750 Norton Commando Engine Rebuild
1970 Norton Fastback mechanical motorcycles Norton Norton Commando parts restoration
750 Norton Commando Engine Rebuild
1970 Norton Fastback mechanical motorcycles Norton Norton Commando parts restoration

750 Norton Commando Engine Rebuild

April 2016

Phil and Herb Becker

This winter I took my lump over to Herb’s Garage. Herb Becker that is, engine builder of the bike that won first place in the 2003  AHRMA’s Formula 750 races in Daytona. Oh, he also makes things like the double engine supercharged ‘Double H’.

One of Herb’s famous drag bikes doing some tire roasting at the CVMG rally.

I managed to talk Herb into a full rebuild on my engine. I was concerned about the off-idle knock, the general leakiness, and occasional smokiness of the engine. Perhaps he felt somewhat responsible for the bike as I bought it from him as a rolling basket!

Good news was the pistons and barrels were in great shape, they are already .020 over from some previous owner. It needed a crank grind and I had the dubious distinction of having the worst crank wear that Herb has seen (ahem – he sold it to me!). It was an even 30thou down from what is normally a thou. The wear was even, not oval (?!). The shells were worn down to copper, barely a trace of Babbitt left on them.

Double H
photo credit: Doug MacRae see more at https://www.bikeexif.com/supercharged-norton-drag-bike

I joked and said “I guess I shouldn’t have been taking it up to 6500!” Herb’s response was “You shouldn’t have been riding it!”

The head received a set of new valves (brand?), seals (guides?). The gearbox was rebuilt (parts?)

He presented me with a box of used bits, keeping my old valves for building some very early Harley replica engines he fobs off to Muricans.

The Sparx 3-phase rotor has lost all magnetism and the stator is falling apart having lost most of it’s epoxy coating which was lying in bits on the bottom of my primary. The alternator was purchased in Janary 2005 and used for less than a thousand km per year (the last three years probably less than 400km/yr), the bike has been stored in a heated indoor garage. I contacted the owner of Sparx and he didn’t seem to care or offer any discount on a replacement.

“hi philip
it sounds at first glance that the rotor may have been rubbing the stator for it to de-magnetise is very rare however i didnt sell you it and it has been a long time so i cant help
andy”

I am pretty disappointed at the response and don’t recommend the product. I reinstalled the original 45 year old Lucas equipment which still works like a charm.

I can’t wait to put the engine back in the frame and to finish the new red paint job I’ve been working on.
It should be a good year for riding!

2 Comments

  1. Bob

    Hi Amigo, I live in western Canada, Ab, but I lived in Hamilton in my 20s, and was actually born there.
    In Aug this year I acquired a 70 Fatback in California, red similar to yours, reputed to be a 1970 but with a lot of 1971 in the mix.
    I also have a derelict Puch moped hanging from the ceiling in my shop..
    a reminder of my first bike but a touch newer
    I found your site somehow just surfing and looked around it to see if I could find images of the fastback rear section parts, as mine seems to be a bit of a put together id like to correct some.
    I believe I did see some pics on this website, but cant find them now.I have l have looked at the parts pages for instance on Andover Norton .and they seem to have parts ignored and left out…and recently I got a 68-70 parts manual that excluded the tailpiece mounting arrangement as well..
    I was wondering if you could send me some images of your disassembly of your tailpieces? I think it all changed in 71 and there are 2 variants, and yours would be the early one, and mine the later, but pics would be a start for me
    Thanks
    Sorry not much for typing lol
    Bob

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