I usually suggest that one use a curved file, or heavier grinding instrument, cut the front mount groove to match the angle on the bike tube, if you do a nice job you can get an engine lower, with better center of gravity. This also helps drastically with the wobble a motor can have if it's only making minimal contact on the front mounts. This also brings the chain from the engine to a more level point across the pulling surface of the gears.
If the motor is higher up, the more the motor pulls itself down into the frame to reduce resistance. Also why many people experience chain tensioners issues and what they think is chain stretch. The motor over time will sit itself into the frame, by using files on the grooves to match better you sit the engine where it can't get any more stable.
I believe I also recommended this elsewhere, possibly in a private message, but either way it's one of the best starting points to longevity, and it's usually easily found tools to do it. Consequently the first time I did it I used a hand held belt sander. Stuck it in my vise, and used the very end to make a rather perfect mate.
Files work but take more time obviously, angle grinders throw a lot of crap but work much faster.
Get it all depends if you have good goggles or not and the right tools at the right time.
Just f***ing put the bike together already and ride it so you can stop reading so many threads. Experience comes through time not Google believe it or not.
Popcorn chicken would sound good right now. Ee eye ee eye Oh.
