Rattle with new piston ???

Hi,

Hope someone can help me, as I'm unsure what I can do to remedy the problem I'm having.

I own a 2000 KDX200 and recently had to replace the output shaft, due to the splines being badly worn. I had bought my bike 2nd-hand back in the spring, had ridden it nearly every weekend all summer, and decided to freshen the top end while I had it torn down.

When I removed the jug, I found the cylinder and the piston to both be in great shape. Since the had never had any top-end rattle, I cleaned the piston, lightly honed the cylinder, then cleaned it, installed a new set of rings, and reassembled the bike. When I started it, the bike had slight increase in compression. It also had a noticeable rattle in the top end... especially during idle. :yikes:

Next, I removed the jug again, replaced the stock piston with a Wiseco Pro Lite, and replaced the rings again (with those accompanying the Piston). When reassembled, the bike still rattled. :yikes:

Any ideas?

I'm wondering if the added compression might be causing another part (such as the small-end bearing), to fail? I'm also wondering how I might be able to tell if the previous owner had ever replaced the rod with a Hot Rod or such, and if so, would the Hot Rod require a different small-end bearing than the stock OEM?

2000KDX200

Mr.250 said:

Rattling............I am afraid to say it but.....your bottom end might need to be overhauled.

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Does it make any sense that I could ride the bike into the garage (without it rattling), tear it down, replace the rings, and suddenly it rattles? How could that be the bottom end?

gowen said:

What is the rattle? Is it a tap tap tap? Or a clunk clunk clunk? Does it do it pretty bad when idling and go away when revved? Give more information. I've had 3 KDX's. All have rattled when idling and it is due to the powervalve. If it rattles when the throttle is hit or let off, it is a bearing or slap, but if it rattles while idling and then leaves when revved, that is a typical KDX, check the JustKDX forum, they all have to live with it.

Click to expand...

Hi,

Thanks for your input.

I ride with my son-in-law and grandson. We all three have KDX200's. My bike definately rattles more than either of theirs. It didn't rattle like this until we tore it down to replace the output shaft. When I rode it into the garage, it was running fine.

The first time I reassembled it, since the cyclinder and piston looked great, I tried just putting in rings to freshen it up. As I mentioned, when we started the bike it rattled. I then tore it back down and replaced the piston and rings. Again, when reassembled, it rattled.

The rattle definately sounds and feels as if it's coming from the top of the cylinder. We did clean the Kips valves by removing the cover from either side of the cylinder (with the cyl off), and blasting it with carb cleaner.

Since I didn't have a small-end bearing, we didn't replace that. I'm going to pull the bike down this weekend, check the cylinder again, and replace that bearing to see if it helps.