How about a Desmo Norton?

grandpaul · Mar 31, 2016

Nice that this thread got woken up after a ONE YEAR sleep.

That is one beautiful desmo Norton thumper.

J. M. Leadbeater · Mar 31, 2016

Desmo Velos did not catch on...... Anyway did not Norton try desmo operation way back in the 1950s ??

grandpaul · Mar 31, 2016

J. M. Leadbeater said:
Desmo Velos did not catch on...... Anyway did not Norton try desmo operation way back in the 1950s ??

2 posts back.

mdt-son · Mar 31, 2016

acotrel said:
A nice new DOHC 4 valve per cylinder Norton Head, chain driven off the RHS might not be all bad .

In the late 80's, one of the brit m/c magazines (I believe Classic Bike or Motorcycle Mechanics) had a brief notice of a one-off Commando featuring a belt-driven DOHC head. I remember the development was by an Israeli, possibly a college project. No details were given but the engine was pictured. I wonder what became of the project.

-Knut

mdt-son · Mar 31, 2016

J. M. Leadbeater said:
Desmo Velos did not catch on...... Anyway did not Norton try desmo operation way back in the 1950s ??

BMG Motorcycles (UK) developed a kit providing desmodromic valve operation to stock push-rod Velocette single engines. The technology was patented in the 60's but as reported the Veloce factory never took interest in the technology.

Pictures in this link complements Jim's initial posting nicely.
http://velobanjogent.blogspot.no/2008/1 ... t-for.html

-Knut

acotrel · Apr 2, 2016

The valve gear of a commando is far from being the main limiting factor for the usable rev range of that engine. DOHC and four valves per cylinder with the possibility of using a much higher comp. ratio, might actually give some gain.

acotrel · Apr 2, 2016

The difference in power between a two valve and a four valve speedway Jawa is usually about 10 %. However it is possible to get a two valve Jawa going almost as quick as a four valve.

Bernhard · Apr 2, 2016

mdt-son said:
J. M. Leadbeater said:

Desmo Velos did not catch on...... Anyway did not Norton try desmo operation way back in the 1950s ??

Click to expand...

BMG Motorcycles (UK) developed a kit providing desmodromic valve operation to stock push-rod Velocette single engines. The technology was patented in the 60's but as reported the Veloce factory never took interest in the technology.

Pictures in this link complements Jim's initial posting nicely.
http://velobanjogent.blogspot.no/2008/1 ... t-for.html -Knut

re; "The technology was patented in the 60's but as reported the Veloce factory never took interest in the technology."

They didn’t take any interest because I the factory was run by die in the wool old cloggers and they had no money

lcrken · Apr 2, 2016

acotrel said:
The valve gear of a commando is far from being the main limiting factor for the usable rev range of that engine. DOHC and four valves per cylinder with the possibility of using a much higher comp. ratio, might actually give some gain.

Been done by Merlin Engineering. See this thread:

want-one-these-t20648.html

I don't think they made more than one or two, and I haven't seen one anywhere for the last 30 years or so. Besides, it's hard to still call it a Commando without pushrods. Interesting exercise, though. It was back in the '80s, and that was before we had stronger crankcases and crankshafts so readily available. Probably more limited by durability than valve gear.

Ken

acotrel · Apr 4, 2016

I haven't even lightened and polished the rockers in my motor. The bottom end will probably explode long before the behaviour of the valve train is a problem. If the motor was short stroke with a DOHC 4-valve head and billet crank, it is possible it might cop 8,000 RPM reliably. However you would be playing with an entirely different beast. I have said many times on this forum, that for a race bike to be successful it depends on the whole package and that includes the gearbox and frame. You can theorise about a lot of things which in practice become very nasty.
I raced my 500cc short stroked 650 Triton for about 12 years. Even though it taught me a lot, I wish I had never done that. It turned me into an instant DUD !
- 'TORQUE WINS RACES'.

Rohan · Apr 4, 2016

acotrel said:
- 'TORQUE WINS RACES'.

As we keep pointing out Alan, engines make torque all through the rev range.
So it would be surprising if it didn't win races .......

Bernhard · Apr 5, 2016

acotrel said:
I haven't even lightened and polished the rockers in my motor. The bottom end will probably explode long before the behaviour of the valve train is a problem. If the motor was short stroke with a DOHC 4-valve head and billet crank, it is possible it might cop 8,000 RPM reliably. However you would be playing with an entirely different beast. I have said many times on this forum, that for a race bike to be successful it depends on the whole package and that includes the gearbox and frame. You can theorise about a lot of things which in practice become very nasty.
I raced my 500cc short stroked 650 Triton for about 12 years. Even though it taught me a lot, I wish I had never done that. It turned me into an instant DUD !
- 'TORQUE WINS RACES'.

Re; " I have said many times on this forum, that for a race bike to be successful it depends on the whole package and that includes the gearbox and frame. "

+1