KX Guru Racing

There are many reasons a head gasket will leak.
This article will cover a few of the most common reasons and potential solutions.

1. Head is not flat.
You might be able to lap it providing it isn't too bad.
If the warp is really bad you will have to have it cut.
And honestly it wouldn't be a bad idea to have the combustion chamber re-cut as there is some potential power there to be had

2. Cylinder is warped.
It happens... Again you might be able to lap it providing it isn't too bad.
If the warp is really bad you will have to have it cut.

3. Bad head gasket.
Regardless of which gasket you used, any of them can go bad.
However, If you used a Cometic or OEM your chances are very slim they sent you a bad one.
Replace your head gasket and use a OEM or Cometic.
If you want extra insurance you can use a product such as copper tack.
This is not a replacement for your head gasket, it is to be used on both sides of the gasket.

4. Wrong squish cut on the head.
If you had the head re-cut you better check the squish clearance BEFORE running it.
IF your piston knocks on the head, plan on replacing the rod and crank bearings.

5. Over tightened head nuts.
Take a look at the pic below.
This is how a standard cylinder looks after the studs have been pulled.


Over tightening head studs can cause the aluminum around the studs to pooch out slightly.
The fix is to take a counter sink (Doesn't really matter which degree you use) and chamfer all the holes around the studs.


This is what it will look like when done..

Just for grins, I like to clean up some of the areas where the water passages transfrer from the head to the cylinder.
DO NOT get carried away.
Just clean the very edge up enough to insure there is no material ready to come loose and go through your water system.

6. The alignment pin is too long.
If you had the cylinder decked, the head shaved, or you changed gasket thicknesses the pin may be too long.
Take a look at the pic below...




If the alignment pin is to long, you will never get the head to seal.
The solution is to grind it to the correct length or drill the alignment holes slightly deeper in the head and the cylinder.
Don't over do it... To deep will be BAD
Measure the length of the pin.
Then subtract the depths of the alignment hole in the head and the cylinder.
That will tell you if you have a issue.

Or, without a gasket, place the alignment pin in the cylinder hole.
Then install the head without a gasket.
Turn the cylinder and head on the side facing a light source.
IF your head is flat and your cylinder is flat you should see no light where the head and cylinder meet.




If there is no light showing you should be good to go..

7. Head nuts are loose.
When you install new studs use Blue Loctite and they should be tightened all the way down and snug but not tight perhaps 6 ft lbs or less.

Using never seize on the head nuts, torque the head nuts in a criss cross pattern to 6 ft lbs.
Once done, torque them again to 12 Ft lbs.
And finally to 18 ft lbs.

You could start it right away but if you used copper tack I would let it sit a hour or so...
Then, ride the bike normally for a hour checking for leaks.
At the end of a hour, check the nuts again to insure they are maintaining 18 Ft lbs of torque.