Hi all, I'm new to the KTM forum, and am a new KTM owner.  I usually perform basic maintenence myself and leave motor work to the pro's, but figured I owed it to myself to do it myself.  So I apologize if these questions seem obvious to some..

I have ordered a new top end kit from my local dealer, went with the vertex rather than the oem based on the 130 or so dollar difference between the two.  The piston I removed was a vertex, pretty out of spec, but wasn't terrible.  Was this a bad call?  I ride a small track at my house, and up north twice a year or so.  No real track use for the bike.

When I removed the cylinder I noticed that I would not be able to use a tourque wrench for the installation.  What is the best way to be sure the tourque is correct?

Other than the top end and the forks seals it is a real pretty bike, and ready to rip!   I'm amazed at the difference between it and my kx, which I thought was pretty nice.  The fit, finish and feel of the bars and levers, the shifter, bet the kx has a little envy, it might not get much use anymore.

Here are a few pics...


the tear down


Thanks for looking, and any advice you have.  Oil and mix ratio is a big one for me right now.  Have a great day...

Vertex supplies the OEM piston and Motion Pro(I think) makes an adapter for your torque wrench.

Edited by timmyp8823, 21 February 2012 - 07:57 PM.

timmyp8823, on 21 February 2012 - 07:56 PM, said:

Interesting....I wonder what the difference is then?  Piston A was a ktm piston kit for 265 bucks, piston B was the Vertex and was 122 or so.  Maybe the piston I pulled is the original stock piston?  I was told it had a cp piston when I bought it, apparently the bike came with the stickers, not the piston.  Not suprised about that.

I will look for the tourqe wrench adapter, thanks for the info.

I generally mix the kx at 32-1, Klotz supertechniplate with premium pump gas.  Will that work for the ktm?   I've heard everything from 40-1 to 50-1, depending on the type of premix oil.  I would like to run both bikes the same if possible.  The kx is pretty dialed in.

Last one for now... I usually run bel ray 80 weight gear saver in my tranny, I assume this will be fine for the ktm.  I live out of town a bit, these oils are available locally, and I have been happy with them, but if the ktm is a different animal I don't mind getting different oils.
Thanks again for the help, hope to be putting the top end in this weekend!  Michigan has not had much for winter this year, track is snow free!!!!!

Sounds like you're on the right track. Belray is good for the trans. I like to run the 125's at 32/1 also.Vertex would have been my pick.Measure the base gasket you take off. You will have a choice as to what goes back on.

Thanks wheels, I learned about the base gaskets while ordering yesterday.  decided to go with the "stock" thickness, I'm old, and am pretty sure the bike will be fine for me.  No real need to up compression etc.

I really appreciate the replies, if this bike works out for me I might sell the kx and try to get my hands on a 200 mxc.  Any good or bad info?  Always wanted one, but shopping for used ones is literally the needle in the hay stack.  Don't tell my wife though...lol

I have a 04 125SX
I had a steel sleeve installed and went 2mm over, so now it is a 134cc
Runs great since 2008, never been apart since then.
I ride often and ride it hard.
Lately I had a good fall so I am taking a break until I get all the damage
repaired, just need a front wheel now.

I have used AMSOIL for lubricant and have mixed it 50:1 but the last few years
I have used 100:1 with no issues except for super crisp throttle response and
very low smoke.
I also use the 10W40 motorcycle oil in the transmission and no issues there.
since 2008 I have only changed the trans oil once, suprised that it was full.

Well good luck on your build I have had alot of great times on my KTM!


Javier