Sticking cam followers

The tappet clearance for the camshaft installed in your bike at the factory is .002" inlet and .003" exhaust. And that is the spec used on all Model 99 Nortons except for the Nomad Scrambler and SS models built in 1961 onwards. So unless a later cam has been swapped into your bike you have a lot of excess clearance there.

Of course after 56 years unless you know the history of the motorcycle, it may have parts installed in the engine different than it's original equipment. If someone in the past had it apart and back together, and made mistakes or left some shims or other parts out then the engine itself would not be a good guide for reassembly.

Filing metal off tappets is going to make them a sloppy fit? Scoring of the tappets would indicate debris, metal bits or loose casting sand, or maybe a lubrication problem.

The Dominators of that era need a restriction in the oil return to force oil up to the cylinder head. Sometimes swapping oiling system parts out for later or different ones will change the amount of oil going to the top end.

You can take off the oil filler and put your finger over the hole where oil is spitting back into the tank to force extra to the top end and see if things get more quiet. Watch because if you do this long enough you can force oil to come out of places where it is not supposed to, or maybe even blow off one end of the oil line.

Loose timing chains can make more noise than ones adjusted correctly or that are not worn so much.

Apart from incorrect assembly or some oddball parts failure that is about it.

Valve guides can be loose in the head and go up and down with the valve,should be able to see this, rockers can sieze and release.Use a metal tube to listen round the motor.Piston slap gets less as the motor warms up.

Loose valve guides will be evident from excessive smoke in the exhaust from oil going past the guide and into the head.

Asuming there is oil getting there.

Previously wrote:

The scoring marks were removed from the cam followers not the tappets.

Surely cam followers & tappets are the same thing ? Have been all the years I've been in the trade.In the valve trainyou have the cam, followed by the cam follower (or tappet) followed by the push rod, thenthe rocker, & finaly the valve. Can you confirm which part & where on that partthe scoring was removed from ? A picture may help.

Regards, Tim

Previously wrote:

The tappet clearance for the camshaft installed in your bike at the factory is .002" inlet and .003" exhaust. And that is the spec used on all Model 99 Nortons except for the Nomad Scrambler and SS models built in 1961 onwards. So unless a later cam has been swapped into your bike you have a lot of excess clearance there.

Of course after 56 years unless you know the history of the motorcycle, it may have parts installed in the engine different than it's original equipment. If someone in the past had it apart and back together, and made mistakes or left some shims or other parts out then the engine itself would not be a good guide for reassembly.

Filing metal off tappets is going to make them a sloppy fit? Scoring of the tappets would indicate debris, metal bits or loose casting sand, or maybe a lubrication problem.

The Dominators of that era need a restriction in the oil return to force oil up to the cylinder head. Sometimes swapping oiling system parts out for later or different ones will change the amount of oil going to the top end.

You can take off the oil filler and put your finger over the hole where oil is spitting back into the tank to force extra to the top end and see if things get more quiet. Watch because if you do this long enough you can force oil to come out of places where it is not supposed to, or maybe even blow off one end of the oil line.

Loose timing chains can make more noise than ones adjusted correctly or that are not worn so much.

Apart from incorrect assembly or some oddball parts failure that is about it.

Hello Ben the tappet Settings on a Standard dominator 99 are inlet 0.003 thou and exhaust 0.005 thou of a inch and its the same for a standard or De-lux models of (88) and (99) machines yours AJD

I'd like to attend a gathering of Norton twins expressly to compare tappetty noises (piston slap? Wide clearances? Loose push rod ends? Worn cams? Worn little ends (probably not - but maybe)? Slack timing chain?)

Probably we should just follow the simple principle - "An engine has no sense or feeling. Thrash it until it breaks -then fix it" Isn't that what Joe Craig used to say - or have I mis-read?

Ear plugs are just BRILLIANT!

My car motor was knocking badly so i took the head and sump off,replaced big end,mains shells etc, made no difference,took it down again,still could not see the problem,drove it till it broke a few weeks later.The crank came out in two bits!!.Problem solved.

Hi Mike, Tappets = "Cam followers". They are one and the same. At the top endare rockers and valves, where you set the valve clearance. Filing metal offollowers (as we generally call them on Nortons, though not on cars!)is NOT a good idea as theyshould bequite a close tolerance fit in the tunnels. It is possible to get the tunnels relined - then you would have to get new standard size tappets, or you can get the tunnels rebored to take oversized tappets. The former is better than the latter. You haven't said if it's possible to see what the state of the tunnels is.

I would have thought that larger tunnel clearance would give more oiling to the camshaft (a GOOD thing!) rather than upwards to the head, as Colin suggests.

There is no doubt that a large valve clearance will make a noisy "tappety" (!!) engine. As Anna says, the books settings for 88 and 99 valve clearancesis .003" inlet and .005" exhaust for all 88/99 models after 1957. This is probably better than the original 1956/58 book settings of .002" and .003".

Another obvious cause for mechanical noise is worn rockers/rocker shafts. As there was an oilproblem perhaps the exhaust rockers and shafts are sloppy? Having said that, I would have thought that it would cause more oil to drop into the combustion chambers and cause blue smoking. Did you check them when youre-assembled? The only practical way is to do it dry and twist the rocker sideways to see if there's any movement. Again, this area relies on very close clearances so the rockers shouldn't 'rock' sideways! A bit subjective obviously as it isn't easy to measure these clearances.

Cheers, Lionel

Adding to the discussion regarding valve clearances. It is interesting to note the advice given by PL Garratt, Repair Manager, Norton Motors Ltd in his Motorcycle Maintenance and Repair Series Book. See the attachment for the full table printed in 1961/2.

In this book, the suggested clearances from 1949 to 1960 were 0.002" and 0.003" for standard engines. There is no mention of the change of cylinder head material in 1955, camshaft profile in 1956, pushrod material in 1957 and follower profile by 1961. All of which really needed someone, in authority at the Norton Factory, to rethink the valve clearances necessary. More so as Dominator owners from the start had followed the sporty bike magazine advice, of the times, with regard to adding oomph to their engines. Presumably, those in charge believed that the alloy head and pushrods would expand at the same rate and therefore a greater valve clearance was unnecessary.

W.C. Haycroft spotted the problems that were likely to arise and in his Pitman Book of the Dominator Twins, published in 1966, suggested that standard engines built after 1958 had 0.003" and 0.005" clearances and all the sporty versions 0.006" and 0.008". It was also recommended that early engines run hard and fast for long runs also had greater valve clearances.

With regard to Mike's 99 problems. I have seen camshaft followers go tight in their tunnels after being mixed up when refitting and also when the locating plates have been disturbed. The followers are like pistons and wear definite patterns into the running surfaces they act upon.

But.........as suggested by others, the real problem might lay elsewhere. eg seized rocker.

Interesting that Garratt'sand Haycraft's listed valve clearances were at odds with Nortons' own contemporary maintenance manuals. The earliest Norton manual showing the larger clearance wasn't until P100 for the 1959 models. P98 for 1957/58 Dominators still had .002" and .003".I used Garratt's book for my first Norton "experience" in 1964 and it has the oily fingerprints to prove it!

It's only in relatively recent years that I've started collecting all genuine Dominator manuals I can find. The only one available in 1965/66 was "the big green one", covering all current models.