Hi,

I converted my 25cc to 30cc by changing the barrel, piston and conrod only. (ie. the block and crank is from the 25cc motor) The motor runs well but seems to have more vibes than with the original 25cc. I was told that the crank was the same (it also looked the same) but im wondering if perhaps the crank from the 30cc will have a little more mass to counteract the bigger piston? The mass difference would explain the vibes. Maybe its because the motor is still a little tight (300cc fuel run so far)?

The vibes are enough to cause foaming in the primer bubble and the fuel tank (on my test jig), not good I reckon....

Cheers
Mark