Topic: four car coils in a cb650 w electronic ignition OK?

[thehammer]

anybody ever replace dual output coils with four car coils a la cycleworld 1977? (tech section),on a bike with electronic ignition?

-Eric

[kslrr]

I would think that since 2 coils would be charged at a time, the igniters would over heat and possibly fail.  You would need to create four ignition trigger points like how a typical 4-cyl auto engine works.

[Duke McDukiedook]

What are you hoping to gain by doing this?

[cb650]

on the DOHC4 750 site several have used later gm coils with np.  Something I want to try some day.  I think Pinhead did it too.

[dave500]

mazda mx5 coils.

[Hush]

And exactly where are we going to fit these car coils, they won't fit under the tank?

[dave500]

late coils i guess hush,not the big metal canisters of old(which i like)im looking at mx5 coils ,they have 5 ohms and would fit under a cb tank,single little coils with dual outlets,use leads of your choice.

[thehammer]

What are you hoping to gain by doing this?

Well Im hoping to gain positive or negative validation. I'm working with a cb650 for my boss that boggs down under any load. have done the carbs and am fairly certain theyre alright, bike idles fine and carbs are in sync, but dont know much about the electronic ignition system.

What I do know is that after idling 30 minutes, exhaust pipe #4 is cold. I also know that the resistance of the coil for 1-4 is around 10 ohms and the resisntance for 2-3 is a steady 2.2 ohms. I am hoping to verify that replacing coils with dyna dual outputs will fix it. I also know that all 4 cylinders have low compression and the head gasket leaks.

I was hoping to have a case to get my boss to open up his wallet so I can fix a motorcycle that is in the way at the shop.

I'm also worried that the 4 coil setup would ruin the ignition and i dont want to screw this bike up any worse than i already have.

[Duke McDukiedook]

I can't imagine you would get much performance boost over buying a stock set of replacement coils.
You would only probably want to go to a setup like this if you hot-rodded your cams along with a big overbore and got a programmable CDI- see where I am going with this? $$$$$$. I'm not sure if your wallet is that deep for that kinda job.

Those coils that are in there sound a little suspect with the primary measurements, measure your secondary windings- they are probably off also. If they are way off replace with maybe a 5 ohm Dyna or stock Honda coil.

[thehammer]

I can't imagine you would get much performance boost over buying a stock set of replacement coils.
You would only probably want to go to a setup like this if you hot-rodded your cams along with a big overbore and got a programmable CDI- see where I am going with this? $$$$$$. I'm not sure if your wallet is that deep for that kinda job.

Those coils that are in there sound a little suspect with the primary measurements, measure your secondary windings- they are probably off also. If they are way off replace with maybe a 5 ohm Dyna or stock Honda coil.

Yeah, the dyna coils I think are ideal. I was only trying to diagnose what i suspect to be an ignition issue. I though about putting the coils from my 75 cb550 in the 650 but after measuring the resistance of MY coils yesterday . . . the primary resistance of one of them is only .7 ohms!?! My bike runs great, but with such low resistance im worried the 650 would burn my coils, though it seems they need replaced anyways . . .

realistically the first thing that should be done is a top end rebuild, because with such low compression, the bike is junk. still i've seen honda 4s that run fine with 50 psi of compression, so I have a feeling once the motor is built, the bike still wont run right.

[thehammer]

late coils i guess hush,not the big metal canisters of old(which i like)im looking at mx5 coils ,they have 5 ohms and would fit under a cb tank,single little coils with dual outlets,use leads of your choice.

what year mx5 uses dual output coils? Are you putting this into a cb500? with points or dyna?

[HondaMan]

The power budget for the whole Ignition in the 650 is about 3.5 amps for 2 coils and the electronics. Car coils use quite a bit more current than that...

[Hush]

Hammer, take the pick-up cover off the right side of the crankcase and adjust the pick-ups slightly either way and see if that makes a difference, the bike bogging sounds suspiciously like the timing is a smidgen off, 650's are like that.

[thehammer]

Hammer, take the pick-up cover off the right side of the crankcase and adjust the pick-ups slightly either way and see if that makes a difference, the bike bogging sounds suspiciously like the timing is a smidgen off, 650's are like that.

I should have mentioned that I checked timing and it's spot on idling a 1500 (that is to say the adjustment of the whole timing plate)

[scottly]

I should have mentioned that I checked timing and it's spot on idling a 1500 (that is to say the adjustment of the whole timing plate)

Just so we are perfectly clear, when you say the "whole timing plate", do you mean you checked both the 1-4 timing and the 2-3 timing? To test both, you have to move the timing light pickup from a 1-4 plug wire to a 2-3 wire.

[Pinhead]

I ran Ford COP's along with an ignitech programmable ignition for a day before I tore my CB650 down... Ignitech has a selectable high/low coil primary resistance setting.

Chevy Cavalier coils have been suggested to use  in conjunction with the GM HEI conversion.

I'll probably use the Cav coils when I finish my engine rebuild until I decide on a solid mount for the COPs.

[dave500]

hammer i think they all do,i spied some on a bench at an auto supply place when i was getting something else for my car,i picked one up and was talking to the guy how these would fit on my bike with a little mounting tweak and quizzed him on the current draw etc,they look ideal for us,im still using the stockers,but ill bet these will be as good as anything else out there.

[thehammer]

I should have mentioned that I checked timing and it's spot on idling a 1500 (that is to say the adjustment of the whole timing plate)

Just so we are perfectly clear, when you say the "whole timing plate", do you mean you checked both the 1-4 timing and the 2-3 timing? To test both, you have to move the timing light pickup from a 1-4 plug wire to a 2-3 wire.

correct, timing was checked and found to be accurate on all cylinders.