Saturday, 12 April 2025

1938 DKW SB350 Restoration Update March 2025


It's been a while since I've reported on progress with the DKW SB motorcycle so a recap is in order. I dropped my bike to some mechanic friends to sort out the carburetor and ignition issues back in November 2024. Those issues were quickly resolved, but like the proverbial loose thread on a jumper, other issues quickly unraveled. https://dkwautounionproject.blogspot.com/2024/11/1938-dkw-sb350-restoration-update.html

New tyres were obtained but when the guys removed the old tyres they found that the rims were completely rusted through from the inside. It was probably the rust that was holding them together. New rims were built from NOS stock rims and new spokes.

As the rims were new, they needed to be painted to look 'age appropriate.' They look great.

The guys managed to remove the old speedometer from its housing and install the new speedometer. Apparently there were some very tiny screws in the speedometer back holding it on. The original speedometer housing looks much better than the modern reproduction, which was not a match at all.

Next step was to start her up and take her for a test ride. The clutch proved to be barely functional. Well, after 80 years this is hardly a surprise. We pulled off the covers and took a look at the clutch.

Prewar DKW motorcycles used plates with cork plugs, approximately the same size as a cork bottle stop. Over time these decay and fall apart. As soon as we opened it up some cork plugs fell out.

This ring of cork plugs looks like it was original. All the plugs were consistently sized but blackened and inflexible. You can see some plugs are missing from the disc.

This ring of cork has been repaired / replaced at some point. Some cork plugs are original but replacements have been cut from square pieces of cork, probably from a cork bottle.

It's much more apparent in this disc. A little pressure on the plugs and they all came out easily enough. The metal plates were in good condition.

A new set of corks is on order. Below is a video showing how the cork is fitted.

This will be my next job!

After soaking the plates in petrol....

The cork arrived on 11 April 2025. It only took two weeks from Germany. Generally post from Germany takes 4-6 weeks, but it was a light package.


November 2024 update: https://dkwautounionproject.blogspot.com/2024/11/1938-dkw-sb350-restoration-update.html

Saturday, 15 March 2025

1934 DKW SB350 Motorcycle Restoration Video Series


This is a series of movies by Wedvik Mekaniske following the engine restoration process of a DKW SB 350 1934. The motorcycle was found in a shed, totally dismantled after being started on a restoration process decades ago. The bikes origin is around Femunden in Norway and the bike was probably barely used for transportation purposes. There was very bad infrastructure and barely no roads around Lake Femunden in the 40`s and 50`s and the bike shows evidence of being used in the forest on bad roads. Quite common for woodsmen to use motorcycels for "easy" transportation to work. The bikes life cycle is now ended and the DKW is again back to the same family where it was new. I`m doing the rebuild of the engine and the owner is doing the complete restoration of the bike. The last episode in this series of videos will be with the finished running bike. Hopefully on the nicest DKW´s there is!

Part 1: Dismantle and measuring of piston, piston rings and cylinder

Part 2 - Vapor blasting of head and piston

Part 3: cylinder honing and lacqueringPart 4: carburetor restoration

Part 4: carburetor restoration

Part 5: Nickelplating / Electroplating of bolts and nuts

Part 6: Engine teardown / disassemble

Part 7: Blackening of bolts using engine oil

Part 8: Crankshaft truing

Part 9: Gearbox restoration

Part 10: Cork Clutch rebuild

Part 11: Mounting of crankshaft and cases, measuring of crankshaft sideplay

Part 12: finishing the primary with clutch install and measuring of gear backlash

Part 13: Deburring cylinder ports and adjusting piston rings before mounting

Part 14: Installing electronic ignition and setting the timing - machining needed!

Part 15: Brass casting of new exhaust port cap

Part 16: Finished engine walkthrough