HELP - Right cylinder not advancing...

Hey guys.

So I just bought a XS 400 SECA from 1983. When I bought the bike it hesitated in the mid-range acceleration. I figured that it was just a carb adjustment. But no! After checking the spark plugs I found that the right sparkplug was very sooty (running rich) and the left was perfect. And then I began checking everything and located that the ignitor box was faulty. It didn't advance the ignition on the right cylinder, and therefore making an incomplete combustion making the spark plug sooty...

I changed the ignitor box, and suddenly the bike ran great for about 75 km. Then it went back to not advancing on the right cylinder... below is what I have done on the bike until now, to figure out the problem.
Do you guys have any idea to fix this or similar experience??

So this is what I’ve done:

New complete rebuild kit for both carbs.

Synchronized and adjusted with the correct jets.

Closed off the choke for the right carb - didn't work...

Done a compression test on the engine - Spot on in both cylinders.

New sparkplugs

Switched the ig. coils (Left and Right) and trimmed a bit of both sparkplug-wires

Checked the Pick-ups

Changed the ignitor box with a used one - problem solved for about 75 km.

And now the problem is back...

Rewired the pick-up's between the sensors and the box.

Hi Alexander,
Did you verify lack of advance with a timing light and see that the flash didn't leave the timing marks? I just recently checked a SOHC, assuming the process is similar for a DOHC. "Checked the pickups" is a little vague, is there a resistance spec that you measured? Perhaps some more checks would be beneficial. Maybe an AC voltage check from each side to ground would show some discrepancy? Some fancier multimeters have RPM and dwell (degrees or milliseconds) that you could check both the pickup lines and also low side of each coil.

That's a fairly esoteric problem, much less to happen with a pair of ignition modules. I'd also be tempted to suggest borrowing or buying an oscilloscope to verify the pattern of both the pickup signals, and both the high and low side voltage of each coil. An electronics hobbyist might be willing to help you out too.

If you're willing to buy one I've been pretty happy with my Hantek 6022 2-channel PC scope. Uses the PC for controls and screen, which is both good and bad honestly. Available for under $100 in the U.S., you can hopefully find a similar offer to your place.