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Oil pump drive

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My understanding is that the lightweights had a 3 start worm to drive the oil pump, later on a 6 start worm was used.  Is that correct?  Presumably done to increase the oil flow through the engine.

If so, any advantage in replacing the 3 start with a 6 start drive?  Seems like there would be.

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There has been plenty of coverage  of  changing the pump drive to 6 start.  This doubles the wear rate of the pump and tends to overwork the pressure regulation  and over oil  the engine unless the extra flow  is put to good use.  Usually makes for more problems  .

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Thanks for the reply.   I've read through the Heavyweight section comments on doing this, the conclusion is that its not worth bothering with.  Except for something I didn't notice mentioned, much improved scavenging. 

As for over oiling the engine, some of the comments didn't add up.  I can believe the head will get more or even too much oil but the crank?  It seems the con-rods were "drilled" to help get the extra oil through the engine.  Struggling to believe that was necessary.

Still not sure what to do, needs a bit more thought.

 

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The earlier Big twins  have  suffered with seizures , usually on the drive side,I suspect the oil holes in the rods were to provide some extra lube and cooling  for the pistons. The 6 start gears  provided the extra  oil  and allowed pressure feed to the head .

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I've been wading through the information on this website regarding 3 start vs 6 start pump drives.

Seems someone checked the outputs.  As might be expected the 6 start doubles the output but most of that output is discharged through the PRV.  So little or no gain at the crank.  At least the scavenge side will be able to clear this oil from the sump quickly.  

Started me thinking about a positive oil feed for the cylinder heads, not just bleeding oil off the return, taking it from the pressure side of the pump.  Something to think about.

Reading through the information available on this subject, there is some useful stuff  but also a lot of contradictory information.  Sifting through that has been interesting but also made somewhat frustrating by the way this website functions, slowly with a mind of its own, sometimes!

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At least the forum  works (sort of!)  ,  Lots of other bike forums seem to be  almost dead , without regular fresh posts  there is no reason to enter. 

 


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