Phoenix SU carb conversion

The Phoenix Engineering kit was the SU carb mod that was available back in the day. Others have fitted SU's but have had to make the manifold (quite a squeeze to get the carb in) Phoenix shortened the dashpot top to get it under the main frame tube. The supplied air filter with the kit will be long gone now. (it was a spring stiffened foam job) so an K&N is usually pressed into service. Set up is dead easy, a five minute job. I have the original set up notes if you want a copy. A thin sheperds crook shaped pipe on a syringe makes topping up the dash pot easy. Use loctite on the manifold to head screws.

Pros. No more carb balancing. or tickling carbs so your riding gloves should stay clear of the stuff they now call petrol. More M.P.G. I regularly exceeded 80 mpg when touring europe with a friend.

The  previous year i recorded 90mpg in switzerland, much to my amazement!

Cons. It will send your exhaust header pipes blue, in just a few minutes as well. You will need to use the choke, to start and until the engine is warm enough. The petrol pipe spigots (there are two, one on each side) have no barbs, they are just plain brass pipes. You must wire the fuel pipe clips together around the back of the carb to stop the fuel pipes coming off the carb (happened to me a few months ago, lucky not to go up in flames) modern Petrol is more aggressive at leaching the plastisier from fuel pipe, causing it to go hard. Replace the fuel pipes every year or use ethanol resistant pipe like tygon.

Regards

Peter         

had one of these for many years on my 750, found it a vast improvement on twin Amal set up, similar performance, but smoother running and better miles per gallon. however all good things come to an end as needle jets wear and mixture changes over many miles and years, till eventually I had rich mixture at tickover and very weak mixture at 60/70 mph. cured richness with new jet but could not solve weak mixture higher up range which was causing overheating, suspect it was no longer raising needle as it should. gave up on it and fitted single Amal.

To sum up great till it wears out, so watch out for very hot engine as a sign.

Martin.

I took mine off & have it in storage, in case I ever decide to go back. Spoke to Phoenix a few times, but then they moved & I've no idea what happened to them.

I found that if it wasn't run to 'empty' after a run it could be a pig to start the next time used. Mpg was excellent, over 300 miles from an interstate tank - the carb runs very lean hence the blueing. I  finally got fed up with the heavy throttle action & throttle cable fraying at the carb, interesting when it jams, so switched to twin Amals. Somebody in the NOC has a neat way of avoiding the fraying problem (saw & spoke to the owner at a rally) but I forgot to take a photo or note his name!

IIrc, low oil in the damper results in more backfiring on rundown (needle bounce) - but it's been off for 10 years or so, so I'm a bit vague on that. Topping up is a pita due to the top fouling the spine & need to remove the tank.

There's a Haynes manual for the SU Series &  of course Burlen for parts.

Just my 2 penn'orth, experience of others may vary.

I have a quadrant fitted to the carb throttle arm that gives the cable a much easier life and easier action. I don't have to remove the tank to top up the dashpot. Just unscrew the cap and get the syringe pipe in there. Will post a photo tomorrow 

As promised a photo of the cable quadrant

Yes it will. The oil acts like an accelerator pump enriching the mixture by preventing the throttle piston flying up too quickly when accelerating. SU recommended engine oil  #30 or 20/50. The thinner the oil the less rich.

The quadrant is of my own manufacture. I'm not sure if Burlen (who now own the SU brand) supply something similar.

Regards

Peter 

Mike, would you be interested in either parting with it, or letting me view it? Thanks