Hi, I bought a '68 750 fastback with a replaced engine: The points are on the inside of the case facing the middle. The tach and speedo cables come out of the casing to the headlight. There's no "Norton" symbol on the casing either. Everything else fits perfectly. I'd really appreciate any thoughts on this. Thanks, VicG
1968 frame
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kommando
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By casing do you mean Timing case ?
Details on timing case changes over the years.
Details on timing case changes over the years.
kommando
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1967 earls court show, it's effectively a prototype and there were changes before final production but the Atlas engine which became the Commando engine tilted forward with some other changes did not have the Norton cast into the timing cover either, just a small badge unless it went into a Matchless and then no badge. So without any more info, a guess would be you have an Atlas engine or a Commando engine with an Atlas timing cover.
So do you have this small plate with Norton or two holes showing it was there at some point.
So do you have this small plate with Norton or two holes showing it was there at some point.
kommando
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All guesswork, until you post pics we don't know, but from past experience in the 80's when spares were in short supply desperate and/or novel solutions were found to keep bikes on the road for as few £ as possible. Just post the full engine number with X's instead of a few of the numbers and that would move things on.
hybridracer
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20M3/126358 is a Commando engine from 1968
possm
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"20M3/126358. Is there any chance this is an Atlas?"
No 20M3/ is early Commando with points mounted where a magneto would go, 20M3S has points in the timing cover.
An Atlas timing cover is different to a 20M3 cover, I believe the gallery for the pressure release is different.
No 20M3/ is early Commando with points mounted where a magneto would go, 20M3S has points in the timing cover.
An Atlas timing cover is different to a 20M3 cover, I believe the gallery for the pressure release is different.
No change of timing cover oil gallery that I am aware of. Tacho gearbox mounting was slightly altered, presumambly to improve oil sealing, so this prompted a new part number (06-0716). All other parts carry on using 067xxx part numbers, which means standard Atlas/G15 parts (1967-68).
The only changes to the engine from 1967/68 Atlas/G15 spec that I'm aware of are pistons, crankshaft, and the angled engine (which necessutated a different hole pattern for fixing the inner primary cover, i.e., new crankcases).
Because work on the P10/Z26 had taken so long, time was very limited for redesign of the Atlas/G15 engine, so it was largely used as is.
- Knut
The only changes to the engine from 1967/68 Atlas/G15 spec that I'm aware of are pistons, crankshaft, and the angled engine (which necessutated a different hole pattern for fixing the inner primary cover, i.e., new crankcases).
Because work on the P10/Z26 had taken so long, time was very limited for redesign of the Atlas/G15 engine, so it was largely used as is.
- Knut
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I looked into this and you are correct. Here is an image of crankases #126574 which shows the OPRV release into the oil pump inlet, so this was definately introduced on M3 engines. The timing cover had to be amended for this oilway.
Thank you for adding another piece of history to our knowledge base!
AMR-Tucson claims the relase into the oil pump inlet allows "in many cases" oil to pass backwards through the pressure relief valve in the timing cover into the sump when the engine isn't running, thereby adding to the wet-sumping problem. For a tight-fitting OPRV, I wonder how large the problem really is ? AMR's modification places the discharge point back to its original point, directly into the timing case/sump, and requires that the oilway from the feed line in the engine case be plugged with a set-screw. This appears to be the alteration done to your engine. Did you experience increased wet sumping in your engine after removal of the plug and fitting the correct cover?
- Knut
