General => Douglas Motorcycles - General Discussion => Topic started by: bmwmyplace on 05 Nov 2004 at 11:08

Title: New member, DT Crankshaft and Connecting Rods
Post by: bmwmyplace on 05 Nov 2004 at 11:08
Hi Just joined the group.....I  belive I have a 1929 Dirt track 500cc which I have owned for 14 years and done nothing to it.....time is approaching to do something.....problem is crank and rods are not in very good shape....does any one know of a method of recovering the crank and a sorce for new rods.....My alternative is to put a bmw crank into it...but this would shorten the stroke and I am loath to do this plus it is an excessive amount of work.... and help would be appreaciated  Thanks in advance regards Peter
Title: New member, DT Crankshaft and Connecting Rods
Post by: Doug on 05 Nov 2004 at 13:37

Part of your answer is already here on the forum!  See the following link:

Crankshafts are a difficult matter.  Depends on what is wrong with it.  Scoring of the web face or damage to the counterweights can be repaired.  Torn up tapers can be lightly skimmed, heavily skimmed if you are prepared to make an insert for the flywheel.  The crankpins are another matter, about all that can be done is to grind/lap them up to -0.003" to try and clean up the surface and fit oversize rollers or undersized connecting rods.  The crankpins can not be re-ground significantly as the case hardened surface is only about 0.040" deep at most; but long before that stage you would not be able to reassemble the big end due to installation issues.  

A small batch of crankshafts were made some ten years ago, but have sold out.  I have been checking into having some made myself, but the cost is very high.  As there is not much demand for new connecting rods, even though available, it is not reckoned that crankshafts would sell.