Rebuild stuff..

[Bill Hibbs]

I'm doing a top end on my 99 ktm 300exc. I've heard often one of the crank seals leaks and causes an air leak. How do you change these or This crank seal? Which side is it on? I was thinking about doing this while I had it apart anyway.

Another question. What would make me want to buy a new piston instead of using the old one? The old one is a little discolored and had a slight bit of carbon on the top but over all it looks fine. The cylinder's smooth and no scratches. I just want to make sure I'm not missing anything.

Overall the engine and powervalves are very clean. Just a little carbon but not too much really. I doubt I even needed to do a top end. It's been a couple years and thought I'd tear it apart to be safe.

Thanks!

 

[agitt73]

piston may look fine but it will wear down just like a set of rings which the cylinder is
so hard it dose not wear as easy the piston and rings

 

[Bill Hibbs]

Well, considering the piston kit was 280 dollars I'm just going to go with rings at 40 bucks a pop. Ouch!

I still need a step by step on how to replace that seal. It's on the ignition side. I thought it was a common thing. Maybe I'm wrong if no one here's heard of it.

 

[TM-Frank]

Remove ignition cover, remove ignition flywheel (you need a special puller tool for this, don't use a generic three-arm-puller!), remove old ring with small screwdriver or similar, pop new one in and reassemble everything.

 

[KiwiBird]

Bill, an easy check for the ignition seal is to remove the cover and spray Engine Starter fluid at the seal while the engine is running. If the seal is bad the rpms will increase.

This is a good method for checking for almost any intake leak like base gaskets or inlet manifolds. Make sure the overspray doesn't go into the aircleaner or you will defeat the purpose of the test.