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50 or 47.5 degree Pazon?

Rob H

Well Known and Active Forum Website User
VOC Member
Looking again at ignition systems and noted that Pazon list their system for 50 degree vincent v twins.
I thought that the twins were 47.5 degree V?
If so how does that work one of the cyclinders must always be slightly out if the ignition trigger is based on 50 degrees!
or is it just a typo in the Pazon literature?
 

Rob H

Well Known and Active Forum Website User
VOC Member
Just had a quick trawl of the internet and quite a few references list the engines as a 50 degree V twin,
Even one at 45 stating same as a H**** D*****!!!
 
Last edited:

Magnetoman

Well Known and Active Forum Website User
VOC Member
No they are not. Series A Twins are 47 degrees!
Various sources state 47.5 degrees. But, aside from what is written, a half degree isn't much. Has anyone ever taken the time to carefully and accurately measure the angle between the faces on at least two sets of Series A engine cases?
 

Magnetoman

Well Known and Active Forum Website User
VOC Member
I used a Wiki Article on Vincent Motorcycles.
Hmm, not exactly the most authoritative of sources.

If the design had called for, say, 47.0 degrees, but the machine shop made them 47.5 degrees, there are a couple of ways to create that error. The surfaces for the cylinder bases could be 47.5 degrees apart but verticals through their centers could meet at the crankshaft. Or, they could be 47.5 degrees apart and the verticals could meet above or below the crankshaft (known as desaxe if done deliberately, the most well known motorcycle example being the Moto Morini 3-1/2). Let's assume the former for simplicity of calculation to see what the consequences would be.

A rough measurement from the outside of a Vincent engine, guessing where the centerline of the crankshaft is, has the mounting surfaces at the top of the heads 12" away. If the angle was accurately machined in the crankcases to be 47 degrees the horizontal spacing between the centers at the tops of the heads would be 16.214". If, instead, they were 47.5 degrees the spacings only would be ~1/8" further apart, at 12.368". Since this would have little practical effect during assembly, holding a tolerance better than 1/2-deg. wouldn't necessarily have been an issue. So, independent of whether the design called for 47 or 47.5, it would be interesting to know what an accurate measurement of the angle reveals.
 
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