Sleeve

[atvman2010]

So I've had a top end noise, took the top end part and found that it sure was time for piston rings and something with the cylinder went to machine shop and decided to put a sleeve in place of the coated cylinder what's what's your thoughts on this move positive or negative!?!?!

[C George]

run it ,,, it will be fine

[pumpguy]

Have no personal experience with sleeves, but IMO, you're better off with nikasil coating. Again, IMO, better heat transfer, longer wearing, and holds lubrication better.

Sleeves are just iron with a pressed in mechanical bond, whereas nikasil is ............ not exactly sure how to describe it, but it's what all OEMs use these days, and not just an old school sleeve.

In the end, you're probably okay either way, but when I did mine, I had Millennium nikasil coat it, and was very pleased with the result. Be sure to send the piston too so they can do the bore for proper clearance.

If you are doing a 220, be sure to use an aftermarket forged (Wiseco) piston. OEM 220 pistons have a bad reputation of breaking up in service and really ruining your day, and engine too.

[doakley]

This is probably a bit of a hijack of the thread, but I don't get the need to send a piston when you have a cylinder recoated. When you have to replace your piston again later, which is a pretty routine thing, you certainly don't send your cylinder back to be recoated. Seems to me if they coat it and hone to finished OEM spec they should have no need of a piston. Changing pistons (and/or rings) in a 2 stroke has always been pretty routine maintenance to me.

[pumpguy]

All interchangeable manufactured things have tolerances. That's the difference between how big and how small all of its various dimensions can be and still be acceptable for use in it's particular application.

A tire might be ....... I dunno, maybe + or - 1/32" in outside diameter (OD) and still be acceptable. On the other hand, back in the day I worked in the fuel injection dept of a Diesel engine plant, and there the tolerances of some critical parts were + or - in the millionths of an inch.

So, if you have a piston that is at one end of its tolerance range, and you make your cylinder bore at one end of IT'S tolerance range, you could end up with the running clearance between the 2 parts thats either way on the loose side of the tolerance range, or way on the tight side.

When fitting a cylinder bore to a piston, the most important dimension is the CLEARANCE between the piston skirt and the cylinder bore.

For our KDX 200, the manual says the clearance between the piston skirt and cylinder bore is 0.079 -.089 mm or .0031 to .0035". So the clearance tolerance is only .0004". That's less than half a thousandth of an inch.

Now, I have no idea what the manufacturing tolerance on those pistons is, but IMO, if you don't know YOUR piston's OD and YOUR cylinder's ID, well, IMO, the clearance is like a box of chocolates, you never know what you're gonna get.

For these reasons, it's always best to have the new piston on hand when re-doing a cylinder bore. Then you know EXACTLY what the clearance is, and can compare those dimensions to what it's supposed to be.

For me, a guy with a long machinist background, these things matter. For others, well, maybe not so much.

Sorry if this sounds like a rant.

[doakley]

Doesn't sound like a rant at all, just good discussion. Take it one step further though. What do you do when it is time to replace the cylinder you had matched up to your newly plated cylinder? You can't tell Wiseco to send one that measures exactly to your cylinder. You have to take what is shipped to you, put some new rings in and go with it. Seems to me pistons are made to a certain tolerance as are cylinders. The extremes of each of these tolerances must work together or you cannot order replacement parts. Said another way, the matching of cylinder bore to piston diameter is good only for that one, initial time. Afterwards, when you buy a new piston, you are dependent on manufacturing tolerances matching up. I don't know anyone who has their cylinder replated every time they install a new piston.
Sorry, I don't mean to rant either, please don't take it that way.

[C George]

So I've had a top end noise, took the top end part and found that it sure was time for piston rings and something with the cylinder went to machine shop and decided to put a sleeve in place of the coated cylinder what's what's your thoughts on this move positive or negative!?!?!

For the money spent , I wouldn't worry about having a sleeve.

Yes , a true nickasil coated cylinder is the BEST but not always needed.

[pumpguy]

@doakley, that's a good question. I would think when it comes time to replace the piston, the cylinder bore would be bad too. That was certainly the case for me.

IMO, the key issue is the clearance, and then judgement. Ideally one would measure up his cylinder bore, and then obtain EXACT OD dimensions of available pistons from supplier of choice. I don't think it's realistic to ask a supplier to measure up a bunch of pistons in his stock and then sell you the exact one you want. Besides, his mic will be different from yours, and whose to say they're they're both dead nuts accurate, so errors can creep in that way too.

I believe some manufacturers use letter codes to denote where their pistons lie in the tolerance range, so that may be helpful in choosing a big one or a small one. Other than that, I guess you just pays your money and takes your chances.

[Julien D]

A well plated cylinder, barring some form of catastrophic failure, will be able to run the stock size piston for many many top ends. In the case of the KDX, probably longer than you will own the bike. Not so for a sleeve.