Topic: Coil/ spark firing order

[hogsnhondas]

Anyone help out here. 77 CB750. I have a Clymers and Hynes manual. Problem is, I do not see the specific order the coils/ spark wires go. Sounds like a stupid question, any one know?

I have tried several different ways, some misfire, others not start at all. I have had bike apart for a couple months and have not done anything major. Help! I going nuts.

Thanks

[Patrick]

The one and four plugs fire simultaneously. So do the two and three plugs. It's a wasted spark system. You can have either wire from the coil feeding one and four go to either plug. Same with the coil feeding two and three.

Patrick

[azuredesign]

I believe it's 1-2-4-3 with 1 being on your left when you sit apon the throne.

[lostinthe202]

The cylinders are numbered 1-4 from left to right tho I don't remember at the moment from which perspective.  1 + 4 are one coil, 2 + 3 are the other coil.  Each coil fires both wires at the same time like Patrick says.  The cylinder order I mentioned is how they are numbered in relation to the little tags on the spark plug wires and how they should be plugged in NOT the firing order (the order of TopDeadCenter as the motor moves through it's cycles) which I don't know but is probably what Azuredesign says.  if those little tags that say which plug wire is which are missing, pull your tank off and look at your coils, the 1/4 coil has a blue wire plugged into it, the 2/3 coil a yellow wire.

Good Luck!

[hogsnhondas]

As always this site bails me out. Thanks for everyone's two cents. I think I have it figured out now. Thanks again - have a good one.

[The_Crippler]

The one and four plugs fire simultaneously. So do the two and three plugs. It's a wasted spark system. You can have either wire from the coil feeding one and four go to either plug. Same with the coil feeding two and three.

Patrick

This is a totally ancient thread, but I thought I'd ask:  is this the same for the CB650C?  I'm having trouble with two and three and thought that maybe I had the coil plugs backward.  If the above is correct, it shouldn't matter, right?

[BVCB650]

same same.

[BobbyR]

The one and four plugs fire simultaneously. So do the two and three plugs. It's a wasted spark system. You can have either wire from the coil feeding one and four go to either plug. Same with the coil feeding two and three.

Patrick

This is a totally ancient thread, but I thought I'd ask:  is this the same for the CB650C?  I'm having trouble with two and three and thought that maybe I had the coil plugs backward.  If the above is correct, it shouldn't matter, right?

Yes 2 & 3 come off the same coil and fire together. The engine block is part of the circuit so if you were to pull #2 wire, #3 would not fire either.

[Slayer]

I believe it's 1-2-4-3 with 1 being on your left when you sit apon the throne.

It is 1-2-3-4 starting from left to right

[BVCB650]

1 and 4 fire together, same as 2 and 3. The meat of it is only one of those is at TDC at a time.

[tlbranth]

only one of those is at TDC at a time

actually, two are. Only one is primed to explode however.

[Bodi]

Usually that's the coil wires reversed, firing all four cylinders at the wrong time. Swap the blue and yellow(?) wires at the coils and see what happens.
If correct, check valve adjustments... ok but still doing it? - confirm cam timing.
A valve leak big enough to backfire will cause an audible hiss through the carb throat as the engine is kicked over.

[Patrick]

I cannot believe this thread came back to life! I typed so young then....

Bodi is right, your problem is more than spark timing. It would be helpful if you gave a more thorough description of anything you did to the bike or that you know a previous owner did. Problems like yours often are the result of operator error. What was done can be redone correctly.

You might want to start a new thread, though.

Patrick

[tlbranth]

thanks guys if i switch the two wires on the coil it just cranks. i changed the spark wires and i think i got it, but it only runs on 2 and 3 cylinder so i cleaned the points and now it wont start lol. fml......if anyone lives near me that can help me out will be cool if not i appreciate the help online.

And where would you be?

[cseely]

I have the same problem. Lost two cylinders after a ride. Replaced the supected coil, new condensors, new points. tested all wires for continuity. everything checked out. started 750 out and found 1 and 4 cylinders dead cold. at a loss so i pulled blue wire and scraped it on the outside of points 1-4. fricking thing backfired. woke up the dead...... ok i have two missmatched after market coils.
one has + on left, and other positive on the right. Blk and white to both positives and blue to left coil and yellow to right. Still dead. WTF. I ordered OEM coils from 4 into 1. I have the suspect coil on bench and ready to test with 12 volt battery. I think its defective as power checks out and no spark. Timing is right on the money as she runs fine on 2-3. Only other think i can think of is something is grounded weird on that circuit???any thoughts? (new caps, new plugs, etc too) thanks. One i find the answer i will post the fix and any relevant info on ingnition system.

[Rong1234]

I have the same problem. Lost two cylinders after a ride. Replaced the supected coil, new condensors, new points. tested all wires for continuity. everything checked out. started 750 out and found 1 and 4 cylinders dead cold. at a loss so i pulled blue wire and scraped it on the outside of points 1-4. fricking thing backfired. woke up the dead...... ok i have two missmatched after market coils.
one has + on left, and other positive on the right. Blk and white to both positives and blue to left coil and yellow to right. Still dead. WTF. I ordered OEM coils from 4 into 1. I have the suspect coil on bench and ready to test with 12 volt battery. I think its defective as power checks out and no spark. Timing is right on the money as she runs fine on 2-3. Only other think i can think of is something is grounded weird on that circuit???any thoughts? (new caps, new plugs, etc too) thanks. One i find the answer i will post the fix and any relevant info on ingnition system.

any solution to this? I bought the same coils from 4 into 1 and have the same issue

[Medyo Bastos]

New cpas screwed in tightly?


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[TwoTired]

Dual Output coils should have coils of wire inside wired as depicted below.

The simplified drawing does not show secondary resistors which can be in the plug caps or the spark plugs.  The stock bike had resistors in the plug caps.

The red coil is the primary where one side is connected to 12V power and the other is connected to contact points and a capacitor/condenser.  Closing the contacts charges the coil. Opening the contacts, with the aid of a capacitor, rapidly discharges the coil.  When the charge collapses it makes voltage in the Green coil, creating spark in the gaps of the plug.

You can measure the powered off resistance of the internal coils.  The red primaries should measure in the vicinity of 5 ohms (unless 3 ohm coils are employed).  The green secondary coil can be in the 15,000 to 13,000 range or thereabouts.  (Aftermarket coils can be made different from stock and should be specified by the manufacturer)  If you can get these measurements and neither coil has continuity to any other protruding metal bits of the coil.  The coils should fire.

If the point contacts don't make clean contact, the coils won't charge and you get no spark.  If the capacitor/condenser doesn't provide the proper aid to coil discharge, the coil may not spark the plugs.

Now you have the information to determine why your bike isn't making spark, provided you can verify the coils are well connected to 12V.

Cheers,

[Rong1234]

I got new coils leads and plug caps to suit. I do get spark on each plug but bike doesn't fire, I get a massive backfire every now and then on turn over but no sign of firing up. I have plug leads from one side to 2/3 and other side 1/4 (from memory, it may be different but is what I've seen on multiple other threads). I'm assuming I have coil wires going to right coil terminal, I have black/white going to - terminal

[Medyo Bastos]

Switch  your blue and yellow wires and report back!


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[Patrick]

Yours sounds like a timing issue, Rong. Did you work on the motor? Did you, but any chance set the cam chain timing? If you have spark, but only an occasional backfire, your fire isn;t comign at the right time. You could have the cam chain one tooth off or you could have the plug wires switched. But somehow you are delivering spark at the wrong time. I don't think it can be that far off at the timing plate.

Patrick

[Patrick]

Yours sounds like a timing issue, Rong. Did you work on the motor? Did you, but any chance set the cam chain timing? If you have spark, but only an occasional backfire, your fire isn't coming at the right time. You could have the cam chain one tooth off or you could have the plug wires switched. But somehow you are delivering spark at a really wrong time. I don't think it can be that far off at the timing plate.

Patrick

[Medyo Bastos]

You’re 180° out! Read my previous post!


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[Rong1234]

Ah OK, no at current i am at the first step of an unknown project, the guy I got it off didn't know anything about history. All I've done so far is source some coils/leads for it, flushed the fuel, tidied up the jacked ignition and fitted a new solenoid, then turned over to see if she will fire over.

[Bodi]

"I got new coils"
"I get a massive backfire every now and then on turn over but no sign of firing up"

If you changed nothing else, and the bike ran previously... swap the coloured wires at the coils. You describe what happens when the 1-4 points is connected to the 2-3 coil (and vice-versa). You do not say what the backfire is, but that misconnection will often backfire through both the carb and the exhaust.