Quote:
Originally Posted by rjmorel
So I got to thinking today about my 70's racing motocrossers that had 2 stroke motors. Which motor would last longer if you had an air cooled 4 stroke and an air cooled 2 stroke or both water cooled for that matter and rode them basically the same, like commuting same distances and same speeds. Would they roughly last the same amount of miles? Or would 4 stroke last longer with pressurized oil lubing it. Or would 2 stroke last longer always having clean oil lubing it either from a oil injector or premix in the tank.
Anyone have any hard data on this? Say between 250 single cylinder motors with same cooling and same carb or fuel injection?
rj
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No hard data but from experience I can tell you that the 4 stroke will last much longer between rebuilds. I used to have to do bore/piston/rings every other racing season with all my MX 2 strokes. On my street-ridden 2 strokes, I'd just let them slap, even though they were losing performance. Plus, with a 2 stroke you're counting on the crank seals to help maintain compression and they're a seriously wearable part. Not only that but the rings passing over ports will start to wear them quickly as the piston begins to slap. Not an issue with a 4 stroke.
The upside of a 2 stroke, as you know is that they're much lighter, less moving parts and much more power-per-displacement. I do miss all that power! As you remember, all you needed to so was clean up the ports and add an expansion chamber and it would make them monsters. :-)