Lightened camshaft followers and other bits

An interesting project Phil. I will be keeping my beady eye on your progress!

I think that the oil which drips from your drain holes in the corners will miss the lobes, though, as the latter only bear on the centre of the followers. However, any oil in that area is good!

Of course lightweight valve train components are available; titanium and dural valve spring top collars, titanium and alloy pushrods, lightweight hollow tappet adjusters, titanium locknuts etc, but I am not sure what can be done to lighten any original items. More a case of throwing money at it really.

The rocker arms can be lightened, but quite how, and by how much, I don't know. RGM used to do it, for around £90'ish a set, lightened, balanced and polished, but don't anymore. They recommend not taking off too much metal. The rockers in my 650SS had been polished before I got it, but whether they are lightened as well I don't know. My top-end is stripped at the moment, awaiting new rocker spindles, so if you would like to weigh an inlet and an exhaust rocker, I will do the same. If mine are lighter, I can post up pictures, and if you do likewise, we may be able to identify from where the metal has been removed.

That's a start!

Phil. I agree about the pushrods. The attached picture shows what appear to be the same, as found inside my engine when I stripped it in 2009; chunks out, bits broken off; not what you want to find in your p&j. Definitely best avoided.

I have done some weighing, and to my shock, the hollow steel pushrods I have bought from RGM weigh 69.3g inlet, 66g exhaust; nearly 2 1/2 times the weight of standard ones! They are going back....

Dural adjuster nuts 1g; standard 3g. Quite a saving, for £6 set.

Standard tappet adjuster 6.2g. RGM hollow allen key version 5g; mushroom head version 5.6g; 20% and 10% saving respectively. Expensive at £36 and £50.40 a set respectively. You could grid a bit off the adjuster square head, and run a drill part through the standard ones, I guess, provided the faces are ok.

How did you manage to shave all that weight off the standard valve spring caps? Titanium ones weigh 10g each, 1g more than your lightened ones! £58.58 a set, too....

My rockers are lightened, inlet being 103g, a little more than yours. It seems that much of the saving is around each end of the arms. I see that you have tapered the outer main body, whereas mine are still parallel, hence the difference. Did you use a bench grinder, or an angle grinder intially? I want to do the sameon my Commando ones.

All the above prices are current, from RGM, including VAT. Since I bought these items in 2009, the prices have rocketed by 50% (adjusters), 63% ( valve spring caps), and 100% (dural adjuster nuts). That's some inflation....

Phil.

Yes, the spring caps look like dural. I thought you meant they were original steel ones which you had lightened; you had me going there! The dural ones are thicker, and a bit lighter than the titanium ones.

You could try drilling the nuts, but a set of dural ones is only £6, and you could never save that much weight by drilling the standard ones. I reckon you could save a bit on the adjusters, though. Every little helps....!

By the sound of it, I am lucky that my 650SS rockers have already been lightened. I really want the same done on my Commando Proddie Racer ones, but maybe not by me! There is so much weight to save there...

be careful with dural valve spring caps they vary in quality and the collets can either pull through or lock thereselves into the dural cap ,,,,,,,,,,,best of luck with it Nick

All sounds jolly exciting. Two tiny caveats though. A good friend of mine used to race prepare Velocettes. I watched him do a wonderful job lightening a pair of rockers - a work of art. However they both snapped mid race. Don't take metal off the wrong bits. The other one is that inertia in the valve train leads to valve float at high revs. Lighten the valve train and valve float occurs later. In my case with a lovingly prepared 99 engine, a conrod broke before valve float set in. Had I not lightened the valve train, just possibly valve float would have stopped the engine reaching catastrophic rpm. The flailing rod cut the engine in half. Quite impressive. 650 rods should take the stress rather better than 88/99 ones though. Always best to ensure the inlet valves float before the exhaust valves - nature's rev limiter.

Phil. I think that 5g for the adjuster is a good result, and would stick with that, to avoid weakening. Likewise with the nut, which needs to be tightened hard. You wouldn't want one to fail, as in break asunder, whilst the engine is running. I have actually had a nut come undone, which thankfully nestled in a corner of the rocker box, doing no harm. I was alerted by the increased tappet noise! If one broke up, I wouldn't be so sure of the same result.

Nick. Yes, even RGM, who supply both dural and titanium caps, recommend the titanium for their extra strength, despite being a nat's heavier. I have titanium ones ready to go in my Commando.

Gordon. I imagine that slimming the arms down just behind the adjuster would create a weak point. There is lots of metal around the adjuster and ball-end, which could usefully be removed, whilst leaving plenty of meat on the arm itself. Tapering the main shaft casting could no doubt be safely done, as Phil has. One imagines these were over-engineered originally for reliability, but as you say, proceed with caution.

With regard to your 99, maybe it was your right hand whch caused the failure, not the lightened rockers! I have Commando rods in my 650, which are stronger again. Gear ratios come into play here, in that, with the correct ratios one should not need to max out the revs in the intermediate gears in order to drop it into the power band when changing up. The standard ratios leave something to desire here. A 5-speed semi-close ratio box sounds like a good idea, but mucho dinero, unfortunately. Closing up 3rd & 4th would help. Rambling thoughts....

I fitted lightened rocker adjusters to my Commando more than 10 years ago, with the alien head. Made the adjustment a piece of cake and more accurate and never needed to adjust these tappets since!

In fact it was only reading this that reminded me I fitted them, bought from RGM. I must remember to put them on the 99 and 650 when that motor comes apart after Christmas to reveal goodness knows what!

More about that later.

Fair point David. I imagine that is why who ever lightened mine did not lighten the shaft boss; see attached photo of my lightened 650ss rocker alongside a standard Commando item. The areas most lightened are, as you say, at the far ends of the rocker arms. The remainder just appear to be polished. I am not even sure of the benefit of polishing them, unless someone can enlighten me as to the advantages?

Polishing should eliminate any obvious imperfections which act as stress concentrators. It doesn't take much of an imperfection - a scratch will do - to act as a focus for crack propogation. Of course, once polished it looks rather smart so that's reason enough.

I'm convinced! Polishing it is, then.....

Why would you want to lighten the valve gear in the first place?

There is two reasons for lightening the valve train. First the lower inertia reduces wear, especially on the camshaft. Second it allows higher rpm before the springs force can't close the valves fast enough. As said before polishing is always a good thing to do.

Another reason is that we always has regarded British motorcycles as raw material, which with love and care can be improved to something much more goodlooking and efficient.

Fair point Bob. If you are going to ride your bike remotely sensibly - i.e. keeping generally below 5,000 rpm, there is no need. Camshaft and cam follower wear are minimal in normal use. However, if you are heading into the realms of 6,000+ rpm it does make sense as valve train loads become severe. What a lightened valve train can do is permit the use of softer valve springs for a given max rpm. No bad thing. Valve train flexure at high rpm is quite fascinating. My uncle used a strobe light to view the exposed valve gear on his Rudge. As rpm increased, the pushrods flexed to a remarkable degree. Quite amazing, and yet Rudge pushrods have a reputation for reliability.

Previously bob_johnson wrote:

Why would you want to lighten the valve gear in the first place?

Well Bob, you might as well ask "why ride a Norton?", when modern bikes are faster, and handle as well, or better. We all have different reasons, in my case nostalgia for lost youth. Few would go to Phil's extremes, to extract the ultimate performance, but, you must admire his dedication.

In the late 50's, I built an Austin 7 special. Top speed was over 90 m.p.h. ( not bad for a 750cc side valve), was it worth the effort? To me "Yes!", but not many would agree. Polished com-rods, gas flowed ports, lightened flywheel, been there, done that!

Surfers wax their surfboards to get a layer of sand to stick to the wax so that their feet don't slide around.

Back to the thread, about 2 months ago a well known Norton racer in the States posted a picture of his blown up engine on the Access Norton website. His Maney crankcase, Carillo rods, Maney alloy barrels and one piece crank were all trashed. Whilst I didn't comment, I thought, "thank goodness no genuine Norton parts were damaged"

Also, When changing push rods for ones made of a different material, How will they expand compared with the original and how will that affect your valve clearances?

Previously david_evans wrote:

Also, When changing push rods for ones made of a different material, How will they expand compared with the original and how will that affect your valve clearances?

Good point David. There are probably not many twins running with the old steel pushrods (as fitted to iron head engines). A previous owner had put alloy rods in my '54 Dominator, this caused endless problems, until Phil put me right. I was going in circles, changing timing, carb settings, cleaning the mag, ext. All was due to the extra expansion of the alloy. Increasing valve clearances was an instant cure.

After reading this I am doubly determined to to keep my Atlas in a gray porridge rough casting state of tune.

Ah yes, this isn't the first exquisitely lightened and polished rocker I have seen that has snapped. The older I get, the more I am inclined to Jonathan's school of thought.

A thought: Is it better to have a low-tuned engine you can thrash with confidence or a highly-tuned one you are frightened of braking?