Saturday, February 21, 2009

R100S BMW Side Car ---R90/6 BMW Side Car preparation

This photo shows the frame reinforcement done on the R100S frame. This also traps the battery in the frame. There is also a down tube which attaches to the lower main loop frame. This allows for a stable upper , rear sidecar attachment point. The lower mounts attach to a large I-Beam which sits parallel to the main frame. Very ingenious set up. Below you can see the vertical reinforcement tube and the upper rear attachment point. The frame is thoroughly tweaked and I don't think it is repairable. I decided to go ahead and tear the bike down today. I will talk to a neighbor who welds and ask him if he could weld the extra tubes onto the R90/6 frame if I cut them out of the R100S frame. On the other hand I may just utilize the lower I-Beam sub frame as the lower mounts are the weak points on my present side car set up. The upper mounts would then simply clamp to the frame as they do now. This would also get away from the "entrapment" of the battery. I don't really want to pull the rear fender and tire each time I need to remove the battery. I noticed that a small weld is broken on the cross brace on the rear of the /6. Nearly all BMW's of this design suffer from this same problem. I have purchased 4 different /6's over the years and without exception every on had the same broken weld.

Below you can see the stock R90/6 frame without the reinforcement tubes. I gave the old R90 a few kicks in an attempt to start it but didn't get much result. A whimper now and then was all. I will stop the attempt and probably remove the engine from the frame. I am nearly sure that the cylinders have some surface rust and will require a hone job to get it into running order. I would like to keep the top end for a 900cc spare for the Black Hag.

The previous owner modified the front fender to clear the shocks. They pretty much butchered the fender and cut way more off than necessary. I will end up cutting a bit off the Blue fender but hope to do a much cleaner job.

The R100S BMW was torn down pretty quickly today. I removed parts starting from the rear and moved forward. The axle was bent and took a bit of work to remove. I removed the final drive (a 32/10) and it appears to be in very good condition. With the frame reinforcing , the battery is trapped in the frame. This means that with this set up a person must remove the rear fender and wheel to remove the battery. I removed the carbs, air boxes and then the transmission before removing the engine. The left side carb had rust leading into the intake port so the engine will definitely need to have the top ends removed for a cylinder hone at the least. The engine oil had no debris in it and the final drive / transmission oils were very clean. The transmission out put splines were showing recent lubrication so I think the transmission was rebuilt right before the bike was crashed. (the previous owner said the transmission was fresh) The shock absorbers all look usable and there are quite a few good pieces from the R100.

Down to the bare bones pretty quickly. I started the tear down at around 10:00AM and stopped at 5:00PM. I was able to remove all wiring without cutting anything. I see someone had changed the starter relay to what appears to be an automotive type relay. There were also a few wires added here and there so who knows if it is any good at all. I got down to removing the front end and have found that the head bearing shaft is pretty much stuck. I will use penetrating oil and let it soak until it gives. The throttle control was shot and the gears are stripped in the mechanism.
Next I will begin tearing down the R90/6 to prepare it for the frame reinforcing, engine swap, front end swap and transmission. I think I'll use one of the 1974 kick start 5 speeds as I have two of them now.
I had never pulled an engine without first removing the heads and cylinders. Surprisingly it was not difficult at all to remove the engine as a unit. I did remove the transmission 1st.
I received the old BMW Cop Tank back from Mexico today also. I installed the aluminum fuel cap, the tool box lid and lock, and the new BMW roundels. I was going to install the knee pads but don't have the proper glue. I have two sets of knee pads and neither fit that well. I may just order a new pair. I also bid and won another Tuetonic QSL 1000 Mile Solo Seat on EBay yesterday. I limited my bid to $130.00 and won it. The last one I found was over $350.00 so I am happy with that purchase. I will figure out a way to mount it, although all the center reinforcing tubes would crowd the mounting of the seat. All the more reason not to use the extra tubes on the new setup. I'll figure something out down the line.
This new sidecar tug project will not be completed any time soon. It will take a lot more time and effort to get it into any sort of running condition. My present goal is to get everything mounted into the new frame and then go from there. I would like to detail / paint and really clean things up as I go. This Cop Tank will be the tank for use on this bike. The Heinrich Tank I have will not work with the under fuel tank master cylinder that the /6 uses.

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Gila Mtns.

Gila Mtns.