Author Topic: 600 Aero Valve Lifter  (Read 508 times)

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Offline Hamwic

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600 Aero Valve Lifter
« on: 19 Jan 2021 at 13:14 »
Hi All,

My 600 Aero has particularly good compression, and the PO warned me about possible damage to the kickstart mechanism, which is known to have its shortcomings. I note from the Pitmans book covering this model that a valve lifter was available as an optional extra. I am designing a mod to go in the original valve chest covers, but does anyone have a machine, with this extra fitted? I'm guessing this could possibly be also used on the 750?

Should your machine have such a thing, a picture or a sketch of the arrangement would be good to see.

Many thanks
Doug

Offline Hamwic

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Re: 600 Aero Valve Lifter - update
« Reply #1 on: 29 Jan 2021 at 09:24 »
Hi All,

Aero valve lifter project update. AKA "Gearbox and Knee Saver"

I have made up some replacement valve chest covers that carry valve lifter components that when fitted seem to work. Because of the cylinder offset, and the proximity of the generator, the rear is more difficult to arrange than the front, but it has been done.

I was going to utilise some readily available Ariel parts, but because of the minimal available space, I was only able to use the lever. These turned out to be brass castings, and needed sleeving to fit my pivot shaft flats.

As the valve only needs to be just lifted off its seat when easing the engine over at starting, lots of travel is not necessary. However, a long lifter nose should prevent an unwanted "Over centre" event that would hold the valve open.

The pivot axis needs to be very close to the valve chest window edge at its base to get sufficient clearance from other things, such that the lifter cam will fit under the tappet head. On the rear the bearing is entirely inside the chest. On the front the bearing is mostly outside. Both levers can be lifted with comparatively little effort and the engine swings over a treat once the compression has been popped.

All the parts needing permanent joins are silver soldered. This was primarily done to avoid distortion and to keep the cover flat. The milled surface of the plate is poor, but will give a key for the paint!

I intend mounting a cable stop on each plate, and holding the external lever in the "Off" position with a volute spring. The cables will be paired at a 2 into 1 cable stop under the tank, and then off to a handlebar lever.

More later!

Cheers for now
Doug

Offline Hamwic

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Re: 600 Aero Valve Lifter
« Reply #2 on: 29 Jan 2021 at 11:27 »
Here are the pictures of the Aero Valve Lifter Rear - note different offset of the bearing bush.

Offline Hamwic

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Re: 600 Aero Valve Lifter
« Reply #3 on: 25 Feb 2021 at 09:58 »
Valve lifter update.

I have now finished making up the Valve Lifters for the Aero, and so far so good. Getting the cable lengths just right was a fiddle, but now both levers lift just enough to pop the compression on both cylinders, making the engine easy to swing over. Getting a nice cable run to the 2-into-1 junction box was also a little problematic, but managed it in the end.

The result is much easier on the kickstart mechanism and also the right knee, which for me is good. It also gives another way of stopping the engine other than looking for  the somewhat iffy magneto kill switch, which is something I have not had to deal with before. Looking forward to a run out soon!

Cheers for now
Doug