850T won’t run on left side

[NCAmother]

Hi all, I just rebuilt the engine for my 850T. LeMans pistons and heads in new gilardino 950cc cylinders. The bike had been in a shed for 30 years.  I’m running a new Sachse ignition, and new keihin 39mm carbs.  I also get 155 psi compression.  The bike will start, on the first try, and runs strong only on the right side.  The left cylinder runs cool to the touch.  Tested the bike, and there is spark in the left cylinder with the bike running.  The compression is good, and the carb seems to be working fine.
I swapped the coils and no difference.  I tried starting the bike on the left cylinder, didn’t start but there was one backfire.   What should I be looking for?  🙏

[Offcamber1]

Since you obviously have both spark and fuel on left side, I would say your right cylinder is firing on the left cylinder's timing, leaving the left side with a wasted spark at the wrong point in the cycle.

Just guessing...

[nc43bsa]

^^^^  I ran into the same problem on a Harley Sportster race bike at Roebling Road.

[matt franklin]

Did you static time the engine?  After the rebuild, I would be concerned that the timing marks are correctly positioned. 

[egschade]

Try changing the plug. I've had seemingly good ones that spark outside the engine not work when installed. Check the plug wire too.

[fotoguzzi]

Try changing the plug. I've had seemingly good ones that spark outside the engine not work when installed. Check the plug wire too.

me too. Easy to change to new plug. Also, is the lead seated into the coil? And the plug end screwed into the lead Nice and tight? Maybe trim back the lead for a fresh connection.

[NCAmother]

Since you obviously have both spark and fuel on left side, I would say your right cylinder is firing on the left cylinder's timing, leaving the left side with a wasted spark at the wrong point in the cycle.

Just guessing...

Right on the money, I adjusted the rotor and now it fires on both.  Thanks