Scooterotica

That should pull 17/46, my GT200 with BGM Clubman, phbh30 and 58 stroke crank does with ease. I tried this with the 186, 60 stroke crank and expansion but that struggled, so ended up with 16/46. 16/47 you will lose a little top end but should be a nice ride.

I've found the Gt 186 and 200 variant to pull 4.8 final ratio with expansion and 30mm.
Did try 4.6 with rm pipe and found that a tad too much.
What ever you decide as a final ratio, fit a rpm gauge and make sure it pulls revs in top gear

It also depends on your riding style, how well nourished you are, and where you ride.
If you aren't 90kgs, and you do most of your riding on the open road, 17t primary might be fine.

Burnside wrote:That should pull 17/46, my GT200 with BGM Clubman, phbh30 and 58 stroke crank does with ease. I tried this with the 186, 60 stroke crank and expansion but that struggled, so ended up with 16/46. 16/47 you will lose a little top end but should be a nice ride.

16x 47 for my 186..........flies up hills and pushes into headwinds really well the best gps i,ve seen is 74mph at 7300 rpm, 13 stone pilot ,jl3 and 28mm delly on li150 box.

Thanks for everyone's input, much appreciated