Bike in question: 77 cb550k, pd46 carbs, foam air filter, 4into1 mac exhaust, 45 pilot (previously 42), 90 main, mixture at 2.5 turns out.
So I have been riding my 550 around town this summer and it has, for the most part, been running smoothly. After her first ride two up one night, I suspected I had overheated the engine. No seized pistons, but definitely had some white smoke coming off the bike when we stopped 15 minutes later. Let her cool down, rode home an hour later and had trouble not stalling out (turned out to be a dropped pilot jet, I think).
Fast forward - changed the oil to 20w50, I removed the carbs, did a deep clean, soaked in pine sol for an hour, ran a guitar string through all the ports, dried and clean, reinstalled, tightened everything, and bumped my pilot jets up a size (was running 42s, now running 45s, still have 90 main). I suspected lean because the engine was so hot: headers just beyond the exhaust flange brackets were running between 450 and 500 F. Plus there was tons of coughing through the carb body and hesitation when cracking the throttle. Bigger pilot jets and no more coughing or hesitation. However, the headers at the exhaust bracket is still running around 450 F at idle. Have not synced yet or pulled plugs to look at them yet, will do so after syncing and riding a bit. But I'm concerned about riding if the headers are still running upwards of 450. The only other post I found listed temps in the 300F range for headers, if not lower. I don't wanna cook my oil again, or burn a hole in my piston, so I'm reluctant to ride again until I think I'm in a safer temp zone.
Other factors to consider 1) I tried running the bike with the mixture screws turned in all the way across all four, and then turned 3 turns out just to see what difference it would make. I thought that turning them in all the way would lean out the mixture enough to prevent it from starting, but it still ran. Only difference was an increase of idle RPMs by 100. Not sure if this is to be expected or not, but it makes me feel like the mixture screw is mostly for decoration. Am I crazy or does this screw actually do something and I am just not experienced enough to notice?
2) oil change was first one after splitting the cases and installing a new primary chain, cam chain, a few bearings, and new rings. There was some metal in the bottom of the oil pan, which I know was to be expected, and one small piece, probably about 1/4 inch long, about the size and shape of a small, torn fingernail clipping. Very small in absolute terms, but potentially huge in tolerance terms.
