37 600 sv aero

[polly]

just removed the timing chest following a breakdown of no oil returning to the tank, resulting in all the oil stopping in the engine!!, and possibly the fault maybe the bush in the timing cover was loose and had turned 90 deg, possibly stopping the scavenging side to work??, can anyone advise me on replacing this bush which appears to be eccentric!!
regards david

[polly]

pics!! sorry what are the oilways in the chest for??

[Doug]

David,

Most all of the oilways dealing with the oilpump are located behind the pump. See this post here for an illustration:

https://www.douglasmotorcycles.net/index.php?topic=4288.msg15399#msg15399

It is for an A31 engine, but it is virtually the same system.

The bush that spun, is just a support for the steel post the the oil pump drive worm spins on. Douglas wanted to provide something a little harder than their aluminum to press the pin into. The gutter leads oil running down the face of the timing cover to the drilling through the side wall. This passes through the bush to a groove on the outside of the post, and a spiral groove that in turn leads oil to the bronze bush inside the worm. It sounds like the worm may have seized on the pin, and the pin has been spinning in the locating bush? 

The image below is from my 1936 Aero, and you can see the bronze bush in the center of the worm and the end of the steel pin it rotates upon.



-Doug

[polly]

many thanks Doug, the bush I referred to was the one in the face of the timing cover which acts as a outrigger support for the end of the crankshaft with the scroll and nut driving the oil pump, this looks different to your set up?? regards david

[Doug]

David,

If your oil pump worm is attached to the crankshaft, then indeed it is different from the 1936.

I had a look in the 1938 Spares list (sadly not illustrated), and it seems to collaborate this. Part number 18213 is the oil pump worm; not much can be told from that alone. Part number 18309 is the key for the oil pump worm and generator pinion. In the 1936 arrangement, there is no key required for the oil pump worm. Unfortunately I do not have a copy of the 1936-37 spares list to cross-eliminate the part numbers, but it does seem they made a change. It would seem like a retrograde, as the worm driven by the tang of the crankshaft nut allowed some latitude on the 1936-37 models. With the worm attached to the crankshaft in 1938, the alignment of the outrigger bearing in the timing cover need to be precise. The EW had the worm attached to the end of the crankshaft, but it was simply cantilevered; no outrigger bush.

Anyway, the gutter and oilway serves an identical purpose except that it oils the journal directly. Ya learn something new everyday here on the Forum!

-Doug