Help me I’ve tried everything 2 and 3 misfire

[NickleNdime]

Hey guys new to the forum I have a serious problem with my baby and I’m hoping Tools or someone can help me . It’s a 1980 CB750 cafe . Straight pipe with baffle  Murray’s vm34 mikuni carbs made my own harness Harley’s wheels busa front blah blah blah you get it I’ve done as much as I can but it won’t run on 2 and 3 I have done the leg work I have spark tested spark units the timing its on  f and advanced when the throttles hit . Compression is 150 all across . The plugs wires and coils and plugs are new and I have the stock ones none of them make a difference . The pulse generator checks out at 555 on yellow yellow and blue blue . Did the screw driver test and got spark . Thing still won’t run on all 4 . I’ve tried multiple plugs and gapped to 26 Any ideas ?

[TOOLS1]

Since #2 and #3 run off the same coil, it most likely is an ignition problem, but I would not rule out the carbs. Have you tested spark using the plugs that are currently in the engine? Have you tried a shot of starting fluid to see if it fires on it? If it fires with starting fluid, then it is a carb problem.
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[NickleNdime]

I’ve tried the fluid and it does have spark when put the plugs against the block . Doesn’t work on stock carbs or the new ones from Murry

[TOOLS1]

You need spark when the plugs are in the engine, not when they are hanging off the side of it. Have you tried spraying the starting fluid into the breather when the engine is running (with the spark plugs installed) to see if it picks up those two cylinders? Do you have compression on those two cylinders? Have you tried swapping the coils to see if the problem moves?
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[NickleNdime]

I have 150 across all 4 cylinders when I swap yellow and blue on coils it won’t start at all just back fires through carbs I am running the Mikuni vm34s that are brand new and had the same problem with stock carbs

[NickleNdime]

[TOOLS1]

I mean swap the coils over, not just swap the power wires. When you swap the power wires without swapping the plug wires, you are just setting it to be 180* out of time. You diagnose a problem like this bt swapping over one part at a time until the problem moves, then you know what part is causing it.
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[NickleNdime]

Swapped plug wires and still nothing on two and three plug wires plugs and coils are all brand new

[TOOLS1]

Now swap the igniters between the two systems.
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[NickleNdime]

No change ! I greatly appreciate your help and don’t want to sound like a jerk but I’ve tried everything already and am going through it all again with you and no change . I’m not a noob in any sense I know every inch of this bike and have been trouble shooting for a month before I came here .  im here because I can’t figure this one out on my own . I have tried multiple spark units and have them on my gl and they are working I’ve swapped plugs and wires and coils 10 times im thinking it has to almost be the pulse generator except it checks out fine on resistance and spark test

[TOOLS1]

That does not mean that it cannot have a problem. I would switch them to. Just because it is firing a plug outside the cylinder does not mean it is firing inside the cylinder under compression. I once fought a problem like this and it turned out to be the new NGK plug that I had installed. I kept testing spark with another plug because I did not think the new one could be bad.
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[NickleNdime]

I hear ya . I have swapped all the spark units I had and coils and wires . The only thing left is the pulse generator or my wiring harness right ?  . I’ve gone over every wire 10 times And everything checks out as far as ignition goes .

[shinyribs]

Nothing helpful to add on the diagnosing, but I LOVE what you did with the swingarm brace and rear shock. Is that a CBR600RR shock?

[NickleNdime]

Thanks  That is off a zx14 it works perfect and is very adjustable . Any one that can help me I’d really appreciate it