Good news Scott!  At this time,

I really doubt you will need a leak down tester.  The tool is nice to have for diagnosing valve and ring issues, but right now, you don't need to use it.   It is one of those tools that will sit in the tool box for a long time between use.  Unless you are working on other stuff.  Best if you need a test done to borrow one or pay the one time shot.   LOL, I don't have one in my box because I know a couple of places to borrow one from.  

After looking at you plug pictures it is clear you don't have an oil issue. The black soot should clear up with the needle in the correct spot.

Ride it and enjoy it.  St.

I’m presuming since you verified that the needles were in the correct position, that it was also verified that both needle jets are 2.68’s. Also important.

Posted by: @4949

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I’m presuming since you verified that the needles were in the correct position, that it was also verified that both needle jets are 2.68’s. Also important. 

BMW was one of the first to start complying with early Federal DOT standards. This means the jetting tended to be on the lean side on all "US models". They could do this because the Airhead runs much cooler than other motorcycles, but still valve seats and overall performance suffered in the long run. 

David's advice is spot on. It is possible to find these bikes fitted with leaner 2.66 and 2.67 needle jets, but they should with 2.68's (listed as the "European model" jetting in many resources). This will cool the combustion down, give you back your acceleration, as well as give you a "ideal" plug color when you do your "plug chops" on the freeway.

Hey everyone, 

It's been a while but I have updates on my original post.

I did leak down test - all's well!  No leaks in either cylinder.  A pleasant surprise.  I checked the timing with a strobe - it's dead "on." 

The carbs looked good, tbh, but I took them apart and replaced the o-rings and gaskets (aside from the butterfly o-ring).  That done, I adjusted the idle mixture screws more aggressively than before:  now the left cylinder screw is open (only) 1/2 turn, the right is open 3/4 turn.  Idle is much smoother than before.  The left cylinder is a bit thumpy compared to the right, but it doesn't shake the bike, and it smooths out when at operating temp.  The carbs are sync'd from idle throughout the rev range.

A benefit of the mixture adjustment is that the rich condition is much improved. See the picture.

The right plug is still a bit oily.  There's dark coloration - glossy/satin and it baked on, unlike the velvety powder that used to accumulate on the left plug. I just noticed that the previous owner put a helicoil in the right spark plug hole...

Since the leak down test is good, the oil is probably coming from the breather valve.  So I took a look at it, thinking that I might install a modern reed-style valve.  Guess what?  A reed valve was already there!

The bike is running great. I got 41 mpg on a country ride this morning.

There are still things to sort out: replacing the gaiters (sigh) and rerouting the turn signal wires

Hey Scott, nice to see the update and news.  

The left plug looks fine, how about a picture of the right?

Yes, some oil mist could cause a bit more oiling of the right side plug.  Be careful not to over fill when doing an oil change.  

Take a look or search other forums and Snowbum for information on this issue. This has been an issue for years with either complete success in solving or living with it and not worrying.  

Long term riding regularly will perhaps sort out the issue.  Get a few more miles on. 

Personally at this stage I would ride the bike and not worry.  As long as oil consumption is not excessive and you aren't fogging for mosquitos, you will be fine.  St.