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Kawasaki MX & Off-Road Dirt Bikes
2T Engine experts -> your opinions on top end rebuilds
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[QUOTE="adam728, post: 1408742, member: 55463"] I understand the area against the cylinder wears faster, I thought that could be implied from my post. The comparisons with a Detroit diesel are far from apples to apples. Specific power output is massively different, not to mention the architecture of the engine (Detroit's ring design is such that it gives up sealing pressure for longer life, bikes are a no-compromise performance design). One might make 280 hp/L at 10,500 rpm, the other might make 40 hp/L at 2000 rpm. It's like saying a 40 hp 250F spinning 12K can't wear out valves and cams because my 210 hp / 4500 rpm TBI 350 in my truck doesn't. Parts are under far greater heat and stress, and see far more cycles per hour. 2 strokes put out much more power per cc than a 4 stroke thanks to the fact that they fire every revolution. Unfortunately this also means they see double the combustion cycles of a 4 stroke at the same rpm, making piston cooling more difficult. I also think that due to the dynamics of a 2 stroke there will be improvements made in life-span with DI, as fueling and lubrication can be much more precisely controlled. EDIT: My opinion here. I think one reasons bikes seem so "short lived" is because they are rebuild as preventative maintenance, where we rebuild pretty much anything else as-needed. I do top ends on my 250 every 50 hours, even though it's usually within speck and showing great compression still. I might get 100 hours before things get outside the limits, and maybe 200 hours before the engine just plain out dies, but we don't tend to do that with our bikes. With daily driver cars/trucks we don't typically go "wow, there's 120,000 miles on it, I better rebuild." No, we run em until something fails, then rebuild (which could be 300,000 miles). Going to the specific power output thing again, it's not what an engine can make for hp, but what it does make in use. Someone riding single track at a leisurely pace on a 250F might average single digit hp output, and get WAY more life from the engine than say, Justin Barcia. Same as a gently driven Mustang might go 300K, but one that is used soley for 1/4 mile drag runs will be worn out long before seeing that number on the odometer. [/QUOTE]
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Kawasaki MX & Off-Road Dirt Bikes
2T Engine experts -> your opinions on top end rebuilds
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