JS1 cam valve lash specs please

I am making a guess at .008 inlet and .010 exhaust....correct? Same as combat

The literature that came with my radius cam kit say's " Use .005" inlet & .007 ex valve running clearance Check for minimum .040" valve clash clearance, .050 is preferred"
Hope this helps.
JUG

Jim told me, set tappet clearance to .004 in
.006" ex. With full cam kit from him.

Thats right

.004 to .005" inlet

.006 to .007" exhaust

rock and roll.

will do, thanks

I have always wondered how valve lash clearances are determined. 1970 Triumph T120R: .002" intake, .004" exhaust. 1967 Royal Enfield Interceptor: Intake, nil, exhaust nil to .004 (manual says to set exhausts at .004" for extended "high speed" running. Norton 750 Commando, non Combat .006" intake, .008" exhaust, standard factory cam, .008" intake & .010" exhaust, Combat.

All my examples have cast iron barrels and aluminum heads, with alloy pushrods. Do the pushrods grow at a greater rate than the head/barrel combination? What about setting the valve lash at near zero (.001/,002) wit engine at full operating temperature? Does the cams' acceleration ramp play into lash? I would think that any clearance would be subject to resonance at some RPM, don't know. I can see that the lash dimension would dictate when and where the tappet (or cam) would make contact with the acceleration ramp and where it would "disconnect" from the deceleration ramp; is the lash dimension a general protection for manufacturing tolerance? Wouldn't you want more lash on a motorcycle that haunts the streets of Phoenix, AZ versus the streets of Boston, MA?

The manufacturer of any cam I've installed supplies the lash dimension, I remember a friend in the 60s installing a Duntov cam in a small block V-8 using .030" for both intake and exhaust, what noise. Is lash a dimension that can be calculated? How much lash is equal to a degree of advance/retard? I can see the consequences of too tight and too loose, but in many cases there is a lot to (potentially) play with.

I run lash caps on my Ex Vv's (RHS rocker misalignment from factory in the RH10 head) and as Im using a JS2 cam run 0.006" & 0.008" when cold in my race motor.
Regards Mike

Tell us a little bit about the barrel and pushrod you are using seattle##gs. Is this for street or race? Alloy or steel barrels and pushrods?

If you are running an alloy barrel and steel pushrods you may want to get guidance on running tighter clearances. If cast iron barrels and alloy pushrods go with js guidance. For that matter, if you are going with something else, let js know and he can guide you.

As an example, with a very short stroke 750 I campaigned we ran a Megacycle +D and an N480 and in each case the motor was very happy with perceptible clearance (maybe 0.002") with steel pushrods, and 1/2" shorter alloy barrel.

I have the Maney aluminum cylinder and the JS cam kit with aluminum pushrods. I set the valve clearance to JS specs two days ago and all seems well. Just a mild tic tic tic when running.