New top end for buddy's 125SX

[Kyleb15]

Ok guys, I need some top end info. I ride with a friend of mine and he has a 2004(I believe) 125SX. He dosent have but I am guessing 10hrs on it, I am not really sure. He is a friend but we are not really good friends yet. I want to save him a little money, get to be better friends and show him how to do a top end. I regulary do the top ends on my 2000 Yz 125 and it is cake. What I bascically need is some info on the KTM top end change. Also what kind of cylinder plating is there? Do I need to hone it? When do you KTM guys usually do your cylinders? 20-30hrs? He doesn't race or ride it too hard but he does ride it on the pipe. Thanks

P.S. What would a dealer charge him to do a top end?

 

[elf]

cylinder plating is the same as your yz, Top end should last about the same as your yz, under the same riding conditions. You don't need to hone, just clean it up with a scotch brite pad.

Dealer would probably charge a lot, the stock ktm parts are pretty expensive. Better off doing it yourself with a weisco kit.

 

[Kyleb15]

I just read about all this y-axiz and x-axis stuff. What is this about? Do I have to measure alot of stuff on the KTM or can I just put in the kit. Also I read about different base gaskets, what is this?
The Yz is easy but after reading that I am a little worried. Thanks

 

[elf]

Really the only thing you need to check is the X . That is changed with the different base gaskets. So try to use the same thickness on the base gasket. If you want to check The X , put the cylinder on the bike and bolt it down. Then move piston to top dead center. The outside edge of the piston should be even with the top of the cylinder.
The ktm cyl and head is a little different than the yam. When you check the X make sure your looking at the inside lip where the o-ring sits.
The Y is for the powervalve, If the bike runs good now just leave it alone. you can take it apart and put it back together and that wont change the y
One other thing, the pv arm that comes out of the cases fits into a arm that comes down from the cylinder. when reinstalling the cylinder make sure that the two get conected properly.

It might sound complicated but its really not any harder than your yz. I know, I have a 00 yz125.

 

[Kyleb15]

When you buy a new gasket set, like Cometic, will they have the different base sizes in there? It would be better to use a gasket a little bigger than what the x is, right? For the squish factor. Is there a top dead center mark anywhere or do I just call it by looks? Thanks

 

[elf]

No, they come with one. I think its a .25mm its middle of the road, there are thicker and thinner ones.
You can go either way on the X a small ammount. Thicker gaskets will give you more squish and a little better top end power, thinner will add a little low end.
Take off the flywheel cover and you can turn the motor with the flywheel by hand to find top dead center. You should be able to get real close by looking at the piston while moving the flywheel back and forth.
Btw most of the base gaskets are cheap from the ktm dealer so it might be worth your while to take the one off the bike and try to match one up at the dealer.