Pin hole air leaks in the diaphragm or intake hose. Both hoses ought to be replaced, then check both diaphragms.

You'll also want to be using a Top Tier Fuel with cleansers in it.

The choke and throttle cables and were too tight on the right cylinder. That fixed the elevated engine idle RPM.

Now working to resolve an engine vibration problem. My understanding is the R65 engine is notorious for vibration between 4300 - 4700 RPM.

The choke and throttle cables and were too tight on the right cylinder. That fixed the elevated engine idle RPM.

Now working to resolve an engine vibration problem. My understanding is the R65 engine is notorious for vibration between 4300 - 4700 RPM.

The choke and throttle cables and were too tight on the right cylinder. That fixed the elevated engine idle RPM.

If the throttle cables did not have the same slack on both sides, then it is clear that both throttles are not opening the same amount at running speed. That will lead to lots of vibration.

Using some type of gauge, you need to sync the throttles at idle using the idle speed screws. THEN you need to sync the throttles at 1500-2000 RPM using the cable adjusters.

Also check the ignition timing using a strobe lamp at very high RPM (full ignition advance) and the flywheel 'F' mark.

All of the motor mounting threaded fastener's as-found torque was below spec. Re-torqued and most vibration is eliminated save for handlebar vibration. After valves adjusted and carbs synchronized, we'll add some bar-end weights if needed.

We adjusted the valves and synchronized the carburetors. Engine mounts were torqued to ~45 ft-lbs. Most of the engine vibration is gone The handlebars are still buzzing however.

When the throttle is briefly cracked open, the engine revs but is slow to return to idle. It hovers at 2000 RPM for several seconds before settling to 1400 RPM. This bike has a bean can. I'm thinking the centrifucal spark advance flyweights are sticking open or the return springs are weak.

Auto Advance Unit was my first thought at the very beginning, but I was assuming your model had electronic ignition, so I discarded the thought. But 'Yes', if you have points, then them being situated inside a "bean can" virtually assures us that they and the associated AAU haven't been properly serviced in 20 years.

At this point we need to change the conversation. If you are really serious about engine vibration, long mileage trips, and optimal performance then you should consider installing an electronic ignition. Unfortunately, a lot of myths about EI have built up over the years and lingered. First Gen units were plagued with chip set reliability. (I remember purchasing an EI in 1976 and printed right there in the instructions were "If this unit fails in the first 2 weeks, it's faulty transistors and we'll replace it free.") Second Gen units were susceptible to battery voltage issues. If the battery went below 12.0V then the transistors simply wouldn't fire. You'd have dim headlamps, but no spark. But all that is behind us now.

These days with battery start only, if your battery isn't strong enough to turn the engine over, then you're not going anywhere anyway. And with most riders opting for more reliable AGM, sealed cell, and lithium batteries, well, all the issues with EI are simply things of the past.

I learned at https://www.bmwr65.org how to troubleshoot the centrifugal spark advance (ATU) as follows: Aim timing light into timing port.
With engine operating in high idle condition, select a gear and let out clutch a bit to drag down engine RPM. If the "S" mark isn't moving into view when engine is dragged down to 1000 RPM then the ATU advance weights are stuck and/or the springs are sacked.[

With all due respect, you are dodging the issue. The AAU has been ignored and as soon as it's running as good as it can, it will be ignored again.

My points....
• Mechanical advance was never precise, even when new it was only just barely "good enough"
• 40 years later it's flat worn slap out, and will never be "good enough" again
• Install an EI and be done with it

It's my riding partner's R65 and he has purchased an EnDuraLast electronic ignition system. He's a computer science engineer but I'll still help him 🙂

My preference would be to service the stock bean can but it's not my bike. I don't like electronic ignition systems because if/when it quits then you're dead on the side of the road. No one in the Airhead community and no amount of the Airhead's operating experience is going to get a dead electronic ignition functioning again.

My own bike is a 1973 R75/5 and I adhere to the KISS engineering principle which is the same as Canon #2. It has a mechanical ignition trigger (Norris contact breaker points) which are user serviceable. My experience is the reverse-engineered, far-east points are poor quality with incorrect dimensions. A mechanical ignition trigger system requires one to periodically lubricate the felt, check the gap and timing. Full disclosure: I'm a mechanical engineer and accept this concession in the interest of KISS.

If the points gap were to become too narrow then this system provides a warning (engine stumble when starting off). The engine doesn't simply quit running as would occur with an electronic ignition. I do carry a spare set of points with me.

I'm not here to argue, but IMHO your thinking is out of date.

As I explained previously, there was a time in the 1970's that 1-2% of chips failed. I'm also an ME, and one of my first jobs was working at a company that supplied computers to the military. We had to run all those at extended temperatures (140°F) for 48 hours to stress the chips and hopefully force weaker components to fail. But that was the 1970's, and it's no longer true.

Consider the irony embedded in your statement: You tell me you won't use an EI with maybe 15 transistors because one of them might fail. And you defend your position by sending a message using a home computer having maybe 10 or 20,000 transistors. Connected to your home's wireless network with routers and modems through a million more transistors. None of which have ever failed.

Or did you use your smart phone ? 😛

All the best.

I want a machine that can tolerate the electromagnetic pulse of a nuclear blast 🙂 My ignition points would take me to Prudhoe Bay and back.

If service was needed I hope I could do it myself on the side of a dirt road, in the dark while it was raining. No electronic diagnostic equipment necessary but bug repellent highly recommended.

There would be no help available from the Airhead community via computer or cell phone but it sure would be nice if a well-armed friend stood watch for grizzly bears 🙂

PS Computers, modems and wireless networks fail all the time. I like the convenience of an electric-start and the availability of a kick-start.

You and I think alike. I too got burned by EME whose EnDuraLast points are sourced from the far east. Also, they sent me a fuel pump suction filter inlet "sock" which didn't fit right. Their customer service offered no resolution other than "It fits on other people's BMWs."

Prior to my friend's ordering the EME EnDuraLast electronic ignition, he asked me to choose between Rick Jone's Alpha or the EnDuraLast electronic ignition. I told him to go with the Alpha primarily because of Rick Jones' stellar reputation (I used that exact same superlative!) within the Airhead community. I also pointed out that his resistor spark plugs will cause the electronic system to quit.

As for coil compatibility, EME states "The EME ignition is NOT compatible with conventional electronic ignition coils, which typically have a primary resistance of around .7 ohms. These coils will fry the EnDuraLast ignition."

My friend now has buyer's remorse and is reconsidering his choice. He indicates the EME system looks like a PIA to install.

My experience with EME has been less than satisfactory; I somehow end up with the blame for their failed components. Contrarily I've had stellar service from Rick Jones at Motorrad Elektrik and Ted Porter at the Beemer Shop, both of which sell and provide no questions asked warranty service for the Emerald Island line of parts.

We're going to install Rick Jones' Alpha ignition instead of EME's EnDuraLast electronic ignition. The optically-triggered EnDuraLast ignition has a more complicated and time-consuming installation procedure than the Hall-Effect-triggered Alpha system.