Gents. The previously gummed up and well sealing decompressor pistons have now unseized themselves and because the arrangement on the end has been removed, compression is now exiting the engine before I have got the value out of it. I sorted this last night by fitting bolts and washers and have excellent compression again. However, I did quite like the ease that my engine was starting in its low compression state and fear that the extra grunt required from that stupid starter chain would speed up its demise.
So, since a lot of folks seem to have got rid of their decompressor stuff, does anybody have any spare I could buy please. Mine is the spark plug at the back engine from 1920 and I have the castellated nut holding the outer piston in place with the inner piston inside it. Nothing is on the end and I assume that to be a spring, nut and lifting / hingeing thing. I have the 2 inch long plate held by two bolts that fixes onto the outside of the barrels and appears to make up where the hinge goes. So it doesn’t seem much but maybe I am missing something. Maybe they were a poor idea and that is why they are not generally in use. Advice most welcome.
Just to confirm your thoughts, years ago Ken Lack told me that I should ALWAYS use the decompressor when starting a 2 speeder in order to ease the load on the various fragile kickstart components.
I am doubtful if I have any spares but will have a search later and get back to you if I find anything.
Will – I think what you need is what is rereferred to in the parts lists as “1/2 compression valve actuating arm “. The attached picture is from the 1914 catalogue – in the Document Archive – and I don’t think that it altered in form throughout the development of the two-speeder engines. In any event if your engine is 532 cc standard should be the same as a 1914 bike. By an amazing coincidence I was gifted a spare one last night and I can send it up to you if it is what you need.
Err, yes please. That sounds like divine intervention there Lewis. My postal address is Holly Bank, Heath Lane, Boughton, Chester CH35ST.
That is much appreciated and thanks for confirming my fears Martin so I will park the bike to one side (Yam cylinder studs to sort) until I get the decompressor fettled because the starter does now seem to have much more load on it and they must have been leaking somewhat for a bit.
I will have a look at the parts catalogue in the document archive too. Not sure of the arrangement.
Progress comes in fits and starts.
Hi Lewis. I had a look at that document and I have got part nos 66 and 67 on the bike and the two plates nos 69 and 70 so with your bit it seems that it is nearly complete. I see on parts 66 and 67 that it looks like there is a nut and spring on the end which I do not have, assumingly these return the pistons back home. I think I might actually have them unused and unneeded on my other bike so Bob is possibly your Uncle.
So with your part added and me having a look at the decompressor lever parts in the catalogue, my brain still can’t visualise how the bowden cable connects to your part and operates it and possibly holds it. That looks like a special lever which I can overcome I am sure and I can get a lever and a cable and I am pretty sure I have the frame mounted recess for the engine end of the cable. Is there a picture you can point me towards that shows the arrangement at all please. By the way Lewis I don’t have your number any more as my phone lost most of its contacts. I am on 07531781196. It’s probably more simple than I imagine or is it just a hole the cable goes through. Thanks again.
You are probably well aware of this, but I wasn’t sure from your posting: the decompression lever on the handlebar had a dual function. The first half of its movement lifted the decompression bar on the front of the engine, the second half of its movement activated an ignition cutout. The handlebar lever had a sprung pin which, when the lever was fully pulled in, contacted a pin through the handlebar thus cutting the magneto. I have attached some photos…….
Apologies if you were already in the know on this point!
Hi Will, I was only able to post one photo and then crashed out of the website. Here are the others….
Hi Martin. Very useful thank you. I had read that it also operates as a cut out and I thought this was a necessary function of the decompressors somehow but I have a separate cut out button on the bars so I am assuming I just need a normal lever then. I read about the peg and was wondering if this was used to hold the pressured decompression lever owing to the number of arms I possess. Some of the literature that Lewis put me onto has you holding your hand over the carb intake and somehow doing other things whilst holding the bike because you shouldn’t start it on the stand.
The picture is building and basically, a word oft used mistakenly, both valves are sprung so that they are always closed and operating the lever presses the valves in against the springs and decompresses the engine. Once I get the bits it will make sense. Still looking for the springs and ends of the decompressor valves if they are around though as mine were full of sh=== and I don’t want to mess with them if I have to.
Hi Will, I took a photo of the engine end of the decompression device on my Squirrel. It may or may not be helpful. Also attached is a photo of a pair of decompression valves. I don’t know their mechanical state but if they’re of any use to you I’ll put them in the post – let me know…
Hi Martin. Thanks very much for that kind offer which I might take you up but Eddie Shermer is sending me a pair over which might be suitable. I see yours has got a spring at the end in the photo. I was thinking of a making a direct drive to the actuator arm but the spring thing might end up as an option depending on how much force is needed. Interesting and thanks again.