ok, ive been playing with this idea for a while now. the problem with living in the Middle East is that parts arent easy to come by and shipping from the states takes weeks. which means having a 2 stroke Engine which could die at any given opportunity isnt a great idea. we do however, have an abundance of 4 stroke quad bikes (ranging from 50cc-600/750cc).

my plan (and please tell me if you think this will/wont work or any problems i might run into) is to transplant the Engine and gearbox from a Honda TRX450. find a way of removing the driven clutch from the FL350 and replace it with the sprocket from the same quad bike. that way i will have a reliable 4 stroke Engine (which i can get parts for easily) a 5 speed gearbox plus the forward/reverse box of the FL350.
i was hoping to go for a chain direct to the rear axle of the FL350 (sacrificing the forward/reverse box) but i cant think how to do it, im not an engineer but the way i see it is the stock gearbox is the biggest/only support of the rear axle.

anyway, any help/suggestions or unforseen problems would be greatly received

There was a guy on ebay and craigslist trying to sell one with a 600 streetbike motor (( Internal Combustion Engine ? )) for $2000, and I believe there was a member on here with one that he was dropping a 450 quad motor (( Internal Combustion Engine ? )) in. You got the right general idea if you are going to do it, keep the FNR trans and fab a gear to mate to the input shaft on the trans.

Look down in projects to the post "NEXT"by DaveM he is doing exactly what you are thinking about he has pics good luck.

Yeah, that was the one I was thinking of, just couldnt remember.

Yeah...those single chain pictures in the other thread are before I realized the error in my gear ratio calculation. It would have topped out at about 35mph. oops!!
I missed the 2:1 primary reduction between the crank and the clutch basket. I have corrected it by stepping up the output rpm with w jackshaft and a second chain. Not ideal, and not proven, but my fingers are crossed.