stock '71 L24...

The latest problem: I've got puff of smoke popping out of the SU closest to the radiator. The other is fine. Both air/gas screws were tightened, then brought out 3 full turns.

I've changed the points (gap .016-.018), cap, wires, plugs. Did not pull the rotor out. The pistons in the carbs do move up and down, the fouled carb does move just a barley easier than the other that's closer to the cab.

The symptoms before this would-be-easy endeavor: First the engine would die when I exit the highway. Then when driving casually the rpm would totally stop, as if the motor lost spark, then pick right up again. After this, about a day later, some mean backfiring. I'm mean like a shotgun, in fact my muffler is not sounding perferct anymore.

This seems like timing to me, so to duoble check. The firing order is 153642 and the pistons go 1-6 from front to back, right? And the dizzy spins counter-clockwise, right?

Bad gas? Something sucked into carb? ??? thanks, jessz

Did you check the float levels? Because if they aren't the same, screwing the mixture screws out the same number of turns means nothing. I'm betting on radically different mixtures in the two carbs.

Have you adjusted the valves? Do the fuel nozzles move up & down ok, or is one stuck?

Has any work been done on the engine recently?

BTW the firing order is 1-5-3-6-2-4. Did this begin after you changed the wires?

the valves were ajusted about 3000 miles ago. It did not feel like a gradual loss of power or vavle hesitation to me, but I'm not an expert. And the valves sound tight.

The fuel nozzles that you talk of, are those the piston type things that can be checked by taking off the filter and just putting your finger inside the carb and pressing up on it?

the wires are correct I just typed the firing order wrong

OK, that rules that out. I'm basically and EFI guy so I'll defer to the others now.

I always ask this because it's a common occurrence that has bit more than one guy before: The Timing Advance Roller Plate. That little Lazy Susan type pressure plate that allows the Vacuum in the engine to advance it's timing, and RETURN to it's zero vacuum advance position.

Once your dizzy's plate is shot, and the little ball bearings fall out of their holders, then your vaccuum CAN and oftentimes DOES rotate and advance the timing. It's that it doesn't always allow it to RETURN, until the springs can jostle it into place via the vibration of the engine, that causes the problem. Then when you go flooring it, it REALLY forces it to move until it reaches a point where the spring isn't strong enough to overcome the friction generated by the plate having been rotated without the ball bearings.

In either of these cases, you'll have all sorts of weird fluctuations of performance that just do not make sense. That's because the springs in the dizzy will EVENTUALLY force the plate back into position, but all it takes is the first offset to throw everything off.

E¢

That response sounds very promising. I will check that, thanks alot.

Hi Jezze, the fuel nozzles are located at the bottom of each carburetor. Look for the little rubber hose at the bottom of the carb. One end connects to the fuel float bowl, the other end connects to the fuel nozzle.