Can't start 83' KZ750

Finally I started it and it idles just fine. But when it idles at 1000 rpm I hear chatter noise (chain tensioner is changed). If I rev it the noise disappears. Also when I rev it revs drops slowly (throttle cable-OK, pilot screws two turns out).

Great
The primary chain (connects the crankshaft to the transmission) on the 750 will rattle quite a bit at idle particularly if the carbs are out of synch. I've heard people say it rattles like a bag of hammers :laugh: Not totally sure but think idle should be about 1200 rpm which is where I have mine at . If you have less rattle at 1200 and it dissapears when you ride then probably the primary chain.
Cam chain rattle tends to be higher pitch and primary chain rattle tends to be lower.
You can use a long screwdriver as a crude mechanics stethescope to pinpoint where the noise is coming from. Put the handle to your ear and the tip to various points on the motor when the bike is running

If the noise is primary chain then a carb synch will reduce it but not eliminate it. I have never heard of a primary chain breaking or needing replacement.

rpm slow to come down
may be air leak
Mixture may be a bit lean - vary the pilot screws by + or - a 1/4 turn. Sorry but I can remember if turning in or out increases air. I'm thinking turn in to reduce air but unsure
Idle advancer may need lubrication

I lubed timing advancer before. Tried many different settings of pilot screw (1; 2;2,5;3;4;5 turns out). Still the same. Checked for leaks with WD, none found. And how it will behave when mixture is lean/rich. Last setting was 5 turns out and when I give revs I hear pop from exhaust.

karoliens wrote: Finally I started it and it idles just fine. But when it idles at 1000 rpm I hear chatter noise (chain tensioner is changed). If I rev it the noise disappears. Also when I rev it revs drops slowly (throttle cable-OK, pilot screws two turns out).

What ended up being the solution? My saga seems to be very similar to yours.