I'm fairly new to Rotax but not to 2 strokes. The quote �A Rotax revs at about 1000rpm less than a TKM but has about 10bhp more. It therefore follows that rebuild intervals should be pretty similar � has two problems. The first is the Rotax has more cc and would gain BHP from that, but probably the main reason why the Rotax has longer rebuild intervals is that it is water cooled. A water cooled 2 stroke, if built properly with no weak or faulty parts and treated well, shouldn't really be much more susceptible to failure as it gets older. This is because as it wears it produces less power and revs less. In theory it should run until the ware prevents it from running at all. Obviously, if it has badly designed or manufactured components, it will be susceptible to failure at any time. Probably the main reasons why the Rotax is getting rebuilt at shorter intervals than recommended, is that people are rebuilding when not necessary, and people don't look after them properly. I do see people revving them on the stand but very few could rev it past 1400 revs while stood next to it with no helmet on because it's to scary. The worst thing I see all the time is people going out on track and hitting full revs before it is up to temperature. High revs when it's cold probably halves it life and makes it much more likely to go bang at some point. The other thing mentioned in this thread, and often suggested, is run more oil in the petrol. This makes it run lean on high revs.
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