Here's the issues with that type of build that many just don't seem to understand,these are 2 stroke and the bigger is better theory doesn't really apply here.This is because the chainsaw/quick cut cylinders are designed to make their power at peak rpm and compared to other single cylinder engines of similar displacement for performance engines lack hp and torque lower in the range witch is needed for single speed bikes! The biggest sthil cylinder (ms880) is only rated at 7hp and we can make 10 hp from a properly done china girl that makes more torque at lower rpm to be able to pull through the load of a single gear.Then we have the loss of ccr due to case volume difference and this loss takes away from low end power also due to the lack of pumping efficiency in that range.Next there is the geometry difference in that most saw's have a short stroke being 34mm on average and this makes the port timing and the time over area all wrong and needing to be corrected for the longer stoke that is commonly used,these are the main two issues that alter it's performance ability.Then there are the fitting issues where the bdc doesn't line up,the wrist pin is a different size and alot of machine work needs to be done for them just to fit on the case.I personally think it's not worth the time or money when for the same money or less and far less work and frustration you can have the china cylinder corrected and treated with nikasil that will last as long as any quality cylinder (when used properly) and make more usable power thru out the range.
