New Carb Specs


by J. D. Slater

Reprinted November 1973 Keeping Track


Bing and Amal and 125cc 30mm Amal

With our constant testing of the carburetor on the 175cc we have come up with what we feel to be the optimum set-up available now. This is for the Bing Garb on the Frame Breather models.

Some of the machines may have some or all of the correct settings so check it out before getting new parts.

The result is a higher needle position, a needle jet 276 and vaporizer 51-596. The vaporizer must be put in properly so that the shield is pointing to the air filter. If it is installed in the wiong position the carb will not operate properly.

*Tests show that in some altitude areas you may still experience a little pinging in the mid range. If so, we suggest using a 280 needle jet and dropping the needle all the way to the first notch.


If you have an Amal on your 175cc or a 30mm Amal Conversion on your 125cc we have also brought these specs up to date.


Size 30 Pilot Jet
Size 260 Main Jet
Size 106 Low Orifice Needle Jet (*updated)
#2 Long Needle to Match
#4 Slide

Pilot Air Screw ¾ turn out

Needle starting in all the way down position. You can also update the Amal if it isn't already with a plastic float bowl, nylon tipped float needle and a tickler conversion. You may find all or many of these things done to your carb already.

For the 125cc 30mm AMAL CONVERRSION

Size 20 Pilot Jet
Size 240 Main Jet
Size 106 Low Orifice Needle Jet (*updated)
#2 Long Needle
#4 Slide

Pilot Air Screw ¾ turn out.

Needle starting in about middle position.

The major note to make and remember is the air adjusting screw and setting on the Ama l carb. CAUTION! The air adjustment screw is very, very, very delicate in setting. The slightest little movement on the screw will affect the engine throttling in the most major way.

This is ninety percent of what you need to know about the Amal carb and if you don't know this, you will think as Dirt Bike Magazine that they are junk carburetors.

Remember! Screwing in the air jet is giving it more gas and less air. When starting the air adjustment, start with air screw ½ to ¾ turn open. After you have this air screw set, then 3M the screw so no one screws with it.

If the carb ever acts up, then nine times out of ten, the pilot jet is plugged. If so. remove the air adjusting screw, pull gas line off of bottom of carband blow in the air screw hole with air pressure nozzle. Put air screw back in, gas line on, and readjust air screw.

We have found with proper installations, settings and operation that the Amal carburetor gives as good as or higher performance than any other two stroke carb in the world torlay. Evidence of this statement is that a major portion of the European Grand Prix Motocross machines use Amal and the entire Zundapp six Days entry has used Amal carburetors.

The problems with Amal for two strokes have always been that these Amal people have never had two stroke service representation here in the states. I always make mention of the British Amal, not the Spanish Amal. The Spanish have had service representation and enjoy a good reputation.

We now have available a 30mm Amal conversion for the 125cc Penton. We have found this carb to give improved performance and speed for the motocross rider. The kit #1002 consists of a 30mm Amal carb, (properly set-up), manifold adaptor, quick throttle, cables and choke lever along with tuning instructions. They should be available at your local dealers now or very soon.