Commando Motors

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christulin

christulin

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I was riding a friend's 750 Commando when the engine cratered, destroying the whole bottom end beyond repair. I have not seen very many motors for sale but I have seen a few rolling frames for sale. My guess is that more 750 Commandos suffered from engine failure than from crashes. If there is a scarcity of commando motors, is there an alternative? Can one make a Triton with an isolastic frame? Fortunately, the owner is footing the bill.
 
If you are asking if you can find a good running Commando ENGINE and drop it in and ride, probably not. Parts are available, (cases, cranks, barrels, heads)on fleabay (and on various forums, local Brit dealers, etc.) every day, but a proper build up is the only real option. Be sure to choose wisely the engine builder, the horror stories about "local pros" abound. Shop, get references, ask on this forum BEFORE you hire a shop to do it (that is, if you're not doing it)
 
I tried to avoid mentioning this, but the motor went off to a shop two years ago and the formerly reputable builder is not answering calls or returning emails....One could buy a complete running bike for what replacement parts might cost. Would an 850 fit in a '72 Commando frame?
 
christulin said:
I tried to avoid mentioning this, but the motor went off to a shop two years ago and the formerly reputable builder is not answering calls or returning emails....One could buy a complete running bike for what replacement parts might cost. Would an 850 fit in a '72 Commando frame?
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Yes, complete running bike, but that engine would probably need refresh. Where are you located? (fill in your info, it's helpful) I'll let the masters chime in with what fits what.
 
I'm in Colorado; the complete motor went to the elusive Greg Isles. There, I said his name out loud.
 
I saw a motor for a grand recently at a jumble near Niagara Escarpment from a real reputable man but you are far away...
 
Distance is not a big issue, since parts are shipped all over the world. I also visit family in Connecticut fairly regularly. My friend is retired and can always go himself. I would do the mechanical work.
 
A nice big Nourish Weslake engine would cure it's tappet rattles . And it would probably end up cheaper in the long run.
 
I would like to see my friend install an 850. That way, if he ever gets his original engine back, then I'll take the 850 motor as a spare.
I updated my profile after the reminder.
 
Hi Chris. Look up our club here in Colorado. Nortoncolorado.org. There are many good references for Norton motor rebuilds in your area. Gregg Isles has re-opened his shop. I would not expect anyone to honor a 2 year warranty.
Look for a motor on e-bay and have it rebuilt here in Colorado. I rebuild them also but the best man in this country lives a few hours South of Denver. His name is Jim Comstock and he does machine work for CNW.
There is a shop in Fort Collins, Acme Machine, that does my machine work.
Clubman Racing sells beefed up cases.
I assume that "cratering" means that the cases are shot. How do the other internals look?
The residents of this site love to see pics :lol:
Colorado Norton Works does great work and is not very far away.
Bottom line is that you can get anything for these bikes but the price can be high.
Good luck and keep your check book "loaded".
Mike Gallagher
Lafayette, Colorado
 
Thanks all. I'm in the BMAC and Norton Colorado Club. I may see some of you in Wyoming next month. Fortunately, it is my friend's checkbook, but I volunteered to do the wrenching. I had been storing the bike for my friend and I was riding his bike when the motor seized. I pulled the motor in my garage and it looked like a grenade had gone off. The cases were wrecked, the cranshaft bent, one con rod bent and broken, bottom of barrels broken. The only undamaged part was one of the con rod nuts that was lying in the bottom of the cases. The poor guy bought the bike from Randy Baxter for about 5k and has given Greg Isles about 4k up front.
 
christulin said:
Thanks all. I'm in the BMAC and Norton Colorado Club. I may see some of you in Wyoming next month. Fortunately, it is my friend's checkbook, but I volunteered to do the wrenching. I had been storing the bike for my friend and I was riding his bike when the motor seized. I pulled the motor in my garage and it looked like a grenade had gone off. The cases were wrecked, the cranshaft bent, one con rod bent and broken, bottom of barrels broken. The only undamaged part was one of the con rod nuts that was lying in the bottom of the cases. The poor guy bought the bike from Randy Baxter for about 5k and has given Greg Isles about 4k up front.
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Any knocking/rapping before it ground to a halt?
 
Absolutely no warning noises. I was in the middle of a turn from a side street at only about 25 mph. Fortunately, I grabbed the clutch before I had time to think about what was happening, so I was able to coast to a stop upright. I don't know if the nut had not been torqued down at the factory and slowly turned itself off or if the big end bearing seized. I know he had flooded the engine once with gas by leaving the petcocks open, which is unhealthy and who knows what previous owners had done or not done. He had had some wet sumping problems, too, so there may have been an oil pump problem. When I stored it at my house (he didn't have space), I would ride it periodically, and do maintenance, keep the battery charged, etc (the owner is not much of a mechanic). In exchange for storage and maintenance, I had a Norton to ride. Plus, his Norton had 8 other Brit bikes for company in a nice heated garage.
My own 850 motor has never been apart, so if I can get my friend's bike fixed , I'll probably tear my own down for inspection.
 
If you found an undamaged con rod nut in the sump, perhaps whoever worked on the engine last re-used the old nuts, they are deformable lock nuts and should only be used once.
 
As far as I know, the motor had not been apart since leaving the factory. I was thinking poor workmanship, Monday morning or Friday afternoon build in 1972.
 
A lot of things can happen in a motor over that time and how hard it has been ridden over those years, it all adds up over time.

Ashley
 
christulin said:
I tried to avoid mentioning this, but the motor went off to a shop two years ago and the formerly reputable builder is not answering calls or returning emails....One could buy a complete running bike for what replacement parts might cost. Would an 850 fit in a '72 Commando frame?
Click to expand...


christulin said:
As far as I know, the motor had not been apart since leaving the factory. I was thinking poor workmanship, Monday morning or Friday afternoon build in 1972.
Click to expand...

Now I'm confused...
:?:

I thought it was rebuilt two years ago
 
christulin said:
As far as I know, the motor had not been apart since leaving the factory. I was thinking poor workmanship, Monday morning or Friday afternoon build in 1972.
Click to expand...

poor workmanship = 40 years without being apart , what do you expect of a midweek build motor , last a century ?
 
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