Will modifying the air box hurt the motor on my scooter?

by Izzy

I just set my valve on my 150cc motor to: Intake .004 & exhaust .005. I was then having problems running at mid throttle. Spitting and sputtering.

I then took the carb. off and cleaned it, all jets and the needle jet. I put everything back together. I went for a ride and still the same thing.

I then replaced the air filter, and still no better. I then decided to modify the air box to let more air in. That has given me more power than I thought the scooter had.

My question is: Will this hurt the motor? The scooter starts fine, idles great and has great takeoff. I just don't want to ruin the motor.

The only problem I have at this time, is that the motor will back fire out of the muffler from time to time. Since I added more air, do I need to add more fuel too? Any answer will be helpful. Thank you.

Comments for Will modifying the air box hurt the motor on my scooter?

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Jun 04, 2010
Bigger Main Jet
by: Jim Zeiser

When you start letting in more air into the engine you have to add more fuel. A larger main jet will help eliminate the lean backfire you have now and give you a little more performance.

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