Tired Two-Stroke

My dad gave me a 2003 MXZ Adrenaline 600 HO a few years ago. When he gave it to me it had about 8000 miles and that was in 2006. Now I’m 15 years old and it has 16,000 miles. I’m afraid that I’m going to blow it up. It still has the original pistons and is lacking somewhat in compression but it still runs great. I’m a very aggressive rider. In fact, I beat the tar out of my sleds. I know that year that they used the same bottom end as the 700 twin so that’s probably why it’s lasted so long. But I’m just wondering, what should I do to prevent it from blowing up? And if it does blow up, I’m screwed aren’t I?

Peter Healy

I agree that 16,000 miles on a two-stroke would make me nervous. Larger bore engines are harder on the pistons than smaller bore engines, so the 600 isn’t going to be in as bad of shape as an 800, but 16,000 miles means you are getting more and more likely to have an issue. I would want an experienced technician (sled mechanic) to take the motor down and check the pistons, rings, cylinders, and the crank bearings. There are specifications for things like piston skirt to cylinder clearance, piston ring end gap, and cylinder trueness, but I would install new pistons and rings if the motor is taken apart, regardless. Cheap insurance. If it “blows” you might be looking at more damage than simply parts and labor for pistons and rings and a gasket kit. Damage to the connecting rods, head, cylinders, power valves, crankcase, crankshaft, it is all possible and far more expensive. It all depends on if something breaks or if it just suffers a seizure of some sort. Being proactive is always better than being reactive when it comes to high-mile engines.

Maybe we should ask you what it sounds like when you start it up? Any knocking sounds? When an engine is cold, the pistons are at their smallest diameter and the piston-to-cylinder clearance is at its largest. When an engine gets really worn, the cold pistons will be “rattling” around in the cylinders before they expand slightly and take up some of the room that let them rock and knock. This typically occurs at the bottom of the stroke as the connecting rod is changing directions, and the loose piston rocks from one side of the cylinder bore to the other.