I'm using the HF engine on a BMP friction drive. I have no complaints with the 1" or 1.25" roller. AS far as what's the largest engine you can use, you didn't say legal or illegal. You need to check your local laws on that one. I'll bet GP460's are illegal in all 50 states.
Unfortunately in Alabama you would be illegal with any motor you put
on a bicycle to drive on the streets. I was just trying to find out what the
largest displacement engine I could get that would still bolt right up to
my BMP friction drive unit (78mm clutch). I'm ok with the monster scooter
49cc just wanted to know for future builds. As for as displacement goes I
always think you can go BIGGER!!!!:
Maybe when I get this engine broken in it will be better. I have only
went wot a couple of times and then only a few seconds, waiting to get a few more tanks run through it.
I'm very pleased with it on the flats, its just the hills in my subdivision are kindof steep. To get up them just pedaling reguires using the lowest gears.
Oh well these things weren't meant for mountain climbing anyway,
but if you come across a bigger engine than the ones listed on the BMP site
please let me know. Thanks