Widening valve clearances

Having fitted the head, I was struggling to get correct valve clearances, with adjusters wound right up into the rockers. In fact there is no clearance on the exhausts.

There are several possible causes for this happening.

1) The head has been skimmed. Most machinists like to take 20 thou off to get an even cut. This then deducts 40 thou from the adjusters.

2) You have the later longer valves fitted. These are 0.10" longer than pre 1966 heads and once again robbing the adjuster.

I was given a set of the solid barrel alloy pushrods and chose not to use them once I had weighed each and found they were double the weight of the originals. 66g as opposed to 37g. To get the steel ends off I clamp the rod in a vice between ply wooden pads. A very quick heating with a gas torch followed by a tap with an open ended spanner + small hammer usually knocks them free. To get them back in place I first freeze the rods and then mount them vertically in my vice. Next I heat the ends up and they generally just drop staright in place with a gentle tap to fix.

Hi Ian, Seems like the more we do the more problems we get with "new " parts, I fitted Six start gears a long time ago ,but left all else standard. I had two worries at that time, poor supply to the head, a well worn crank and a siezed drive side piston.My simple logic thoght that a bit more oil would help all these.20 years later its still going. It does chuck out a bit too much oil from the breather and is a dirty motor. In hindsight I should have fixed the crank and stuck with the 3 start gears. Your situation is complicated by the rod bleeds which may need the extra pressure .With regard to the Halfords Classic 40 ,it appears to have too few additives .

Previously ian_cordes wrote:

Phil.

Thanks for the tips on removing and re-fitting the pushrod ends. I will have a go!

Actually, the weight of the new alloy pushrods with steel ends are about 41g exhaust, 45g inlet, as opposed to about 34-37g (from memory) for the originals. As I don't have originals, there is no choice for lighter ones, unless you go into production with your carbon-fibre ones! The tubular steel ones are 63g exhaust and 71g inlet!

I took an inlet and exhaust valve out yesterday to re-check the lengths, and they seem to be about right, 3.95" inlet & 3.9" exhaust, according to RGM's data, whereas the later ones seem to be 4.0". I did have .008" skimmed off the head to level it, so if that doubles up, then .016" will certainly contribute to the problem, which in the end may be a combination of things. The new pushrods are longer than they should be though, as I got clearance ok with the steel ones. The chartof pushrod lengths, showing the inlets as being 8.21" and exhaust 7.36", whichyou posted the other day, are slightly different to my manuals' data, 8.194" & 7.351", but only 9-16 thou' difference, whereas the new ones are 10 times that, which is where most of the problem lies.

Any thoughts on the oil pipes?

Now this sound all very well but no one as checked the drain holes in the cylinder head on the inlet side, and you can feed oil too the rocker via the timing cover there is a blanking nut just above the pressure releave valve

, you can take banjo from there too the head , instead of from the return oil pipe , banjo, and discolouration on push rod this is a sign of a lack of oil, and for cylinder heads with poor or worn rocker spindle hole can be machined out and fitted with Bronze insurts bushes and locating peg must be machined so the bronze insurt bushes line up with the oil holes, and I alway used a good 20/50 for the last 40 years now and I have had no problems with its, I have even raced on 20/50 ,And the Norton 650 Manxman has a breather pipe from the inlet cover via the Dommed NUT and Banjo fitting , helps with breathing of the engine now I do hope this help in some way, have Fun yours Anna J

I don't think the rocker gear needs that much oil anyway,it just needs some. My 99 head was running dry with no sign of flow ,as long as its flowing it will be ok. My Rudge used to get by on a squirt from an oil can if i remembered.An it would thunder along at 90mph till the piston tightened up.

Before I switch back to the 3 start gears I would like to try fitting a breather to the head, so I'm interested in what you did Ian .

Previously ian_cordes wrote:

Robert. I am attaching a couple of pictures I have just taken of the breather mods. I will have to attach one to each message, as 3 times now I have attempted to attach 2 pictures to this message, and each time I press 'add another attachment' it wipes the whole thing! Perhaps our webmaster could give some tips?

Here is the inlet rocker cover, outside. I drilled a 1/4" bolt right through, then drilled and tapped a suitable sized hole in the cover, screwing the bolt into place, with a fibre washer and some threadlocker. A pipe then goes from it to a catch tank, a plastic bottle, which I have wedged between the battery box and oil tank. See subsequent pictures.....

thats inlet cover breather is not like my one, there is no drill holes in the cover for a start you have a longer 5/16ths stud then fit the cover and its gasket . then fit the banjo fitting and speaical domed nut its breather very niceley thought a 1/4 pipe and banjo fitting and thats it, no need for any more mods this it not a modifaction this was fitted as standard right from bracebridge street , I have even got the part numbers,

Previously ian_cordes wrote:

Anna. When the head was off, I blew through all the oil holes with an airline, and there were no blockages. I then thoroughly cleaned it, blew it all through again, then squirted oil through every oilway to ensure flow. That is how I found that the rocker ball ends had been fitted the wrong way round. That, as you rightly point out, is what caused oil starvation at the top of those pushrods.

I could run a feed from the take-off by the pressure relief valve, but at this stage I don't want to, and don't think it should be necessary. As Robert has pointed out, the rockers don't need much oil; just enough.

Fortunately the rocker spindle holes are not worn, so no worries there.

I have modified the inlet rocker cover to have a breather pipe.

Likewise I use a good 20-50 with a full-flow filter, so I am hoping that a careful rebuild this time should sort it.

Many thanks for your input.

Did you blow out the two drain holes by the side of the inlet springs this drains down the back of the cylinder bloc and come out into the timing case , there is a elbow in the timing side crankcase it gets blocked up and is ever often over looked,

Hi Ian,From your photo it appears that your tank return and rocker feed banjo and piping are all non standard, If they are the same internal size and ratio as orriginal then the low pressure feed should still work, Otherwise all bets are off and you have to experiment!, but i expect you know all this. Annas inlet cover breather sounds very tidy ,why was it not used on the home market bikes?.

This section of the oil feed needs to be at least 1/4" and preferably 5/16" to match the higher capacity 6 speed oil pump, if this is fitted. Running the engine on a 20/40 or 20/50 oil would not be a problem but using a straight 40 or 50 might lead to some over-pressuring while cold.

Below info is from John Hudson Notes ...Circa 1980

At engine number 125871 the valve stem lengths were increased by 0.1" above the shoulder where the spring retaining cotters fit and the push-rods were shortened by the same amount. None of the 500cc engines were affected by this change as they were out of production by this time, but the models 77, 99, 650 and 750 Atlas before 15871 had pushrods with the following lengths:

bare assembled

inlet 7.625" 8.210"

exhaust 6.781" 7.366"

All 650, 750, and 828cc engines after 125871 including all Commando models and the Mercurys:

bare assembled

inlet 7.525" 8.110"

exhaust 6.681" 7.266"

To the nearest fraction the short valve stem measures 7/32" from cotter shoulder to end of stem and the long one measures 11/32" between the same points.

John Hudson

From engine 125871. Valve stems lengthened above cotter shoulders by 0.1" and push-rods shortened by similar amount. Note that all Mercuries have the long valve stems and short push-rods as their engine numbers start above 129000.

Previously ian_cordes wrote:

Phil. Thanks for that. It has the 3-start set-up, so how would that affect it? I use 20-50.

My first Atlas had a 3 start pump and the original conrods with no oil holes. It worked fine for 130,000 miles. I think that your plumbing mods will be ok. The advantage of the 3 start drive and a 20/50 oil is that on a cold start-up the pump is not trying to push oil round its system at 70 psi plus. Thus giving the pressure release valve and seals a hard time. The thin base 20/50 will flow quickly throughout any of the plumbing, so reaching big-ends, pistons, camshaft and rockers very promptly and doing its job..

Previously robert_tuck wrote:

Hi Ian,From your photo it appears that your tank return and rocker feed banjo and piping are all non standard, If they are the same internal size and ratio as orriginal then the low pressure feed should still work, Otherwise all bets are off and you have to experiment!, but i expect you know all this. Annas inlet cover breather sounds very tidy ,why was it not used on the home market bikes?.

the answer too that is AMC Cost cutting , the Export Bikes had to be top notch bike , the home market bike got anything that was avilable other than export models, as that is were the big money came from and not the home market these just did break even there was not much profit out of home market Nortons, that why it was Export or die attitude back in these days,

but now history has been repeated with the 961 Commando As lots of early bikes were for export that why UK buyers had too wait up to 2 years or longer

but these are not built on a production line , like at Bracebidge Street works

they built around 30 machines a-day

back then ,

Yours anna J

Quite a few years ago I took a 650 Head up to Norman White for new valve seats as the old ones were well recessed. While the new seats were being fitted the head distorted and subsequently needed skimming which then messed up the rocker arm angles. Adding to the problems, the valves had to be changed to cope with the new unleaded seats and valve guides. The valves ended up having their ends chopped off and replaced with new Stelite pads, ground to shape.On reflection, using the later shorter pushrods would have helped.

Previously ian_cordes wrote:

Anna's rocker breather arrangement was not one I was aware of. I bet mine is cheaper though! My bike is non-standard, a 650SS engine in a wideline frame, so originality is not a big concern. Mine is a copy of the arrangement I saw on a couple of Commandos at the Norton Rally in Paignton last year.

Whilst my oil return pipework is non-standard, as it goes via an external filter, I understood that the banjo and pipework to the rockers is standard. It was on the bike when I got it, but that doesn't mean it is right, of course.

Another question I raised in an earlier post regarded the metal pipe bends which I had made up to avoid the flexi pipes to the inlet and outlet of the external oil filter from kinking. Whilst the o.d. of the tubing provides a tight fit in the flexi pipes, the thick walls reduce the internal diameter, and I don't know whether this could cause any issues. In theory it is much the same as the recommended sleeving inside the return fitment to the oil tank, in order to increase the oil flow to the rockers... any thoughts anyone?

Well my rocker cover inlet breather banjo fitting cost me nothing as I made one up from photos sent me, and I had the part numbers and mesurements

too the banjo was a filed down banjo from a BSA c15 rocker oil feed I all ready had from owning a number of BSA C15 and B40 motorcycles in the past, I had the longer 5/16th stud just had to make up a sleeve of it then slot made in the dome nut at one side just enoght to let air out and it can breath in to a 1/4 pipe than the pipe it T -fittting into the breather pipe from the oil tank to the rear chain cover witch as this oil feed fitting so any excess oil is then injected to the rear chain the crankcase breather in the same oil line, with a T-fitting , so the rear chain get oil to it better than a scott oiler , and cost nothing , yours anna j

Just to say that my problem was the end coming loose on a new pushrod.

Ok agian now (I hope ) with another new pushrod.

Hi Ian, I don't think you should fit 6 start gear set to a later (bigger volume) pump and run this in a motor designed for the smaller vol pump and 3 start gears.The oilways are too small and the system will overload. Fitting a set of 6start gears to the orriginal pump is sometimes a bit too much anyway. I have gone back to the 3 start gears and am keeping a close eye on the oiling to the exhaust area.