500 twin crank survey

I have two 500cc alternator cranks apart at present.

The internal oilways are:
Std Model 88:  1 inch
88SS:   5/8 inch.

Yes they are both alternator cranks as initially mentioned 

I could find a spare dynamo crank and check it as well if that helps.

No problem just take me a few days.

Drg dated 1951 says 1'' 

Hi Ashley - there must have been a drawing amendment for the 88SS and also for the alternator version of the crankshaft so was there an amendment for a 7/8 inch journal ?  Cheers, Howard

Its well known  that older cranks are more suseptible to fracture due to the larger core  hole together with an  internal stress raiser ,and genuine later  88 SS cranks are a better bet with a smaller core hole .  These are old motors and the fabled 88ss cranks are not easy to find . If looking for reliable performance I would think 650 SS.

Hello Pete,  As one of the contributors to assemble the Dominator Service Notes publication I have been looking for evidence of the mysterious 7/8 inch big-end journal hole on Dominator 500 and 600 crankshafts.  Only this morning I was reminded that all Nortons in the Bracebridge St era were virtually hand built and assembled as far as possible to  the customer's wishes.  Hence all manner of frame parts, gearbox ratios and engine-tune parts could be specified and Norton were keen to oblige.  When the factory closed the experimental department and the race shop many hitherto unseen components became available and crankshafts with all manner of different dimensions came to the market place particularly in the racing fraternity.  Crankshafts with 1/2 inch holes and 1.75 inch big-end journals (using Matchless big-end shells and con-rods).  Also 5/8 inch holes with 1.6 inch shells and - dare I say ?....Triumph rods were purchased.   So if a bike was intended as a private entry to Daytona, Sebring , Mosport or Thruxton all manner of different specifications were possible and likely.  Needless to say these modifications did not get included in revised Drawing sets or Parts books.  Some of you lucky readers will have owned a genuine 88SS.   These engines had a 5/8 inch hole in a 1.5 inch big-end but some of these crankshafts found their way into some of the later 88 Standard and De-Luxe models.  I personally had a 1962 88SS that had a semi-downdraught head with 28 mm inlet ports and no tin tube.  Most of these models had 1 1/8 inch inlet ports and a tin insert sleeve to reduce the port to 1 1/16 inch to match the 376 Amal Monobloc carburettor.   So, to me it is unsurprising that a rogue crankshaft may occasionally turn up ( from an ex-race engine) but searching for the evidence may be impossible.  My "head" too could have been a rogue but I hope it is still performing on an unsuspecting 88SS rider's steed.   Good Luck  Pete - buy an alternator crank with 5/8 inch hole.       Howard

It would make sense variations are out there, even back in the old days there would have been a MOQ for someone to machine and I suspect the race shop may have had an initial requirement of say 20 cranks, so ordered 20. However they may have only built 5 bikes and I doubt back then the extra cranks would have been wasted and used on road going models. Just like we often see Atlas crank drive ends on 750 Commando cranks. It no longer amazes me what turns up where, we see it all the time.