Boxerworks.com

Giving the bike a thorough tune-up might do the job. My approach was to check the cheap and easy fixes first before I began to look in fear at things like head rebuilds and the like. Check the spark on both sides. (Do not just pull off the spark wires when it is running as this will fry and electronic ignition and/or knock you on your butt if the wire is damaged.) Check the PO's records and see if he (she?) replaced the carb diaphragms with the last tune-up. Some carb cleaners will attack them and the symptoms can look like fuel starvation. Do not fear the Beemer, respect it.

Duane Ausherman wrote:It is not proper procedure to file points. . .

How about telling us why Duane. I know that advice is given a lot. But we have bare tungsten on tungsten which can become eroded and "titted" over time, especially if the capacitor, uh, I mean condenser is going bad. It's true that a points file has a hard time making any headway on the tungsten, but nowadays we have diamond files that will do the job. So if the tungsten surfaces are now clean and touching each other well, what would be the problem, especially if a new set of points isn't on hand (as would have been prudent) and you need to go riding?

Ken

Ken, I typed it out once and put it on my website. Just use Google search phrase "bmw motorcycle points file" or here is the #1 Google result, http://w6rec.com/duane/bmw/points/index.htm

I thought for sure Jean would have heard the work "condenser" and logged right on!

Thanks for all the responses. I'm mechanically inclined and have worked on my share of cars and motorcycles. All modern though. The reason for not wanting to really tear into things is due to time. The first time you go into things it always takes long as you're both learning and making sure not to mess anything up along the way. Since my time is somewhat limited to be able to work on it, I didn't want to leave something half done and all taken apart.

The bike ran good, came back to ride it later and it's going nowhere under full acceleration. Back to running crappy although better than it was before.

Hopefully this up coming weekend i'll have the time to go through everything. The bike has been well maintained, so the wiring all looks clean. I do have a manual and have gone through it a bit. Seems like most things are fairly straight forward and not overly difficult to do. Hopefully I have the same outlook afterwards, but regardless it'll be fun to learn everything inside and out.

In the event the points, condenser, coils and so on need to be replaced, where are some recommended places online to pick new ones up? Stick with oem? Any aftermarket brands to stay away from? I suppose using the search function could answer those questions though.

Again, thanks for all the replies, I'll be posting after I've had time to sort things

Spark plug leads and caps probably won't look cruddy and deteriorated unless they're really, really old and left out in the weather. Nonetheless, if they don't consistently maintain 5K ohm resistance, they'll produce the episodic one-cylinder operation that you're seeing. BMW OEM plug leads and caps are surprisingly expensive, which is why you'll see lots of airheads with NGK caps. Either are fine. A multimeter can tell you whether your plug wires/caps are doing the job or not.

khittner1 wrote:Spark plug leads and caps probably won't look cruddy and deteriorated unless they're really, really old and left out in the weather. Nonetheless, if they don't consistently maintain 5K ohm resistance, they'll produce the episodic one-cylinder operation that you're seeing. BMW OEM plug leads and caps are surprisingly expensive, which is why you'll see lots of airheads with NGK caps. Either are fine. A multimeter can tell you whether your plug wires/caps are doing the job or not.

I would add a couple things. As I understand it the resistive caps or resistive plug wires aren't used to improve performance. Rather they are to be kind to your fellow motorists by not interfering with their electronics, especially AM radios. An airhead will perform just fine with good solid copper spark plug wires and no resistive cap.

A plug wire can be "bad" in more than an end to end resistance check. An old cracked or otherwise compromised cable jacket can provide a lower resistance pathway to ground. New spark plug cable, though not exactly cheap, isn't expensive. And you don't need to buy fancy "premium" wires either.

Were it me I would go buy the NGK resistive caps and some conventional rubber jacketed solid copper core leads and make up a set of plug wires.

And, as I think has been previously discussed, coils can be a real problem, especially old stock coils. I chased my tail for the longest time on my R75/6 years ago on an intermittent problem. The bike would run just fine and then after a while it would go bad on one cylinder. New coils fixed the problem. Later I learned what was happening. Coils heat with use and the windings inside, especially the secondary windings, are very fine. As the coil heats the insides expand and causes the wiring to "squirm". A coil with a severed winding can work just fine cold, but when it heats the wire ends move apart. I've had coil problems on two airheads now and I now stock a new set of coils against the time when I will need them. New coils are kinda expensive, but compared to worrying and working an ignition problem for days, weeks, or even months, buying a set was good insurance money for me.

And as might be expected, I haven't needed the coils yet.

YMMV

Ken

If you have fitted an electronic ignition You will need spark plug caps with resistance. Usually 5000k ohms are specified, otherwise you might fry the electronic module and this won't be covered by GTee

chasbmw wrote:If you have fitted an electronic ignition You will need spark plug caps with resistance. Usually 5000k ohms are specified, otherwise you might fry the electronic module and this won't be covered by GTee

Good point. I should have said "stock" airhead.


Ken

Ken in Oklahoma wrote:

chasbmw wrote:If you have fitted an electronic ignition You will need spark plug caps with resistance. Usually 5000k ohms are specified, otherwise you might fry the electronic module and this won't be covered by GTee

Good point. I should have said "stock" airhead.


Ken

To my knowledge, that's still not good enough. 81+ models with Hall Effect sensors are also supposed to have 5k resistor caps.

Edit: Just checked, and both Oak and The Bum say to never run the 81+ models without the 5k caps.