Norton Commando: 750 "Domiracer"

Might be good if you ran out of road on a race circuit.

Yea….pass on these new ones. It’s an old guy thing.

Did He Build It Himself ??




Justin Case anyone was wondering .
" Tom Phillis 1961 Senior TT "


Woulda dunbeta witha 5-speed . 104 / 108 inna the quater mile , issa bout whatcher need . in fird .

71 750 motor

ILLF8ED said:

Yea….pass on these new ones. It’s an old guy thing.

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It is an old one. Bodywork mirrors a newer one.

He kept the isolastics on the motor and gearbox, but mounted the swingarm to the frame. Must be hell on the chain and sprockets, no?

Wheels look too small to me.

t ingermanson said:

It is an old one. Bodywork mirrors a newer one.

He kept the isolastics on the motor and gearbox, but mounted the swingarm to the frame. Must be hell on the chain and sprockets, no?

Wheels look too small to me.

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Cosmetically in part is a bit of a fail for me and could have been finished/mounted alot better to replicate a new Domi for the desired effect ...The tank and seat tail look like Omega alloy parts from the states and the bar choice dont look right.

The brake/suspension/swingarm frame modifications interested me mostly and is a credit to the guy.

Solid mounting the swing arm gives the drive chain a leverage point which means the rear wheel will yank the iso mounted power train backwards hard under acceleration. This will give the isos, the chain & sprockets and the exhaust pipes, a hard time.

Cosmetics are a personal thing of course, it’s not my cup of tea at all, but I’m sure he’d say the same about mine !

'Eye of the beholder' and all that....
New one suggests 'muscle', IMHO, old one looks positively anorexic by comparison.

Anorexic by comparison....your not wrong there.

KiwiShane said:

Cosmetically in part is a bit of a fail for me and could have been finished/mounted alot better to replicate a new Domi for the desired effect ...The tank and seat tail look like Omega alloy parts from the states and the bar choice dont look right.

The brake/suspension/swingarm frame modifications interested me mostly and is a credit to the guy.

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I really like the metal work he did on the frame.Very talented builder.
Mike

Fast Eddie said:

Solid mounting the swing arm gives the drive chain a leverage point which means the rear wheel will yank the iso mounted power train backwards hard under acceleration. This will give the isos, the chain & sprockets and the exhaust pipes, a hard time.

Cosmetics are a personal thing of course, it’s not my cup of tea at all, but I’m sure he’d say the same about mine !

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The rubber mounts could easily be sorted by copying the yam fj1200 system which is a couple of rubber smarties in dished metal cups
Seems to cope with the chain alignment on a 130 odd bhp engine
Or even the xjr13 setup with the double pivot

Looks a few cards short of a deck to me. Might work well in heavy crosswind conditions with all that space around the engine. Rear sets and high bars are a fashion error aren't they? A well-polished poser would have clip-ons.

The one big advantage I see is the low slung oil tank. This allows 10" long manifold length from the head to the end of the velo stack and this is where Nortons run best (impossible on a Commando with regular oil tank). Beyond that if you make it with adjustable manifold length you can tune it to scream at top end then shorten for low end (elect servo extensions as used in some modern bikes). This would give you the best of both worlds with a wide powerband and increased HP throughout.

jseng1 said:

The one big advantage I see is the low slung oil tank. This allows 10" long manifold length from the head to the end of the velo stack and this is where Nortons run best (impossible on a Commando with regular oil tank). Beyond that if you make it with adjustable manifold length you can tune it to scream at top end then shorten for low end (elect servo extensions as used in some modern bikes). This would give you the best of both worlds with a wide powerband and increased HP throughout.

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8.5" of intake tract is a good compromise for the street, but I agree there is plenty of room. Too bad they stuck a single mickeyrooney on there.

Schwany said:

8.5" of intake tract is a good compromise for the street, but I agree there is plenty of room. Too bad they stuck a single mickeyrooney on there.

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Supposedly 16" between the head and the end of the velostack promotes a secondary air ram wave that acts as a supercharger at over 7000 RPM. But kills everything at low and mid range. Would be fun to experiment with adjustable telescoping velocity stacks.

The length of a standing wave is the ratio of the speed of sound to it's frequency. The power band I use is from 5000 RPM to 7500 RPM. So the optimum for my inlet tract length is always probably somewhere near the optimum. The same applies to the exhaust system, and the two systems interact. However we usually only change one variable at a time.
When I was racing years ago, if a fast bike appeared, I usually had a look at it. It is what works which is important - not necessarily the theory. With race bikes, they usually fit a pattern. What applies to a two-stroke, often does not apply to a four-stroke. But sometimes it does, and vice versa.
A Commando 850 based bike is totally different to the short stroked Triumph 500 on which I learned to race. The Commando is always much safer. When I ride my Seeley 850, I do not need to think, it all just happens. If I ever did that with the Triton 500, I would be dead, I needed to be 110% every second. These days I try to never remember what it was like, even though it probably helped me to become better.
No kid should ever do what I did, when I was young. Fortunately neither of my two sons ever raced motorcycles, after they watched me crash. So I did not have to to watch them.

Ran 14 inch , valve face to jets on the MkIIs on mine initially .
Cant recall exactly , but think in town it wouldnt run on two below 1000 and sometimes 2000 .
The extra volume didnt help starting , either . Mightve waited till 3 or 4000 to even out ,
depending on barometer .

Putting a side draft / down draftish S U on a elbow over a 1200 Mk 1 Cortina manifold had a similar effect ,
It'd crank over for a while before chiming in , had to build up vacume before It'd draw fuel .

At least you wernt kick starting THAT . So a decent ' enfichment ' system would be called for .

W

Matt Spencer said:

Ran 14 inch , valve face to jets on the MkIIs on mine initially .
Cant recall exactly , but think in town it wouldnt run on two below 1000 and sometimes 2000 .
The extra volume didnt help starting , either . Mightve waited till 3 or 4000 to even out ,
depending on barometer .

Putting a side draft / down draftish S U on a elbow over a 1200 Mk 1 Cortina manifold had a similar effect ,
It'd crank over for a while before chiming in , had to build up vacume before It'd draw fuel .

At least you wernt kick starting THAT . So a decent ' enfichment ' system would be called for .

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Sounds like you had about 12" from the head to the end of the carb. Even further if you had velo stacks. Isn't that what Peter Williams ran with the monocoque? Leo Goff and Ron Wood ran 10 or 10.5"

Would be out of a Book Somewhere .
Was a bloke Walby , young Peter . NOT JAMES . Who new everthingg & everyone except had his finger stuck .
So we provided kicks in the arse & he provided kicks in the head , metaphorically speakin .

Likely Axtel / C R Wood - Jorgenson Artical . Mixed with Two wheels ( magazine ) annual J P S Norton Update .
These were well worth a look , The 72 showed the Daytona Gearbox sprocket . Think it was 33 Teeth . Amougst other things .

The British Stuff was still current then . Regular updates of ' progress ' was usuall , as well as the slinging off about outdated Pre War Designs .

Wonder if the TRIUMPH was such a sucess because it WAS Pre War , when thety still had a decent test track at the back door , UNLIKE NOW .


142.6 mph

prefer a Lear Jet ? Brooklands Made . Coser in tecnology & performance to a Commando TOO .

Todays isnt comparable in performance to a Lear Jet / is it ! . Must be Toy Ones . Or course , people were much tougher in those days ,