Piston and rings: HELP!

[TD3]

I bought a stock new "factory" KDX200 piston and rings on ****. The part numbers are definately for my 89. The piston seems fine, measured out perfectly, until I went to install the rings. The bottom groove is fine, the ring slides in and moves freely. The top groove on the piston appears to be slightly tapered on the top of the groove. Both rings I received are identical. Does the KDX stock piston require 2 different rings?

I looked at the old set and the top groove is tapered and the ring has grinding marks on the inside of the ring. Did someone grind the inside top of the ring down to make it fit? Seems like a hack way of doing it, no? I don't want to order a new ring set from BikeBandit and receive two more identical rings. Please respond if you have any ideas, remember I'm talking about a Stock factory piston and ring.

Thanks in advance.

 

[dsndblm]

I would measure the ring grooves on the piston with a good set of calipers.Make sure the grooves are the same all around the diameter of the piston. Measure the ring thickness, they should not vary. Do you have a manual for the bike? If not, now would be a good time to get one. All the service limit dimensions are in the manual. Are you sure you have the rings postioned correctly to align with the pin on the piston?

I remember seeing some marks on my rings but I dont think they were grinding marks. They looked to be more of a mark left when the rough edges were taken off the rings during the deburring process.

 

[jdbrusch]

Should be able to put the rings in either groove,only thing to keep a eye on is that they go in the right way,they have a small letter or number etched into the top of the ring at the end gap and this faces up.
Not sure if this would make a difference but I recall the piston was upgraded for the 90 model for durability and am not sure if they may have changed ring design also. :think:the upgraded piston and rings do work in the 89.

 

[kdxepp]

Do a search on rings. I had the same question on my '94 ring job a couple years ago. Found out the top ring has a tapered profile. This info is NOT in the Kawa. Svc Manual. J.F. actually verified this as well.

 

[kdxepp]

Here ya go. I found it....
OK, Just to put us all straight, I called JF today to order the KIPS rack rod seal and maybe a piston. He said that the top ring groove is tapered and the bottom groove square. Therefore the rings ARE different. The shinier of the two is the tapered (cross section) top ring, which can be seen with the naked eye. I mic-ed the piston and bore and both fell exactly at the high edge of the standard limit per the manual, so I'm staying stock original. Remember all of this info is about OEM parts, aftermarket pistons etc. may be different. Thanks to everyone for the input and thanks to Master Fredette.

Search "Ring" and my screen name "kdxepp" if you want the whole story.

 

[TD3]

Thanks to all that replied!

Great find kdxepp!

It looks like I was sent 2 bottom rings (the package was opened...grrrrr). I guess that's the chance you take with e.b*y! I only paid $34 for the piston and rings, or should I say "ring", since I now need to buy another set.

I'm guessing I should be all set if I order a ring set from bikebandit.

Thanks again, this forum is a great resource for information!

 

[TD3]

Follow up

Well, I got the correct rings from BikeBandit and all went together fine.

I bought this 89KDX200 a month ago to ride with my kids this summer. Since it was -17f the morning I picked it up I didn't even bother to start it. The guy I bought it from seemed honest enough. He had only owned the bike for six months. He got for his 14yr old who was scared to death of the power and went back to his 4-wheeler ;) Once I got the bike home I decided to clean it up a bit and check the top end. Well, there was a ton of carbon build up so off came the cylinder. I then searched around the Internet for info on KDX's and found this awesome forum, JustKDX.

Based mostly on info found here, so far I have:
*Removed and cleaned the KIPs assembly
*Replaced the piston, rings, wrist pin and cage bearing
*Removed the stock pipe inner insulation and mesh
*Modified the stock muffler, repacked and shortened 5"
*Installed Boyeson 607 reeds
*Rejetted as per JF
*Modified the air box lid
*Changed tranny fluid, replaced with ATF Type F
*Replaced worn clip on kickstater

I completed the above work this morning. I just couldn't wait to hear it run (and check my work for leaks and or other issues). So I shoveled and scraped a path down my driveway to the pavement. The bike started on the 3rd kick and boy does it sound nice. It's very crisp and a bit louder than I expected. I've been out of the offroad bike sport for a good 15 years (my last ride was a 84 YZ125) and I'm really looking forward to riding this thing. I did putt up and down the driveway a few times but that was just a tease.
Anyhow, I thought I'd take a minute a share my story and say THANK YOU to all that take the time to post and answer questions. I am amazed at the amount of GOOD information available on this bike.

Thanks again,
-Mike

 

[2wheeler]

Have Fun!!!!!!!!!!!!!!!!!!!!!!!!!!1