I purchased this project in early 2018 but it had been sitting while I finished other projects to make room on both the bench and in my head to begin this one. Finally, I began on October 4, 2018.
Plunger frame BMW motorcycles are becoming rare to find and if you want one, you have to pay up for it. I purchased this project from an old acquaintance/friend. I had purchased a 1956 R69 project from him many years ago and that project, like this one, was exactly what he said it was. I wonder what the next project I purchase from him will be?
Much of this bike came to me in a semi-completed condition. Both the motor and transmission were rebuilt by a very reputal and now deceased BMW mechanic. Most of the paint work and pin stripping was also done…a great way to start a project.
As usual, there were some hidden aspects to deal with which were unknown to both the seller and myself. Work on these types of restorations have been made easier with the introduction of the Barrington Manual for /3 and plunger bikes from Barrington Motor Works in Barrington, NH. Chris and Barbara Betjemann have done a superb job in compiling and publishing manuals on /2 and US model twins, Singles and the BMW R51/3 – R68 guide. These manuals are true labors of love and dedication to their love and art of restoration of these old motorcycles.
The R51/3 is a very beautiful and elegant design. The unique elements of the plunger frame, standard tank with its rear sloping design and the “elephant ear” front fender, really make the R51/3 stand out in the BMW line of post-war BMW motorcycles. My project shows a bit of shelf wear as do so many of these projects when finished. They take a long time and a great deal of money to get to the end so they spend a lot of time in the shop and on the shelf, so to speak.
All parts were carefully evaluated and inventoried and the missing parts identified to get a full picture of what was needed to get this project started. At some point, this bike sat outside and the weather got into the cylinders and final drive unit and the seal and piston mating surfaces were badly damaged and in need of replacement, which was a costly venture.
In order not to have to bore the cylinders 4th over, I was forced to go with a pair of used R50 standard bore cylinders and have them bored to first over. Not a perfect match but locating a good pair of R51/3 cylinders is almost impossible. The original cylinders will eventually go with the bike and the new owner may decide to re-sleeve.
The final drive unit had serious pitting on the seal mating surfaces, no shims, pitted and missing bearing needles, damaged and frozen parts and other problems that led me to send the unit out to Benchmarkworks and let the experts with the correct parts available to rebuild the drive. As usual, they did a superb job with a quick turn around and also kept me in the loop through the process. I have ordered the first of many parts and hardware orders and when it all arrives I will start the process of slowly putting this beauty together.
In March 2019, the project was slowly coming together as you could see in the new photos. This has been a long project but progress is being made. With the running gear, suspension and wiring in the frame, the bike was close to completion. Once the wiring connections are made, I can finish the project.
As you can see from the photographs I have added a 12 volt charging system to the project. The system is from Benchmarkworks and I have used this system on 90% of my restoration projects as well as my daily rider a 1967 R69S. I find the system is virtually bulletproof. What is gained from the 12 volt charging is brighter lights and the ability to use the accessory plug for minor needs. The brighter lights are important because these older bikes have so little lighted exposure. Benchmarkworks now has an LED tail light unit for both /2 and /3 models which works VERY well in terms of visibility.
The carbs have been totally rebuilt and the bodies media blasted using a 9 mil glass bead. This creates a very nice surface similar to the original. I hope to get the bike wired and the project done within the month…
- Triple matching number motorcycle, engine, frame and head stock plate
- Frame, tank, fenders painted Avus Black single stage paint
- Hand pinstriped
- Original half-hubs black powder-coated
- New chrome spokes laced to new black/silver rim
- New stainless steel axels
- All new wheel bearings properly pre-loaded laced and balanced with new 350 x 19 Metzler tires and tubes
- Motor and crank rebuilt by Karl Schmit with new bearings and seals
- Replaced original R51/3 cylinders with /R50 cylinders, rebored, new Kolben Schmidt first over pistons installed
- Original heads fit with new guides, seats, and BMW valves
- Final drive and overshaft rebuilt and shimmed by Benchmarkworks
- New front end components, shimmed and sealed
- Speedometer is original, correct black face with domed glass and rebuilt by North Hollywood Speedometer
- Carbs are correct, original, 1/22/61-62, cleaned, bodies media blasted with 9mil glass bead, fit with new jets, needles, floats and gaskets
- Correct new 30″ handle bars
- Chrome Parts all re-chromed
- Aluminum parts all professionally polished
- New Pagusa solo seat and rear fender rack
- Rebuilt magneto
- 12-volt charging system by Benchmarkworks
- New wiring harness, switches, and cables
- New /3 petcock and fuel line
- Correct /3 spark plug caps
- New headers and swallow tail mufflers
- Sealed battery in period correct battery box
- Original 6 volt Bosch horn and R51/3 cylinders included. New owner may decide to sleeve old cylinders