crankshaft radius

Rohan said:

Just how many here get their cranks crack tested then, if this is such a "fatal flaw".
Have you dismantled and crack tested your crank ??

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I crack test every crank I work on.
Once in a while I find a crack -usually at the mainshaft. Jim

Matchless said:

Do people actually stroke Norton cranks by offset grinding? They would get a bit thin on one side of the journal, due to the sludge trap. Triumph/BSA triple cranks are welded up & offset ground on a regular basis, but these have solid journals.

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Good point. I don't know, I've only ever stroked a triple in this way!

Any of our resident Norton experts know?

One of the auto modifiers websites commented that FAA inspectors would be horrified by what goes on in the auto world. !

I'd comment that I sighted recently a neat multicylinder US made bike crank that had been reclaimed by hardchroming ALL the journals,
so we will watch with interest how it goes. Operator apparently had no doubts...

comnoz said:

From Sky Ranch maintenance manual

http://s658.photobucket.com/user/comnoz ... 4.jpg.html]

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It's time...



I'd say "Go buy a new crank, have it checked for cracks (by some other than the last shop), then send that same shop the bill." Of course, if you were to do this, what would we have to talk about?

Fast Eddie said:

Matchless said:

Do people actually stroke Norton cranks by offset grinding? They would get a bit thin on one side of the journal, due to the sludge trap. Triumph/BSA triple cranks are welded up & offset ground on a regular basis, but these have solid journals.

Click to expand...

Good point. I don't know, I've only ever stroked a triple in this way!

Any of our resident Norton experts know?

Click to expand...

The engine in my EFI bike has a stock crank that has been offset ground up to 91mm stroke. It is not welded -just ground undersize by .100 . Then I put a bar through the center of the big ends and bolted it through the cheeks to hopefully keep it together. Jim

Nater_Potater said:

what would we have to talk about?

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Shirley, discussing whether a crank can be reclaimed or not so is scrap is a valid point for discussion. ?

Here is an .060" rad from the factory

...and an .090" rad on the same crank

To get your crank back to being useable, here is an idea that was given to me by a Norton engine builder here in NZ after I broke the drive side stub off at the 'pork chop' in my race bike last year.
Set the crank up in a CNC station, centre off the crank on both sides , drive and timing,to set a datum .
Do this with the crank bolted together, in my case it was done centreing off the timing side shaft.
Drill out the offending broken bit (in my case) drill it all the way through the pork chop, lathe up an identical part to the drive or timing side stub, press the new part all the way through the pork chop and TIG weld new the stub on the inside of the pork chop closest to the counterweight
Grind new part to suit main bearing. Balance completed item to suit.
You now have no need for a radius at the pork chop /stub interface , as the stub is now a shaft all the way through.

This was for the main shafts, reread your post and now see it is on the big ends!

Food for thought
Not sure this would be ideal for a race motor, certainly a great fix for road bike.
Regards Mike

After the fuss for adequate satisfactions of custom one off or recovered stressed factory component, do consider some insurance on investment.

Crank is NFG in it's present form but might be a candidate for a small journal, low friction test piece assuming suitable bearings.