Thanks to all for great input. At Richard's suggestion I checked the spark color. It looked ok, but not blue, so I went looking for info on that subject and a comment showed up regarding the dreaded pinched contact wire. I remember doing that to mine some time ago, but I thought I had 'repaired' it, as I haven't had any symptoms and, I figured incorrectly, if the points weren't working, both cylinders would be affected, not just one. Well, you can guess the rest of the story. I don't understand how the bike even ran on one cylinder as the wire was totally sliced through. I guess she just wanted to get me home, and I appreciate the hell out of that. Replaced said points wire and all (mostly) is good. Still a slight misfire after coming off choke, but at least she doesn't want me to pull the heads yet (I was reviewing the process for that when Richard's post showed up). Well King, this case is closed.
Congrats !
Sorry to push so hard, but I knew the issue had a very low likelihood of being internal to the cylinders. And I definitely knew opening up the top end(s) would bring a significant expense.
Now that you can thoroughly warm up both sides, you'll need to re-balance the carbs. Once for idle using the Idle Speed screw, and a second time at 1500-1800 RPM using the throttle cable adjusters.
"We always get our man !" 🤣
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
So good to have those “Eureka!” moments!
I had an situation years ago when my bike would just randomly quit, then restart. I could hardly put 2 and 2 together trying to find the issue. Then I found it! A set of points I had installed the previous season was a little wonky, and the point spring was able to touch the mounting screw below. That’ll make it stop! Eureka!
That is a tight fit. I know if you don't get that wire holder just right the points sit on top of it. I never thought it would interfere with the spark, but that sounds logical. I'll recheck mine - the points have been in and out a few times in the last couple of weeks! BTW, what kind of grease do you put on the pad - dielectric?
Just a smidge of lubricant, photo attached.
The old stuff on left, then new stuff I bought. Enough for 40 lifetimes.
That is a tight fit. I know if you don't get that wire holder just right the points sit on top of it. I never thought it would interfere with the spark, but that sounds logical. I'll recheck mine - the points have been in and out a few times in the last couple of weeks!
Thoughts...
• Not only check the points, but also lube the auto advance unit and replace the AAU return springs. Tighter springs will retard the advance curve making the ignition much better suited for modern fuels. Remember, the OEM AAU was constructed for 100+ octane fuels which are no longer sold.
• On my own bikes, I have the front engine cover ON/OFF so many times that I find it handy to glue the "points wire" (mechanical or EI) out of harm's way by using a dab of appropriately located silicone sealer. Common silicone sealer has an adhesive quality that is strong enough to hold and electrically/ thermally insulate the wire. You'll need to wipe the area of application with alcohol to remove all oil, and you may need to make the wire behave for 20 min with a small strip of duct tape. But it's a great help... and if it needs to be undone to get to the cam chain, then it's completely reversible.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
You rebuilt the carbs...did you also replace the needles and needle jets?
Just a SWAG since the bike isn't here, pull the gas tank and see if one of the choke cables has pulled out of the splitter. An improperly adjusted set of cables can sometimes allow the cable end to pop out and hang when you turn the handlebar.
Also swap spark plugs.
Let us know what happened
NAPA sells ML 1 for distributor cams. Same application.
Bob
@1405 replacing the pinched points fixed the non-firing cylinder and I thought it was up but now get a bad spot between off idle and about 2k. Just before all this mess I rebuilt the carbs (my first time) and, as with other first time events, I probably gooned something. Although, it did work pretty well for a while. It's February, and I want to replace the leaking pushrod tube seals so I'll do that and probably replace the bings with the set of mikunis I have and also try an electronic ignition. Thanks to all for your great advice! Hope to see on the road.
It's February, and I want to replace the leaking pushrod tube seals so I'll do that and probably replace the Bings with the set of Mikunis I have and also try an electronic ignition.
For your own sanity, please DO NOT install both at once ! Install one or the other, get it running great, then proceed to the second.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
@wobbly Not sure what you're saying here, Richard. I have the Bings installed and I think they are the current problem, whether they are out of adjustment or something else. I am able to get them balanced OK with the carbtune, at least at idle, but they are stumbling up to 2K RPM and running rich on one side so I'm going to switch to the Mikunis, when I put the jugs back on after replacing the seals and cylinder base gaskets 'cause I'm tired of dickin' with the Bings. I'm pretty much halfway insane, so going the distance won't be much of as jump. My wife is a psych nurse and I'm her long-term case study. Why else would I ride an almost 50 year old bike?
You'll be creating a 2-variable problem, which normal humans will find daunting to solve.
It would be like being given the math problem... "X + Y = 9,567,837. Solve for X and Y."
While there are numerous solutions, you need to find the answer that I'm thinking of.
And thus it is with engine issues. You must find the exact solution that the engine has in mind. A single-variable issue may only have 50 solutions, but a dual-issue might have 300 to 500 solutions to work through.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
I wouldn’t go through the trouble of pulling the head off if there’s compression. Have you synchronized the carbs with a vacuum gauge or carbmate? Also, what prompted you to replace the floats in the first place?
I believe the issue is finally resolved. The last bit was an arcing between the points connector wire and the advance unit. I replaced the worn out advance unit and insulated the bare wire at the points connector (new from bmw!) and she now seems to be feeling much better. Have to wait a couple of days to make the final tune, but I'm closing this one out. Thanks to all.
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