Hi all,
Having what seems to be a compound issue, and I wanted to give the better brains than mine a chance to mull them over (which means that this is probably gonna be super simple and y'all are gonna make me feel dumb for not getting it quicker
). The bike is a '75 CB378 (with GS850 pistons/overbore per CrazyPJs mod), and carbs rebuilt by the man himself, and a PAMCO ignition.
I've got it dynamically timed pretty close to happy; she fires right on F/LF at a 1200 rpm idle, and advances perfectly on the right cylinder and just a hair shy of the range on the left cylinder at 3000 rpm. The problem is, she backfires like a sumbitch half the time when I'm starting it up (like, bad enough that I no longer use the kickstarter because it nearly broke my ankle last time), with smoke out of the filters. Once it starts though, it runs fine! Except the idle is a bit high, and nothing I do to the idle adjustment screw will put it under 1200. I've got a new throttle cable on the way (there's a hair at the end of the rotation that I can close by pushing it forward), but that seems inconsistent. I haven't changed the plugs since timing it, so I'm 100% sure they're sooty, but could those be causing the backfiring/high idle? The valves are a little tappy, but not too bad... also wondering (in my nightmares) if I could be a tooth off on the cam chain.
Any thoughts much appreciated.
Pat
Having what seems to be a compound issue, and I wanted to give the better brains than mine a chance to mull them over (which means that this is probably gonna be super simple and y'all are gonna make me feel dumb for not getting it quicker
I've got it dynamically timed pretty close to happy; she fires right on F/LF at a 1200 rpm idle, and advances perfectly on the right cylinder and just a hair shy of the range on the left cylinder at 3000 rpm. The problem is, she backfires like a sumbitch half the time when I'm starting it up (like, bad enough that I no longer use the kickstarter because it nearly broke my ankle last time), with smoke out of the filters. Once it starts though, it runs fine! Except the idle is a bit high, and nothing I do to the idle adjustment screw will put it under 1200. I've got a new throttle cable on the way (there's a hair at the end of the rotation that I can close by pushing it forward), but that seems inconsistent. I haven't changed the plugs since timing it, so I'm 100% sure they're sooty, but could those be causing the backfiring/high idle? The valves are a little tappy, but not too bad... also wondering (in my nightmares) if I could be a tooth off on the cam chain.
Any thoughts much appreciated.
Pat