If the K3 550 is like my 1976 CB550F then it has an internal chain for the primary drive.
My 1982 Kawasaki Kz550 *also* had an internal chain-operated primary drive.
It's a big hefty 'hy-vo' type of chain inside the engine that transfers the rotation of the crankshaft onto the 'output shaft' that sticks out of the engine, the front countershaft sprocket mounts on the 'output shaft.'
I accidentally messed up the carb synchronization on the Kz550.
And all sorts of engine 'hard mechanical noise' was coming from the tranny area.
The way it was explained to me was this:
1) "One of your carburetors is open a lot more than the others -- they are not synchronized"
2) "so when that cylinder fires, it wants to increase the engine RPMs"
3) "then BAM the carb on the next cylinder that fires is not open as much and that slows down the engine revs.
4) "so your out-of-sync carbs are telling the engine "SPEED UP/SLOW DOWN/SPEED UP/SLOW DOWN" in very quick succession at idle, where you're normally at 1000 revs per minute, or 16 engine revolutions PER SECOND"
So every second at 1000rpm idle speed, the engine turns over 16 times -- and thus every second at idle, my out-of-sync carbs were telling the engine "SPEED UP/SLOW DOWN/SPEED UP/SLOW DOWN" -- sixteen times.
It rattled like hell. Just think of a chain with a bit of slack in it.
16 times per second, that primary chain was going tight/slack/tight/slack etc. as the one cylinder with the out-of-sync carb fired off.
Just a #$%*load of grinding sound, scared the crap out of me, "damn my gearbox is toast."
Pulled the carbs, put them right (set the throttles to open the same on each carb) and PURRED LIKE A FREAKING KITTEN at idle. Nothing wrong with the tranny.
If someone not familiar with how a motor with a chain primary drive can sound with out-of-sync carbs they may not believe it or guess correctly.
It's still amazing how much mechanical noise that primary chain going tight/slack/tight 16 times a second made.
And I also noticed the grinding sound 'went away' at higher speeds. Not sure why. Maybe once the throttle is open far enough, carbs being out of sync don't have the same affect because the air/fuel flow is so much higher? Not sure.
