AJS & Matchless Owners Club

Clean the tank & carb. Put in a drop of fresh clean fuel and start the bike. If it does not smoke, you have found the answer without any dough's. I have heard so many stories of these sealants causing problems, even long before ethanol petrol came about.

Rob Harknett wrote:Clean the tank & carb. Put in a drop of fresh clean fuel and start the bike. If it does not smoke, you have found the answer without any dough's. I have heard so many stories of these sealants causing problems, even long before ethanol petrol came about.

Thanks Rob, I'll swap out the tank for another from a friends bike that I've used before as a test tank.
I don't use ethonol fuel, but only God knows who puts what in fuel these days. I try and stick to one fuel, BP 95 octane 'Premium' as it is known as in OZ.
We only have a few varieties of ethonol fuel here, and I don't know anyone that uses it in old or new bikes here.

Will swap out the tank and clean the carb and see how I go.

UPDATE: Seems that after fuel tank swap out, snuffing out continues. More over, I rode the '56 again, and it did it also, amazingly, as aggressively as the '55 this time. WHY?

So I finally got a piece of clear tube the right size to shove onto the pilot jet and check the float level. It's WAY high. well above the 'dot' and level with the top of the 'AMAL' lettering.

That being the case, I have reason to believe on a steep hill, it seems that the increased draw of fuel conbined with fuel level, and angle in the bowl, causes the bike to 'FLOOD' and when you button off the throttle, it seems to come good, as it can flow the fuel and burn it?

Mere speculation... but I'm fishing here.... is that plausible? I suspect the '56 float level is the same as the '55 that I checked.

Why is the fuel level high???? I assume you have mono bloc carbs. Take the cover off the side. Hold the float up, now drop it, the little odd shape plastic needle should then drop down on top of the float. If you cannot raise the float, is the needle not able to rise and cut the fuel supply off. If that seems OK, hold the float up, turn on the fuel. None should flow if the needle is doing its job cutting off the flow. This test should prove the needle is working OK. They can stick/get damaged and cause flooding. I assume you have checked the bottom of the mixing chamber, to make sure jets have not come unscrewed.

http://archives.jampot.dk/technical/Car ... t_1957.pdf
Check you have all the parts., like the float spindle spacer pt. no. 376/094. Just a long shot, you may have a small part missing on both carbs.

Rob Harknett wrote:http://archives.jampot.dk/technical/Car ... t_1957.pdf
Check you have all the parts., like the float spindle spacer pt. no. 376/094. Just a long shot, you may have a small part missing on both carbs.

Thanks Rob, Yes I have got that spacer. And yes, I have 389 monobloc Amals on both bikes. I'll check the float operation, but after the rally on the weekend.

Why is the fuel level high? I'm not sure. I've read that on new monoblocs, it is possible that the float can stick or jamb somewhere (one of the lower screw hole bosses in the body - possibly needs filing) in the body of the float chamber, which can cause the float not to drop down far enough, and cause the high fuel level. Seems odd, that both bikes have 'new' carbs, and both have high float levels, AND, both do NOT have the spacer/washer under the float needle seat body.

Cheers for the help Stay tuned!

Absence of the washer under the float needle block would not cause the problem, in my view.
More generally, failing under load, then recovering on shutoff just doesnt sound like richness, its more like over-leanness.
Have you tried closing the air slide ("choke slide") when it does this? If it revives the motor you have a petrol starvation problem.
Steve

If your fuel level is high it isn't because there's no fibre washer under your needle setting. On a new model it should have this fibre washer. It's machined differently than the old monobloc. Amal offers a kit to alter the fuel height if necessary. In the kit there's 4 different thicknesses of alloy shim from 0.15mm to 0.25mm, amal part number RKC/SHIM.
Dave

dave16mct wrote:If your fuel level is high it isn't because there's no fibre washer under your needle setting. On a new model it should have this fibre washer. It's machined differently than the old monobloc. Amal offers a kit to alter the fuel height if necessary. In the kit there's 4 different thicknesses of alloy shim from 0.15mm to 0.25mm, amal part number RKC/SHIM.
Dave

Dave,
Cheers for the information. I have ordered shims and will check the setup after 'another' rally this weekend. At the moment I seem to be able to ride around the issue. Definitely seems to be the high fuel level in the carb, as the ol' clear tube on the pilot jet shows the float level to be around 1/4" too high, above the little dot in the middle of the float cover. I suspect it's just flooding as I tap on the throttle to negotiate hills, and it's not burning it as quick as it's going into the float chamber. This phenomenon does not seem to happen at full throttle on the flat, why? I believe the bike is revving higher on the flat because it can, so burns the fuel, ... but on the hills, it's just bogging, not revving, so not burning it, and flooding.

Am I correct to think that lowering the needle setting/housing?

sjr wrote:Absence of the washer under the float needle block would not cause the problem, in my view.
More generally, failing under load, then recovering on shutoff just doesnt sound like richness, its more like over-leanness.
Have you tried closing the air slide ("choke slide") when it does this? If it revives the motor you have a petrol starvation problem.
Steve

Steve,
My carb isn't set up with a choke. Never needed one in my part of Australia.
That said, its definitely not lean, but, have done the test by covering the air intake with my hand when it has happened (partly) and it only died worse.
Also, puffs black smoke so, shouldn't be lean. Also, burns oil... by the gallon, so that doesn't help. ahahahah.

Marty