'81 R100RT; Bean Can Problems.

1981 R100RT in very good shape, reasonable miles, etc. The previous owner installed dual-plugged heads. The work appears to have been done well. However as of late the bike's idle was hanging up after it got fully warmed up (around 2200 rpm for about 7-10 seconds before settling into a smooth idle at 1000 rpm). So.....I got into the bean can and actually found evidence of light corrosion, hardened grease, etc. I cleaned it thoroughly and re-fitted it to the bike. In cleaning it however I accidentally washed off the paint marks I used to index the timing so I had to time it using the my timing light to the "F" mark. I realize now that this was probably a mistake.

The problems:

After a nice long test ride I noticed that the pipes "blued up" signifying that it was running hotter. I know that a general rule of thumb is that when running a dual plug setup you must use about half of the original advance. (I read somewhere that on a single plug setup the advance is 29º...if you're running dual plug it should be 22º) However, wouldn't that also retard timing at idle? I think I read somewhere that with the normal advance range with the timing retarded for dual plugs, at idle it would be firing at about 3º after TDC...is that ok? If not how does one limit the range of advance? Is that even necessary to worry about?

The second problem is that cleaning the advance unit inside the bean can may not have worked. It still coasts up to 2000rpm on idle sometimes but the problem doesn't seem as significant this time and is more inconsistent. I cleaned the pivot points on the advance unit THOROUGHLY making sure to means test it extensively...the weights moved very freely and returned to their stops easily. I am willing to consider that I missed something BUT!!!.....before I go back in there should I also consider that the severely advanced ignition timing might be creating this problem?

Also....I am willing to throw money at this problem. I know that the bean cans were somewhat problematic in nature. I have another Airhead with an Alpha ignition setup I got from Beemershop that I LOVE!!! Should I simply consider buying one of those and not worrying about this? (Addendum: not TOO much money)

As for timing, I think in the end, you really do want to have full advance at the F-mark. There are two was to do that. One can either restrict the range of advance so that static is still at 9 deg (whatever it is) and the F-mark ends up in the window. To do this you must build some kind of stop on the advance unit to prevent going past the F-mark. The other way is to time the bike so you get full advance at the F-mark and accept what you get at idle. It might be close to TDC but as long as the bike is in good condition otherwise, it should still start and idle. Tom Cutter has a primer on dual plugging on his website. As I understand it, most of the info about parts to use, etc., are out of date and should be considered. But the early discussion I think is more or less still the general rule.

http://www.rubberchickenracinggarage.com/Downloads/TomCutterDualPlugIgnition.pdf

In regards to the high idle, this can also be attributed to carb problems. Often times, a high shows up when adjustments are made to the carb settings when the engine is cold. High idle shows up later when the engine warms up. You can test for this. When you have the high idle, pull in the clutch lever and shift to a gear and step on the brake. Slowly let the clutch out to drag the engine speed down to around the normal idle, say 1100 RPM. Pull the clutch lever back in. If the issue is the carbs, the engine speed will go right back to high idle. If it doesn't then maybe the issue is the advance unit is sticking at high idle.

Vacuum

Vacuum leaks in the carbs or more often the "rubber" inlet between the carbs and heads will cause idle problems.

FYI, If you want to spend the bucks, the newest system on the market for dual plug bikes is the Australian Wedgetail system. I see Tom Cutter and Rick Borth at MotorradElectrik are selling them. I don't even see the Alpha system advertised or for sale on Rick's MotorradElectrik site anymore. St.

STEVENRANKIN said:

Vacuum leaks in the carbs or more often the "rubber" inlet between the carbs and heads will cause idle problems.

FYI, If you want to spend the bucks, the newest system on the market for dual plug bikes is the Australian Wedgetail system. I see Tom Cutter and Rick Borth at MotorradElectrik are selling them. I don't even see the Alpha system advertised or for sale on Rick's MotorradElectrik site anymore. St.

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As far as the carbs are concerned, before I removed and disassembled the bean can it ran fine except for the high idle after warm up. Once the idle settled down there was no more problem...no overheating either. If the fuel system wasn't the problem before, how likely is it that it became a problem coincidentally right after I pulled the bean can?

STEVENRANKIN said:

Vacuum leaks in the carbs or more often the "rubber" inlet between the carbs and heads will cause idle problems.

FYI, If you want to spend the bucks, the newest system on the market for dual plug bikes is the Australian Wedgetail system. I see Tom Cutter and Rick Borth at MotorradElectrik are selling them. I don't even see the Alpha system advertised or for sale on Rick's MotorradElectrik site anymore. St.

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Also....I've heard from many today that the wedgetail is the hot setup. But MAN......$500 ($570 with the dual plug module)?

banzaibob said:

Also....I've heard from many today that the wedgetail is the hot setup. But MAN......$500 ($570 with the dual plug module)?

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That is about the same as two tires I could burn up before the summer is over, or about 4,500 miles of fuel at today's prices.

In my case

So in my case, I removed the Dyna electronic ignition system I had installed on my 78 RS back in 97. I was going to install the Alpha system however as I said Motorrad Electrik didn't have them listed.

I installed the single plug system from Wedgetail.

Frankly I was skeptical there would be a noticeable improvement in performance over the Dyna system. I am very surprised there is. Cold starting is vastly better with the WT system. The bike idles smoother and power is smoother. Installation was very easy, used all the factory wiring and connections, any additional wiring mimics factory wiring so any troubleshooting will be easy. Once installed, setting the system for timing was a snap, easier than the factory system. Unlike the factory set up, the ignition module actually has the means to control the advance curve. I don't know if that makes any sense?

The Dyna system allowed me to get rid of points and I loved it for that. The WT system is so much better.

If the system in my 84RT fails, I will be most likely installing a replacement WT unit.

Now neither of my bikes are dual plugged, I have never needed to convert so I can't say how well the WT system would work for a dual plug bike. I can only go by the company's video and write ups. I only know that my bike runs a lot better than it ever has. This so far has been one of the upgrades I have done over the year that made a fair amount of bang for the buck. St.

I replaced my points with the ENDURALAST & SACHSE Part #: EDL-BOIGNS from EME last fall. I give it high praise. It is configured for dual or single plugs. This is on a single plug '77 R100S. I have the 3 curve module, with an upgrade to 9 curve module, maybe for spirited riding or racing.

I would love to get a Wedgetail ignition system. Sounds like THE hot setup. However......I think that the prudent think is to first try to get it to run correctly with what I've got. So.........the definitive answer for specifically what the ignition timing on a 1981 R100RT with DUAL-PLUGGED HEADS is...........?

I'm not sure you'll get a definitive numerical value for degrees of timing, if that's what you're looking for. I've not seen any set in stone. I'd suggest you peruse the following regarding the dual plug timing, there are variables. https://bmwmotorcycletech.info/dualplugging.htm

banzaibob said:

I would love to get a Wedgetail ignition system. Sounds like THE hot setup. However......I think that the prudent think is to first try to get it to run correctly with what I've got. So.........the definitive answer for specifically what the ignition timing on a 1981 R100RT with DUAL-PLUGGED HEADS is...........?

Click to expand...

We had an R80/7 double plugged. Oak Okleshen provided the parts and had the head work done. He said to retard the advance by 3 degrees. The idle timing mark was at 6 degrees so I set it halfway between OT and that mark. It worked fine.

That should be a good starting point.

kinterridge said:

I'm not sure you'll get a definitive numerical value for degrees of timing, if that's what you're looking for. I've not seen any set in stone. I'd suggest you peruse the following regarding the dual plug timing, there are variables. https://bmwmotorcycletech.info/dualplugging.htm

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Someone PLEASE tell me if it is just me. I have read both articles from Snowbum and Tom Cutter and I simply cannot find stuff specific to the '81. I'm assuming that '81 was the first year electronic ignition right? My thinking on this is; if dual plugging requires less advance then wouldn't that be less RANGE of advance? In other words....in using the stock electronic ignition with the stock advance unit...wouldn't the amount of advance at IDLE be the same as it would be for single plugged heads? Therefore wouldn't you need to alter the advance unit to limit the range? Feel free to criticize my comprehension skills on all of this.

banzaibob said:

Someone PLEASE tell me if it is just me. I have read both articles from Snowbum and Tom Cutter and I simply cannot find stuff specific to the '81. I'm assuming that '81 was the first year electronic ignition right? My thinking on this is; if dual plugging requires less advance then wouldn't that be less RANGE of advance? In other words....in using the stock electronic ignition with the stock advance unit...wouldn't the amount of advance at IDLE be the same as it would be for single plugged heads? Therefore wouldn't you need to alter the advance unit to limit the range? Feel free to criticize my comprehension skills on all of this.

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In a perfect world, with modern computer controls, you are right. But in the crude world of spring loaded advance weights and poorly lubricated advance mechanisms you have to take what you can get. And that is a single compromise setting you can live with. Or alter the springs, alter the weights, etc. And how to do that is a pure guessing game because nobody is spending a lot of time, effort, or money to modify 40 year old air cooled, carburetor equipped motorcycle ignition systems.

So....here is what is going to happen (Shout out if you hear something crazy that is going to blow up my bike)

I am going to re-set the timing on the bike to 28º BTDC. I have one of those Chinese Innova timing lights that I believe allows you to set the timing advance value on the display screen. Once I figure that out, I'm diving in. My understanding is that at idle, the timing on '81 and up R100s is 6º BTDC...right? So....at idle, the timing will then be set somewhere between the "OT" and "S" mark, correct? And at full advance it will be approximately 5-6mm before the "F" mark, right? Observing the stock flywheel marks will be unnecessary though if I can accurately program the timing light to indicate the 28º...simply tighten it up once it hit 28º at 3500rpm...right?

Also.....my experience has been that engines that are hot because of too much advance do crazy things...like have a high/inconsistent idle. I am therefore not going to go down the carburetor rabbit hole just yet.

If none of this works it is "Hello, expensive Australian ignition components"....which may just happen anyway.

Snowbum mentions that advance units ending in -007-012 have full advance at 34 deg. So you're going to drop 6 deg on the F-mark which suggests that static will be right at TDC. I don't think that's a big deal...the bike should run. If not you might have to go from 28 to 29/30 in order to find a compromise.

I've never used one of the "dial-o-matic" timing lights. My understanding is they're a bit gimmicky. Maybe things have changed...Snowbum seems to consider them usable especially the more rugged or name-brand types.

Somebody

LOL, somebody is taking the time to improve 40 and older airheads. There are quite a few improvements for them which are on the market now. Both for ignition and charging systems.

While the people spending time and effort are small compared to BMW, they love airheads and like me want to keep them on the road forever and ride them. They are improving upon the almost perfect motorcycle ever made. St.

STEVENRANKIN said:

LOL, somebody is taking the time to improve 40 and older airheads. There are quite a few improvements for them which are on the market now. Both for ignition and charging systems.

While the people spending time and effort are small compared to BMW, they love airheads and like me want to keep them on the road forever and ride them. They are improving upon the almost perfect motorcycle ever made. St.

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Yeah.....I got 4 of them.

banzaibob said:

So....here is what is going to happen (Shout out if you hear something crazy that is going to blow up my bike)

I am going to re-set the timing on the bike to 28º BTDC. I have one of those Chinese Innova timing lights that I believe allows you to set the timing advance value on the display screen. Once I figure that out, I'm diving in. My understanding is that at idle, the timing on '81 and up R100s is 6º BTDC...right? So....at idle, the timing will then be set somewhere between the "OT" and "S" mark, correct? And at full advance it will be approximately 5-6mm before the "F" mark, right? Observing the stock flywheel marks will be unnecessary though if I can accurately program the timing light to indicate the 28º...simply tighten it up once it hit 28º at 3500rpm...right?

Also.....my experience has been that engines that are hot because of too much advance do crazy things...like have a high/inconsistent idle. I am therefore not going to go down the carburetor rabbit hole just yet.

If none of this works it is "Hello, expensive Australian ignition components"....which may just happen anyway.

Click to expand...

So....here is what happened:

I could not figure out how configure the timing light. So instead I simply timed it to the marks. At 3500rpm full advance, it wound up being approximately 5-6mm below the F mark. At idle, it was just a notch below OT. I warmed it up, took it out on the interstate....the problem persisted. THIS is where it starts getting even MORE interesting!!!

I noticed a "tick". I donned my trusty mechanic's stethoscope and traced the "tick" to (you got it) the bean can. Valves, pushrods, timing chain...all OK. Bean can, not so much.

HOWEVER, while test riding it I was able to notice the nature of the problem even more. Decelerating from highway speeds, the rpm stays up around 2000 until the bike naturally slows down...after maybe 6 seconds. On surface streets, around 40mph, it stays up around 2000rpm for maybe 3-6 seconds. Shifting into neutral from 35 mph it does the same thing; hanging up at around 2000 rpm for about 3-6 seconds and then settling down to about 1050 rpm, normal idle, running smoothly. What I'm now wondering is if there is perhaps some internal drag through the transmission that may be is masking the problems? Clutch in, clutch out, in neutral....it behaves the same. HOWEVER....when sitting parked and revving the engine it DOES NOT have this problem. Hmmmm....what am I actually looking at here?

After my trial ride on the interstate I thought the performance was mediocre but not seriously out of character. When I got home I immediately took a temperature reading with the infrared thermometer at the apex of the header pipes....about 450º on both. I don't think that's unusual.

At this point I'm probably gonna get the new ignition system BUT......I'm I gonna have this same problem?

Can

Well, I can't say much except nothing in the tranny or drive train will be causing your problems.

I don't know just how bad your bean can looked or what condition it was in when you took it apart and cleaned it up. It is very possible it is just plain worn out.

Snowbum has written a bunch of stuff up about high idle after warm up. https://bmwmotorcycletech.info/Ignition.htm His write up covers not only the bean can but other things that can cause problems.

The information is in this website along with links to rebuilding the can.

You are a bit too far for me to ride over to help you out, and to be honest, I don't know much about setting up ignition for dual spark bikes. LOL, my late uncle a hot rod builder used to say he set up ignition timing advanced just to where it started pinging and backed off to retard to where it just stopped pinging. NOT the best advice but in my old cars, it worked.

I will look in my tool box, I think I have a bean can and if the shipping is not too much, I could let you try it or buy it if nothing else works out. St.

STEVENRANKIN said:

Well, I can't say much except nothing in the tranny or drive train will be causing your problems.

I don't know just how bad your bean can looked or what condition it was in when you took it apart and cleaned it up. It is very possible it is just plain worn out.

Snowbum has written a bunch of stuff up about high idle after warm up. https://bmwmotorcycletech.info/Ignition.htm His write up covers not only the bean can but other things that can cause problems.

The information is in this website along with links to rebuilding the can.

You are a bit too far for me to ride over to help you out, and to be honest, I don't know much about setting up ignition for dual spark bikes. LOL, my late uncle a hot rod builder used to say he set up ignition timing advanced just to where it started pinging and backed off to retard to where it just stopped pinging. NOT the best advice but in my old cars, it worked.

I will look in my tool box, I think I have a bean can and if the shipping is not too much, I could let you try it or buy it if nothing else works out. St.

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Thanks for the moral support regardless.

As far as the issue of "transmission drag". We know something is causing the rpms to rise. However it is NOT rising while warmed up, sitting in neutral and revving the throttle. Engines with air leaks "coast". and they will do that while sitting and revving the engine up. It isn't doing that. In this particular problem it only occurs upon deceleration while the bike is on the road. You have to admit, all other things being equal, the only force acting upon the engine other than normal carb and timing settings would be the mechanical drag. Even then....that defies credulity. If it was actual drag, it would continue and the rpms would continue reducing at a slower rate, right?

Hmmmmm.......