Intermittent spark

My 77 KZ750 twin has intermittent spark on cylinder 1 but consistent spark on cylinder 2. Any suggestions?

Check for leaky spark plug wire arcing across to the head. Especially if it is more prominent as you increase the rpm's.

What do your spark plugs look like?
Have you done a compression check?

F64 wrote: What do your spark plugs look like?
Have you done a compression check?

Compression is 135 on cylinder 1, 145 on cylinder 2. Plugs are carbon fouled.

You could run hotter plugs, but that's just a bandaid.
Unless, you don't mind running rich.
Which plugs are you running?

Have you done anything to the carbs or the intake side of the engine?

F64 wrote: You could run hotter plugs, but that's just a bandaid.
Unless, you don't mind running rich.
Which plugs are you running?

Have you done anything to the carbs or the intake side of the engine?

NGK B7E S plugs
Filter pods, #52 pilot jets, 140 main jets. Cleaned carbs and checked float height

Well, without knowing your mixture at different parts of the carburetor circuit, it's hard to suggest jets and needle positions.
You could do plug chops on new plugs and that would get you to see what the carbs are doing in each circuit.

Plugs
The factory states anywhere from a B8ES to a B6ES.
See if you grab a pair of B6ES.
The plug will run hotter preventing the fouling.
You can also close the gap to make it easier on the ignition system to fire the plug.
Run your point gap to the smaller end of the spec. It may be .3mm. This will give your coil a bit more of a charge.
Check timing to make sure the gap adjustment didn't shift your timing

What you are trying to do is keep the tip of the spark plug above 900 degrees Fahrenheit but below 1600f.
If the tip of the plug is below 900f, you will foul the plug. Above 1600f and the plug will cause pre-ignition.

Photo:https://www.sparkplugs.com/Data/uploads/Charts/NGK_Plug_Chart_1.jpg

Just went thru that with my 79. Took me 2 weeks of tinkering and brain work . Bet a dollar your timing is off a tiny bit...First step is adjust timing chain tensioner. . 2 set points. And static timing . If that don't solve it loosen point plate just enough that you can yep with a tool and move it and I think I advanced it a C hair (while running) and bingo run perfect and has all season ... If I remember I rotated point plate clockwise.... and check and recheck point settings

Your timing is off ...here what I did to diagnosi..moved point plate while running. Think it was clock wise and bingo..adj timming chain tension triple check points. I chased same problem for a week or 2 ... 79 kz750 twin...has run perfect all season sense

BobberDan wrote:

Australia? :laugh: Ed

Thanks everyone for your input. I had set the points and timing right already. I replaced the coil and it fixed it.