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So I know that there has been an ongoing debate about the reliability of the R80g/s hall sensor and how folks like me put switch them out to points.

So yesturday I was 80miles from home and it started to intermittently backfire. Halfway home the backfiring got worse. Figured I'd stop for coffee and let things cool down. Started back up and sounded like a tommy gun. Pulled into NAPA. Figured that perhaps a condensor was going bad. Figured that I would test that therory of the benefits of a BeanCan over a Hall, in such if something goes south you can stop by any auto parts store and get the parts as we all know they should be easy to find. Well, it failed and the closest replacement was in 2000mi away. Rode the rest of the way home on 1 cyl and put in my spare, readjusted my points, and greased the lobe. Runs good now......

So, although a simpler system, cheap to fix...but the parts are NOT easily available at any NAPA as much as I used to think. Lesson is to always carry a spare.

The Raven wrote:So I know that there has been an ongoing debate about the reliability of the R80g/s hall sensor and how folks like me put switch them out to points.

So yesturday I was 80miles from home and it started to intermittently backfire. Halfway home the backfiring got worse. Figured I'd stop for coffee and let things cool down. Started back up and sounded like a tommy gun. Pulled into NAPA. Figured that perhaps a condensor was going bad. Figured that I would test that therory of the benefits of a BeanCan over a Hall, in such if something goes south you can stop by any auto parts store and get the parts as we all know they should be easy to find. Well, it failed and the closest replacement was in 2000mi away. Rode the rest of the way home on 1 cyl and put in my spare, readjusted my points, and greased the lobe. Runs good now......

So, although a simpler system, cheap to fix...but the parts are NOT easily available at any NAPA as much as I used to think. Lesson is to always carry a spare.

FYI, for future reference, if you can't find a condenser that fits in the bean can, there's no reason it has to go into the bean can. The positive side of the condenser is electrically continuous not only with the points, but also with the negative side of the two coils. Most any automotive capacitor will work fine with the BMW points system. Just connect the insulated lead to the negative side of the coils and connect the case to the handiest ground you can find, probably somewhere on the frame tube. If your problem was, indeed, the condenser, then the bike will run fine.

Which brings me to what you said about having to limp home on one cylinder. All other things being equal a bad condenser should affect both cylinders. Spark plug condition, electrode gap, coil wire condition, and coil can make things unequal, meaning a marginal condition might show up on one cylinder.

I would be concerned about one of the coils in particular being bad. Coils have a nasty habit of giving problems when getting warm. That's because the very fine wires inside the coil can squirm around with the heat. If there's an open in the windings, or the windings have bad unsulation, thus shorting windings together, that can generate a problem.

I keep a couple new coils in stock. Twice now I've chased my tail for days trying to figure out what the hell was causing my ignition problem. New coils fixed the problem.

I don't know if your GS has twin coiles or a twin fire single coil. But either way one cylinder can quit firing.

Something that can be done on the road when you have a problem is to swap the plug wires side to side. If the problem switches to the other cylinder, that tells you a lot about where to look for a problem.

Ignition systems can be maddening with their sometimes they work and sometimes they don't behavior.

You may already know this stuff, fair enough. Never mind. But there might be somebody else reading this topic who doesn't.



Ken

Don't recall who originally posted this but I kept a copy - not on the bike though which is kinda dumb.


Points and condenser for 1979-80 points style beancan ignition only!

Bosch number 01011 for the points denotes softer spring, greater swing of the points arm, and fibrous material tab that rides on the lobed cam. Comes from VW type 009 distributor.

Bosch number 01030 for the points denotes stiffer spring, less swing of the points arm, and plastic tab that rides the lobed cam and stripes on the wires denoting the nickname "tigertail". It was the high performance points for higher rpm VW type 009 distributor.

Bosch number 02093 for the condensor is also used in

BMW 2002 (1975 - 1976)
BMW 320I (1977 - 1979)
VOLVO 142 1974
VOLVO 142 GL 1974
VOLVO 144 1974
VOLVO 144 GL 1974
VOLVO 145 1974

What is said makes sense regarding not effecting just one cyl. I had doubted that it was the condensor but after switching out the wires, new plugs and checking grounds the only thing left was the condensor. Once I dropped in the new one all problems became resolved.

I had new NGK wires, a Dyna Coil and 40hr points. The only thing origional and not new was the sparky can.

So...how could the condensor effect just one cyl? Simple. The BMW single coil and point system fire the spark on both the strokes. What I believe was happening is that the condensor was not recharging quick enough to fire on both strokes, only one which would basically limit it to one side of the bike. To add to the story I have an inductive tach that was connected to the bad side. It was reading about half of the actual RPM it should have adding weight to my suspicions

barryh wrote:Don't recall who originally posted this but I kept a copy - not on the bike though which is kinda dumb.


Points and condenser for 1979-80 points style beancan ignition only!

Bosch number 01011 for the points denotes softer spring, greater swing of the points arm, and fibrous material tab that rides on the lobed cam. Comes from VW type 009 distributor.

Bosch number 01030 for the points denotes stiffer spring, less swing of the points arm, and plastic tab that rides the lobed cam and stripes on the wires denoting the nickname "tigertail". It was the high performance points for higher rpm VW type 009 distributor.

Bosch number 02093 for the condensor is also used in

BMW 2002 (1975 - 1976)
BMW 320I (1977 - 1979)
VOLVO 142 1974
VOLVO 142 GL 1974
VOLVO 144 1974
VOLVO 144 GL 1974
VOLVO 145 1974

That was the part number that no one had in stock

The Raven wrote: So...how could the condensor effect just one cyl? Simple. The BMW single coil and point system fire the spark on both the strokes. What I believe was happening is that the condensor was not recharging quick enough to fire on both strokes, only one which would basically limit it to one side of the bike. . . .

Hmmm, I can't visualize how that could happen. If I understand you correctly, in effect the condensor is taking two revolutions of the crank to gather enough energy to spark two plugs at once instead of none or just one.

A condenser is a pretty simple device. With the points closed both ends of the condenser are in effect shorted together. While the points are closed there is no charge stored in the condenser and any charge that might have been left over has been shorted out. When the points open the current that has been flowing through the coil is interrupted and the coil starts building a voltage in the primary higher than the nominal 12 volts that was across it with the points closed. The rising voltage in the primary winding is induced into the coil's secondary windings, which, because they have many more turns of wire generate a high voltage, high enough to create an arc across the sparkplug gap. The role the condenser plays is twofold. First, it keeps the points from arcing (and burning). It does this because the condenser is capable of absorbing the charge that would have cause an arc across the points. The second function of the condenser is to feed it's stored energy into the coil primary windings. This stored energy modifies and enhances the energy of the spark.

The point I'm heading toward is that the condenser can't know that a spark has or has not happened on the previous engine revolution. And since the points close between every engine revolution no energy can have been stored in the capacitor to affect the sparking of the plugs from one engine revolution to the other. The condenser has no way of "knowing" what happened during the previous revolution.

What can happen to cause one sparkplug not to fire is that the conditions from left to right can be different. This can be a few things, condition of the coil(s) secondary windings, condition of the spark plug wires or caps, and condition of the plug in cluding sharp edges on the electrodes, and energy bled away from the plug gap by fouling. It is entirely possible for the overall conditions on one cylinder to be enough different from the other cylinder such that one cylinder fires while the other one does not. (For example picture a gap way too wide on one plug or the electrodes closed together on one plug.)

My thoughts for what they're worth.


Ken

I agree, Ken. His description of what he imagines was happening is more like the function of the coils than the condenser.

My guess of how this could affect only one side is: a bad condenser will have a more profound impact on a weak system than a good one, so perhaps one element of the side which was failing to spark was weak enough that a bad condenser made that side fail while only weakening the spark to the side with stronger components.

Ok...so I have a brand new coil, wires and points from Motorrad Elektric, as well as new plugs from my on the road attempt at fixing the problem. But nothing changed until I did two things....regap my points as they were too close, and change the condensor

Here is my troubleshooting steps as well as problem progression and result

Pre-issue: Found the bike somewhat hard to start when cold, and had a intermittent low idle.

1. Bike misses and backfires in sweet spot doing 35-40, remedies with more or less throttle
2. Later bike misses at higher RPMs, remedies at less throttle.
3. Bike then starts to miss under any load...but still goes when coasting and at idle
4. Bike badly hesitates and backfires at acceleration, remedies at coasting
5. Bike stalls at idle, starts right back up, runs fine slow
6. Bike starts on one cylinder and backfires very badly and loudly, check plugs, white with sediment on them...ethanol stuff?
7. Bike backfires at idle, replaced plugs, switched coil terminal on wires, wiggled wire, and isolated it from any contact point on engine.
8. Bike loses all power on one cylinder with occasionally hits every 5-10 minutes, wiggling wires make no difference.
9. Stop halfway home, pull bad plug and see mild spark, replace and pull wire, bike stays running. Do with opposite plug and bike stalls. Got shocked off of good plug, but not off of bad plug. Exhaust hot but not hot enough.
10. Get home, check plug and find it mildly wet. Put in good wire, no change.
11. Open beancan, check points. 1/2 closed to spec...opened them to spec. Changed condenser to new Bosch. Lubed shaft.
12. Started bike and found spark on both sides to be identical and strong.

I did find another case in my search that a similar problem was solved by a new condensor by someone with an R90. Rick at Motorrad said the BMW condensors are crap.

One other thing I need to mention. The compression on the bad side is at 90. Oil on ring test caused no change in compression. The valves are loud so I need to get in there and adjust them. The good side is at 135 and quiet valves.

I did just go for a ride tonight and for the first time for a long time the bike started without the need for any choke....though the low Compression side was slow to catch up and start firing..but did after a few seconds.

The Raven wrote:One other thing I need to mention. The compression on the bad side is at 90. Oil on ring test caused no change in compression. The valves are loud so I need to get in there and adjust them. The good side is at 135 and quiet valves.

I did just go for a ride tonight and for the first time for a long time the bike started without the need for any choke....though the low Compression side was slow to catch up and start firing..but did after a few seconds.

AHHHHHHHHHHHH.

So, you have a bad cylinder. That totally explains how a problem that would normally impact each cylinder equally might have much more impact one one cylinder: the bad one.