Decompressor

[Veg]

I’ve finally managed to remove the decompressor valve having soaked the head for a week. I’ve tried to clean it, however really it needs stripping apart. Is this possible? The reason is as soon as I put it back in and you kick it over it makes a tweet sound
as though it’s leaking. It’s an odd size not a normal plug size thread etc, if not possible to strip can you still get them? I’ve emptied Gary.
thanks for all your ongoing support to this Greeves/villiers newbie

[John Wakefield]

Put the original head back on, a de-compressor has no real use on a trials bike, although some riders used them for engine breaking in sections, they were also used on the Bond Minicar and vehicles fitted with a Siba Dynastart to reduce load on starter motor.

[Veg]

Unfortunately John the original head is a 200 hence why I got a 250, I’ve had conflicting advice re decompressors some swear by them, especially in low speed descents.

[John Wakefield]

Villiers services do a blanking plug but its expensive at ?23 plus vat and postage https://villiersservices.co.uk/produ...pressor-blank/ but probably cheaper that finding a good de compressor plus cable and operating lever.

[whitehillbillies]

Same as fitted to my RE350 bullet I believe?
decompressor - Mickey Spares

whitehillbilly

[IanCordes]

They help prevent the engine from stalling and locking up the back wheel in slow speed slippery descents.Greeves never fitted them on their ali top ends, though.

[Veg]

That’s interesting as I’ve measured mine and it’s 17 mm so the Enfield one doesn’t fit, (I know it’ll be imperial). I may get the head machined and get one fitted. TBH down hill I deffo need it in tricky sections, trying to balance braking, clutch etc without one is a challenge for one with little talent such as myself.

[Veg]

I’m trying to work this out, I’ve now bought a decent head and built a decent decompressor from ones I’ve bought. So the decompressor works by opening a valve through compression. However all the ones I’ve seen are like this picture. The cable seems to be pulling rather than compressing? How does this work then? I’d have thought it needs to be the other way, pulling the valve not pushing the valve? Help needed please. TIA

[John Wakefield]

The the valve works the same as a valve in a four stroke engine. Its open when compressed. The inner cable is connected to a fixed part of valve housing, and when lever is actuated the outer cable compresses the spring and opens valve.
As a matter of interest where did you find the pic. I believe this bike is a 24TCS 60/1759 reg 137BUE. I have it on survivors records with the engine number 863B1118 (same as in pic) untaxed and last V5c issued 22/12/83 but no other details.

[whitehillbillies]

That is interesting as my 24TCS is 1756.
Original engine number was 863B1124
Original Reg 392ALT
First registered with the Greater London Council ???
Must be a cousin.

whitehillbilly

[Brian Catt]

I had a decomp on my OSSA 6 Days Replica and found it useful, as above, on slippery down slopes and on long downhills on both tarmac and loose, for giving the motor some oil without giving it power. Also it was better than a kill button for stopping the engine when the bike landed on top of you....

[Veg]

John
its a pic I took of some bikes on the Greeves stand at stanford.
im calling villiers services tomorrow who will explain it, basically the valve is always shut and needs actively opening to engage it, however the cable is in a position that it is in effect going against the way to open it, if the cable was on the reverse I’d understand it pulling it open. I just cannot understand how it it is supposed to be activated.

[John Wakefield]

Veg. Did you take a pic of the complete bike?

[Veg]

Sadly not John this is the best I can do

[John Wakefield]

Veg. Thanks maybe owner my come forward and confirm if it is 137BUE