfires through the carb. I can't see any cracks in the intake, and checked valve clearances which were OK. I'm starting to get frustrated. Any ideas? Thanks in advance for your help!

Your probably jetted too lean. most carbs come factory jetted for scooters which use smaller jets and/or are leaned out to pass by the polution police. Especialy if you got a e-bay item. Use the main and pilot jet from your old carb. See if this helps.

Thanks for the reply! That makes sense. I'll change jets out and see if that helps.

Well, we finally figured it out. One of the wires going to the coil was partially unplugged. It was a simple fix to crimp the terminal a little, but it took me a long time to figure it out. Thanks for the help!