[Two Tone]

My 404 was running just great.

Suddenly while driving, it backfired through the carb. Since then, once the rpm reach a certain level it backfires throught the carb.

This change occurred very suddenly so something must have changed.

Its been running great until just now. I've recently installed the civilian ignition kit which included a new cap, wires, plugs, rotor and ignitor and I've recently checked the fuel filter which was very clean. The timing was checked when I installed the kit and then once a week later. I've got at least 20 hours on it since this was done, during which it has run perfectly.

Backfiring throught the carb suggests a timing problem to me.

Any suggestions as to what I should check first would be appreciated. Like I said, something changed suddenly to cause this, one second it was business as usual, the next second it was running poorly.

It starts normally and idles fine. It just won't run well above a moderate rpm level.

I've got it here in my shop right now so if you think of something let me know before I dive in.

Thanks.