Drew,
In rotax you have your hands tied. If you have done a back to back test of the engines using the same carb, reeds, power valve, coil, fuel pump, exhaust and airbox, and one is over a second behind the others, get it to your engine builder as something has gone south!
With regards to barrels, the post 09 ones are more consistant, but it is a bit of a lottery as to whether you get a monster or not. From experience, I've found the choice of builder has made a big difference too. I'll not name the builders in question, but I bought a freshly sealed engine from builder 'A' with a new piston and ring. The engine performed well. I partially cut through the seal fitting the exhaust so gave my engine to builder 'B' to get it resealed. He completely stripped and rebuilt my engine using all of the original parts (except gaskets) so that he could provide the dimensions to JAG (it had only done five hours on the new piston and ring). Builder B commented that the power valve and barrel height were not set correctly by Builder A (he provided specific details that I won't go into here). When I came to run the engine next, it was noticeably quicker, particularly at the botton end.
My other observation with Rotax is that a well prepared carb is essential. It's worth paying someone to do that properly as there is too much to get wrong and at least one setting is counterintuitive if you don't fully understand exactly what it is doing - again buyer beware, there is at least one seller on ebay claiming to clean and set our carb up that is incompetent! Get a recommendation from someone for this task.
|
|