Hi Chris, remember, fuel, air, compression, and ignition, and fire. Most modern engines idle with firing between five and ten degree before top dead center. I you have all those things, it will run, the vapor carb means you'll have good fuel air mixture, you know you've got compression, and the only question is when it's firing. I don't know about all hall effect pickups, but some are sensitive to a particular pole, and if you use the other, they fire on the magnet leaving the scene, not entering, and can have your timing off by the width of the magnet. If you're not sure, take a disc of cardboard or a degree wheel if you have one, and rotate the engine until the plug fires, noting where it is by having a pointer near the edge of the disc or degree wheel, and figure out when you're firing. If you're using a piece of cardboard, mark where the firing happens, and mark TDC, and then put the cardboard on your rotary table or something like it and figure out the degrees. This will easily show up if you have pole sensitive pickup, if it's firing way late, it's probably firing on the magnet leaving and can easily cause the popping without getting it to run. Each engine has its own personal preferences too, so they can want things a bit more advanced or retarded than standard, or be a bit easy to flood and the like. Make sure you've got a wet plug when you've been at it a bit, or it's not getting fuel. I used to squirt a smidge of lighter fluid in the plug hole of engines that didn't want to start, just to make sure they were getting fuel, and the same can be done with starting fluid. Sometimes an engine just needs a demonstration, 'cause it doesn't know what it's supposed to do, and getting it to fire on lighter fluid will give it the idea, and get it going, and understanding what's demanded of it. Watch your con rod as you rotate the engine through, you'll see the last eight or ten degrees before top dead center doesn't move the piston much at all, nor does the first eight or ten degrees, so advance on the cam is essential, because it needs to start lifting while the piston's not doing much of anything, so that part of the rotation isn't wasted, and the cam action being in the middle part, where all the work's being done. Your valve should be fully lifted by five or ten degrees after BDC, and bear in mind, oil on the intake valve face or seat can be enough to keep the valve from lifting off at low speed, and keep fuel air from getting in, particularly if you've been getting pops, meaning fire in the hole, and making for more sticky oil. That's when a squirt of lighter fluid ensures you've got fuel and air through the plug hole. I spent many hours with various small engines thrown out, and fodder for my learning as a boy, and the lighter fluid was a good diagnostic tool. If one of your valves is not seating fully, you will see fire out it, if you have lighter fluid ensuring you have fuel, and a slightly unseated valve will prevent the vacuum for the intake, while still providing compression, being fored to seat, and giving a false sense of seating well. Sometimes it can be easy to forget when you get frustrated, when everything is right, they always run, period. I kick started my bike for almost five hours changing ignition, timing, two carburetors, changing from points to electronic and back, and finally got it started, ran it for a couple weeks running horribly, finally discovering Harley changed their timing marks during the years I was raising my kids, and I had it timed with the advance set on top dead center, and got it to run, and ride there. Once I got the timing right, it's been a one kick starter, but it was running with the timing more than thirty degrees retarded. When everything is happening at the right time the right way, it will run and run great, the only question is niggling little details and the ease we can over-look those. Ta ta for now,
Cheers, jack
