Hi all.
so, back to just after the lock down and I bought a Norton jubilee for too much money, moving swiftly on and I am now in the process of stripping it down. Now, the con rods did not move smoothly around the crank so I decided to investigate and found the shells to be in very poor condition and three score marks around the con rod journal as pictured. What would have caused this so I can ensure it doesn't happen again. Any suggestions for local machine shops to get this and a damaged crank case repaired, I live in Stowmarket, Suffolk.
thanks in advance Gary
Others might disagree but…
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Foreign bodies
The score marks on the big-end shells and journal look like some fairly large foreign objects have been in the oil. Oil tanks not thoroughly cleaned after shot-blasting are a favourite, or not flushing/cleaning out oil passages after mechanical failures or repairs.
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Gary, make sure you clear…
Gary, make sure you clear out the crankshaft 'sludge trap' accessed by two big grub screws at each end of the crank (a pig to get out!) The sludge trap can get blocked by debris / hardened sludge in the oil sufficiently to seriously limit the flow of oil to the big ends and end up with them failing very quickly after a rebuild if you don't clear it out after having the crank regound. Good luck - it will be worth all the hard work!
Nick
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Nobody ever gets the oil…
Nobody ever gets the oil tank clean enough after grit blasting it.
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No one should ever grit/sand…
No one should ever grit/sand blast an oil tank - end of!
Dan
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Others might disagree but that damage looks like it might just be worth grinding smooth to lessen the chance of cracks spreading. It's not a load bearing flange. It's there to provide a backing to the oil seal, which can't escape.
Otherwise it's welding, machining, worrying about welded distortion affecting the bearing housing...open a can of worms at your peril...