Jump to content
Sign in to follow this  

Should I get a new Top end?

Recommended Posts

Hey everyone this is my first two smoker and my first KTM. Its a 1996 300EXC. I bought it for 900 hundred bucks but it needs some work. I was wondering what you guys think about replacing the piston? I was already planning on replacing the rings but was on the fence with the piston. Here are the pictures of the piston head and a somewhat good view of the cylinder wall. There is a little wear around the intake ports but that's it.

100_4239.jpg

100_4236.jpg

100_4235.jpg

I looked on the Wiseco web site and the whole top end rebuild was about $200.00. Should I go with an after market piston and a set of rings or order a set of stock parts? Here is a link to the Wiseco site that has the bike info on a 1996 piston. Now it says I need to re sleeve it or re-plating is required. Do I absolutely have to do this? Any other tips are appreciated.

OK so I did some price checking and for an OEM piston assembly they want $320.00 not including gaskets. Then I can get the Wiseco piston kit for $175. So I am going to go with the wiseco kit. I took off the jug today and got a better look at the piston. There is a wear mark on it. I can take my nail over the area and feel the groove on it. I take it its time for a new one for sure right? Or would some fine sandpaper do the trick? Heres the picture of the wear on the piston.

100_4248.jpg

Thanks guys,

Derek

:)

P.S. Here is a picture of the bike the day I bought it. Its in rough shape but I have all kinds of pictures of my rebuild that I'll post once she is all done and running.

100_4144.jpg

Share this post


Link to post
Share on other sites

If it was my bike, I would just replace the piston and have everything checked while its all torn down.

Share this post


Link to post
Share on other sites

I would use stock parts, put in a piston too. No plating neede unless flaking off or worn thru. The stock stuff lasted all these years, why go with anything else??

Share this post


Link to post
Share on other sites

Go with the stock stuff it may be a bit more expensive but well worth it in the long run.

Share this post


Link to post
Share on other sites

i did a top and bottom end plus labor for around $400. I would look around for places that seel the same parts for cheaper. Its probably good idea to redo the top end rince you have it all out. If it hasn't been rebuilt in the past year or two its defintely time

Share this post


Link to post
Share on other sites

its only time if its worn out, to get worn out it has to have been ridden quite a bit thru the years. Im guessing a bike this old should be to that point. BUT it could be a real low hour bike and may not need it, measure and see for sure. It wont hurt anything to put new parts in, maybe just needs rings, you will have to decide. A good cleaning of the power valve parts will make it run like new again.

Share this post


Link to post
Share on other sites

I have a 97 300 exc and my cylinder is still in really good shape. Just hone it

with some wd40 and it will clean right up. I run the wisco pistons, they are

way cheaper than a stocker and they last a long time. I do a topend every 2

years and I have had no problems. these older ktms 95-97 are great bikes. They have a ohlins shock that works better than the wp stuff on the 98-07 bikes. I have had mine for 11 years and I still cant get rid of it. Ive ridden the newer 300's but I still like my older one.

Share this post


Link to post
Share on other sites

OK so I did some price checking and for an OEM piston assembly they want $320.00 not including gaskets. Then I can get the Wiseco piston kit for $175. So I am going to go with the wiseco kit. I took off the jug today and got a better look at the piston. There is a wear mark on it. I can take my nail over the area and feel the groove on it. I take it its time for a new one for sure right? Or would some fine sandpaper do the trick? Heres the picture of the wear on the piston.

100_4248.jpg

Share this post


Link to post
Share on other sites

that is a problem. The rings look as if they are high right there and it looks like the rings have some smear to them in the photo. Are they stuck or free moving? Remove the rings from the grooves and check again. Also look at the plating in the cyl for this same rub mark. How bad is it?? Try buffing it off with a scotch brite pad.

Share this post


Link to post
Share on other sites

Also might check cheap cycle parts.com for the OEM parts they seem to be about 60 cheaper than anywhere else I have seen for a KTM piston kit

Share this post


Link to post
Share on other sites

The rings move freely within the grove. Even though there is a visible witness mark (discoloring) of the cylinder wall, the cylinder feels smooth like the rest of if the unaffected areas. The piston on the other hand, has some small groves to it. As mentioned, if you take your finger nail and slide it across the piston, your nail will sink into this small groves, not the case on the cylinder.

This on the ares right next to the exhaust port.

Should the piston be replaced at any cost?

Share this post


Link to post
Share on other sites

I would. for what its worth you dont want to have to be in there again anytime soon do you.

Share this post


Link to post
Share on other sites

ok then, just clean it up n put new parts in it, make sure you clean the power valve while the cyl is off.

Share this post


Link to post
Share on other sites

That is a pretty good groove in the piston, I would replace it if it was mine. Clean the bore up and see how it looks. CJ

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×