I was quoting from the 'Motor Cycling' Maintenance Series, for Matchless Motorcycles 1939-55, published in 1958. The section on WD models includes tips to improve performance of the de-tuned WD models, including 'Remove the compression plate, then machine away the ridge in the cylinder barrel at the limit of the piston-ring travel'.
Could it be that they were just looking at a heavily worn barrel when they stripped the ex WD engine?
They were referring to the (possible) wear ridge and/or carbon build up at the top of the barrel...If you drop the barrel by removing the plate the top ring would then 'crash into' any wear ridge or carbon deposits resulting in a broken ring.....Ian
tom I normally don’t fit the plate, the barrel should fit ok, if I can remember I’m sure when the compression plate is fitted there’s two thicker washers that go under the bottom push rod tube seals to take the extra gap, I think if you was to fit the plate on the G3 engine then the rocker cover won’t fit on, its very close to the frame due to the slightly higher barrel,
Well my G3L de-compression plate remains firmly in place and will stay that way. I am a bit surprised that people usually so punctilious in preserving the EXACT original specification should think it acceptable to chuck away this bit of the bike's history! It is plainly in view and would have been there in WW2 so why take it off - do you really need to extract a couple more horsepower? Shame on you!!:innocent:
I see your point FerG3, I haven’t worked out yet where I feel the compromise is between originality and usability. The engineer in me can’t resist tuning the engine to get the best out of it, just as many budding motorcyclists would have done with their mounts after the war. But the Historian in me wishes to keep the bike as original as possible. If I understand correctly, the plate was put in to compensate for the war departments poor quality/low octane fuel? Which is not an issue anymore.
It’s a balance, as subtle modifications make the vehicle more usable, and sometime safer to use. My 44 Willys Jeep is a veteran of the Rhine Crossing, having been used by 53rd Light Regt RA to tow a 25 Pdr gun. There’s lots of history there, but I’ve also fitted modern LED lights and indicators. It doesn’t necessarily sit well with the historian in me, but that’s why I o make modifications as subtle as hidden as possible and completely reversible.
The compression plate in the G3 is something I will think more about.
Agree - my G3WO did not have the plate AND this model was recognised as being much nippier than its successor. Alas, it was also about the same awkward lump to work on!
