Testing the Ariel the other week, I noticed that the power fell off in the upper part of the rpm's. Cannot go beyond 55 mph at all. That was a bit disappointing, as it could easily go 55mph as an original W/NG. Also the mid-range lacked the expected "umph" from the cam and hc piston. I also noticed that the exhaust jointing compound I used on the exhaust pipe/silencer joints had blown out of the joint, and was to be found as white dots on the clutch cover and gear box. That tells me that the back pressure is too much, even with two pipes. The exhaust pulse comes to an abrubt stop, before it has to go 90 degrees for exiting through the perforations in the pepperpot. I have now wacked the blind plate out of the way, and am waiting for the weather to clear up a bit (it has been snowing and raining for one week now), before a new test ride will tell me if it's running better (I clearly expect so). But, I have started it up, and by the sound it produces, it will get some attention from kids, old ladies and local law inforcement I believe. I have to do something about it, and a friend tipped me about an "old school trick" - fit VW Beetle exhaust end tips to the end of the Ariel exhaust pipes, and put back on the empty silencers shells to cover them. So, I have now ordered a pair of VW exhaust end tips to try this trick out. They are free flowing straight through design, and should be big enough for up to a 1600 VW four. This guy stuck a couple to his Triumph Scrambler 900, with nice results: https://www.youtube.com/watch?v=73369IxR4EA&t=94s
I ended up buying these, with 28mm inner diameter and 35mm outer diameter: https://www.ebay.com/itm/161698007039
Ariel W/NG '40 "Bitzer", Triumph Thruxton '04, IZH-49 '56, Tempo Standard 150 '54.