Some info about updating the valve train of the M72.
I’d updated a few engines after one spring broke on Anoushka during a ride-out !
Seems the tension is not very high and not the same on all of the valves.
Under plates are also not very sturdy and have a bad fit on the springs.
I measured the spring tension and got values of 30 – 50 lbs tension.
Mate of mine flowed and made the valves lighter.
Adjusted the angle of 45º on the valves.
And changed them to fit collets with a ridge in the spring retainer .
The springs used are from Kent Cams, type VS56 38mm.
With use of a thinner seal, new cnc made under plate, upper plate, where the new collets fit in, the tension is now 70lbs.
I flowed the cylinders for better airflow, in and out!
Left, the original spring, easy to push together and a lot of windings.
Right the “Kent” spring, less windings, a bit wider diam and harder to push together i.e. stronger.
The engines – motorcycles that we have, need a lot of fosfor and zinc, 1000 PPM (parts per miljoen) = 0.1% , which percentage we need at least, is not in the motoroils nowadays ! Specially the camshaft and valve train needs it, and when you’re in the proces of starting for the first time and running in the engine it’s vital to have an adequate amount of zinc in the oil ! (specially with new parts !)
ZDDP = Zinc Diakyl Dithiophosphates, here a photo of two examples for an additive.
Some examples of brands that have a mineral oil with a higher zddp amount .
- Valvoline VR1 ZDDP
- Lucas Hot Rod Engine Oil
- Miller Classic Pistoneeze
- Classic Oils Heritage 20W/50
- MPM Motoroil 20w50 classic High zinc
- Castrol GTX Classic
- Eurol Supreme Classic 20W-50
Break in oil or additive
- Kroon-Oil Running-In Monograde 30
- Champion Racing Power Shield
- Lucas Oil Engine Break-In Oil TB Zinc-Plus
- Rislone ZZDP
- Engine Pro Hi-Zinc
It’s a matter of opinion to use an additive and a mineral oil, or use a high zinc oil ! Some oils are rather expensive ! The additive amounts are mostly enough for two or three oilchanges and you can use reasonably cheap mineral oil. But in case of rebuild with new valve train parts and new camshaft, I would go for a break-in oil, fosfor and zinc is already mixed and ready to lubricate. I have no idea how that goes for adding a additive !