Hello again all, I have just serviced the van, jobs included: Changed to Electronic ignition Changed coil and HT Leads and Spark plugs Changed fuel filter Changed air filter element (aftermarket pancake) Changed Oil, strainer and gaskets Set the timing by strobe light The van starts very easily and ticks over nicely, previously it died after about ten minutes but that is sorted. When i accelerate smoothly and gently it reacts effortlessly. When i press the accelerator down quickly it dies for a couple of seconds and then back fires or almost stalls. I have been working on the van all day trying to get a solution and have just finished so on my chin strap. Just need to know what i am missing so that when i attack the van tommorrow it is with some one elses knowledge. Or if no help i will attack the van with a birch branch and see how far i get
if the engine is properly warmed up (ie driven around for a good half hour or so) rather than ticking over on the drive for ten minutes) and you're getting a near stall when you dump the throttle, that would suggest (to me) that there is a brief moment of fuel starvation. Essentially, the engine requires a specific amount of fuel for a specific load placed on it. At barely open throttle the idle jet is responsible for metering out the fuel...increasing the rpm by opening the throttle allows more air to be drawn into to system which obviously requires more fuel...this being metered by the main jet(s) or some kind of transitional port/jet. when you dump the throttle to wide open, there's a time lag between the air being introduced and the fuel being sufficiently atomized, so various methods have been employed to counteract this hesitation...usually along the lines of a pump jet that squirts a measured amount of fuel directly down into the venturi. on most half decent carbs you can tailor the amount of fuel, and the point at which it is introduced by adjusting the pump jet mechanism (I'm being non specific here because not all carbs are the same). It's easy to overcompensate resulting in too much fuel being introduced (or at the wrong time).. you'll get a similar hesitation accompanied by 'spitting' and a strong smell of unburnt fuel out of the exhaust...if your carb and dizzy drive are old and worn (or in the case of bocar carbs...brand new and badly made) don't be suprised if you can't get the thing to run sweetly at all revs in all situations...hope this helps Also, the weather plays a part >
Done a bit more research today, I need to tune my carb after changing all the parts for the service. The only articles i have found for tuning the carb involve the use of a taco/rev counter on the timing/strobe light or the rev counter on the dash to first get the idle revs to anywhere between 700 - 900 depending on the article. i am sure that not everyone has a rev counter or a timing light with a taco/rev counter on it, so can some one let me know how us mear mortals can carry out a carb tune with just a mark 1 ear to listen to rev fall and rise and two differently sized screw drivers. P.S. i am sure that since the service and changing to electronic ignition, new coil and leads the idle speed is a lot higer (not off the ground but in speed b4 any one came up with that comment ;D ;D)
I'd go closer to 900 than 700 to be honest. A lot if timing lights have a rev counter mode, if not use your Mk1 ear and it's a fairly quick tickover!
^whs. You're previous post implied that the engine died after 10mins, implying that it possibly never ran right anyway once the choke came off. I'd do the usual and check for air leaks, and maybe give the carb a good scrub. Does the choke really open fully once the engine's warmed up? Does the accelerator pump on the carb work? There's nothing much you can "tune" on the carb - you can set the idle mixture and idle speed, but that's it. I'd take the carb off and give its innards a good cleaning.
Not alot of immediate help, But i bought a relatively cheap multi meter from ebay with a Tacho/rev counter on it
question is, did it run right before? If so, and you didn't mess with the carb then the problem is something you did mess with. So, did you fit the fuel filter correctly, have you replaced your ht leads correctly so its firing right on all 4? Gapped the plugs right? Have you set your electronic up correctly? Module located correctly in the bottom of the dizzy, gapped properly and the magnetic ring pushed home all the way? Cap on right? You've set the timing by strobe light, where have you set it to? Did you check your valves?
