99 770 Air leak ???

[37fordtruck]

I have a 99 TS 770 with a new top end that is 1.0 mm over stock bore. I followed the breakin proceduce of SBT for the !st tank. Today I was riding on the 2nd tank of gas and being careful to no hold it wide open. I was about 2 miles from the ramp when I got caught in an electrical storm and begin to run about 45mph. After about a mile it made a funny sound and quit pulling, although it would still run. When I pulled the plugs the front cylinder was ash gray and the back was black and slightly rich.
Why would the front cylinder be lean and not the backcylinder? An Air leak is all that I can figure. I assume that at high speed the air leak leaned out the mix in this cylinder.
Any information would be greatly appreciated.

[Technical Support]

Either an air leak or something wrong with that carb - you should pull it out and pressure check it, and go from there.

[37fordtruck]

Since the first post I have pulled the engine and found the damage. The piston has a hole about 3/8 by 1/2 inch, which is in the middle of the piston. The strange thing is the hole is tapered from the top to the middle and from the bottom to the middle. From either side it apperas to be knocked to the other side, is this normal?
The plug was grayish white and the gap was not closed, also the head has no marks on it. I would think this would rule out foreign material from parts other than the piston. This cylinder is full of tiny aluminum particles, from the piston. I did not find any other damage, such as a broken skirt.
You said their could be a problem with that carb. It has a single carb that feeds both cylinders. Does this confirm the air leak?
Should the crank seals be reused or replaced? Can I apply some type of sealing compound to them and reuse them?

[dank]

That is the result not the cause of your problem.
Either that carb is cloged and running very lean or there is a major air leak with the front crank seal or reed cage/manifold gaskets.
You should be running BR9ES or I use BR9EYA plugs.

[37fordtruck]

I am running br9eya plugs. Is it possible that the oil line is blocked going to that leg of the intake manifold, it has only one carb.
I still think it was an air leak. Can crank seals be reused or should they be replaced when the cases are split?

[Technical Support]

That type damage has nothing to do with oil, it's detonation. Seals can not be reused.