1993 GSX600F only firing on 2 cylinders

[Damianharris]

Hi guys my bike is only firing on 2 cylinders. I have tested the coils and one was bad and I have replaced the pair but it still isn’t producing spark. I have tested the wiring and it has the live like it should have but still no spark. I’m thinking the coil isn’t getting any pulse from the cdi telling it to fire. Any ideas if it could be anything else? 
I have checked the battery and that’s fine. Thanks for any help.

[Fazz711]

Which two not firing? 

[Damianharris]

1 and 4

[TonyGee]

check continuity on the wire from the coil to the CDI first before you start replacing parts. 

[Damianharris]

I have already done that . The wiring is fine.

[TonyGee]

do you know anyone you can borrow a CDI off ? 

[Damianharris]

No I’ve managed to get a second hand one cheap so hopefully once I fit it and the new coils that will sort it . I will test for spark before I bolt everything back together .

 

[Upshotknothole]

Had this happen with a teakettle 750, if the lead that goes to the tach is grounding out, the coil that it’s hooked to won’t fire. Everything will test fine, but you’re not gonna get spark. Also try grabbing one of the old coils and a plug and check both leads to the coils with that. Easier than trying to plug and unplug the coils when they’re bolted to the frame. 

[Damianharris]

18 minutes ago, Upshotknothole said:

Had this happen with a teakettle 750, if the lead that goes to the tach is grounding out, the coil that it’s hooked to won’t fire. Everything will test fine, but you’re not gonna get spark. Also try grabbing one of the old coils and a plug and check both leads to the coils with that. Easier than trying to plug and unplug the coils when they’re bolted to the frame. 

The coils are already unbolted and off the bike. Only one of the coils don’t work. I wired the good coil into the bad side and didn’t get any spark. I run a multimeter from each end of the wire and the wire is good. 

[Upshotknothole]

Check the wiring diagram and see if it’s the coil that has a wire running from the coil to the tach. If so, check that wire. Went through a second set of coils and buying another CDI before finding that wire grounding out in the connector to an aftermarket gauge. Everything tested fine, annoying as hell. 

[Damianharris]

I’ve done that. I’ve just checked the pick up  again. The manual says it should read between 135-200 ohms . Mine is reading 164 so that’s ok. 

[vizman]

If your coil went down, the plugs are probably fluffed on those two cylinders, have you tried cleaning/replacing them?

[Damianharris]

18 minutes ago, vizman said:

If your coil went down, the plugs are probably fluffed on those two cylinders, have you tried cleaning/replacing them?

Yes I did that.

[wraith]

Get a side light bulb and holder wire it to the coil leads -/+ (with out the coil on) turn the engine over, as if you're starting it, if the bulb lights up the CDI and wires to the coil are good.

[Buzuki]

When one of your ignition coil broke down that usually causes that one of the darlington switching power transistor inside of the CDI (ignition box) also is pull down , 

replacing that bad transistor (2SD1071) altogether with bad ignition coil usually is enough to successfully solve the problem .

 

[Damianharris]

All fixed now

thanks for the help guys 

[Wagola]

6 hours ago, wraith said:

Get a side light bulb and holder wire it to the coil leads -/+ (with out the coil on) turn the engine over, as if you're starting it, if the bulb lights up the CDI and wires to the coil are good.

Hi @wraith, never seen this done before. Will the bulb be on constantly or will it flash on/off ?

[wraith]

5 minutes ago, Wagola said:

Hi @wraith, never seen this done before. Will the bulb be on constantly or will it flash on/off ?

Flash on/off very quickly

[Wagola]

yeah, thats what I thought. 

[TonyGee]

11 minutes ago, Damianharris said:

All fixed now

thanks for the help guys 

well what was it ?