Amal MK 22930 Slide Replacement Size

[RobinV]

Hello. I am refreshing my Amal Mk 2 2930 carburetors. I see that the slides come in different sizes. Upon closely inspecting my slide, I see a number 2928. There is no other number such as 3 or 3.5 or 2.5.
In this case does anyone know how to discern what slides I would order.? Is this a bore size or cutaway size. Any input appreciated. Thanks, Robin

 

[atomsplitter]

Sounds like a job for Rudie!!!!

 

[Rudie]

slides come in different sizes. Upon closely inspecting my slide, I see a number 2928.

The "size" is the cutaway at the bottom of the 'air' side of the slide, it's how high the middle of the cutaway is in multiples of 1/16" = 3 = 3/16", 2.5 = 5/32".

2928 is the part number: 28 mm is the smallest venturi diameter in a 900 series (the "9" in the part number) body, the first "2" indicates it's for a Mk.2 carburettor.

Amal don't make different slide diameters, one diameter fits all (Mk.2 900) bodies irrespective of venturi diameter. What you should do is get hold of a micrometer (to measure the slide diameters) and a bore gauge to measure the inside of the bodies where the slides ... slide; you need a bore gauge because the most wear on the body takes place just above the engine side of the venturi. Amal have an 'ideal' clearance between body and slide - too little clearance and the slide can jam in the bore, too much clearance and too much air can pass between body and slide, weakening the fuel-air mixture. Too much clearance with new slides, you need either new bodies (probably complete carbs are cheaper?) or existing bodies bored and sleeved to bring them back to standard diameter.

I am away from home at present; email Amal for the clearance figures?

 

[RobinV]

Thankyou for that information. I really appreciate it.

 

[RobinV]

So, as I have really wanted to ride the bike, and as parts have not yet arrived from the UK, I installed a pair of the JRC ($265 US) modification of the the PWK alternative carburetors. Installation was easy. I primed a few kicks, and turned the key.
First kick and she lit up. A couple of minor adjustments and my test drive today was excellent. Plugs are much cleaner, (16 miles, C3 plugs,). I am switching over to the NGK equivalent of the Champion C5 next. Both cylinders are firing evenly and the bike sounds happy. : ) I will still rebuild the Amal Mk 2s, as they are stock.
However, these seem to be an excellent alternative for this rider who does not want to bury the speedometer needle, but instead prefers to have a pleasant ride, while appreciating the motorcycles' dynamics. Robin.

 

[atomsplitter]

As they say on the Bobber forum, "post up some pics, or it didn't happen...."