Crankshaft regrind

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Coolhands

Coolhands

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I blew up my motor a while back and looks like AN has barrels back in stock for my ‘72 commando. The cases look good and the crankshaft looks salvageable. Failure was oddly enough in the connecting rod letting loose?

Recommendations on a machine shop with Norton crankshaft experience?

Any other advice in rebuilding (or not) such a catastrophic failure? Other than and oil pressure gauge…I got one.

I have a 71 engine running like a top in in it now so I’m not in a hurry.
 

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Most engine rebuilders do what's called. Grind to suit .make sure you mating surfaces are clean and burr free, Fit your new bearings to the new rods and they can easily grind to the book clearance , then clean clean clean ,those bits of bearing shell white metal went some where ! buy some gallery brushes and go through every hole with solvent then wash , blow out all holes and threads , chase threads and then clean again with hot soapy water , even a bit of water blasting . Then final blow off and dry , spray bits that might get instant rust , and bag .till assembly. Cheers
 
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That crank doesn't look bad at all, 10 thou will probably clean it up. Take the crank apart, then bolt the two throws together before you take it to a shop to grind. That way they get to the journals easily and can do a proper job. If the shop has the capability, take all the rotating parts along and have it balanced after you put the crank back together. Not too expensive and you will feel the difference. Good luck!
 
Oil starvation is a possible cause, driveside always runs with a lower oil flow than timing side so it usually goes first when oil pressure is low. So oil pump refurb, oil pressure release valve opening pressure to be checked and you have an oil pressure gauge sorted already.
 
"Failure was oddly enough in the connecting rod letting loose?"
Nope. That's what happens when the bearing is not supplied with enough oil, then it continues down the failure path. Be glad you stopped the engine before ventilating the crankcases.
 
milfordite said:
That crank doesn't look bad at all, 10 thou will probably clean it up. Take the crank apart, then bolt the two throws together before you take it to a shop to grind. That way they get to the journals easily and can do a proper job. If the shop has the capability, take all the rotating parts along and have it balanced after you put the crank back together. Not too expensive and you will feel the difference. Good luck!
Click to expand...
Let the MACHINIST do the setup. It's important for accountability reasons.
 
Spend a bunch of money build a motor that can take a beating or take your time and build it close to stock with advice from members here and save yourself a few thousand dollars, and most importantly, ride slower in the future. ;)

That was the motor out of the good deal used bike right? It was an accident waiting to happen with all the oil dribbling out of it. Probably didn't have the oil changed very often either. I don't know if 71's had a spin-on oil filter or not. If not, a spin-on oil filter is something you should install for the used motor currently running like a top, or you may end up with two motors on the bench.
 
Schwany said:
Spend a bunch of money build a motor that can take a beating or take your time and build it close to stock with advice from members here and save yourself a few thousand dollars, and most importantly, ride slower in the future. ;)

That was the motor out of the good deal used bike right? It was an accident waiting to happen with all the oil dribbling out of it. Probably didn't have the oil changed very often either. I don't know if 71's had a spin-on oil filter or not. If not, a spin-on oil filter is something you should install for the used motor currently running like a top, or you may end up with two motors on the bench.
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It was a fairly recent rebuild from a member. Definitely riding this different than my other bikes for sure!
Crankshaft regrind
 
Norton looks nice cleaned up.

What model is the BMW, and what is that hanging off near the shifter?
 
Coolhands said:
S1000xr Not sure what you mean by “hanging off”, center stand springs maybe?
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Yes, it must be the center stand springs. I've not seen anything like it, but I haven't been paying much attention to newer bikes since around 1996. BMW prices are no longer reasonable. Not that they ever were. I've had 3, but they were a lot cheaper last century. :)
 
I’m surprised at how many folks here only have Nortons. Coolest bike I own for sure but motorcycles are better than ever.

I sold my Harley tourer for the BMW. Weighs 300 lbs lighter and 100 more bhp than my road glide. Eats up miles and way more fun in the mountains.

If your looking for cheap fun the KTM 390 duke is possibly the most fun bike I’ve ever owned. Weighs 350 lbs and it’s an absolute scalpel in the corners. Mine is a 2020 and I got it used for 5k cash.

I like my garage so much right now I’ve (almost) stopped shopping for bikes.
 
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