Originally Posted by fatdaddy
I still think metal to metal is best, BUT, if you dont get both mounts flat, flat, flat, on the frame, yer gonna wind up with a corner or edge digging into the frame and it will break.
It all starts where the back engine mount meets the seat tube.
This mount is what makes the engine one with the bike.
It is responsible for handling 100% of the drive force, and ~30% of the twist force the engine will be throwing at the bike frame.
The entire surface of the engines back mount block simply must meet 100% against the seat at a 90 and tight enough to hold the engine in place with no front mount.
The engine wants a ~65-75 degree seat post angle to fit in and operate as designed.
Just to be clear, if you have a different angle you can't make up for it by shoving filler in between the mount.
If that is the case make a new rear back block and back clasp or get it on right and make up for everything else like exhaust, intake, front mount with mods.
The front mount is only responsible for the remaining ~70% of the twisting force, but that is a big force.
Stock front and rear mount blocks are only 1 1/8" wide, plenty enough to transfer power in a horizontal line but not so hot at preventing the engines desire to twist and pull to the left.
I like a muffler clamp and plate pointing up the downtube best.
I won't go into the geometry of how to counter a twisting force inside of fixed structure, just that it is easy to test.
If you are worried about you frame breaking at the seat post at the motor mount just cut ~3" off the bottom of your seat post and shove it down the seat post to where your rear mount attaches.
You don't have worry about any of this with a shift kit.
It gives the back of the engine a 2 point muffler clamp connection ~10" apart and a good muffler clamp front mount to fit your downtube.
In short, they become 'one with the bike' like nothing else.
Just tips from a guy that sells to the public and doesn't cut corners on quality or safety for cost.
It's right or it's not, and I won't sell not's, which reminds me of an old joke...
A piece of string goes into a bar and orders a beer.
The barkeep said "I'm sorry, we don't serve string here, you a piece of sting right?"
'No' said the string, 'I'm a frayed knot so give me the beer'.