Discussion in 'Norton Commando Motorcycles (Classic)' started by jseng1, Feb 12, 2018.
Here's the new head building video.
Great video, thanks
That got me high Jimmy!
I forgot about valve seats sending Peel other wise bare head for cryo tempering, it squeezed em right out so had more delay/expense replacing. Controversial on non iron alloys but I and others think contracts alu so much/hard its sort of like shot peening inside out.
Its the very ends of rockers that matter most for inertia and if done enough, completely solve the pushrod puzzling, 1st time every time, that your big OD pushrods may aggravate. Check out Dunstall's rockers to see how conservative almost waste of time/cosmetic only yours are. The only danger of lightening rockers is exposing the very shallow oil passage on side arms, not the ends. Pushrod mass is insignificant compared to rocker ends so alu is better than steel mainly for the shock absorbing elasticity and thermal expansion matching.
Ever studied up on exhaust valve dia vs flow vs heat exchange limits? Its the main limiting factor in boosted or NOX sprayed Nortons.
Once the valve train good to 10+ grand the stroke friction sucks down benefit in upper gears, so review the piston surface texturing I acidently discovered with worn down perfect knurling.
Very helpful - thanks Jim
Nice video, Jim. You're getting pretty good at this video production thing.
Jim once again a great informative video and as per always you have no fancy tooling just stuff we can all get hold of. Can’t wait to try out some of your products in my bike.
Precious video, thanks Jim
No thanks on that lapping job. You will have concentric rings on the valve and seat. There are only 4 valves so no need to speed through it with a drill.
With a drill - lapping only takes a few seconds. You don't have to get heavy handed with it.
If rockers are radically lightened there is a serious possibility of breakage. Gus Kuhns a one time well known Norton race team and dealer advised against it.
Yes - radically rocker lightening can bring breakage and you can usually tell just by looking at the part to determine if its been dangerously weakened. But reasonable lightening (without going to far) helps guard against valve float and dropping a (raced) valve and improves reliability while reducing strain/wear. That's why I give dimensions of the rocker end diameter. As stock the rockers have some crudely made out of round overweight ends on them.
Same goes for lightweight pistons etc. Reducing weight a safe amount can save your crank and cases from failing. Going too far on the heavyweight or the lightweight side is going to force some expensive adjustments. It all shows up in the testing (usually on the track where you will overrevv the motor to beat that next guy into a turn).
Well said, Jim.
Thought yours pukka-I have seen them as thin as paperknives , not installed mind and one wonders how long they last .Something that puzzles me is that no one seems to have tried using titanium for the tappet locknuts, surely its a worthwhile weight saving for those building racing motors ?
I think that's because the aluminum nuts work well and are even lighter. I've used them a lot, along with the socket head adjuster screws, and never had one fail.
ive got socket head adjuster screws... had unhappy experince with aluminium nuts they came loose ... where do you get yours from?
Never heard of a rocker breaking no matter how ground down their ends are, only grinding too much on the side of arm that exposes/nicks rather shallow cast in oil passage to ball ends. Take arm edges to knife sharpeness but dont get too aggressive near middle of arm sides bulge area. Again main reason/advantage is pushrods never foul installing/removing again *IF* taking off most the very ends of the rockers the most. The rest is just cosmetics as very few will test past 11,000 rpm like me so no worries mate'. I forget which side the oil way cast in, IIRC its on the acute angle side to ball end. Would be nice if someone could tell us w/o learning the hard way but end matter way more. Might catch a glimpse before poopbucket ads cover it over.
As significant performance refinements continue, implies no one yet has obtained the ultimate non Norton but know for certain Norton modified parts could endure over 9grand routinely over 4 decades ago engine wise so gearbox and clutch were the limiting factors back then. Newbies may not know the feats of Norton parts to lend perspective on 'advancements'.
I bought a batch of them from a company called Alloy-Tech many years ago. They had them for Norton, Triumph, and BSA rockers. The company has been out of business for quite a while now. The nuts were made from 2024-T4 alloy. RGM, and probably other suppliers, still supply them, but I have no experience with any except the Alloy-Tech brand.
To be fair about it, my experience with them is all from race bikes that didn't get a lot of total miles on them, and also had regular valve clearance checks. It's certainly possible that they might not be as suitable for higher mileage use in street bikes.
The titanium nut idea sounds good too. The problem would be in finding someone to make them in the proper thread form (9/32-26 Whitworth), and with a suitable anti-seize coating.
I use RGM alloy tappet lock nuts, no problems thus far.
Thanks very much chaps.. will try RGM . Ken thanks for letting me know about alloy grade used... useful info. The problem with small batches from small firms in the UK is that they sometimes use whats to hand rather than a suitable grade of material.
Thank you for posting the video, lots of insight there.
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