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I have recently read that 2 stroke engines most commonly seize rather than blow up. I own a 1989 cr80, it is my pride and joy. I need a few maintenance tips to keep it in good condition and how to avoid my engine seizing up.

 

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air leaks develop over time from lack of maintence. Crank seals and gaskets go bad. Changing top ends and not doing leak down tests will get you eventually. Air leaks make it lean which makes it hot and then it will melt a ring or sieze.

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As seanmx57 mentioned above, un-detected air leaks make the engine run lean and if severe enough may cause a seizure.

 

Not re-jeting for cold weather riding, stock jetting is usually optimal for 68°F weather, same jetting in 50°F or below can become dangerously lean.

 

Long sustained wide-open throttle runs (say a long stretch of dirt road), MX engines just are tuned for that usage,

even worse, suddenly shutting off the throttle after a long WOT run or, compression braking the engine at high rpms.

Throttle closed = no fuel/premix = no cooling  (in a 2-stroke it's the fuel that cools engine internals, not the oil)

 

There is also the risk of a 'cold seizure', when you put a load too soon on a engine that isn't sufficiently warmed up.

Piston / cylinder expand at a different rate, piston grows faster than the cylinder too soon and seizes in the bore.

 

Best bet on long engine lifre and reliability is a preventative engine refresh (top end, inspect play in rod/crank)

installing new crank seals (leakdown test to be sure afterwards) and just making sure everything is within the service manual's tolerances.

 

Edited by mlatour
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