TR4 misfiring under load, fouling plugs

[GTP1960]

As for the choke, I pull out all the way to start, then when it turns over, push in halfway. Then gradually all the way until it doesn't die. Once i can bump up the rpms with the accelerator without too much misfire, I'll drive, but I don't use choke at all while driving. I just drive it a few times around the block and it stumbles with too much throttle or after shifts. Should I keep messing with the choke while driving? Am I not letting it warm up enough? After it's warm it runs better, but I don't push it very much. And it shakes like the dickens when I kill the ignition.

As far as general driving technique, I start driving immediately, using just enough choke so the engine will take throttle smoothly. I do try to be reasonably gentle with it, but I have to turn left across a busy 4-lane road, so that generally involves full throttle. And in just a couple of miles, it is warm enough to release the choke fully.

4 psi is a little on the high side, the original spec was 1.5 to 2.5 psi. Might be OK, but watch for signs that the fuel pressure is overcoming the float valves, especially when the engine is hot. The use of 'Grose Jets' seems to aggravate the problem.

One thing I didn't see mentioned, have you (or your mechanic) checked the valve adjustment? Valves too tight can really mess up the mixture, it is one of the first things to set when doing a tune-up.

The shaking after you turn off the key is known as "running on", and is generally a sign that the engine isn't tuned right (although it might be just high idle rpm). It's also not especially good for the engine, so I would suggest leaving it in gear, with your foot firmly on the brake, and using the clutch to kill the engine just after you turn off the key. With a little practice, you should be able to do this so smoothly that you don't even know if it would have run on or not. My TR3A had a tendency to run on from time to time (never did get the idle rpm down where it belonged), so I just used this technique every time.

No disrespect, but I have seen "professional" mechanics overlook many things. The only solution seems to be doing it yourself. One thing to check is that the carburetor pistons move smoothly and easily. Take off the air filters and lift each piston in turn to the top with a finger (engine not running obviously). You should feel a definite resistance to lifting the piston, but it should move smoothly to the top with no binding or roughness. Then when you release the piston, it should fall quickly and smoothly to the bottom, and land with a distinct click. If you don't hear the click, chances are that the jets are not centered properly, which will cause no end of grief in trying to adjust the carbs. The piston position controls the mixture needle, which in turn controls fuel flow; so it is essential that the piston move in response to any small change in air flow.

Also, if the carbs have been run for a long time with the centering not quite right, it is possible for the needle to wear a groove on the inside of the jet; which will mess up the mixture curve. In extreme cases, you won't be able to set the idle mixture lean enough; but the cruise mixture will be so lean that the engine will overheat and EGT will be way too high. My Dad's TR3A had this problem so bad that the exhaust manifold would glow red after a freeway run!

No charge or slight discharge at idle is normal. If you get the idle rpm down to the book 500 rpm, you may even see the red light glow. The generator just doesn't work at all with the engine below 1000 rpm or so, and won't reach full output until it is turning fairly fast.

However, it shouldn't stay at 30 amps for more than a few seconds. The generator is only rated for 21 amps continuous, and will overheat if it puts out much more than that for very long. If the ammeter stays at +30 for any length of time, it probably indicates a problem with the control box, battery or generator (in roughly that order).