After I acquired my DKW, I stopped riding the Ariel. This was mainly due to the Ariel having British controls - clutch on the right, brake on the left; while the DKW has the standard - clutch on the left and brake on the right. Changing back and forth between bikes always led to some confusion so it was easier to stick with the DKW as my regular bike. However, after the electrics on the DKW caught fire in June 2024, I was forced to return to riding the Ariel until I could get the DKW fixed. I was surprised - and pleased - to discover the Ariel fired right up without any problem - but it did smoke like a steam train. This was caused by the build up of unburnt oil residue coagulating in the exhausts. What the bike really needed was a good long run to get the engine and exhausts really hot to burn out the oil. Unfortunately, due to family commitments I never had the opportunity to ride the bike long enough to do this. Then the bike began to play up. Sometimes after starting the left hand cylinder stopped firing. Changing the spark plugs did not help. I also noted that the right hand piston was seeping oil through the head seam.
Unlike my German DKW motorcycles, which can go for 100,000 kilometers without needing the pistons decarbonized, the Ariel (and other British two-strokes) cannot do this. Comparing the two brands, it seems that Ariel over-oiled their mixture, which increased the amount of oil residue in the pipes and cooked onto the combustion chambers, requiring the owner to regularly remove the heads and clean off the carbon. I had never bothered to do this - until now.
The job was remarkably easy, even for a mechanical incompetent like myself. This was all done with the engine in place and without removing any of the leg shields or bodywork. First, the front wheel is turned hard over to provide access to the top of the engine. The spark plugs are removed and then, using a 3/8 Allen Key, the bolts securing the head to the barrel are loosened. Once loosened, they are easy enough to unscrew by hand.
The aluminium heads and their gasket are lifted off. Each cylinder has its own head. The first head was caked with carbonized residue. This was cleaned up with petrol and a brillo pad.
The top of the piston was equally disgusting. Again, I washed the piston top with petrol and degreaser and polished away the carbon. It wasn't a perfect job but most of the carbon was removed and what remains should be burnt off / fall off with a good run.
The head was reinstalled and a new spark plug installed. The job was repeated on the other cylinder.
The effect was rather instantaneous. The left hand cylinder did splutter to start with but quickly got into the rythym. There was tons of smoke! I took it for a quick run the next day and the bike started promptly and ran really strongly. I now need to take it on a few long runs and clean out the pipes. I know, it would be a good idea to remove the exhausts and flush the oil out, but I'll wait until I get the DKWs back before I do that. I am just enjoying having a functioning bike in the stable again.
