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Duane Ausherman wrote:A head that needs to be decarboned has something wrong with it. The excess carbon is a symptom, not a cause.

Find and fix the real problem first. Then it will burn the carbon out in a few hundred miles.

I intend to find and fix the problem. I did not think normal operation of the engine would clean up gunk that may be built up on the head of a piston.

Manfred wrote:

Duane Ausherman wrote:A head that needs to be decarboned has something wrong with it. The excess carbon is a symptom, not a cause.

Find and fix the real problem first. Then it will burn the carbon out in a few hundred miles.

I intend to find and fix the problem. I did not think normal operation of the engine would clean up gunk that may be built up on the head of a piston.

You've not heard of the "Italian tune Up?" That's when you run it WFO (that's Wick Fully Out, historically) for a few minutes to burn out the accumulated carbon. I had an uncle who swore by it for his old (1960s!) Toyota.

Of course, like my VWs, WFO in that car would not attract the attention of the constabulary. Your bike may have different results.

Then there's the water sprayed into the carb trick that is also supposed to aid in burning up the carbon in a cylinder. Never tried it myself, but a couple people here (in the past) have sworn it worked.

I broke in the airhead just like I did the GS. Lots of acceleration then deceleration. Constantly changing speeds. I probably didn't push the airhead as hard as the hexhead, but I would acclerate up to 5-6k rpm then close the throttle off to decelerate. I really think it is more of a crankcase venting as the right side air tube always has a coating of oil.

How old/new is the engine rear main seal?

The engine rear main seal was replaced 9k miles ago along with all other seals on engine and transmission when the top end was rebuilt. There is no leaking going on. I went on a 350 mile ride two days ago. I just checked the oil level and it is where it was before I left, so maybe it isn't using as much oil as I thought it was.
I am wondering if some oils may foam more than others causing more to exit the crankcase breather? I have mostly used Valvoline MC oil, but I bought BMW (Spectro) and used it last oilchange.

We tend to define the main seal leak by oil dripping just under the transmission. There is another leak that is often the cause of oil consumption. pmonk commented on crankcase venting. If the rear main seal leaks the "other way" that means that it sucks air into the crankcase. It is possible for the seal to not leak oil "out" but to allow air to leak in.

That can be when the crankcase breather shows oil.

Diagnosing air sucking into the crankcase would be pretty difficult to diagnose wouldn't it?

pmonk wrote:Diagnosing air sucking into the crankcase would be pretty difficult to diagnose wouldn't it?

Not with a bubbleometer! (pronounced bubb-lom-etter)

Duane must have one.

pmonk wrote:Diagnosing air sucking into the crankcase would be pretty difficult to diagnose wouldn't it?

In minor cases it is diagnosed by replacement. In more severe cases it is indicated by a very loud honking sound at lower rpms.