Topic: CB750 K1 Wiring & Misfire Issues - Help Wanted

[Brookesy in Oz]

The old girl is running again. The last time she had a heartbeat was 2005. Just trying to get the last bits finished so i can get her on the road. First, thanks to all the helpful people here on the forum. I wouldn't have made it this far without you and i'm starting to get a bit excited. Although, time spent in the shed keeps me from my guitars. Catch 22

A couple of issues:

(1) I'm doing the wiring in the headlight bucket and most of it is (reasonably) obvious, but the horn wiring has confused me. There's a light green wire from the switch with a male terminal (it's working, i have continuity to earth when the button is pushed). Two wires on the horn, light green & black. Both have male terminals and they are not long enough to reach the headlight bucket. Have i lost / misplaced a sub harness?

(2) I have a slight misfire on cylinders 3 & 4. I can hear & feel the misfire on 3. I only know there's a misfire on 4 because i checked some posts looking for answers and one post suggested putting the timing light pickup on to check the pulse (thanks to whoever that was, i didn't think of that) and i checked all of them. I have constant pulse on cylinders 1 & 2. But on cylinders 3 & 4 there's obvious misfires. The spark plug caps are new. Can i put new spark plug leads on the coils or do i have to buy new coils?

[HondaMan]

The old girl is running again. The last time she had a heartbeat was 2005. Just trying to get the last bits finished so i can get her on the road. First, thanks to all the helpful people here on the forum. I wouldn't have made it this far without you and i'm starting to get a bit excited. Although, time spent in the shed keeps me from my guitars. Catch 22

A couple of issues:

(1) I'm doing the wiring in the headlight bucket and most of it is (reasonably) obvious, but the horn wiring has confused me. There's a light green wire from the switch with a male terminal (it's working, i have continuity to earth when the button is pushed). Two wires on the horn, light green & black. Both have male terminals and they are not long enough to reach the headlight bucket. Have i lost / misplaced a sub harness?

(2) I have a slight misfire on cylinders 3 & 4. I can hear & feel the misfire on 3. I only know there's a misfire on 4 because i checked some posts looking for answers and one post suggested putting the timing light pickup on to check the pulse (thanks to whoever that was, i didn't think of that) and i checked all of them. I have constant pulse on cylinders 1 & 2. But on cylinders 3 & 4 there's obvious misfires. The spark plug caps are new. Can i put new spark plug leads on the coils or do i have to buy new coils?

First the wiring: there should be mating females in Lt Green and Black hanging down from near the coils somewhere. That's where the horn plugs in, normally.

The timing light: first, check the sparkplugs to see if they are dark and fouled. If one side of the coil (like $1 of the 1-4 coil) has a fouled plug, it will misfire and the timing light inductive pickup will "miss" the pulse. Also, make sure the sparkplug caps are screwing in tightly: often the very end of the wires are stripped, and you'll need to cut off about 1/4" to get a good 'bite' into the wire with the screw in those caps.

[Brookesy in Oz]

Thanks Mark,

I'm enjoying working on the old dear but it's a bit frustrating at times. I saw those wires but figured they were  for the brake switch, should have tried them but... "Never assume, it makes an Ass out of U & Me" (Prof. Julius Sumner Miller) I'll pull the plugs next weekend and have a look. At least she's running & the carbs are roughly balanced now. The timing is close & the advance is working. I had an "Oh Crap!" moment when i first tried to start her and didn't even get a pop. Check the spark & a squirt up each of the inlets with tin of "Start Ya Bastard" and she coughed politely and then sat on about 3000rpm.