Hi, This is my first time with this carb, as all my others have had either one or two monoblocs. When I got the bike the carb was missing so I got this one off e-bay and have fitted a few new parts in accordance with the BSA and Amal specs but I have no idea on cable runs. New parts include jets, needle, air screw, throttle screw and other bits. A new air pipe and filter are in place. When I start the engine it has to be on full choke, no matter whether the engine is warm or not, and the moment I move the choke lever the engine cuts out even if I increase the throttle. I have stripped this carb three times now and cannot sort it. Disconnecting the kill button at the mag does not help. The first few inches of exhaust are now golden brown with the heat. To me everything seems to point to weak mixture but I have been adjusting the screws for weeks on and off and made very little progress in that I can now get a fast tick-over (still on full choke). Can anyone please suggest anything else I can try with this simple looking carb because I think I must be missing something? A bit long but thanks for reading.
Possibly an air leak at the inlet mounting? Looks like you have two paper gaskets and a heatshield there. Check that you have the right O ring in good condition and also that the face of the carb flnge is not dished to to previous over-tightening. If it is then a rub on some wet and dry held on a hard, flat surface will help.
Cheers,
Bernie
unfortunately, you will ony get a good result from going on a run, the air passing by the exhausts will cool them down, wheras running it in a garage may not allow the heat to dissipate , also you will be running on still air not the circulating ride.
when 2 stroke racers wanted to see how their bikes were performing, they did a plug chop on the slowing down lap, often paddling back into the pits . this allowed them to see how it was running at speed, the higher revs which they couldnt see running it on a stand in the paddock.
also remember if you suspect a leak you can often do the manifold up tighter which can distort the flange, a common fault Amal refer to.
Thanks for these replies lads. I believe the faces to be flat but another inspection won't go amiss. The mating face on the CI head inlet is a little pitted but these should be covered by the gasket. Berniej, are you meaning an O-ring between the carb and the the cylinder head as fitted to some monoblocs? I thought this 276 does not have an O-ring or at least there is nothing shown in the parts book or in the Amal catalogue. I could be in for another surprise here. Thanks again.
I can now close out this topic. I looked at all the areas you suggested and did find some unevenness in the flange face so I corrected this as best I could, but as soon as I tried to remove any choke, the engine cut-out. I contacted Amal and described the problem as fully as I could and they came back 99% sure that the fault must be in the pilot line somewhere and suggested where to concentrate on. I stripped the carb down again and even used a piece of wood to knock out the jet block. I used an ultrasonic cleaner a few times on the body and the block and also poked every hole I could find, even with a strand of wire in one case. On rebuild I found that I have an engine that will behave as it should without choke. I have yet to run it as Chaz suggests because an annoying little gearbox problem has surfaced and the engine has to come out, but thanks again for your help lads.