You would not believe the amount of trouble we have with customers who have hired a motorcycle mechanic to install their parts. Of the number of customers who need to reorder a cylinder because of seizure, I believe a realistic estimate of the percentage that had a motorcycle mechanic do the installation is somewhere around 80%. I believe there are a few reasons for this:
1. Most motorcycle mechanics have very little experience with small engines. Two-stroke, small engine scooters require a good deal of specialized knowledge in order to get them tuned properly. None the of things one must know are especially difficult, just different than motorcycles.
2. Customers who don't know what they are doing typically know they don't know what they are doing and so read our how-tos and forum, and ask a lot of questions before they attempt an installation. Paranoia is a lot more useful than confidence when it comes to not blowing up a cylinder.
With that being said, not all motorcycle mechanics should be avoided. But, if you are going to have a motorcycle mechanic do an installation, I would check on his small engine experience before enlisting his help. It will save you a lot of time, money, and frustration. Don't say you haven't been warned ;)