I can appreciate that you tried to research a qualified mechanic, but you should have never removed the bike from the shop without it running correctly. Now you have the bill, but are still left with a non-runner. In other words, you don't have a baseline to work from.

This should be the tip-off for you... How many 1973 cars did you pass on the road today ? How many in all of last month ? Probably the same goose egg numeral. I say that to point out that your bike is no longer merely "used", or "old", but it has now moved into "vintage" status. As such, it deserves the attention of a dedicated mechanic who is keeping notes on all maintenance and compiling and growing in knowledge about your specific bike. That person is YOU ! (Read ABC club cannon #6 again !)

It's going to go slowly at first becasue you'll be learning. But if you want to ride a vintage bike, then you're simply going to need to get directly involved. Otherwise it's going to cost you a fortune, and you still won't get to ride the bike.

Suffice it to say, Jay Leno is about the only guy rich enough to ride old motorcycles and not work on them himself. But even he doesn't take his bikes to random shops ! 😛

Actions for YOU to take....

• Compression test both sides with carbs removed.
• Replacement of plugs, plug caps and plug wires if over 10 years old.
• Carb repair as detailed in this response.... https://www.airheads.org/forum/my-airhead-needs-help/844-1976-60-6-bing-carb-idle-and-air-adjustments-have-no-affect

Hey, Wobbly, thanks so much for the replies! I really appreciate you taking the time to offer sage advice and some direction. I'm going to chase some of those gremlins you mentioned (compression test, replacing plug wires and caps), and check out the thread you mentioned again. I have done several of the things you mentioned, but could stand to replace jets, needle, etc.

Just to clarify my original post, which I know was pretty long, the last mechanic I went to was on "the list". It's just that he's retired, and so is no longer working at the shop I took it to. It's funny you mention baseline, because that was PRECISELY the reason I wanted to get it into the shop! I hope my post doesn't give the impression that I don't want to work on the bike, I'm just trying to get some experienced advice (which you have so kindly provided).

Thanks again!

Just to clarify my original post, which I know was pretty long, the last mechanic I went to was on "the list". It's just that he's retired, and so is no longer working at the shop I took it to. It's funny you mention baseline, because that was PRECISELY the reason I wanted to get it into the shop! I hope my post doesn't give the impression that I don't want to work on the bike, I'm just trying to get some experienced advice (which you have so kindly provided).

And allow me to clarify, becasue it's very hard for me to convey concern (and yet still be technical) through the written word....

• Having just retired (for the second or third time) from the motorcycle trade, I feel qualified to say that maybe the biggest concern facing the Club is the shrinking number of qualified mechanics. Each brand and type has it's own quirks and foibles, which can really only be learned over time. Guys who worked on these bikes in the 1970's are now nearing 75 or simply dying. The knowledge base is simply disappearing before our very eyes. So I don't envy your position at all.

• It's obviously much easier to keep any motorcycle running once you get it to that state. Then you have that "base line" to work from, and it's understood that anything that happens was probably the result of some sort of misstep within the last few days. In those instances, you can simply backup "one square" and find the cure. It's all based on having the personal knowledge of the repair history. So, with no "finger pointing" at you or your mechanic, it's truly a shame the machine was not in running condition when it was returned, especially in light of the mechanic's retirement.

• All that said, your next best solution is going to be a local Tech Day. But you're going to need to take with you a pile of new parts, becasue it's not really clear to me where your issue lies. So you'll need to take complete carburetor rebuild supplies, and the same for the ignition system, etc, etc.

I used to be a whiz at getting bikes running again. It was like I could walk up to the machine, lay my hands on it, and the bike would tell me what the problem was ! Although it had that appearance, I realize now I was subconsciously reading a host of visual clues. If there were cobwebs, then the bike had been stored indoors and the issues were probably dirty points and gummed up carbs. If the bike was covered with rust, then it had sat outside and had compression issues due to equal amounts of internal rust. If there were fingerprints all over the carbs, they had simply been reassembled incorrectly.

Sadly, there are no visual clues when working over the internet. And that's why you must get the bike to someone who can see it, who knows what they're looking at, and can go right to the problem. Otherwise, you'll end up rebuilding the entire engine (and spending millions) all to find something unbelievably simple.

All the best, and keep us informed of your progress.

Thanks, Wobbly!

I'll put in an order for carb rebuild kits, wires, caps, and plugs. In the meantime, I should be able to check compression this weekend. Don't have the tools to do a leakdown check, but I can still check for air leaks around the hoses.

Will probably pull those wires this weekend and check them with a multimeter as well, but regardless it's probably time to change them out. At least I can know whether or not it's part of the problem!

Will definitely update.

All it takes for an engine to run is: Spark (at the spark plug), Fuel, and Compression. The "Big 3". Test and verify, don't guess. If your bike passes all those tests, then one of the 3 is not happening at the correct Time.

I'll put in an order for carb rebuild kits, wires, caps, and plugs. In the meantime, I should be able to check compression this weekend. Don't have the tools to do a leakdown check, but I can still check for air leaks around the hoses.

In my professional opinion, a "leak down test" is simply a tool to sell more top end jobs. In other words, if it's not a SCAM I'd be hard pressed to tell you what is. Think about it, the complete firing cycle happens in a fraction of a second, but a mechanic is telling you that your cylinder needs to hold pressure for, what, 1 minute ? :S

Try this instead... With the carbs pulled off the rubber intake tubes, place both plugs on top of the cylinder in their caps, place your thumb over one empty plug hole at a time, and spin the electric starter. If the air feels hot and will blow your thumb off the plug hole, then your compression is high enough to start the engine.

Will probably pull those wires this weekend and check them with a multimeter as well, but regardless it's probably time to change them out. At least I can know whether or not it's part of the problem!

The metal-core wires simply corrode due to water over the years, which degrades their capacity. Not much there to measure with a meter. However, the OEM plug caps are known to degrade AND then ultimately fail. You might see that with a meter, but since new NGK 5K Ohm caps are $2 each it's simply easier to replace. And of course, anytime you deal with ethanol fuels you can permanently foul a plug in a heartbeat, so spares (NGK BP7ES) are a must.

All the best.

Didn't read this post until after I'd started on the work, but it definitely helped! And I didn't unnecessarily pay for a leak-down test.

First, pulled the carbs and did a compression test with a gauge (cold). Left side was pretty normal at 120, but right side was around 130. Just to see, I cranked for a few more revolutions and was able to get it up to 140. Not sure what that means, but I figure it should be included here, since I think that is closer to normal-operating-temperature compression. Anyway, compression seems to be good!

I noticed when I pulled the right side carb that there was quite a bit of oil in the air tubes. I know the crankcase breather vents into it, so when I saw a little oil on the bottom of the snorkel I didn't think anything of it. Checked inside, and there was quite a bit of oil around the aperture that the snorkel fits onto (I mean COATED), and a light film all through the snorkel, and even a little on the filter. I cleaned everything out and reassembled.

I pulled the spark plug wires and cleaned all the corrosion off the contacts. I then tested for resistance, which read a little over 4 kΩ. Considering it's usually around 5, that seemed pretty good to me. I applied the slightest amount of dielectric grease to the contact for good measure. (I will be replacing the plug caps per Wobbly's advice regardless.) For comparative purposes, the plug wires were switched (right-left).

I went for a ride, and actually got out on the highway for about 20+ miles. Tried to keep the RPMs up for as much of the journey as I could. Performance was better than anytime in recent months! Got back home and did carb balancing, and brought the idle to about 1,000 RPMs. However, I still need to turn the idle mixture screw all the way in to get it running properly...

Went out for another ride, and things are still great. Put a total of 50 miles on her. Now, I at least have a theory as to what was happening. I believe that the shop overfilled my oil (when I checked, it was a little high, but I assumed this must have been related to old bikes "eating" oil). When the engine heated up and pressure increased, it was probably blowing all of that junk into the right carb, fouling the plugs. Because I had been tinkering so much with the bike, riding around the neighborhood, worrying about bogging down on the highway, I prevented the engine from actually burning off all the junk on the right side. Meanwhile, gas is just flooding the right side as well. I know this is common sense to everyone reading this, and now I know! Get the thing out and RUN IT.

In any event, I can actually run my bike again and enjoy it! Going forward, I'm replacing all the things Wobbly mentioned as I get them over the next week or two. With any luck, one of them will address this weird issue with the mixture screw. That's my update, and thanks Wobbly for all the advice!

thanks for the update. Awesome that you are learning too! and Wobbly's advice is always top notch! thanks, Wobbly.

Went out for another ride, and things are still great. Put a total of 50 miles on her. Now, I at least have a theory as to what was happening. I believe that the shop overfilled my oil (when I checked, it was a little high, but I assumed this must have been related to old bikes "eating" oil). When the engine heated up and pressure increased, it was probably blowing all of that junk into the right carb, fouling the plugs. Because I had been tinkering so much with the bike, riding around the neighborhood, worrying about bogging down on the highway, I prevented the engine from actually burning off all the junk on the right side. Meanwhile, gas is just flooding the right side as well. I know this is common sense to everyone reading this, and now I know! Get the thing out and RUN IT.

Great news !! Congrats.

• Your assumptions on oil in the intake may need some modification. There will be normal blow-by until the piston rings re-seat... which they are now doing. However, excessive oil in the intake can be caused by 2 common things.... 1) plain old dirty air filter. Replace it !! 2) Next to the starter motor, under the starter cover is a small, rectangular plate held on with 3 screws. Remove that cover and there should be a "well" to collect oil vapor and put it back into the engine as liquid. If that "well" is full of liquid oil, the the drain hole into the engine may be clogged. Probing the bottom of the "well" with a guitar string may find and clear that drain hole. (Snowbum has a nice write-up on this with photos.)

• Your valves will need re-adjusting (or at least checking) now that the engine has been run.

• Fuel should Never Ever overflow out of the carb. Replace (don't simply "check") the float needle, the float, and check the float level with the new parts.

• The lack of idle is either the carb flooding, or blocked idle passage.

• Smooth, balanced idle at 1000 RPM is important, but equally important is balanced running at 1800 RPM with good throttle cable adjustment.

Hope this helps.