[Trackrash]

Well at this point we are just guessing.

Is the motor using any oil?

Also, the mag motors are known to pull head studs. You should confirm that during the rebuild that case savers, or inserts were used.

But the first thing I would do is a leakdown test.

You can also get a good idea of valve guide wear by listening to the valves when running. If that valve is clacking louder than the rest, that could be a clue.

You can also pull the valve cover and use a screwdriver to gently try to move the top of the valve spring and retainer up and down. If the guide is very worn it will move easily. Compare that valve to one of the intake valves.

If you are getting smoke on start up out the exhaust, I would suspect rings.

If you are getting a drip on the top of the exhaust, that could be a leak from a number of sources.