single MKII Amal conversion

Been thinking about this for a long time, and my latest pbs with a bunged up carb (following my garage fire) triggered off the movement.
I bought a kit from RGM, and fitted it yesterday.

seems a shame two carbs with their trumpets looked impressive.
Easy installation, I fitted the manifold with just a smear of bleue compound

The only problems fitting concerns the back filter panel which fouls the K&N filter, I was also using it to hold my Boyer Power Box, so that had to move.

Heres's the carb in place

Easy to fit with the rubber mounting and easy to take off and maintain.
The cable was supplied with an elbow which allowed the cable to run just under the frame tube.
I made up fuel pipes this morning put the tank back on temporarily and give it a try..... Started first kick with the new fancy choke lever.
My first tuning session was to tweak the throttle and idle air screw to get it to settle down to a decent tick-over (after a few minutes warm-up).
I have a 15 idle jet and find the air screw has to be arround 1/2 turn out to get a reasonable tick-over.
The plugs a very sooty which means too rich, even with a size 15 idle jet? I didn't have time to go out and try it today so we'll see how she runs tommorrow.
Anyway she starts first kick and has good throttle response (on the centre stand!)

When I was at N-V, we did a test on the 650SS hack we had lying around to see what performance improvements a single carb would give. It was a real simple change - take off one and put the other on a new intake manifold. The single carb was tweaked a bit to get the jetting right, but it wasn't a new, bigger throat diameter carb. BTW the bike (and both carbs) had done about 65,000 hard miles!

What we found was an improvement in low-end torque (about 15 % if memory serves) but less top end power. The test was triggered by an owner query about getting better low-end torque for sidecar use. Interestingly, the owner had complained about poor top speed and acceleration, numbers so bad that he was invited to visit. In his letters, he hadn't told us he was hauling a double-adult sidecar, which explained the 65 mph top speed and 30 mpg quite well!

This particular bike was my ride to work, and when we put the dual carbs back on, nobody realised that the sleeves were each custom honed to the carb body and weren't interchangeable. I nearly went into the back of a bus finding out about that little detail! I rode that 650 to work every day for most of my N-V tenure. For the first 8 months or so, it was a cross coutry run of about 45 miles from Kenilworth to Wolverhampton. Later, we moved to a small village north of Wolverhampton and my commute was only about 8 miles.

During the single carb tests, I used two other "interesting" machines. One was an italian-made 50cc 2-stroke "hot rod", called a Motom. N-V were interested in marketing for a few hours! It had a 4-speed scooter-style twist grip shift, ran up to about 9000 rpm and got about half the gas mileage the 650SS did! The second was a scooter called (believe it or not) the "Villiers Fantabulous". It was made by Villiers-India and we imported just one to try it out. Initially it had the 175cc Villiers kick-start single, but we modified it to have the electric start 9E (197cc) engine. Structurally it was a disaster and after appearing on the N-V stand at the 1968 Motorcycle Show, it quietly disappeared and I've never seen a reference to it since! Riding it to and from work was always an adventure. It skinny wheels and tires had almost no grip in the wet, and its structural deficiencies made it wobble alarmingly at anything less than 35 mph. Scary damn thing - I'm glad it never went on the UK market. Whether there are millions of them in India, I don't know.

Sorry, Jerry - I got to rambling a bit. Feel free to put the second half of my verbal diarrhea into "Classic motorcycles" if you wish.

Hi Geoffrey, regarding your rich issue, I have fitted 2 new Mk1's and to get them to idle properly and the right colour at idle using a colourtune one of the pilot screws is out about 1 turn and the other only out a 1/2, if even that, if I turn them out any further it starts spitting back and popping. I thought it a bit strange so called the Amal people and spoke to a technichian who agreed the screws are usually a bit further out but not to be concerned as the the carb will be tuned for the cylinder and unlikely to be the same for each cylinder never mind different bikes. He didn't think the 1/2 turn out was an issue. If I whack the throttle open from idle it coughs slightly then picks up; I must admit the plugs looked a bit rich when I took them out after idling but I took them out after a run and they were tan. It might be the case with yours that 1/2 turn out is good for idle but a wee bit rich and sorts itself out through the rev range. I am considering fitting a single MK 2 so please keep us informed of your progress.
Robert

frankdamp said:

The second was a scooter called (believe it or not) the "Villiers Fantabulous".

Click to expand...

You're not even kidding!



https://www.team-bhp.com/forum/post-1950/16710-enfield-fantabulous.html

Geoffrey

I fitted a single Mk11 on my wifes Mk 111 commando, a 34mm kit from RGM. The kit fitted very easily but getting it to run right has caused a bit of a problem. The jetting supplied (cant remenber exactly what sizes) ran very rich. After reducing the main jet size considerably, it now runs great, but, the idle is still too rich, even with the smallest pilot jet they make.

I spoke to the man at Burlens (very helpful) & he seriously questioned the desirability of fitting the 34mm carb, sugesting that this was the cause of the rich idle running. His sugestion was either 32 or 30 mm.

So, I will be very keen to hear how you get on. Please keep us posted.

Regards

Bob.

I am not impressed by the build quality of the cold start lever set up, it easily jams slightly open which really screws up the idle mixture.
You need to lift the lever to make sure the cold start valve closes.
I was lured into thinking that I had a good idle set up with the air screw about 2 turns out but in fact I was compensating for the badly closed cold start valve!
So of I went for a trial run and all of a sudden the choke closed fully and the bike started popping and spluttering (too lean) and I had to open the choke again to get back home!
I wonder if the pilot jet should be bigger and the throttle slide also a bit bigger (more cutaway) to give a bit more air, I've sent an email to RGM explaining my theory.
I'll keep in touch

I've been trying to sort twin 34mm Mk2's out for a while and have had similar problems with over rich running at idle.
My recent breakthrough was the fit of slide to body, this can can be quite poor even with brand new parts.
I found there was so much leakage that with the slide bottomed out completely the revs were 1500rpm with no way of controlling it lower except by using the air screw.

My cure was to fit chromed brass slides. I'm still fine tuning but at least things are behaving more predictably now.
Aluminium slides, plain and anodised, both gave bad running.