Stepped key for cam timing

Jan asks: "is there a clever way of starting with a disc and making two at once?"
I think the practical answer is it is not worth the aggravation.
 
Stephen Hill said:
Jan asks: "is there a clever way of starting with a disc and making two at once?"
I think the practical answer is it is not worth the aggravation.
Click to expand...
All I could think of was laser cutting. But even if it is feasible, the cost would massively outweigh any savings.
 
Fast Eddie said:
Coz that’d cost thrupence !
Click to expand...
This was a story I robbed from a mate
It was actually about a clutch Woodruff key that sheared
He was miles from anywhere but either borrowed owned or stole a thrupenny bit and a junior hacksaw and fashioned a get you home woodruff key
 
Last edited:
Fast Eddie said:
Err, you mean cheaper to produce !
Click to expand...
Even British bike factories were in the business of trying to sell a product, in a competitive field.

I don’t believe for a minute that a facility to independently vary inlet and exhaust valve timing was an effective selling point in a showroom full of brand new oil drippers.
 
Triton Thrasher said:
Even British bike factories were in the business of trying to sell a product, in a competitive field.

I don’t believe for a minute that a facility to independently vary inlet and exhaust valve timing was an effective selling point in a showroom full of brand new oil drippers.
Click to expand...
I agree.

But I do believe that having the ability to fine tune in and ex separately is advantageous for tuning.
 
Fast Eddie said:
I agree.

But I do believe that having the ability to fine tune in and ex separately is advantageous for tuning.
Click to expand...
I cannot think of any way a Commando cylinder head could be fitted to a 750cc Triumph. But a Triumph cylinder head could be produced with more down-draft and a squish band. It does not matter anyway - to make something cost effective we need a market. With 60s unit construction Triumphs, the 5 speed gear box from the 70s fits. Anything else would be extremely expensive. So going down that path might not achieve anything. The racing classes for old type twin cylinder four-strokes either do not exist or have rules which do not encourage development.
I suggest the UK engineers in the 60s could not influence the controlling bodies of motor sport. With a bit of imagination some things might have become much better. The Japanese seemed to look at everything which was being raced and collect the ideas. Their rationale is different.
The Rickman 8-valve heads did not do much for 60s Triumphs. But a Commando cylinder head does a lot for a Norton twin.
 
acotrel said:
I cannot think of any way a Commando cylinder head could be fitted to a 750cc Triumph. But a Triumph cylinder head could be produced with more down-draft and a squish band. It does not matter anyway - to make something cost effective we need a market. With 60s unit construction Triumphs, the 5 speed gear box from the 70s fits. Anything else would be extremely expensive. So going down that path might not achieve anything. The racing classes for old type twin cylinder four-strokes either do not exist or have rules which do not encourage development.
I suggest the UK engineers in the 60s could not influence the controlling bodies of motor sport. With a bit of imagination some things might have become much better. The Japanese seemed to look at everything which was being raced and collect the ideas. Their rationale is different.
The Rickman 8-valve heads did not do much for 60s Triumphs. But a Commando cylinder head does a lot for a Norton twin.
Click to expand...
The original Rickman bolt on kit didn’t do a massive amount, you’re right there.

But build a 750 or more, with the right cams and carbs etc, and the performance is night and day different.

The real shame with the 8 valve set up is that Triumph didn’t do it 10 years earlier. I had a TSS and it was an absolute flier. Had that been available in ‘72 it would have been a game changer !

But we digress a tad from stepped keys…
 
I wonder how the sales numbers Triumph Bonnevilles, BSA Super Rockets, Commandos and Internationals, compare with the more pedestrian British models, if a price adjustment is taken into consideration. All of those should have had 6 speed gearboxes - performance bikes ?
Commandos are better than Triumphs because of the separate gearbox.
 
Fast Eddie said:
I agree.

But I do believe that having the ability to fine tune in and ex separately is advantageous for tuning.
Click to expand...
Yes, I mess around with camshafts too.

You and me liking something 60+ years later, for reasons of “tuning,” was not a big influence on them back then. A lot of backyard tuners never bought a new bike and so were of no use to the makers. My current bike was a pile of scrap when I bought it in 1979.

The T110 was a good seller because it was faster than Norton and BSA twins, as purchased new. And it wasn’t too dear. Sales of new bikes were what mattered to the makers.

In later years the 650SS and the Commando were faster than contemporary Triumphs. That meant they had a market.

I’ve never seen individual camshaft adjustment mentioned in a bike advertisement.
 
Triton Thrasher said:
Yes, I mess around with camshafts too.

You and me liking something 60+ years later, for reasons of “tuning,” was not a big influence on them back then. A lot of backyard tuners never bought a new bike and so were of no use to the makers. My current bike was a pile of scrap when I bought it in 1979.

The T110 was a good seller because it was faster than Norton and BSA twins, as purchased new. And it wasn’t too dear. Sales of new bikes were what mattered to the makers.

In later years the 650SS and the Commando were faster than contemporary Triumphs. That meant they had a market.

I’ve never seen individual camshaft adjustment mentioned in a bike advertisement.
Click to expand...
I agree with you.

I’m not sure why you think otherwise, I don’t recall ever mentioning that twin cams equaled more sales, or similar ?
 
I would never use a stepped key for anything - let alone adjusting valve timing. With three keyways broached into the cam wheel at random, it is extremely unlikely that you cannot get to cam timing to within a degree of where you want it. In any case, it is never that critical when you have fitted a muffler to your exhaust. That stuffs it anyway.
I suggest that many people never try moving the camshaft backwards and forwards to find the optimum position which suits the circuits on which they race. Road bikes are not built for racing.
With my bike, my cam is advanced 12 degrees because I have a 2 into 1 exhaust. It was a choice - not based upon experiment. The power band has a very wide spread with most above 5000 RPM. The gearbox and handling make much more difference.
Methanol fuel is a cheat. It hides-up the tuning errors and keeps the motor cooler.
If there was a race class which permitted use of methanol fuel, it could specify water-cooling and engine management systems as an alternative. They offer the same benefit.
If I race, I have an advantage - I know what works,
When I was racing my 500cc Triton, I tried a lot of things to get more torque and make the bike rideable. When I first rode it, I virtually only had to blink and I would crash. My greatest fear was in letting the revs drop below the bottom of the power band. Slipping the clutch to get out of a corner, was extremely dangerous. 5000 RPM in first gear was about 50 MPH.
I got it to the stage where I could outride the Z900 Kawasakis around most of Winton Raceway. The gearbox became the limiting factor - I only had 4 speeds close ratio and desperately needed 6.
 
Last edited:
Lightened cam train just puts more strain on it, especially with a hot cam. If I could put a flywheel on my cam I would.
 
IMHO:

The simple fact that a Triumph camshaft is much shorter is a plus and the fact that each is only stressed half as much and the bushings are stressed half as much is an advantage over Norton. In fact, everything in the timing chest of a Triumph makes more sense to me than a Norton, especially the oil pump and timing gears. It would have been nice if Triumph had built the pushrod tunnels into the cylinders, but that's the only valve train fault I find with them.

The side benefits are the individual intake/exhaust valve timing.
 
You must log in or register to reply here.
Back
Top