BSA Owners' Club Forum

The BSA Workshop => Twins => Topic started by: robin smith on 17 August, 2017, 10:09:02

Title: Rich running Super Rocket
Post by: robin smith on 17 August, 2017, 10:09:02
I have an Amal 389 fitted to my Super Rocket, set up as per book! However, despite removing the air cleaner and dropping the needle to the first groove, the engine is still running rich!
I would be most grateful if anyone has the cure, before I pull out what’s left of my hair! 
Title: Re: Rich running Super Rocket
Post by: JulianS on 17 August, 2017, 10:20:28
The 420 main jet given for some models can be a bit too big. Mine runs on a 400 which is good for a long fast run but soots when pottering around.

Mine has 400 main, 3 1/2 slide with needle in middle groove and an S and B air filter from Hitchcocks.

Expect to have to vary the original settings with the changes in fuel over the past 50 years.

Sometimes the original monoblocs with the thick O ring are assembled with a fibre wsher under the float needle seat which raises fuel height and can cause richness and/or flooding. The washer is only for the later monoblocs with thin concentric type O ring and a machined recess to take washer.
Title: Re: Rich running Super Rocket
Post by: STAR TWIN on 17 August, 2017, 14:13:46
There is some confusion in the published figures. In my experience, a 420 is way too big. My one runs a 300 main jet. If you look at the figures for a 1960 Super Rocket, it states a 290 whereas a 1960 RGS shows a 420. Confusing, huh?
Title: Re: Rich running Super Rocket
Post by: EDDIE SIMPSON on 17 August, 2017, 22:25:30
my iron head a10 would not run with an aircleaner or standard settings. it must be the fuel as ive tried maggie and electronic ign. i now run a mesh bellmouth ,20 pilot and needle in lowest position on a monobloc. i also solder- filled the needle to float wear and the float height is correct. it starts first kick without any choke, which is wrong , but also runs quite hot and ticks over very well. good luck.