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Paul, not sure I understand your issue, isn't it rather too rich mix on low rpm symptom? The same I'm facing?When you try to engage choke that should make mix richer (at least partially) it helps of make it worse?If it helps, your mix is too lean, if it is worse, it is too rich... I'm not expert but this is my exprienceIn my case I have clearly too rich mix and still did not fixed that (you know my thread well )
HAVE YOU CHECKED FOR AIR LEAKS ON THE INLET SIDE..? ALSO CHECK THE COMPRESSION, CHECK THE IGNITION TIMING/POINTS GAP AND REPLACE THE PLUGS, CHECK THE AIR FILTER ISN'T BLOCKED. IF YOU DO ALL THAT AND STILL HAVE AN ISSUE YOU CAN START TO GO THROUGH THE CARBURETOR SETTINGS.
I FORGOT TO MENTION TAPPET CLEARANCES.... BUT I GUESS YOU HAVE CHECKED THOSE ALSO. IN WHICH CASE THE CARBS BECOME THE PRIME SUSPECT. GOOD LUCK WITH IT.
Thanks K2-K6 thats very helpful.Its also odd as since the rebuild I am getting an odd afterfire (popping in exhausts rather than a true backfire) in cyls 1 and 2 that happens only every minute or so (ie not on every firing stroke) which goes away when I wind the idle screws out a bit. Not sure
Haha... i was at work on my pc with caps lock on.... wasn’t shouting, honest.... 😄
Quote from: paulbaker1954 on July 10, 2019, 09:54:46 AMThanks K2-K6 thats very helpful.Usually your first suspect is air leak on the exhaust side of combustion chamber that causes any popping in down pipe / silencer. Or drop out from firing cylinder cleanly so you get occasional unburnt mixture going out of cylinder.Just a thought about uneven running, and your initial problem of pulling away. How confident are you of HT leads? Have you tried running it in the dark and looking for escaped sparks around the leads?
Thanks K2-K6 thats very helpful.Usually your first suspect is air leak on the exhaust side of combustion chamber that causes any popping in down pipe / silencer. Or drop out from firing cylinder cleanly so you get occasional unburnt mixture going out of cylinder.
By drop out, I mean a non fire for one or more cycles of that cylinder. To get a backfire of any size in the exhaust pipe you have to have some proportion of fuel left unburnt. Depending how rich carbs are set up that can vary, but add a little oxygen from an exhaust leak to it, making it more volatile, and you get that characteristic pop. That can be normal with just the exhaust leak as a fault, without that the rich mixture can just pass right through and give you a petrol heavy smell at exit without popping. Your pulling away cleanly problem though suggests you've got at least one cylinder not firing cleanly while running at lower levels of carb range. This would also have the potential to give those exhaust backfire results. So linking the two trait together suggests you've got a no fire result some of the time on one of the cylinders while on idle circuit. The question is, what is causing that? The check of HT leads may show you some leakage which can do this as it can give sporadic sparks. The other is of course carbs, hence the question of what response you get by turning each screw individually to see if you are getting a linear response from each carb idle circuit in isolation.