Misc: Everything Else 1951 Black Shadow Restoration

craig

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Head are being checked for thread fits... exhaust, push rod tubes, cap nuts, spark plugs.
Exhaust nuts seem to be best in natural bronze, I do have patina chrome as well.



20210116_HeadExChk1.jpg
 

craig

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Looking at choices for C3 and see that new modern C3 are quite thinner at the tail of C3 than the earlier versions. The new C3 having a scalloped tail bore pattern due to spline broach. So this either thinner or scalloped bore makes the possibility of tapering for an o-ring questionable.

20210122_C3Lineup.jpg
 

timetraveller

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That is not going to help. I have not seen the later type so could you measure the internal distance between the top and bottom of the splines. It looks as though either the height of the splines must be higher or the internal diameter of the inner end must be smaller. If either is the case then it might not fit, and I assume that they do. My technique of using a valve seat grinding tool to give it a cone shape does not look as though it would work. One of them looks to have a very thick inner end and it might be possible to cut a stepped recess with a flat inner back to restrain the 'o' ring. What do you think? Even if it is possible it would certainly require better machining skills than just using a valve seat grinder in a pillar drill or mill.
 

Chris Launders

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I have just changed mine which was worn for one from another members stock of spares he was downsizing, it is not a recent one and both are the thin type, this is why I have been puzzled about being able to grind a groove and use an "O" ring, I certainly couldn't.
 

craig

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Checking the balance factor on this particular twin crank.
Setting twin crank up in a wheel truing stand , hanging weight until the crank is positionable in 360 degree without movement.
My rough weight on this crank is 220grams.
What has your twin crank balance weight been?

20210124_TwinCrankBalanceGrams1.jpg
 

timetraveller

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That is going to depend upon the weight of the pistons etc. It looks to me from the photograph that someone has already put the extra holes that I have found necessary into the flywheels near to the crank pin but I do not start off with the extra weight needed. I weight the small ends of the conrods, the total weight of the pistons, ring, gudgeon pins and circlips. Calculate 46% of that. Subtract the weight of the small ends and then work out what is needed to balance the flywheels. For racing some people prefer 50% balance factor.
 

greg brillus

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2 cranks we had recently both had Carrillo rods.......One was for a 1200 Norvin, the other for a standard Shadow........ On both we had to machine material away from the big end area of the flywheels to get the balance factors to 60% Norvin and 46% Shadow.......I'd have to go back through my worksheets to see how much material we removed, but obviously they were different from one another. The big end of the Carrillo rods seem to be heavier than stock Vincent rods.
 

craig

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I wasnt looking for balance factor, simply what did it take in gms to counter balance your last crank after balancing?

But here is more crude data

piston, pin, rings (in paper), clips (in plastic)

20210124_PistonRingsPinClips1.jpg
 
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