Interesting Valve Clearance Technique

hybridracer said:

Not to be attempted with 2S, 3S or 4S cams as they use an entirely different type of ramp to the simple constant velocity ramp used on most cams.

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You can do whatever you want. For instance the Harley dirt track ML cam could be adjusted from ,005 to ,020 or more to adjust for track conditions and desired power band. Tightening up the clearance on the 2S 3S or 4S hurts nothing at all. It just runs quieter and gives more duration. The only thing you have to watch out for is valve clash if your valves are too close together.

jseng1 said:

You can do whatever you want. For instance the Harley dirt track ML cam could be adjusted from ,005 to ,020 or more to adjust for track conditions and desired power band. Tightening up the clearance on the 2S 3S or 4S hurts nothing at all. It just runs quieter and gives more duration. The only thing you have to watch out for is valve clash if your valves are too close together.

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Jim valve lash adjustment tuning tips don't fly well here in my experience. Unacceptable if the spec isn't in a Norton manual.

My 2S works well enough on the street with lash set at .010" for both intake and exhaust using a tiny bit of cam advance with your offset key. Engine makes noise, but it's a vintage antique. .020" would really make a bunch of noise. Somebody (and I might be mistaken) maybe old brits had a .013" lash spec for both intake and exhaust for the 2S in a table of cam specs. I may have tried it 30 years ago, but it was too noisy. Tightest I've gone with the 2S is .008 intake and .010 exhaust like the Combat spec in Haynes manuals. When I had your JS02 cam in the same engine I ran it at .004 for a while without valve clash issues. However, my valves are stock sizes at a stock valve angle and I have alloy barrels, which increases the lash when hot due to expansion.

I didn't read the interesting valve clearance technique brought up in this post. Then again maybe I did, but already swept it under the rug and forgot it. lol

You do have to watch out for valve clash on the 2S cam because its a very hot cam with close lobe centers and a lot of duration and the valves are very close in proximity when the pistons are near TDC. Sometimes in extreme cases you do have to run more tappet clearance to avoid valve clash. Another way around this is to sink the valves into the head which should be a last resort.

The 2S is nearly the same as the 4S but the 2S has tighter lobe centers and thats what gives it its extra boost.