Hi! I drive some vintage racing (in sweden) and also has drove lot of other dragracing but i will try to tune my engine more (rotax 537) and for the moment i wounder little about rotaryplate settings.
Just now i have tried to run on 142-72 and engine feels strong and we drove quite fast this winter but my carbon disc has been litte damaged (worn in edges) so now i will try to new ones and my question is.
Porting/engine feels good but what would happen if i set it to 144-76 or 144-78 if i compare to my 142-72,
have had some problem to get it up to right RPM but have with little pipe work got it to near 9000 few moments. it would go up to 9200 and it is not weight problem so van disc have something to do with it??
Secondary spring 8-16 pounds and helix strieght 42 deg? Jetting? Carb size?44-48 Head clearance? (measure with a piece of solider side to side) what weights? 40 -44grams. Ignition timming???And chassis question. Gearing20/40?
It is doubtful that you may gain much on top end with a 144-78 but you may lose some bottom end and mid-range torque. Disc valve timing is good enough for the rpm you are running; it is more likely that pipe tuning will be your next step to get an rpm increase. It has also been our experience with older sleds that they need a stiffer spring in the secondary clutch in order to hold a consistent high rpm without shifting out too early. There are a number of new secondary springs that will do this job. - Aaen Performance
Do not use a carbon disc the chew up rv covers and cases, plus the carbon fiber does not last long. its like putting a piece of sand paper in your motor. A few years back I took a few carbon valves to a laser cutting shop and the made the same valves out of stainless on the laser cutter. I've also found the RV motors make lots of torque you might find more speed with a slightly taller gear. With the cat clutch the green Arctic cat spring in hole 2 will usually produce good results, or the cpc red white in hole 2 or 3.