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Head gasket - slow leak 2000 ktm 200 EXC

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I just finished a complete top and bottom rebuild on my 2000 ktm 200 exc. I have a very slight leak from the head gasket (about 1-2 drips per 12 hours). The bike starts and runs well there are no signs that coolant is leaking into the cylinder.

The 2000 ktm 200 has two gaskets an O ring that seals the cylinder, and a regular gasket that seals the coolant. I torqued the bolts in the head down to the correct settings according to the service manual. I used tusk gaskets on the rebuild. And sent the cylinder off to US Chrome to be replated.

What should I do? I have three ideas.

1. Run it and hope it clears up when the motor heats up.

2. Replace the head gasket.

3. Replace the head gasket and add some high temp gasket sealant of some sort. If this is the route to take what kind of sealant would you recommend?

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I got the habit of placing vaseline on both O rings then torquing to spec in a star pattern. Worked well for me each time (no leaks).

Theory behind it is that it keeps the O ring in place while you torque it down. 

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I would pull it back off, check the head to make sure it's flat.  Lap it on a piece of 400 grit sand paper on a FLAT surface.  Usually after a few strokes you can see whether it is flat or not.  Put copper tex or gaskcinch on the gaskets and bolt it back together.  Hoping it fixes itself is great, but often a path to a larger repair.  

 

Do not use RTV, or any self gasketing material, use a gasket dressing compound.

 

I'm not sure if the older style KTM heads are able to be lapped by hand???

Edited by poldies4

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I got the habit of placing vaseline on both O rings then torquing to spec in a star pattern. Worked well for me each time (no leaks).
Theory behind it is that it keeps the O ring in place while you torque it down. 

This is before they had 2 O rings in that year they have an o ring on the inside (cylinder) and a paper gasket for the outside (Coolant).

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I would pull it back off, check the head to make sure it's flat.  Lap it on a piece of 400 grit sand paper on a FLAT surface.  Usually after a few strokes you can see whether it is flat or not.  Put copper tex or gaskcinch on the gaskets and bolt it back together.  Hoping it fixes itself is great, but often a path to a larger repair.  
 
Do not use RTV, or any self gasketing material, use a gasket dressing compound.
 
I'm not sure if the older style KTM heads are able to be lapped by hand???

What do you mean by lap it?

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12 hours ago, pastorjosh said:


What do you mean by lap it?

https://www.oldminibikes.com/forum/engines-and-modifications/52353-flat-lapping-cylinder-head.html

 

I had to do this to my sons 65, did the rebuild and had a drop or two of coolant coming out.  It was decievingly easy, and fast.  Like I mentioned above, not sure if the older heads can be done with this method?  If not, you might need to send it out.  Generally I've found a small leak like yours is from the head warping.  Often gasket dressing will solve the problem.

Edited by poldies4
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Thanks TeamTT. I will try and Lap the head and see if there are any imperfections. I appreciate the link. Would you have a preference gaskcinch or coppertex? They seem to be the same price spraying it on however seems a bit easier.

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Probably coppertex, but have and use gaskcinch.  Whichever is easier to pick up should work fine. 

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Just lap the head and get a new o-ring and gasket. I do not recommend using any type of sealant. 

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Thanks for all of your input on this guys. I finally got to work on the bike today. Since nothing was leaking into the motor I figured it couldn't hurt to ride it around a bit to see if the leak would clear up when the bike warmed up. I rode it around the block till the neighbors got mad it still had a very slow leak after the ride.

I removed the head but couldn't lap it since it has a small protrusion that goes down into the cylinder and mates with the inner o-ring. I cleaned up the mating surfaces and reapplied the gasket using a very thin coat of Yamabond 5 on the gasket (It seemed to be similar to gaskcinch and I had it in the garage). So far so good with no leaks. Thanks for all the help you guys offered.

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