Re: Correct Crankshaft for 1956 RDE-18

[ADAM GIBB]

I was researching your question, and I think I may have solved my problem mentioned in a previous post at the same time.
viewtopic.php?f=5&t=6136&p=31387#p31387

I was having trouble with getting the flywheel to sit down correctly on an RD17. It seems that the 203655 crank came into use in 1955, was used in 1956 and then went away, as they switch back to the 302530. This coincided with the changes in the seals. The RD series up until 1954 had carbon seals with the washers and springs to hold them in place. Part way into 1955 production, the switched the top and bottom bearings to one that had an integral lip seal. This is where all of the issues with water getting to the lower bearings came from. At some point during 1956 production, they went back to the carbon seal on the bottom end of the crank, and left the lip seal on the top, where there is no water to worry about.

So…..after looking through all of my parts books, I find that the 203655 crank was only ever used with the lip seal on the top end. I have not see a parts list that shows that crank with the carbon seal on the top end. I believe that the cranks are completely interchangeable, as long as you use a top bearing with integral seal.

I think this must be the underlying cause of my problem in the post mentioned above. I may have put a 203655 crank in the engine, and used a top bearing that requires the external seal. Before I tear down the power head again, I will try to get dimensions of of a known 203655 crank and measure one of the 302530s in the junk box and see if the shoulder at the top is in a different place. I think it is…..any want some lightly used gaskets LOL.

I also wonder why they would have changed the crank at all. It seems they could have stayed with the 302530 all along.
Hope this helps.