I’ve been out of town more than usually over the past couple of weeks, so progress has slowed down a bit. I discovered that the paint on the subframe didn’t adhere properly – ripples in some places and soft paint in others :-(.
I suspect the aircraft stripper wasn’t completly removed from the subframe. I took the wire wheel and my hand drill and wire brushed the new paint off the frame. Then, I washed it in the sink several times and finished it off with windex and paper towels to dry it.
This time I primed first and could see the primer was sticking nicely. I did a light sand with 400 grit, washed it again and then shot it with several coats of the black gloss enamel. When I came back from my recent travels, the enamel had no ripples and the subframe was looking great.
While I was out of town, the heads came back from Randy Long at Long’s Custom Services in Pennsylvania. I originally sent him the head with the cracked fin to repair. When he received it I called him to talk over the options for the repair. Since the crack extended past the pin, I had Randy cut the pin off and fix the fin. Upon closer inspection of the seats, Randy conclued the exhaust valve was buried too far into the head to be in spec. I decided to ship him the other head and have him replace the exhaust valves, guides, springs and keepers. Here’s a before, after picture set of Randy’s work. Very nice repair.
Today, Sunday, Branden came over and we started working on putting the backend back together. First, we cleaned the rust off the transmission input shaft and greased it with Honda Moly-60 paste. The BMW greases don’t have a great reputation, but the Honda Moly-60 is recommended by many. I used a toothbrush to put a light coat on the transmission splines. It’s best to coat the transmission splines ONLY and not the clutch plate female splines. This way, any excess grease is pushed past the clutch plates so any thrown off won’t coat the plates. I also put a dab on the end of the clutch throw out rod to keep it and where it contacts the clutch plate from rusting.
Next, we put the transmission back in the frame and carefully inserted it into the clutch spline. I put rags on all the freshly painted frame tubes to prevent scratching the paint job. Here’s Branden getting it lined up.
He put the three bolts and the upper right nut back on and torqued them up. Branden had to leave at that point, so I continued with the swing arm, rear drive and rear wheel.
I cleaned the old gasket off the rear drive and swing arm which took some time. I found using carb cleaner and then working at the old gasket carefully with a paint scraper and brass brush finally got the 35 year old gasket off.
Next, I mounted the swing arm with the bushings and ran them in as evenly as I could. Then, using a caliper, I loosened one bushing and tightened the opposite one until the gap was within .02 inch on each side.
Next, I torqued the bushings to the bearing preload torque and measured the gap again. I had to loosen the bushings and readjust the gap slightly and then retorqued to the preload torque. Then, I loosened the bushings and torqued to the final settings which are lower than the preload. I measured the gaps again and they were within .01 inch.
Next, I mounted the rear wheel. I found that sitting on the rear wheel when I took the transmission/drive shaft bolts off keep the shaft from spinning, so I figured it would keep the shaft from spinning when I tighted them.
I mounted the rear drive to the drive shaft. These splines are lubricated by the gear lube in the drive shaft so you don’t need to grease them. I rotated the drive shaft until the splines lined up, slide the rear drive on the shaft splines, and then put the nuts on the studs. There are no torque settings so I tightend the nuts to a reasonable level.
As I don’t have the BMW tool for torquing the bolts that connect the drive shaft to the transmission output shaft, Clem suggested I use some thread lock and tighten with my 10 mm ring spanner until tight. The bolts and washers are “use once” and get stretched when tightened, so they can’t be reused. I put the rubber boot on that goes between the swing arm and transmission and then pulled the drive shaft up to the transmission. Then, I put locktight on each of the new bolts and finger tighted them onto the tranmission output shaft and then leaned into them while sitting on the back tire.
Finally, I pulled the rubber boot over the swing arm and used the large ring clamp to attach it to the swing arm and used the second ring clamp to attach the other end to the transmission. Here’s the pictures of the bike with the back end reassembled.
Thanks you for this. One of the finest documentations of a project I’ve ever read.
Thanks. It was fun to document the work. And it should help me remember what I need to do on the next BMW restore project I do 🙂