My views on proper engine mounting. Improper engine mounting is one of the major causes of either broken studs and or engine mounts/cases. Most bikes are not built to accept these China HT engines with a proper fit. These are not a one size fits all and adjustments are needed. With that being said, the optimum measurement in the "V" of a bike is 75 degrees. 75 degrees allows for a nearly perfect fit. I know that a variance can be used but I'm talking OPTIMUM FIT. I don't build allowing variances, as it's too easy to correct, for me anyway. Know how, proper tools and materials are needed. What follows is my line of thinking, take it or leave it, but in 5 builds I've never ruined a engine mount, stud or cracked a case. Although on my first build I blew a head gasket, stripped a 6mm exhaust hole and broke a frame in two (had drilled for a front mount...a NO NO). All before I sat back and took a real good look at these China girl engines, what they are made of and how they are put together. What do you expect for a buck and a quarter? In the pictures you will see that I used PVC pipe as a jig. For the perfect fit the tubes need to be 75 degrees apart, and assuming that the engine will be high enough. I have yet to find a bike with those specs.