Motorcycle Repair: pw 50 lack of power, air fuel mixture, gravel driveway

Question
Hi.. we just had the cylinder bored out and put in larger piston, new rings, etc... new air filter, new plug, new oil, etc...

With NO air filter.. the thing has full power.  Lack none.  Straight up a steep dirt/gravel driveway.  No bogging down.  


With air filter.. can barely get it to go straight down a level driveway.  virtually no power.

Could the problem be air filter related.. too thick? need to customize?

OR are there there other parts of the system that are in need of repair and the symptom shows up in this situation?  

I saw one post that mentioned a buildup of carbon in the exhaust.  Not really sure how to check that.  I looked at it and it seems fine, but?

any ideas?

thanks so much..

David Scheer

Answer
Hi David,

The air filter is restricting air flow causing the air-fuel mixture to become too rich. This is what is bogging the engine. The carburetor will need rejetted, cleaned, or other. I would need to see the parts to accurately diagnose the work to be done.

Send me an email address as requested. I'll return carb tuning, cleaning, and other files that may assist you. Review the info and decide if you can perform the work. If not, have the local shop give you an estimate.

Respectfully,
Mark Shively
mshively1@woh.rr.com