BMW Airhead parts and service

[Garandman]

Picking up a 1975 BMW R90/6 this weekend. It's in real nice shape for the age: paint is almost certainly a respray as there's no pinstriping or decals.

There's one odd problem: the tachometer needle is broken off. I understand there are specialist outfits that rebuild them: is it easy to open it up and swap, or should I send it off?

The owner had it serviced by Max BMW for the most part. But I think I'd like to add electronic ignition. Any Airhead specialists around? Chris Harris only works on newer bikes.

[csmutty]

His name is Ching. Has a bunch of old BMWs that he has restored. I'd hit him with any questions.

Band Of Riders

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His name is Ching. Has a bunch of old BMWs that he has restored. I'd hit him with any questions.

Band Of Riders

[Rada]

Gordy's Goodworks in Booneville IN.
Gordy Roth | Facebook

[backinthesaddle]

There is a guy in Hopkinton RI named Av Tenkarian. Works out of his garage and was BMW tech at Razee's before they were called techs.

[02redhawk]

That's a nice looking bike. Should be a fun ride.

[Tom M]

Is Duncan's Beemers in Maynard still around? If so he's been there for a long time so he must know something about old airheads. Nice bike BTW.

http://www.duncansbeemers.com/

[whynot]

These guys on Rte 2 in Gill MA have a great reputation:
AJ Cycles BMW MOTOGUZZI

Nice riding out thataway, too.

[Garandman]

The BPO had some service done at GBM and some done at Max. If I wanted someone to go through the bike from stem to stern, who would you pick? It's probably been 30 years since I worked on breaker points so I'd like to make sure everything is well tuned.

[burnham]

A friend of mine had his '73 R-somethingorother gone through at Duncans a few years ago and was very happy with them.

[csmutty]

The BPO had some service done at GBM and some done at Max. If I wanted someone to go through the bike from stem to stern, who would you pick? It's probably been 30 years since I worked on breaker points so I'd like to make sure everything is well tuned.

Why not just convert it to electronic ignition?

[whynot]

... If I wanted someone to go through the bike from stem to stern, who would you pick? ...

If it wuz me, I'd go the distance to AJ:

"AJ Cycles Services

Full Service BMW & MOTO GUZZI . Certified Master mechanic with 40 years motorcycle experience. Experienced in the latest diagnostic equipment.

Parts and Sales personnel with 50 years motorcycle experience.

We have excellent machine shop services which include: Welding (Fin Replacement, Crack Repair in Cylinder Heads, or General Repairs), Boring, Valve guide and Valve seat replacement"

[Garandman]

Why not just convert it to electronic ignition?

Planning on it, haven't opened it up yet, many of them are already converted. It starts right up even in 30's temps.

[Kurlon]

Why not just convert it to electronic ignition?

Hard to beat points for low RPM fat sparks.

[csmutty]

Hard to beat points for low RPM fat sparks.

I'd rather have reliability personally, but I didn't know points actually provided a better spark at low RPM.

Made a huge difference when I swapped the truck to electronic.

[Kurlon]

Primary gain from electronic is more flexible timing control, you can do more than just a straight ramp advance curve. Points can be very reliable if you understand how they operate, but that's a dying art (that I'm not 100% versed in myself unfortunately). Given all the electronic ignition failures I've fought with on bikes, and cars (I remember my grandfather having to keep spare HEI modules in the glove box for his Pontiac) I'm not 100% inclined to say with certainty that electronic is more reliable, just different failure modes.

[csmutty]

Primary gain from electronic is more flexible timing control, you can do more than just a straight ramp advance curve. Points can be very reliable if you understand how they operate, but that's a dying art (that I'm not 100% versed in myself unfortunately). Given all the electronic ignition failures I've fought with on bikes, and cars (I remember my grandfather having to keep spare HEI modules in the glove box for his Pontiac) I'm not 100% inclined to say with certainty that electronic is more reliable, just different failure modes.

I'll go with easier to set then and less maintenance intensive.

[Kurlon]

I'll go with easier to set then and less maintenance intensive.

Fair point, but when the apocalypse hits with an EMP pulse, points will keep working.

[csmutty]

Fair point, but when the apocalypse hits with an EMP pulse, points will keep working.

If that happens I'll buy points and a condenser, with cash.

[Kurlon]

If that happens I'll buy points and a condenser, with cash.

You mean bottlecaps, or unexpired cans of food, right? Apocalypse after all.

[csmutty]

You mean bottlecaps, or unexpired cans of food, right? Apocalypse after all.

Alcohol will be my bartering chip.

[Garandman]

Primary gain from electronic is more flexible timing control, you can do more than just a straight ramp advance curve. Points can be very reliable if you understand how they operate, but that's a dying art (that I'm not 100% versed in myself unfortunately).

The BMW system is notorious for advance curve problems, largely due to lubrication issues, although some of these bikes were ridden crazy miles. Apparently their first foray into electronic ignition in the next generation wasn't much better.

Because the bike runs and shifts so well and the brakes were serviced a. Few hundred miles ago, I decided to punt and store it in the garage for now.

[Kurlon]

What's the aftermarket offering?

[Garandman]

Just started researching. There are a number of Airhead specialty sites, plus sections on Advrider, BMWMOA, and several experts in Yankee Beemers. Probably take it to a YB breakfast in March or April and get some feedback.


There are at least 30 threads on Advrider on this very topic.

Aftermarket

Boyer-Bransden
Boyer's MkIII (now Micro Digital) and Micro-Power systems replace the entire timing system, implementing an electronic pickup and digital control over timing and dwell. The system mounts in place of the points plate and advance mechanism on '70-'80 systems (inside the canister on '79 and '80 models). Micro Digital works with existing coils, while Micro-Power uses Boyer's own coils and is easily fitted to dual plug heads.

Dyna
The Dyna III ignition is an electronic upgrade, using an electronic pickup mounted on the cam nose. Advance is still handled by the stock advance unit.

Dyna also has a booster module, used to reduce the current load on the points. This is especially popular for dual-plug applications where two coils are charging.

Omega
The Omega system is a pickup and processor unit mounted at the alternator, so it gets the signal directly from the crankshaft position. The points can even stay in place as a backup system. 16 timing curves from which to choose, uses existing coils.

Silent-Hektik
Like the Omega, this is a crank-mounted system. A trigger wheel is mounted to the alternator rotor, and the pickup unit is on the stator. The system also includes a processor unit (with 16 advance curves from 18° to 37°) and their own dual-output coil. The processor can power two of these coils for dual-plug heads.

Max sells the Moto Elecktrik Enduraspark. One thing I've learned is the stock system can be disconnected but left in place in case the electronics fail. This would be very characteristic of ze Germans: they plan on failure of the electronics, not the mechanical parts....

Because the points are under the front cover, even though it's only three bolts I haven't taken it off yet. Owned the bike three days.....

[Kurlon]

So, one thing to consider for cam vs crank mount - Wasted spark. The crank mount setup will be a wasted spark trigger, so half the dwell time for the coils. Counterintuitively firing twice as often means the crank setup will draw less current than a cam setup, but will also suffer weaker spark due to voltage sag easier. It'll also have a lower RPM ceiling for which it can produce a usable spark but I don't expect a BMW twin to get anywhere close to that point.

[Garandman]

I found a survey on Advrider and the vast majority of these older bikes stick with the stock setup. Some add a spark booster to extend point life, but the stock points apparently last 15-20,000 miles if kept adjusted. Guess I should resist the urge to buy a 40yo bike, then start modernizing it.