REBUILDING 2004 KTM 125sx engine

This will be my first time rebuilding any sort of engine. I know the previous owner raced this bike and definitely know it needs a top end rebuild.

What I want to ask of you is whether or not I should try to tackle this job myself because I'm worried about the complexity of the bottom end and whether or not I can do a high quality job. If I should, what kit is the highest quality/most recommended?

If you recommend I not do it this time around does anybody know reliable rebuilder around the Tulsa, OK area?

Ryan

Doing a top end job is not a hard job to do, get a manual, a few tools and a weisco pro lite kit.

If you want the highest quality, get OEM parts. That's why KTM,s have such good reliability.Clinton County Motorsports has a 20% discount on all on-line orders. Just click the coupon button, upper right hand corner.

There are a couple of threads in the FAQ that will help. I recently did the topend on my bike, and it is a fairly simple job. If you are mechanically inclined or have a friend that is, you shouldn't have any issues.

Search "top end" in this forum and you should find one of my pictorial threads on my top end rebuild. My PV pictorial is in the FAQ, that should help you with that.

Moose makes a good gasket kit. Any of the top brand piston kits will work well. Vertex, Weisco, Wossner.

I am on my second Weisco, 200+ hrs on the first.

I am fairly confident I can handle the top end rebuild.

What is involved in a bottom end rebuild? Things such as crankshaft bearing?

that requires removing the clutch, splitting the cases and getting the crank out. Then take it to a shop and have them do the rod bearing. You probly dont need this tho if the bike was cared for and jetted right.

If you have never done a bottom end than don't do it yourself.

Allright, should I do the bottom end or not? I dont want to be riding in the middle of summer and then have something happen and have to wait 2 or 3 weeks or whatever for it to get fixed.

BTW I plan on doing mostly trail riding but maybe try to enter a couple motorcross events and see how I like it.

well if thers up and down movement, go for it, if not, just do the top

Just check the crank. Has it had a bottom end rebuild? If it hasn't had one then go ahead and get it done it'll save you time and money on down the road. :thumbsup:

I disagree, it either needs a bottom end or it doesnt, if you are racing every weekend then it could be preventative maintenance, but for just riding like the average guy does then it doesnt need it as regular maintenance.

What did you pay for your 04 ktm? I"m looking at buying an 04 125sx atm.

Well I was looking at the Wiseco forged pistons and I have another question... It says on the site that cylinder replating for the first and third kits are required but not the second product. I didn't even know that replating might be a mandatory (cost piling up....). Now I was looking at the second product and think that would be the right one (I haven't measured the bore yet), except I thought there would only be 1 ring as opposed to 2?

http://wiseco.com/ProductSearch.aspx

maxamillion125 just pay what you think the bike is worth. If you find out that you paid a little more than you should have then you'll know better for next time around

KTM sizes their cylinders after they are produced, a number I or number II, they sell pistons to match. These are only a few thousands off. It is common proceedure to use a number II piston in a number I cyl after the first piston is worn out. This makes the piston tight in the bore again. Its OK to do this cuz they are so close anyway and the number I is now worn nice n smooth and a liitle larger. So it may be a similar issue with the Weisco, tho I didnt look at your link.

What did you pay for your 04 ktm? I"m looking at buying an 04 125sx atm.

I paid $1400 for mine last May. I think I got a great deal.

We owned the same bike from new.It was well maintained but we did lose the lower crank bearing after several years of use.If you havent owned this bike from new I would definately get the crank rebuilt.When we lost ours we had to get the cylinder rechromed because of it.Its more money right now but it will be less in the long run.

Also I have a brand new SXS head with the three inserts for this bike if you are interested.

Tom

Im sorry I should have said we lost the lower rod bearing.

Edited by Tom_Kramer
misquote
KTM sizes their cylinders after they are produced, a number I or number II, they sell pistons to match. These are only a few thousands off. It is common proceedure to use a number II piston in a number I cyl after the first piston is worn out. This makes the piston tight in the bore again. Its OK to do this cuz they are so close anyway and the number I is now worn nice n smooth and a liitle larger. So it may be a similar issue with the Weisco, tho I didnt look at your link.

My cylinder is a #1, I installed a #2 piston, which are what all the Weisco's are I believe, or what I was told, that are 64mm. My ring gap was perfect.

Tom thanks for the offer but I actually bought KTM OEM piston kit today. Heard some good things and bad things about every aftermarket manufacturer (of course) so decided to try out OEM. Also will be asking around for shops who do bottom end rebuild... Just wondering whats involved in that other than lower connecting rod bearing and main end ball bearings? Perhaps replacing connecting rod itself as well. Probably not replace the crank itslef.

if you are going to do a rod rebuild then I think its cheaper to just buy a complete crank assy. Its seems also that recently I saw on a post about a company that is making a rod kit, Hot rod or something like that.

Create an account or sign in to comment

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

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now