Monday, 19 August 2024

1938 DKW SB350 Restoration update August 2024


Having seen videos of the motorbike being started and ridden I was confident that I would quickly be able to finish up the last few jobs to get the bike back on the road. I never intended a full restoration but would leave the bike 'as is' with it grubby and worn patina. However, after getting her home and trying to get her started, I ran into problems.
Firstly, the bike did not start easily. It took a lot of fiddling around before it finally kicked over and ran for about 8 minutes. It then began to backfire through the carburetor and the ignition was snuffed out. After changing the spark plugs, the bike would start up promptly but was constantly backfiring now. Then old petrol tap began leaking like a sieve and the carburetor began flooding. I had already ordered a replacement petrol tap and carburetor when I bought the bike so I put those jobs aside while I waited for the parts to arrive. Other items I ordered - mainly for general hygiene - were a taillight, a replacement  speedometer in kilometres (as opposed to miles) and all control cables. These arrived this week.

I decided to stick with the old Amal carburetor and used the new carburetor for parts. The replacement was actually a copy of an East German generic carburetor that fitted almost all old DKW and MZ motorcycles. The problem with the Amal carb proved to be a missing needle clip, so that was an easy fix.

This stopped the carburetor flooding and along with a little tightening here and there the steady drip from the carb stopped.

The next job was the replacement of the broken speedometer. After a bit of fumbling around I managed to remove the speedo housing, but then I found the original speedometer was very firmly attached to the housing and I could see no way to remove it. Discussions with the prewar DKW motorcycle owners club on Facebook (there are several groups) suggest this would need a lot of soaking in WD40 and then gingerly attempting to unscrew the speedo from the housing. I guess they made things to last in the old days and did not conceive the need to replace the speedo. I made several attempts to remove the speedo but I was unsuccessful. More advice required!

One long bolt secures the speedometer housing to the top of the forks.

I can see no way to unscrew the speedometer as there is nothing to get a purchase on.

I suspected that backfiring through the carburetor could be a symptom of the ignition being too far advanced. This was not a problem prior to my taking possession as the bike was starting and riding easily. All I could think is that the VAPE ignition has shifted during transport. It took some time to get the generator side engine cover off as it was firmly stuck. Looking at the Vape and the marks made on the housing, I thought the ignition timing may have moved about 3mm from where it should have been. Unfortunately, I didn't have a puller to remove the hub and make the adjustment.

While I was thwarted with the Vape, I attempted to replace the worn out choke cable. That proved to be more challenging than expected. The replacement cables were not the same size as the originals and their fittings did not necessarily fit (why? This seems so common - why don't they make replacements the same as the originals?). A lot of frustration and much swearing was involved in refitting the cable, but the result was less than perfect. The tension was all wrong and the choke automatically reverted to on.

All these frustrations were expressed to various Facebook groups and to members of my motoring club. One of the guys in the club took pity on me and invited me to bring the bike over to his place as he was sure he had a suitable puller.

Vendors I have used so far include:
1. https://www.motorradmeistermilz.de/
2. https://www.Zeitmaschinen-shop.de

Update 11 November 2024 - Adult supervision at last!!
The bike goes to my friends at Classic Gasoline for some fiddle farting.
https://dkwautounionproject.blogspot.com/2024/11/1938-dkw-sb350-restoration-update.html
Acquisition: https://dkwautounionproject.blogspot.com/2024/07/1938-dkw-sb350.html

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