How to lighten commando rocker arms

tonybsa · Mar 1, 2021

jimbo said:
you could just buy a set?

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Thanks for posting the link. As my day job is as a Toolmaker, I can probably manage. The cost of the ones on your link will pay for my new conrods.Thanks to everyone else for the inspirational pics. As I said these are for a race motor,I am awaiting arrival of the JS beehive springs and Valves.Engine will be going in a Classic racing sidecar of my own manufacture.

Fast Eddie · Mar 1, 2021

tonybsa said:
Thanks for posting the link. As my day job is as a Toolmaker, I can probably manage. The cost of the ones on your link will pay for my new conrods.Thanks to everyone else for the inspirational pics. As I said these are for a race motor,I am awaiting arrival of the JS beehive springs and Valves.Engine will be going in a Classic racing sidecar of my own manufacture.

errrr.... PICTURES....!?!

Chris · Mar 2, 2021

Yes Tony photos. What a great build that must be.
Chris

tonybsa · Mar 2, 2021

Chris said:
Yes Tony photos. What a great build that must be.
Chris

I am afraid its slow going {money/time shortages), and as far as the motor is concerned I have started with the head. Will post pics of the rockers when I am done, and of the outfit to date. Just as soon as I work out how to post pics on this site?

edgefinder · Mar 2, 2021

tonybsa said:
No ,I can reface that part at work on a surface grinder.Its the outside diameter,that runs parrallel with the spindle.I have the dunstall tuning guide.

Do what he said in a lathe with cap and bolt. Cutter with big radius turned to not tangle with arms. You can get fancy and turn smaller between end and arms, not that weight matters there.

Beemer · Mar 2, 2021

Looks like a waste of time unless your going to the salt flats

linker48x · Mar 2, 2021

I’m watching this with interest. I’ve never built a Norton race engine so I have nothing to add of any relevance. I’ve built several Triumphs though, which have similar rockers, and always left them stock, and relied on light pushrods and titanium spring tops and race springs. They all worked fine and didn’t break—something the period Triumph hot rod books warned could result from over lightening. I think most Triumph guys leave them alone. I understand why folks would lighten just the ends, too. Seems logical. Carry on!

concours · Mar 2, 2021

Hortons Norton said:
I totally agree that if you are going to take your bike near or to redline it's going to help keep things in place. But for most I think it is just one more thing you can do for no good reason. I bet my bikes have never seen much above 6,000 if that. Go ahead and roast me now.

Roast? Heck no, everyone loves a parade...

Triton Thrasher · Mar 3, 2021

Beemer said:
Looks like a waste of time unless your going to the salt flats

The guy that made time made plenty of it.

Schwany · Mar 3, 2021

Did this long ago thinking it was going to help somehow to take those ugly casting marks off. I didn't weigh the rockers. I only made them look symmetrical in appearance. If I did it again, I would weigh everything. I did not true up the spindle bosses. Never occurred to me.

I doubt cleaning them up makes a lot of difference on a street bike. Just another one of those things to say I did.

A Norton sidehack sounds cool. Good luck with it.

lcrken · Mar 3, 2021

As others have pointed out, the most bang for the buck comes from lightening the ends, not the center. But some folks take pride in turning the rocker arms into works of art, even if the additional improvement in performance is miniscule. Like many of us, I find that sort of craftmanship appealing, even if it isn't strictly necessary for function.

Ken