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pugetsoundsailer

low compression/ smoke'n xr600

3 posts in this topic

I'm looking at this 94 xr600 to purchase and I'd like some advice, and info.

It's low on compression but starts easily, it smokes but clears up quite a bit when it warms up. The engine isn't making any noises and the valves are quite. So it looks like rings.

Where's the best place for parts on the net?

Now I've replaced a ring or two in the past on 2 strokes, what's it like with these engines and any tips or advice?

Thanks

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Replacing the rings is a pretty straightforward operation. Get hold of a service manual and follow the procedure. Measure the bore and piston diameters at several points and at 90 deg. axes to make sure everything is in spec. Check the ring lands carefully for wear and cracks, check for scoring in the bore and on the piston. Place the rings one at a time in the bore per the manual and check the end gaps. If the engine has a lot of hours, a new piston and pin might be a good idea. Inspect the cam chain for looseness/wear and definitely do a valve job including new stem seals. Service Honda is a good place for OEM parts, I usually replace with Wiseco.

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On XR600s the head is usually the first to go. The cam chain and tensioner usually need to be replaced at the same time. On mine the cam chain started making all kinds of noise, but only when warmed up(worse when hot). I did head last year. This year it had low compression and was blowing oil out the breather. When I took it apart the rings were really worn. The ring end gap was like .100, while the limit is .020. So I ordered some new rings. The piston and bore were OK, so I just honed the cylinder. To check the ring end gap carefully remove the ring and place it in the bore. Use the piston to get is square in the bore. Measure the gap between the ends. Mine was so big I didn't even measure it...

After you take the head off, hold it upright and spray some carb cleaner into the intake and exhaust ports one valve at a time. If it leaks through then it's time for some head work. Even if it's good a little will seep through, but if it's worn a lot will.

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