twostroketoowoke
Member
There’s an old post from years ago that talked about belt and clutch life and how it directly correlates to primary ratios that I can’t seem to find. We all know that coveted 2.71 primary ratio (21 engine, 57 pulley) is pretty much the standard for two cycles with a minimum of a 21 driver on the dry clutch. The post I can no longer find talked about how that primary ratio getting bigger eats up belts and is hard on clutches because you actually lower the engagement significantly to match up to the much higher jackshaft speed you’ve created by downsizing the engine driver, say an 18 or 19 Instead of a 21. Can anyone school me a little on this subject and tell me why I should or shouldn’t put an 18 on my engine so I can keep my 21 driver on my clutch and not have to run a 70 on the rear gear for the very small indoor tracks where I need a 9.5-10.0 final ratio? OR what’s stopping me from leaving said 21/57 and just putting on an 18 or 19T on my clutch instead? Isn’t the whole point of a jackshaft to begin with to keep heat off the crank and rear gears out of the dirt no matter what final ratio you need?