• HS High Performance Valve Springs
  • HS High Performance Valve Springs

HS High Performance Valve Springs


HS high performance valve springs, set of 10, in candy red

Designed and made to fit MOKI S 150, 180, 215, 250 and 250 /7.

In order to cope with higher than intended RPM we have a second trick up our sleeves, increase the strength of the return spring on top of reducing the mass of the valve train.

These springs have the same 4NM tension as the stock springs BUT compress in a soft curve, return in a progressive curve. These are custom made by Germany's leading spring manufacturer for us, not a simple "linear" spring. Hence, the load on the rocker does not change, they will compress quicker, release stronger. Exactly what you need.

Think of the cam follower hitting the lobe like you are hitting a speed bump with your car. The stronger spring will help eliminate any "lift off" or floating as we call it.

If you lose pushrods then you experience the minor symptoms of a floating valve train, the major ones being catastrophic failure.

For eliminating this intensive testing was done and a leading German manufacturer of springs was tasked with manufacturing HS’s custom valve springs

Features and advantages of our HS high performance valve springs:

    maximum quality for highest stress

    individually checked

    valve springs made of high strength rust free stainless steel

    progressively and warm formed

    additional surface protection through powder coating in red

    Spring disc made of high strength aluminium, custom-fit for symmetrical force transmission

Technical data:

    Outer Ø approx. 9 mm

    Inner Ø approx. 6,7 mm

    Length approx. 19 mm


    10 springs made of stainless steel, powder coated in red

    10 spring discs made of high strength aluminum

    20 locking clips

    5 spare locking clips

    with install tool

    with install instructions



We have learned a lot during the operation of our Seidel SPX geardrive and how to prepare the Moki for higher RPM. Please keep in mind that the Seidel SPX is a mature and well thought out design, designed and made in Germany, but some of the parts used can be applied should one want to minimize the risk which is created  when running low native pitch adjustable propellers. Again, the Seidel will not see harmful RPM, but your pitch adjustable prop may due to its low native pitch blade. You can tell those by simply holding them next to a “real” 12 pitch or higher blade.

A direct drive Moki radial S150 will run anywhere between a 14 to 18 pitch, a S250 anywhere from 16 to 20 pitch. Keep in mind that these are the extreme values, most if not all will end up somewhere in between. Would you want to achieve that with an adjustable pitch prop, and mind me, one that is preset on the ground, will not be pitch managed interactively in the air, you absolutely need to run a native pitch on your pitch adjustable prop of around -2 of your intended pitch at most. Meaning, on a S150 you would want a native 12 pitch blade or higher, on the S250 a 14 pitch blade or higher.

Otherwise you WILL revv too high. Doubt the common sense? Imagine you wanted an 18 pitch prop from us and I would offer you to cut a 7 pitch prop in half and glue it back together at a “fantasy 18 pitch”. Would you hand me your money?
Now, we are fully aware that some run such low pitch native blades on their Moki. In order to manage the risk somewhat we now offer two different products which should both be used in combination.

Keep in mind: there is NOTHING wrong with the Moki, but if you are running a low native pitch prop at an angle such as you find on some market leading adjustable prop setups you are pushing the risk profile and the RPM beyond what the Moki was ever designed for, you can not blame anyone but your prop choice in that case.