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Crank Truing

timetraveller

Well Known and Active Forum Website User
VOC Member
I have never worked on an H-D but it sounds horrendous. I have done about 20 Vin flywheel assemblies for myself and others and have never come across any which needed the kind of treatment described on that site. I have seen flywheels with bruised circumference which would certainly have had more than ten thou scars but which still could be trued up on the shafts. Assuming that the centres in the shafts are in good order then the flywheel rims should be good to about a thou. The best I ever got a whole assembly up to was about half a thou each side. The worst was a pair where the drive side main shaft had been replaced incorrectly. There was a seven thou run out due to the crank pin centre to shaft centre being incorrect by seven thou on the drive side, compared with the same dimension on the timing side. Those wheels could not be trued and the only proper cure was to remove the main shaft, re-machine the hole and then replace the main shaft with one with an oversized diameter where it went into the flywheel. The crank shaft assembly is the backbone of the engine. True it up and balance it and the bike will be a pleasure. Fail to do either and you will not be enjoying a Vin as it should be.
 
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Vincent Brake

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VOC Member
The crank shaft assembly is the backbone of the engine. True it up and balance it and the bike will be a pleasure. Fail to do either and you will not be enjoying a Vin as it should be.

SO VERY TRUE + TRUE TIMING GEARS SET UP

I Balance a bit more than strd48% but go to 55%, result better for higher speed cruising 120/130km-h

vincent
 

roy the mechanic

Well Known and Active Forum Website User
VOC Member
The quick answer is rarely. The h-d crank is actually very different to the vin. Also the machining on the vin is done very carefully.
 

roy the mechanic

Well Known and Active Forum Website User
VOC Member
The mainshafts on the Hardly Ablesom appear to be tapered, Vincents are parallel.

Tapered mainshafts are only the start. The 'wheels are cast on h-d, versus machined from blanks, the rods on the american job are "knife + fork", so effectively it has 3 big ends (the rear rod is the fork the front fits into it. this allows the bottom end to be only slightly narrower. The main bearings are timken tapers on the drive side (a pair with a spacer ) much like a Velocette. On the timing side main it uses a caged roller rather like an outsized alpha big-end. They all have vibration issues, unlike the (if you are lucky) Vin.
 

vibrac

Well Known and Active Forum Website User
VOC Member
I once got a Comet Crankcase from a rubbish tip (Those were the days!) after I stripped it and cleaned off the surface rust I checked them and they were within half a thou each side....
 

craig

Well Known and Active Forum Website User
VOC Member
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Chris Launders

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VOC Member
I know someone who about 40 years ago had his crank rebuilt at Hillgates in Stockport, when he arrived to colllect it, it wasn't ready "won't be a minute" says this voice from the back area followed by this crash, he dashes into the back thinking someone had an accident, no just the guy dropping his crank on to a large alloy block to "bump" it into line.
 
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