Hi, I’m starting to fabricate a ‘coffeepot’ front expansion chamber, as fitted to short-stroke Flyers from about 1929 to 1934, and I need to know the width of the basic steel chamber, not including the end caps. Could someone please give me that dimension ? Also, do the two inlet stubs enter the coffeepot on its centreline, or are they at a tangent ? Many moons ago I had a drawing, done by John Underhill, but I must have loaned it to somebody, never to be seen again…
Mine is 10 5/8″ to the edges of the cast ally end caps. Just How far they enter I don’t know, probably a 1/4″, I didn’t want to dismantle it on the bike and break the seal. The two stubs appear to enter on the centre line.
I have a complete coffee pot expansion chamber with end caps that I do not need. It was made by Ken Lack about 30 years ago and has had very little use. It was on my 1929 Flyer when I had a S/Stroke engine in it. I later fitted a L/Stroke engine so did not use it as the L/S engine has different exhaust port dimensions.
Hi Ian, The one I am making is to go on 1929 TT3, WX179, which has a longstroke engine with the bigger exhaust ports, so yours would very unfortunately not be suitable. Many thanks anyway !
As more photographs of the 1929 Isle-of-Man Senior TT bikes are slowly coming to light, I have found that about half of them had ‘coffepot’ front expansion chambers, with the others having the 2″ left-hand siamesed pipes. Perhaps a matter of rider preference if they gave different performance characteristics. Sid Gleave even had a celluloid ( ? ) clear windscreen atop his front racing number plate.