scot taco Posted July 15, 2016 Report Share Posted July 15, 2016 It does seem to be a fuel delivery problem. Is it possible that the fuel cap is plugged up and not letting the tank vent causing it to run out of fuel? Sounds like you have covered about everything else,although I,d bin the Amal and try a mikuni. 1 Quote Link to comment Share on other sites More sharing options...
pschrauber Posted July 15, 2016 Report Share Posted July 15, 2016 Mmmh ... that's a task. As you mentioned that the bike dies at less run better when the choke is on, have you looked around the rubber inlet between carb and manifold is there no airleak cause of cracks in the rubber not only in the body of the rubber flange around but too to at the sides from the inside to outside. Sometimes the paper seal between cylinder and intake can have been damaged too this connection is thight too? Last not least just try another plug especially IF there is a plug with inbuilt resistor mounted. In my personal experience the bike runs better with a hotter plug then recommended. For NGK it should be PB 5 ES but that type does fail without warning, now using a PB 4 ES which does the work now for two years, (may be I'am a tad slow too). Quote Link to comment Share on other sites More sharing options...
feetupfun Posted July 15, 2016 Report Share Posted July 15, 2016 feetupfun, thank you for your info, sorry but can you please confirm AMAL Mk 2 choke lever operation: You stated choke Lever up = ON, this places the plunger down "IN" which you also say is OFF, I really appreciate your help but now I am now very confused ! Maybe your AMAL Mk2 is different to this one? This shows one with the "choke" on (plunger out) 1 Quote Link to comment Share on other sites More sharing options...
stevem75 Posted July 16, 2016 Report Share Posted July 16, 2016 I think this topic is being a little " over thought". Engines take three things to run. Timed spark, fuel and compression. The bike starts and runs, so for now don't worry about spark. You have fresh fuel. Clean petcock. It starts and runs on choke which indicates its getting enough fuel. No choke the engine starves. There are a few possibilities. Check first to make sure that the float bowl is filling with enough fuel. Is the float level correct?. Can't remember on that carb if its adjustable but if it is be sure that it is set correctly. You indicate you have new jets etc etc. Be sure they are the correct sizes. Be sure they are clean and clear!!! Yes new jets can be plugged. I've seen it many times. You also mention that the bike runs best with the air screw turned in. Again this is an indicator that the engine is starving and needs more fuel. The passageways in the carb need to be clear. Especially between the pilot jet and the air screw. If you are certain that the carb is in good working order move onto compression. Bultacos have tons of it. You don't need a fancy gauge to let you know what the compression is. If there is quite a bit of resistance felt when kicking through then the top end compression ( that is the piston and cylinder) can be considered ok. Where Bultacos suffer is with primary compression. This is the ability for the crankcases to hold pressure. The crank seals which you've replaced help seal the bottom end. As does the center case gasket. The other place to look for compression leakage is cylinder base and intake manifold gasket. If these gaskets or seals leak the bike will start and run but won't idle down and will tend to "run on" when the throttle is opened and then shut. You don't mention this so I'll go back to fuel. I firmly believe you have a fuel delivery issue. The carb isn't getting enough fuel or the wrong size jets are used or the carb body is plugged or all of the above. I'd go back and check it thoroughly. You're on the right track. Lots of good knowledge on this forum Steve Quote Link to comment Share on other sites More sharing options...
oldmxer Posted July 16, 2016 Author Report Share Posted July 16, 2016 scot taco, I confirm the filler cap hole is clear, again this was one of my first checks but failed to mention this in my forum. pschrauber, thank you for your advise but I have sprayed WD40 around the head, cylinder base and induction while engine is running to see if anything is either sucked in or pushed out. feetupfun, thank you for the choke position clarification. stevem75, thank you for the above in-depth information, I will work my way through this forum and hopefully source this problem. Can I say a big thank you to Trials Central for allowing everyone to pass on this constructive information in this Forum, well done, Graham 1 Quote Link to comment Share on other sites More sharing options...
naichuff Posted July 16, 2016 Report Share Posted July 16, 2016 I have just looked at my Amal Mk2 The choke lever is on the left and the plunger on the right I push the lever down to start and up to run or hot starting and is the same as those on the Amal web site It is the carb that left the left the factory with the bike Quote Link to comment Share on other sites More sharing options...
oldmxer Posted July 17, 2016 Author Report Share Posted July 17, 2016 Hi naichuff, thanks for that, this is the same condition as mentioned in the photo from feetupfun, its good to get the correct understanding Quote Link to comment Share on other sites More sharing options...
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