Something to check if..

[Sirolf]

your engine doesn't perform as it used to.

I bought a used Align 91H a couple years ago to retrofit it into my Trex600.
To do so i had to cut a piece off of the crank in order to get the fan mount and clutch fitted.

A season later i damaged the crankcase in a crash so had to be on the lookout for another engine and found a brand new 91HZ-R for a decent price.
Cause the i already had a modified crank from the previous engine i used that one and kept
the original one as spare.

I don't know how long this crank ran by previous owner but it has such a worn down connecting rod pin that it causes the piston not to reach it's Top dead center.

Originally this pin measures 7.0mm new.. now it's 6.92mm!
Fitted the new crank and noticed the difference immediately by hand.

[marc8090]

Yep, after many gallons have experienced the same thing.