Okay, here's one I'm sure will go unanswered but I'm going to toss it out there anyway.

98 1340 carbureted Evo with a mild cam, V&H ShortShots 34K miles.

When cold, the rear cylinder consistently fires more "violently" every 4th or 5th firing. You can hear it, you can feel it. Place your hand a few inches from the exhaust and every 4th or 5th firing is more powerful than the others... pulse, pulse, pulse, PULSE, pulse, pulse pulse, PULSE. It "sounds" like a mild backfire, but obviously isn't.

Anyone else experience this? It annoys the hell out of me because it's just... not... right.

 

Check the insulator on your spark plug.....

Take the plug out, and shake it... Is it rattling?

Dont just hold it upside down, stand it up as well... Is the insulator broken off....

Also, check the resistance on the wires..... Rear wire could have an intermittant failure...

Don't forget the Coil as well.....

 

Installed new plugs today, tested the wires: Accell wires (non resistor) 86 ohms for the rear, 220 for the front. No change to cold idle properties. I'm going to create a post about the results of my check of my timing. It may be related.