E: Engine Big End Replacement

Chris Launders

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What crank is it, I believe they were all cast iron other than the Inter and Manx so welding a "standard" crank might not be a good idea.
 

Cyborg

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It’s an Inter crank and looks like steel. I recently broke down and bought a TIG and it seems like it it would be relatively easy to run a very thin bead around in there. There are a couple of holes in the flywheels that look like they could be used to pin the two wheels together, but will have to confirm that. With the timing side in the quill and the drive side in a chuck bolted to the mill bed, I can align the two half’s. Then a boring head would get it close to size and I could finish it with another sliding mandre come lapping tool, or actually break down and buy a proper lap. For a hole that size, they aren’t that expensive (just under $150 usd), plus it’s a size that I would likely use again.
 
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david bowen

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At the Vincent Factory, the flywheels were not paired just pick up from the bin and assembled, Con rods and big end pins were colour coded and there was a chart on the wall showing the coding and correct size needle rollers to use, same bench set of centres,and on the floor a block of lead ! which we use to tap the flywheels onto to get the correct read, ( Bob Culver still has that block or lead for the same purpose. ) the lead block about once a month the lead block was cut up put into a cast iron saucepan and cooked to get to shape back. that was 69 years back so whats changed,
 

Cyborg

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Another good trick is to drill and fit a small roller, Half in the flywheel and half in the main shaft, So the shaft can't turn. Cheers Bill.

Too bad this crank didn't have the roller you mention. If a roller had been installed, the fellow could have use a socket to tighten the new crankpin nut instead of a Milwaukee Speed Wrench!

Crank Speed wrench.jpg
 

Cyborg

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Sidetracked again Bill....Actually it had a key which became two keys. Strange.... the M/S was a snug fit and the nut was so tight, I couldn't break it lose with a 2 ft breaker. Had to use a 1/2" impact gun. Guess it tightened itself a 1/4 turn when the key broke.

Inter mainshaft key.jpg
 

Cyborg

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Thought I would dredge up this thread because I’m going to try my luck with a twin crank.
Question #1 is why use Lanolin when pressing in shafts and pins? Yes to prevent galling, but what makes lanolin better than some random petroleum product like vaseline?
Job 1 is to press in a new timing side mainshaft, so hopefully it goes in straight.
 

greg brillus

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Check your big end bores in the wheels first, and the pin diameter to make sure you will have enough interference fit before installing the mainshafts........
 
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