What's next step?

Was non running bike, filthy clogged carbs and crossed plug wires.
Now it's running, but having problems with #2 not firing.
Assumed it was carb related so cleaned again and rode for 7mi to see if it cleared up.
Still no go on #2 so pulled plug (darker then others) and finger checked compression.
Was good for a few cycles and then got REALLY low.
Pulled cover and checked valves, their within spec.
Put some ATF in the plug hole and have good (finger tested) compression.
Soooo... What's my next step?
Read somewhere on here about potentially sticking ring in piston. Possible?
Should I buy a compression tester?
Bike is a 81 kz750 ltd, odometer has shy of 9000mi and is working.
Last title transfer was in 88 with 4750mi, so I'm guessing current milage is accurate.
THANKS!

Have you checked if there comes spark in #2 plug cap? Faulty plug wiring is what I mean..just an ideaB)

Switched plugs & wires w/ same results, and since #3 is going I'm assuming it's not coil/timing related.
It has a compression issue, that seems to be ring related.
Just not sure if a tear down is necessary or if there are any tricks I can try first.
Read in another post about possible sticking rings.
Seemed odd to me that it had compression for a couple strokes before loosing it.
Didn't mention in the first post but it seemed to fire #2 after prolonged idling (smoother, higher RPM, hotter exhaust) but would return to miss after throttle application.
Would actual compression readings help in figuring this out?

the compression check will tell you what is going on, another thing to try is to make sure the valves are closed and fill the cyl with comressed air, and listen to see where its going

Here's what I got cold...Gauge reads in 10psi increments.
#1=130, #2=120, #3=150, #4=140
I sprayed penetrating oil in the bores yesterday so I guess it's a wet & cold reading
When I get the valve cover, coils & tank back on I'll do one at operating temp.
Seeing what other people post cold they don't look bad, but I guess the oil helps bump up the psi...

Back together warmed it up and got the following
#1=130, #2=120, #3=130, #4=130
Carbs cleaned twice, bench syncd, homemade manometer syncd, valves checked, spark plugs rotated
Not sure what to do from here
Anyone got ideas?

I'm not familiar with the 750 size motor but I
have to ask anyway...

Does it have a smog valve hooked to the valve
covers? (like my 79 MKII had). If it does that's
your problem.

Bob

Are you sure that #3 is firing? Check for spark? Since #2 and #3 both spark at the same time on compression stroke and exhaust stroke you could have a bad coil. Could double check timing to make sure.

Yes, Smog is hooked up. Tell me more about that please.

#3 is firing. Plug is clean and the exhaust is sizzling hot.
Yesterday I flipped the wires on the coil incase it was possible to have half a dead coil, but same result.
I'll check the plug wire resistance again, but it had checked out fine.
I have not checked the timing since I don't have a timing light.
I'll see if I can borrow or buy one, but do you think timing would only throw off one cylinder?
Bike starts right up
I as tired of it as I am I may pull the carbs again and clean for a 3rd time

Is it possible that you have a bad spark plug? Try swapping one for another. Sounds like you already swapped wires so that can be ruled out too. Probably if it starts and runs I doubt it is a timing issue on one cylinder.

It was the carb... everyone thanks for the ideas and for listening
I could kick myself that it took me 3x :blush: