valves and guides for NH

[nevhunter]

You will have more maintenance issues with "OPEN" valves. That's just a fact of life with a lot of Old bikes. Everything Dust water etc gets there and grinds things away.. You usually don't run aircleaners either.. Modern enclosure and filters probably triple the life of the engines . BSA and no doubt others put grease nipples on their valve guides in the mid 30's. Nortons ran oil through small pipes from the rockers. Speedway JAP's the same. On alcohol you run bronze guides even in an iron head.
Galling is NOT the result of small clearances. It's caused by incompatible metals and it will still gall as it wears IF the "MATCH" is not correct. Stainless untreated on it's surface, is a notorious material and most of the problematic issues commenced when it went into common use.. Before and after the war Silchrome was used for the exhaust valves. . I still run NOS ones if I have them. Nev

[volker.halbach]

Wade, which year is your head? Ariel tried to address the problem of valve lubrication. Of course, from 1934 the heads were semi-closed. The small pipe running from the crankcase to the inlet valve guide seems to do its job. When I removed the inlet guide there was oil in the groove of the guide. In some years there was also a pipe to the exhaust valve, which seems to be less efficient.

The plan was also that oil mist from the timing gear case would reach the valves via the pushrod tubes and the rocker case. I have no evidence that it works. The passage for the oil mist in the rocker box gets clogged up by grease, when paranoid people like me use their grease gun too often. If you omit the chrome cover, the oil mist, if there is any, will be blown away. Having the correct cam with 1 1/2" base circle installed may help to oil the inside of the pushrod tubes, but whether any of this oil reaches your exhaust valve is another matter.

[nevhunter]

Just to add to the problem there are many types of cast iron. The extruded bar type is too soft. The exhaust has pressure forcing the grease or oil out. A small amount of two stroke oil in the fuel may tip the balance in your favour. Try about an egg cup to a gallon.
For valve guide fit in the head . Rely on the fit of the removed guide as a gauge. Going up a couple of thou is a disaster. Heating one and cooling doesn't help in this instance as the sizes are small and the temps will equalise long before you get the guide in final position. Get the sizes right is the only answer, and it depends on your feel with the micrometer. You don't need a lot of interference in Iron One thou on a good size is enough. It should drift in fairly easily with no excess force needed. You will usually have to ream a bit out after fitting.
Alloy heads are different and cause much more issues. Guides (bronze generally) come loose more often. Bronze is sort of soapy in aluminium and often moves. Nev

[wade.edwards]

Volker, the head is a 37 using the covers. Nev, I like the idea of placing a little top oil in the tank.
The first and last time I used it was 54 years ago in my first motorcycle, a Honda 55 trail bike. I was invited to a weekend getaway at a nearby lake, about 50 miles from home. The best way to get there in a hurry is on the main highway where no one is slowing for anything. In order to attempt to keep up I laid over the bars and and opened the throttle. After a short time the bike started to loose power. I did make it to the lake but at a reduced speed.
Fortunately the host of the getaway was a seasoned rider and he advised using top oil. It worked. The return trip was also flat out but this time under full steam.

[volker.halbach]

Wade, so we both have only the oil pipe to the inlet guide. My NH is also from 37.

Summing up, there are at least three possible explanations for the problems:

1. The combination of untreated stainless valve stems with cast iron guides just doesn't work. That seems to be one reason for problems with the club valves. But that isn't the full story. Even nitrided valves don't always solve the problem.

2. As Nev said, there are different kinds of cast iron. G&S valves also warned me about incorrect valve guide material. I just don't know of any way to tell whether a guide is made from the correct spherical grade of cast iron without expensive equipment. Perhaps the club valves are not the only source of the problem, but also the material of the new guides. This might explain the stuck valve on Paul's bike.

3. The OD diameter of new valves guides varies by up to 0.003". Most are over size. Definitely something to check before trying to fit them.

There are many recipes for disaster. Most work on both, open and closed heads, although the lack of lubrication on open heads will make things worse on the exhaust side at least. I am trying to get my hands on NOS guides and fit them with G&S valves.

People add two-stroke oil or Castrol R to the petrol to lubricate the throttle slide and the valves. But the oil has to go through the entire combustion cycle and most of it will burn before it reaches the exhaust valve - unlike the oil that is pushed from the cylinder walls into the exhaust port on the exhaust stroke.

[Paul Gasson]

Volker , I found my remaining guides and they vary in diameter from 0.6250” to 0.6270” the largest diameter is one from Draganfly. Interestingly, this has the smoothest bore. The others are NOS and the bores on all are much rougher but I used one of these and honed it because of the comments I got about the grades of iron used and previous problems with replica parts, thinking that maybe they used different and better material back when they were made.

[john.whiting]

I use Perkins 354 guides in all my singles,around $10 for a packet of 12......all have the 5/8 and 3/8 dimensions ,and I have standardised on 3/8 stems......These guides also have a short counterbore in the exhaust guide,to shield the exhaust stem from heat and abrasive material in the exhaust.....they dont have a collar ,and I use the old collar as a washer,as it generally centralises the lower spring seat,so is needed.

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[john.whiting]

Delete ,delete,delete...its Daleks.....didja notice Daleks have solved the problem of needing flat floors?.....They can now fly.

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