Replacement parts for rebuild. OEM, reuse or aftermarket?

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danfree
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Replacement parts for rebuild. OEM, reuse or aftermarket?

Post by danfree »

I decided to do a top end check on my 2005 KDX200. I bought the bike used several years ago and probably have about 200 hours on it after the purchase. Compression test was 110-120 psig. Not bad really, but I wanted to do it anyway. The piston and cylinder look pretty good actually so I may just reuse them and purchase new rings. Is there any advantage to get a wiseco piston kit? Or should I get a new Pro X piston. I am looking for dependability over performance. I am an old slow poke rider. Also my clutch plates are within spec, but wear is apparent. I filed down the grooves in the basket and was wondering if the wiseco or ebc plates kit was desirable. I noticed there are kevlar plates available, would they be more or less dependable for another 300 to 400 hours? Of course I could just try to replace every thing with OEM parts too. Any advice?
2008 Yam FZ6
2005 KDX 200
Rjcapt
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Post by Rjcapt »

I went through this recently on my motor. If its a 200, I'd just replace the rings and be done with it. There is really no gain in performance or reliability in a new piston if the old one is in good shape. A 220 is a completely different story, from what I understand.

Clutch plates. I don't know, for me, I just go with the cheaper ones and replace them when needed. I beat them up pretty hard (you're supposed to with a 2 smoke) and change them often. It gives me a good chance to get into the motor more to inspect things anyway. They are so easy to change, it makes it simple.

They both boil down to preference. I'm sure you can find someone who swears by doing things any way you choose to go.

HTH

Pete
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OLHILLBILLY
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Post by OLHILLBILLY »

With a useable compression range of 95-151psi, 110-120psi isn't really bad, but it isn't really good either. If you have over 200 hours on the motor, personally, I'd spend a few extra $$ and put a new piston in it. You can ring it and get it to last a little while if your on a really tight budget, but a worn piston is going to speed the wear process on your cylinder plating considerably. Replates are $200+. Pro-X pistons are less than $100, and are the same as OEM, do yourself a favor, spend a little more now and save a lot latter.
My .02
2004 KDX 200.. Coupla mods
2009 KX250F.. Track Star
2007 Hayabusa.. Street Madness
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Post by Rjcapt »

>|<>QBB<
OLHILLBILLY wrote:With a useable compression range of 95-151psi, 110-120psi isn't really bad, but it isn't really good either. If you have over 200 hours on the motor, personally, I'd spend a few extra $$ and put a new piston in it. You can ring it and get it to last a little while if your on a really tight budget, but a worn piston is going to speed the wear process on your cylinder plating considerably. Replates are $200+. Pro-X pistons are less than $100, and are the same as OEM, do yourself a favor, spend a little more now and save a lot latter.
My .02
Hmmmm.

How do you define a "worn piston"?

If a piston is out of specs, diameter, ring lands, etc. by all means replace it. But a piston is considered a "non wear" item. It will, of course wear out, but unless something is wrong, not in 200 or even 500 hours.

Piston manufactures for years have extolled the virtues of replacing pistons at every rebuild. Wanna guess why?????

The only pistons I have replaced at every rebuild was on a top fuel motor I was on a crew for once. But I'm assuming you're not running 98% nitro under 60lbs of boost (on a wore out blower....).

Again replace the piston if you like, they are cheap, but don't expect any more reliability or longevity out of it. There just isn't a magic pill for that.

BTW, 'busa huh? Cool. I have an 06 -14 that I absolutely love.... I'll admit I have mostly chicken strips on the tires right now, but I do have scrape on my left front plastic that I didn't get from dropping it ....lol

Pete
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OLHILLBILLY
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Post by OLHILLBILLY »

Hmmmm.

How do you define a "worn piston"?

If a piston is out of specs, diameter, ring lands, etc. by all means replace it. But a piston is considered a "non wear" item. It will, of course wear out, but unless something is wrong, not in 200 or even 500 hours.

Piston manufactures for years have extolled the virtues of replacing pistons at every rebuild. Wanna guess why?????

The only pistons I have replaced at every rebuild was on a top fuel motor I was on a crew for once. But I'm assuming you're not running 98% nitro under 60lbs of boost (on a wore out blower....).

Again replace the piston if you like, they are cheap, but don't expect any more reliability or longevity out of it. There just isn't a magic pill for that.

BTW, 'busa huh? Cool. I have an 06 -14 that I absolutely love.... I'll admit I have mostly chicken strips on the tires right now, but I do have scrape on my left front plastic that I didn't get from dropping it ....lol

Pete
200 hours on a 2 stroke dirt bike motor is a lot of time in anybodies book. 100 2 hour harescrambles, or a whole season of riding for even a lucky to have a lot of time to ride person. Unless you just putt around, seldom ever getting on the pipe, that piston IS going to be out of spec by 200 hours. As I said, cylinder replating is a $200+ job anywhere, why try to save $85 and risk having to spend $200 along with the $85? Not to mention risking a complete piston failure from pushing it too far.
Maybe just me, but I always go with the "spend a little now and save a lot later" theory.

And yeah, the Busa is a good time. I've done a few track days on it even. I bought it new in '07, and it's been a pretty much do everything bike. Always fun to give the youngsters on their 600s and liters fits on the Saturday morning twisties rides. What do you think of the new 14R?
2004 KDX 200.. Coupla mods
2009 KX250F.. Track Star
2007 Hayabusa.. Street Madness
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Post by Rjcapt »

Well I'm old and stubborn (and sometimes even wrong), but I'd still be hard pressed to believe that one of these pistons gets wore out in 200 hrs under the worst conditions. I will agree that changing pistons (or anything else for that matter) may be good, relatively cheap insurance.

I have no idea how many hours are on the 97 that I just rebuilt, or how hard it was run, but mine checked out to be good. I'll pull it at the end of the season after I beat the snot out of it and see where it's at then. And I just had my cylinder replated as well. Who knows I might owe you a beer.

I haven't seen the new 14R yet. I can't imagine my bike being any better. At anything. 9 sec 1/4? Yup. 14 hour cross country? Let's go. Twisties? When and where. If only they didn't let George Foreman design the side panels. Oh well.... I only wish I were on a 600 in the really tight switchbacks. But then the road straightens out, and well.... I certainly don't have to tell you....
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David_L6
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Re: Replacement parts for rebuild. OEM, reuse or aftermarket

Post by David_L6 »

>|<>QBB<
danfree wrote:I decided to do a top end check on my 2005 KDX200. I bought the bike used several years ago and probably have about 200 hours on it after the purchase. Compression test was 110-120 psig. Not bad really, but I wanted to do it anyway. The piston and cylinder look pretty good actually so I may just reuse them and purchase new rings. Is there any advantage to get a wiseco piston kit? Or should I get a new Pro X piston. I am looking for dependability over performance. I am an old slow poke rider. Also my clutch plates are within spec, but wear is apparent. I filed down the grooves in the basket and was wondering if the wiseco or ebc plates kit was desirable. I noticed there are kevlar plates available, would they be more or less dependable for another 300 to 400 hours? Of course I could just try to replace every thing with OEM parts too. Any advice?
I am the "Replace it while it's apart" type. Especially if it's a bike I haven't owned since new or haven't re-built personally.

I'd put a new piston in it. I like Wiseco pistons. (I've run a BUNCH of Wiseco pistons in motorcycles and outboards - never had a failure.)

I have Hinson plates in our two CR250s and the plates that came with the Revloc clutch in my KDX200. Again, I'm a replace it while it's apart type. I'd replace the plates. I'd probably replace the basket too....

Once I've completely re-built a used bike I'll consider re-ringing only or clutch plates only, etc.
2000 KDX200 / 2002 CR250 / 2003 CR250 / 2008 TT-R230 / 2011 Brute Force 750 / 2012 Brute Force 750 EPS
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rbates9
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Post by rbates9 »

I would consider reusing the piston if it was in good shape but if you just had the cylinder replated than I would replace the piston and rings.
KarlP
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Post by KarlP »

I think the OP got all the input he needs on piston replacement......

If you do a search on clutch plates there is some good information. XR400 plates fit and have some advantages. They have a bit wider friction surface. I think my four innermost plates are XR400 and the rest are OEM.
'08 KTM200xc
'99 CR/KDX Hybrid with that RB stuff done to it
KX100 for the boy
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