frodus wrote:You will want something higher than a 4:1 on a B&S etek. I don't know of anyone that goes with lower than 5:1 on that motor. I wouldn't go that low because it'l pull a ton of current and cause overheating. If it's a super light bike with low range, it might be ok. But if it's a decent range bike, the weight and that gear ratio is a little on the low side. You should have something in the 55-66 tooth range, 43 is way too low, IMHO.
What's a super light bike for you? I have a 125cc (the '99 model of this bike here: http://en.wikipedia.org/wiki/Aprilia_RS125
). I've found up to 45 teeth ready-made rear sprockets actually (and not 43), and was planning to use 43.
I can image it with a 45 teeth rear sprocket (11 front) which would go for a theoretical 55mph top speed, but higher ratio than that would be too slow... would prefer to invest on motor cooling, or will have to re-think the motor to use. 55 teeth is an exact 5:1 ratio but top speed would be a staggering low 45mph. Almost unusable and unsafe for highway here.
frodus wrote:And it doesn't matter what the chain is, you'll be throwing the original chain out and getting your own. The original will be too short. The motor will be in front of the pivot, further forward than the original front sprocket, so the new placement will require a longer chain.
It does matter, because the rear sprocket ready-made I found so far is for a 520 chain. Or I find a ready-made (or cheap) rear sprocket for my bike and a 530 chain.
frodus wrote:Where are you getting your sprockets?
Where are you located?
There's this brand "PBR" that makes tons of transmission kits for bikes, I think they're from Italy. I'm from Portugal.