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I know this is a matter of debate... I also know it depends how hard one rides the bike. Either way, I'm wondering how many hours one can ride between rebuilds or ring sets. Or if putting in new rings instead of doing a full rebuild is even worth it (do any of you do it, or do you just do a full rebuild while in there?). It's worth mentioning that I have no way of doing a compression test... No one here can do them (but labour is cheap). My bike has just over 60 hours on it. Never changed the rings. I already have a new 66mm piston and gasket set sitting at home as a spare, but the one I have in there is 67mm. My bike started to get hard to start after a long ride (7 hours). However, I haven't cleaned the air filter yet... And ahem... conditions were dusty on the ride. I was going to, but ended up using it to do 3-4 small runs (3km) around town (that's when it got hard to start). I then left the bike at my place in the countryside. Could a dirty airfilter cause the hard starting?

Obviously, when I get back there, I'll do the easy stuff first:
1) Clean the air filter.
I'll then try to start it...
2) Change the spark plug. I have no clue how old mine is, but probably over 2 years so I figure changing it won't hurt. I'm guessing the spark plug could also be a culprit, though the bike i also well-jetted.

Weirdly enough, I switched 2-stroke oils right before the ride, which is stressing me out. But it's the same company, so I doubt it's a "bad" oil.

So anyways, I'm currently ordering a few parts for the bike in anticipation of a big ride in late March, so I'm wondering about the following:
1-Do you ever bother just changing the rings, or do you do a whole topend when the time comes? I'm wondering, because if 30$ rings can keep me going for another 40 hours or so, that would be great. If not, then I'll need to put a new sleeve in and pop the 66mm piston in there. No biggie really, but no point in using the new piston if a set of rings can solve the problem... It's tricky because I can't pull it apart just yet, and parts ordered take a good 3 weeks to arrive here (and cost a lot in shipping). So wondering if getting 67mm rings (and maybe a spare set of 66mm for the other piston for future use) is worth it, or if I should just tear it apart and put in the 66mm (assuming air filter cleaning and spark plug don't solve the problem).

Sorry if my post is all over the place and slightly incoherent.

I do rings only every other new piston

Is there anything preventing you from getting a compression gauge and connecting hardware?

Based on the conditions you are concerned about, IMO, the amount of compression pressure your engine makes is what really matters, not weather you have a new piston and cylinder bore or not.

I can't imagine a compression gauge kit costing a great deal, and once you have one, you can check your compression anytime you want, and then as the numbers go down, you can plan on a top end overhaul.

It's the numbers that tell the story. If I were you, that's what I would do first.

without a way to measure the compression all you can do is go by the ring end gap. I think new is something like .012" and so when the gap is a certain amount bigger then you'd want to change them.
Someone jump in here and please say what the manual says about what the acceptable range is. (.012-.022" would be my guess)
I only changer pistons after it seizes or gets damaged.

Manual says std ring gap is 0.15 - 0.35 mm. Service limit is 0.65 mm. Same for both rings.

Thanks all. I'll look around some more for a compression gauge this week. From what I gather, 100-150 is acceptable. Assuming compression is out of spec (too low), one needs to change the piston regardless, correct? I guess what I'm asking is this: is there any time when it's acceptable to only change the rings? If so, how does one know to only change the rings? Ring end gap? In that case, would it be acceptable to only change the rings, or the whole piston anyways? If there's blowby, then a new piston is in order anyways, right? Just wondering if there's a point in getting a spare set of rings... I already have a new piston with rings, wrispin and bearing. Is a spare set of rings ever handy on a 2-stroke, or is it pointless in the sense that one is being pence wise, pound foolish?

royadams wrote:I do rings only every other new piston

I'm not sure I follow. You mean you sometimes put in new rings, sometimes you don't? For 30$, I'm not sure it's really worth it unless it ads a lot of life to the topend. A new piston is around 80$...

If you have put a weisco (or other High quality piston) in on your last top end, your cylinder coating is in good shape and haven't had anything break inside the cylinder, then a set of rings on your next rebuild should be just fine. If you have to have the cylinder recoated, you must use a new piston AND send it in when recoating the cylinder so that it can be "matched" to the cylinder.
Replace the Aftermarket piston when; There is damage to the piston, piston skirt or cylinder wall, a ring or power valve breaks, the piston has "collapsed" enough to be out of spec.

.15-.35mm is .006"-.014"
If my compression significantly drops down then, unless there is a head gasket leak or the spark plug is loose, I know the ring gap is excessive.
Eventually, if you have a gauge, you will know how the compression correlates to the ring end gap and use the test to know when to tear down the engine to check the rings.

I picked up a cheap compression tester for 30 bucks,is there a Cambodian tire over there?
http://www.canadiantire.ca/en/search-re ... ion+tester