Engine dies when I pull right side spark plug cap

[Kurt V]

1965 R60/2. Title says it all. My bike is really running quite well. A little rich on the left side, but not too bad. But it has a quirk that I don’t quite understand. When I pull the spark plug cap on the left side, the engine continues to idle at the same RPM. If I try to twist the throttle and raise the RPMs it will stumble badly. Which is what I expect. However, when I pull the spark plug cap on the right side, with the engine idling, the engine dies immediately. Any idea of why this is?

[MikeL46]

I would have to say your bike is only idling on the left cylinder. If the right was pulling its weight the engine would at least slow down when you pulled that plug. Probably not ignition, but the carb. Is it possible the really small idle jet is blocked on the right side?

Mike

[schrader7032]

If the engine was only running on one side, wouldn't it run badly? I gathered from the post that it runs well.

I've thought about this and I'm having trouble understanding how the engine can run well...ie, smooth idle, no engine rocking...with a spark plug pulled. That would have to indicate that the cylinder is still getting spark!!

If you pull the plug, the spark energy has to go somewhere and it should be going to ground through the safety gaps at the magneto. But that doesn't mean that the cylinder got spark.

[Kurt V]

I will check the idle jet. I did just clean both carbs, but will check it anyways.

I am at a loss as to why the bike still idles the same with the left cap removed. Does act like the spark plug is still powered up. Doesn’t act like the power to the plug stops until I rev the engine up. Is that even possible?

[312Icarus]

The slide on one side could be pulled just a tad higher. Try raising the slide on the weak side by running the knurled idle screw in a bit, while backing out the one on the strong side. A good carb clean, and sync is in order. Also check to make sure the carbs are tight to the manifold gaskets.

Icarus

[Kurt V]

Carbs were just cleaned, but I will double check. Also synced the carbs but will up the idle on the weak side to see what happens/changes.

[312Icarus]

Don’t forget cable adjustment! Each slide should lift off at exactly the same time, and from the same starting position.

Icarus

[FL54]

Classic troubleshooting a problem that appears is to go back to the last thing that was done. (Clean carbs? ).

[Kurt V]

Mikel46 and 312Icarus are our winners! I rechecked and adjusted the idle screws on both carbs. Once I got them rebalanced all is well. At least for now. thanks to all for your help!