just started my 73 750 i've been working on yesterday. the motor was totally rebuilt by a brit bike shop thats been around since the 60's, so i'm pretty sure they know what they're doing. The owner of that shop said he wanted to start the bike for the first time and confirm oil pressure and everything was assembled right before he would warranty his work on the motor. so he started the bike yesterday, and told me everything was good, except the left side was running rough, and he thought it was a problem with the carb because he couldn't get a good adjustment from it. I took it home, and started the bike, heard the left side idle rough, and when i pushed down the tickler on that side the engine would surge and the miss would go away. Sounds like a fuel problem. So today i decided to go ahead and switch the plug wires around and just rule out anything in the power arch system. For whatever reason, when i switch sides with the HT wires, the bike won't even start. It kicks back, back fires, smokes out the airbox. Switch the wires back, fires right up, and idles rough on the left side!? What the heck could be causing this? multiple factors adding up?