650 or 750?

i have a Norton engine that best i can tell is an atlas, but is there any way of telling just by looking if its a 650 or 750?

First 650 started with 93601 engine no and first Atlas 750 with 100795 and first export model to USA 103897. Check the NOC site for more details.

engine # shows 2c/119514/p the c i'm guessing is a mis stamp and should be an 0 would this be a correct assumption?

Atlas crankcases had the L/H end camshaft breather.

Prefix:
20 = Atlas
18 = 650

flick said:

engine # shows 2c/119514/p the c i'm guessing is a mis stamp and should be an 0 would this be a correct assumption?

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Sounds very likely - a Commando should read 20M3 as it was intended to be the MkIII of the Atlas as long as they were dreaming up on the new engine.

To be sure check the breather installation. If it has the elbow at the LH end of the camshaft and the machining on the drive side has two shoulders - one for the pressed steel chain case and one for the Alternator bracket - instead of only one for the cast aluminium primary chain case then it is an Atlas engine. IIRC the earlier/smaller Dommies had a diifferent setup and the breather elbow is in the list as #24300 for "all 750". If the engine has a speedo drive on the crank case and not on the Timing cover it would be a Commando but then the "2C" would be "20M3S" anyway.


Tim

what does the M stamped in the top of the head signify?

thank you for the info Tim . i am new to British motorcycles so any info is a help till my Norton books arrive.

The books are not always accurate though, depending on your level of picky-ness. ...especially on some of Roy Bacon's stuff I'd try to get a 2nd opinion.

flick said:

what does the M stamped in the top of the head signify?

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Probably nothing. They were keeping track with punching letters into parts which underwent modifications but this info is probably lost I'd guess. BTW the P behind your crankcase no. is also not standard, my Atlas also has one. I was told by one of the German Norton gurus (not ZFD this time.... :wink: ) that this most likely means it is a replacement part and nothing more exotic.

And the credit goes to LAB as usual, can't post quicker than him .... :wink:


Tim

hi flick,an atlas engine also had 5/16 head bolts{the ones each side of the spark plugs]which to my knowledge no other heavyweight twin had