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Decompression devices

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Both Forty Years On and Another Ten Years have articles about decompressors as an alternative to the Vincent valve lifter mechanism. I believe Royal Enfield were the ones most popular.
Has anyone any recent experience of such devices? Were they fitted to the second plug 'ole some heads were given? What is involved in fitting one? Do they work?
The main driver for this is that my handlebars look like the aftermath of an explosion in a spaghetti factory, with twin choke cables, twin brake cables to the 2LS brakes, twin throttle cables, and clutch and valve lifter. Some of these function so well that I won't change. But a 2-into-1 choke, and removal of the valve lifter gubbins would help. Might clear that leak from somewhere around my new, improved, ET168 too.

Tom
 

timetraveller

Well Known and Active Forum Website User
VOC Member
Hi Tom. Bruce is correct. The Enfield items require a cable each so you might even end up worse off with those. I recall seeing some items a few years ago which might have been off a Harley or perhaps a chain saw. With these items one had to push down a lever on top of the gadgets which fitted into a second plug hole. This latched the valve mechanism into an open position and once the engine had fired the pressure was supposed to be enough to overcome the latching mechanism and close the valve. I have no personal experience of these and do not know of anyone who has.

The leak around the ET168 can be completely cured by taking the whole thing out of the rear of the timing cover and modifying the part which it fits over (ET169). This should be bored at its rear and a metal plug made which will be a tight fit into the newly modified part. There has to be a hole through this circular metal plug to allow the spoke (ET165AS) to pass through easily. A new rubber seal is made up, perhaps from one of the rubber disks which fit into the timing cover and guide oil to the cam spindles etc. The idea is that the seal now works by the base of the motion block on the outer end of ET165AS sitting on top of the new rubber seal which is now held in place by the metal disk which is pushed into the ET169. The base of the ET169 is peened over to prevent the metal disk escaping and destroying something. The idea is that oil is now prevented from getting into the valve lifter mechanism and the two silly and ineffective rubber seals (ET187?) can now be left out and there is no need for sealing compound or other bodges. Cheers.
 

bmetcalf

Well Known and Active Forum Website User
VOC Member
VOCSC and Vin Parts list modified seals. I have used the VinParts one for several years with no leaks.
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Hello Tom , I used them many years ago, And found them not very good. The valve is so small it don't let much gas out, I was useing big pistons, I don't know if that made it worse Cheers Bill.
 

vibrac

Well Known and Active Forum Website User
VOC Member
I will report back, I have purchased two of these 10mm button release items and will be experimenting-my interest is in easy starting a comet perhaps later in conjunction with reinstaling an electric start on the twin (the last time I stripped the teeth on the sprag gear). For stopping of course I use a cut out. I have used the RE item for years on the Trials Comet and the Alphabet twin with a cable and a little (AJS?)lifter lever.
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Very perceptive, oh temperate one.

I have just reversed the long sleeve on my super-duper aftermarket sealing assembly, to see if that would stop the leak. It was that way round because I had previously concluded it must be wrong the way I had it. Which was the way it is now, so I don't have high hopes that it'll work this time. However, with an electric starter, I don't actually NEED a valve lifter, I could stop the motor with a mag cut-out, which I have in the "potentially useful spares box", hence the search for possible alternatives. However I do like the idea of stopping the leak before it gets started, so will have a look. Keep me busy this winter...
 
Last edited by a moderator:

ET43

Guest
Hi Tom,
I have just found that Venhill do a 3/4inch compression release for Hardley Dangerous machine, in brass and with a cable and small lever, and that's what is going on to the trike. Cheers, ET43
 

timetraveller

Well Known and Active Forum Website User
VOC Member
Temporate, temperate or temporal? Temporate invokes visions of temples (moi?) Temperate invokes visions of moderation (moi? again). Remember that it has been written that 'moderation is for monks. To enjoy life take big bites'. Very useful information on the batteries. It is likely to save some of us lots of time and anguish at some time. Cheers.
 

bmetcalf

Well Known and Active Forum Website User
VOC Member
Hi Tom,
I have just found that Venhill do a 3/4inch compression release for Hardley Dangerous machine, in brass and with a cable and small lever, and that's what is going on to the trike. Cheers, ET43

It must be a very new product. I couldn't find it on their website.
 
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