Amal Mk2 needle jets

I'm still chasing a rich running problem on my Atlas. It's got a pair of Amal Mk2 36mm carbs and when it's opened up it goes like a rocket.
However up to 1/4 throttle it blacks the plugs. I've tried various things without much luck but on stripping the carbs again, I've noticed that the new needle jets I fitted are Mk 1 needle jets. They are slightly shorter and don't have a groove marked around the rim.

Now, Amal's website seems to indicate that 2000 series ( 36mm and above) have the Mk1 type needle jet, ( 622/122-106) and smaller Mk2 carb have the Mk2 type needle jet (2928/122-106)

Is that correct? Does anyone know which is the correct needle jet for a 36mm Mk2 and what would the effect of running the wrong one be?

Thanks

john

John

Yes the 2000 series does run the shorter MK1 jet 622/122

due to the increased choke diameter it actually lowers the deck height and a shorter needle jet is required

Rich mix low down could require a smaller pilot jet fitting or it could be a result of an unseated choke plunger drawing excess fuel

I'm not sure about Atlas but Mk2's on a Commando have various problems with setting a good idle and pickup even with the right needles and jets.

If you get the right parts and still can't get the low end to control then the best bet is to fit the larger deep floats and chromed brass slides, standard floats can't hold the valve closed and all the aluminium/zinc slides including the anodised ones leak badly when full down.

Took me a long time to get mine sorted, hope you have an easier journey or if you want a stress free life fit sleeved Mk1's.

Cheers

Rich

Thanks for the help. I'll put the correct needle jets in.

I've tried everything except brass slides.

I have a pair of Dell Orto 34mm pumpers on my bench. But they can be complex things to set up and I might be starting from scratch.

John

It may also be worth checking if you have the correct needle seating / float bowl for application fitted

back in the old days Amal sold 4 versions of the MK 2 float bowl ( you may be running a pump feed or alcohol without knowing )

2622/055 2.5mm seat
2622/056 1.6mm seat pump feed
2622/057 3.2mm seat gravity feed standard
2622/058 4.0mm seat Alcohol

Fitting the deep float will shut the needle valve sooner as rich suggests ( but it will have less available fuel in the chamber )
if you use the 2.5mm seat for gravity feed you will still retain your fuel volume within the float chamber but increase needle to seat pressure
if you do move to a smaller needle seating and are running large main jets always check the flow rate of the needle seating is sufficient

I had a chat with thE guy who helped me build the bike so many years ago and his opinion was get rid of the Amals.

I made a call to Allens in England to get a 2:1 manifold so I could fit my dellorto, but they were so unhelpful I gave up. I think a 2:1 manifold from the Mikuni kit will fit ( the Dellorto has a 44mm spigot and the 36mm Mikuni has a 43 mm spigot) , so I think the rubber mount will be close enough.

I'll try to source one here in Aus and run a single dellorto.