The Latest On My R-100RS Barn Find

[Hawk Medicine]

Hello fellow inmates:

If you have missed my Airhead project thread, you can catch up by going here:

http://www.advrider.com/forums/showt...hlight=R-100RS

A couple of weeks ago I declared the resussitation of my RS complete but as fate would have it, the electrical gremlin came back with a vengeance. Let me explain...



In my last installment, I had taken the RS up to Auburn, CA for the 49er Rally as a shake down run and during that trip, the ignition began cutting out unexpectedly. My friend Pat and I checked the bike over again, cleaning up some connections that I missed and after that, the bike performed flawlessly for maybe 200 miles. I was convinced that the electrical crap had been put to rest once and for all.

Last Wed Pat and I made a date for me to ride down to his place in Concord, to balance my wheels, so leaving at about 9:AM, I rolled the 72 miles down 101 to Rt 37 and then RT 180 without incident. Once we got the bike into the garage and cooled off, it took longer to remove the rear wheel than it did to balance them and Pat was nice enough to use a couple of his special vintage wheel weights on my bike. Nice!



Getting done early was a good thing. I had gotten a late start from home because of rain in Santa Rosa and I still wanted to hit Key Kraft in SF for two sets of bag keys, plus I wanted to shop for a pair of riding boots.Therefore, with the real work done, we hit the road for the City.

Needless to say, after that build-up, 20 minutes of fairly hard riding left me, with my bike, standing by the side of the road. Again... At first we thought that it was fuel starvation but after a system check, the bike started and ran perfectly. Ok, we're off! The next time it quit on me, we removed the tank and checked the ICU's connection. A little more fiddling and the bike ran again, so we thought that we needed to replace the ICU. That led to a Bonzi run into Castro Valley to hopefully buy a new module. To make a long story short, no one had one. Not one at any of the local auto parts stores or at the Buggy Shop. Finally, out of desperation, we called and then rode over to Recommended Service, owned by Dave Gardner. He had the part and it was only $229.95! (Choke!) Dave's been around Airheads forever and when we were discussing problem and Dave asked:

“When the bike cuts out, does it backfire?
Yup... It sure does.
Does this happen when the bikes hot?
Uh huh...
When the bike cools down, does it run ok again?
Uh... Yeah! Pulls like a freight train!
Well, I'd suggest that you replace the Bean Can. The ICU is probably fine.
Huh?
Yep.. Seen it a million times. The can gets hot and then the it becomes intermittent.

Dave was perfectly willing to go along with our reasoning and sell me a new ICU for $229.95 if I wanted one but a new Bean Can? That costs $500+!! I had to sit down for a minute... I thought: "What if the problem turns out to be the module, even after we swapped in a new BC? Or even worse, what if I install a new ICU and then discover that it was a faulty Bean Can at 10PM, half way to the Chief Joseph Rally in Oregon, on a back road, in a rain storm?"

Pat, Dave and I threw ideas around for a little while but in the end, I ducked into the office and handed my Master Card over to Dave's wife, before leaving with a brand new bean can Ignition and a few rubber parts that I needed.

We got back to Pats garage about 7:00PM and immediately pulled the tank and the front cover off, yanked out the plugs and began preparing to install the new ignition, by disconnecting the ground and setting the engine at TDC. Then, working with one of us on each side of the engine, we unplugged and pulled out the old BC and installed the new one. When we checked for spark, there wasn't any...



Now get this... Over the course of the next several hours we tried everything we could think of multiple times. We connected the BC, disconnected it, put the old one back in, reconnected everything, disconnected everything again, traced out the wiring, checked for continuity, disconnected and reconnected the ICU, cleaned the contacts, checked battery voltages, amp drops, supply voltages, pin polarities and grounds. Nothing... It was late, we were both tired, I hate doing electrical stuff anyway (I once fried the wiring harness in my R-75 while trying to install a fuse.) so I was almost happy to toss in the towel and hit the hay on the foldout.

Thursday morning, after going through the whole list again... Twice... We opted to try replacing the ICU next and luckily, we found a brand new one at a VW restoration shop for a bargain basement price, came home, installed the part and... Nothing...

This time we stopped and thought the situation through one more time and realized that the only thing that we hadn't examined carefully was the plug that connects the Bean Can to the ICU and when we pulled on it to get a better look, the plug's case came away in Pat's hand, leaving the wires with the connector clips, waving in the air. When we examined the clips, the barbs that hold then into the plug were flat and unmarked. They appeared to have never been properly installed at the factory. Thats a new one! Then we examined the original Bean Can and noticed that the top screws had been removed and reinstalled using too small a screw driver, that ginched the heads. Pat said: “Someones been in here before. I wonder why?” Well without dwelling on the question, we traced out the wiring, reset the plug's wireing as per the reinterperited diagram, plugged everything together and... Nothing...



By now, I was 100% frustrated and calculating how much of my money I could recover by parting the bike out, so I told Pat that I was going to go upstairs and lay down on the sofa for a few minutes, while he elected to get on-line and look for a better wiring diagram. I directed him to Snowbums site. I had worked my sales estimate up North of $4500 when Pat gave a whoop and called me into his office. As it turned out, both our diagram and Snow bums drawing showed the plugs wiring based on polarity but Pat had reassembled it using the diagram pictorially, meaning that the wires ended up reversed. Then it was back down to the torture chamber, where we had the bike running 10 minutes later.

To test things, we did another Banzai run through rush hour traffic, to Key Kraft. We wanted to make the bike fail 'right now' if it was going to, so we ran to the bridge at 80 to 85 MPH and then crossed the bridge at a crawl, splitting lanes,all the way and finally crossed the City in more stop and go stuff, ending up at Church Street in Castro.. The bike ran flawlessly!

After ordering my lock work, we then crawled back across SF and had a fine $20 dinner in China Town, before I got back on the RS to go home. I ran North, crossing the Golden Gate Bridge and then rolled up HWY 101 in the dark at high speed, back to Santa Rosa. Once again, I was trying to get and keep the engine hot. Luckily I had no problems what-so-ever.

Saturday, I was up early and headed into the city again, this time to pick up my keys, and did another 70 to 80 mph trip, combined with an afternoon's worth of city riding, without incident. Therefore, I'm relatively confident that we solved the problem but OTOH, theres still a question of exactly what problem we actually addressed. Was the bike cutting out because the Bean Can was bad? Pat and I agree that B Cs usually either work or they don't but Dave Gardner's experience is too vast to ignore, so we installed a new one. Was the ICU bad? Maybe. I certainly thought so and the ignition did respond to plugging and then replugging that unit.

OTOH, Pat is entirely convinced that the root of the problem was the faulty plug connecting the BC to the main harness. Probably a $.50 part. Heres his reasoning:

The real key is the ginched screws on the Bean Can's case, indicating that the canister had been opened up before. We also knew that it had not been taken completely apart. That means that someone had been poking around in the ignition canister and judging by the corrosion and dirt on the case, it was a long time ago. Also... There was a very good reason why the PO parked his bike in that barn with a full tank of gas and never rode it again. What was it?

We now think that the ignition failed on the PO in the same manner that it did me and because he was an electrical engineer, who also considered himself to be something of a gear head, he tried running down the problem and had no success. How did he miss it? Because the problem was intermittent and was hidden inside of the plug's casing. How many times have to traced an electrical to a misassembled plug? Right. Never. But the end result was that the PO parked the bike in frustration and somehow, over the course of the next six years, never got back to his 'unsolvable' problem.

So thats it for a while. The bike has a few new parts, my wallet is a few hundred dollars lighter and the RS is running well enough to land me in jail. I'm also learning to use the Garmin GPS and I really like having it on board. This coming week I intend to find time to reinstall the lowers, along with some auxiliary LED stop lights, to be hidden in the turn signals. Then, I can reinstall the seat lock, along with the original ignition tumbler and start cleaning the bike up a little more.

I just hope I'm done with hard-core wrenching for a while but I am intending to learn some more about electrics, starting with "classic Boxer Charging" by Rick Jones.