Hitchcocks Forum

Hi Friends, i have an Amal 376/29 Monobloc carb with following specs Needle jet 106, Pilot 30, Main jet 180, Slide #4 and Needle type C. I have installed it on my 1959 Royal en-field G2 350CC bullet, it is running rich with black smoke and within miles of riding , the spark plugs worn out. I have tried following troubleshooting steps but no solution. First, i have changed Main jet to 160 and Pilot jet to 25. Still the problem persists. Then, i have ordered new Type C needle, Main jet 150, 140 and tried this new jets with new needle. Still carb is running rich and emitting black smoke also spark plug worn out. Can someone help , what we can do for this issue.

Hi Hercules - do you have a choke slide fitted? I ask because on more than one occasion I have fixed Amal equipped machines which were behaving like yours, just by pulling back on the choke lever, to open the choke. Otherwise, make sure your float needle is the right length - the old white plastic ones are - and that there is no washer under the float needle housing. The float should stop or top out just after it is concentric with the float chamber body. Regards, Paul.

Hercules - Please take note of Paul's excellent advice before you ruin your bore and piston (or worse). If you are changing carb. jets etc. to cure your perceived problem, you are simply going the wrong way about it.

Hi Paul, thanks for your valuable info. I have no choke fitted to the carb. Sure, i have not tried, float height checking. Hope, my carb has old white plastic needle in it. Will check the float needle and let you know tomorrow.

@John, sure will follow.

Thanks you gentle mans.

Hercules - Is there any visible sign of the carb. flooding/leaking ? Fuel pouring out, etc. Amal 376/29 is the correct carb. and correct spec. for your bike - there should be no reason to change any of the standard settings. If you have no air slide fitted, does your carb. have a "solid" throttle slide, i.e. one with no aperture for an air slide ? You don't state your location - temperate ?

Hi John, i am from India. There is no leak in carb but when bullet is in idling , petrol showers out in exhaust pipe , which we can feel keeping our hands near exhaust. Also sometimes, i can see petrol on Air filter box too. I too have Choke item but i have not fitted yet. If you want to try with that, then i can do. because i don't have any solid slides with out gap for Air items.


Thanks in advance

Hi Paul, i have checked there is no fiber washer under Needle housing. Also, float is at half level of the float chamber. Still , i am facing the same issue. Thanks in advance,

Hercules there are a few possibilities re you problem: the float sticking, or the float needle not seating itself correctly, or a float (if its the old soldered type) leaking... also is it a new Monobloc manufactured recently (Burlen) or a vintage one (made in Birmingham)? There is a difference between the 2 in the seating of the float needle, the newer Burlen carbs are machined differently & that's why they offer a shim kit for setting the float height. As far as I know the float height on the vintage Monoblocs was set in stone. Hope this helps

Hi Marko, thanks for your reply. Mine is Vintage made in Birmingham model 376/29. And it has brass float without any soldering .

Hi, check that the slow running jet is properly seated. I am dubious that raw petrol would spray out of the exhaust while engine running without a big bang! Are you sure it isnt water? Vince