I got a bike in my garage (1994 CBR 900 RR) that was working fine the other day and the next day I did not start anymore. I guess this is the reality for may in this forum, well anyway I started to debug the system and found that I have NO spark when I ground the sparkplug but get a spark when I lift off the spark plug a few millimeters from the ground. I don' t get it.
I have new plugs, I have tested the coils and they are within spec, tested with or without ignition cables, I have trimmed the ignition cables and made sure they have good connection to the coils, measured the resistance of all cables coming from the stator, checked the rectifier as well. I noticed that the cables/ connector coming from the stator had melted just under my seat. Replaced the connector with a new one. I still experience the same issue... no spark when the plug is grounded. Pickup coil has correct reading, Cleaned the killswitch. Batttery connectors are clean. Battery charged and tested.
Please help - what could be the issue here? Why do I not get a spark when grounding the plug??
My next move will be to remove the stator and see what is going on there despite the fact that the DMM showed correct values when measuring. Perhaps buy a new rectifier and also try to source a new ECU.
Grateful for any hints what I should be checking here

 

Greetings & Salutations!!!

Stator & RR has nothing to do with ignition. Could be you've got some wires crossed in ignition system, perhaps from heat melting some insulation and shorting wires together? Let's test:

1. disconnect blk/wht wires from igntion-coils

2. key ON/kill-switch=RUN, measure voltage at each blk/wht wire at ignition-coil connector, volts = ???

3. check both ends of spark-plug wires. Make sure metal parts only touch centre of plug and not ceramic.

 

Thanks for the swift reply and comments dannoxyz! Greetings to you as well :-)
Good point - I will measure the voltages asap and come back.

 

Alright, done some tests now:
[dannoxyz]: 1. disconnect blk/wht wires from igntion-coils
[MotoHot] : done

[dannoxyz]: 2. key ON/kill-switch=RUN, measure voltage at each blk/wht wire at ignition-coil connector, volts = ???
[MotoHot] : Killswitch in "RUN" position, ignition on: Voltage at the blk/wht is about 70 mV below the battery voltage. Battery: 12,60V and blk/wht wires about 12,53V
Voltage drops to 0,00V when flicking the kill-switch as its supposed to. turning back to "RUN" will keep the voltage at 0,00V as supposed to.
Observation: I keep the multimeter connected to the blk/wht leads and I turn the ignition to "OFF" and back to "ON" again (all lights on dash illuminated) and now monitoring the voltage o the blk/wht lead. To me it is a bit strange that the voltage does not come up immediately. It will take at least 4... 5 seconds for the voltage to rise to battery voltage level. is this normal?

[dannoxyz]: 3. check both ends of spark-plug wires. Make sure metal parts only touch centre of plug and not ceramic.
[MotoHot]: Will do, I have not done that yet but will later today The strange thing is that the bike was running smoothly and then the next day didnt start properly. I measured the temperature on the exhaust pipes and was evident that cylinders 3 and 4 was running while 1, and 2 was more or less dead, later everything seemed to malfunction and got some backfire but nothing else.

Looking forward to your comments - what would be the next step ?

 

2. dead battery. With kill-switch=RUN, voltage to coils should be exactly same as battery voltage instantly. Also good battery should be > 13,0v

 

The battery voltage is there at the blk/wht leads instantly if I just turn on the ignition e.g. On - Off - On
The delay happens if I hit the kill-switch, turn off the ignition and then turn everything on again. At that point it takes about 10 seconds for the voltage to develop on the blk/wht lead to the battery level. Why is that? Should it not be instant? Feels like there could be something strange going on with the ICM ?

You are right that the Battery voltage was pretty low, it was measured after some start attempts but I do not think the battery is dead and the Cranking capacity is still there. I measured the CCA and it is over the spec of a fresh battery. I also recharged everything and also tried with another good large battery hooked up in parallel to ensure good voltage and enough amps for the starter/system. still the same issue. This is hopeless
Any ideas?

 

No ICM not involved with power to coils. They are directly connected to battery through ignition & kill-switch. Should power ON to full battery-voltage as soon as kill-switch set to RUN. Test power going through switches

4. measure battery voltage with everything OFF.

5. measure voltage going into ignition-switch, red wire volts = ???

6. measure voltage leaving ignition-switch, red/blk wire, key ON volts = ??? instantly ???

7. measure voltage going into kill-switch, blk wire, volts = ???

8. measure voltage leaving kill-switch, blk/wht, kill-switch = RUN, volts = ??? instantly ???


Re-do tests with battery-charger hooked up

 

Thanks a LOT for the debugging advices! I think you have solved my problem!! The measurement results below:

4. measure battery voltage with everything OFF. 13.34V

5. measure voltage going into ignition-switch, red wire volts = 13.27V (Vbatt: 13.27V)

6. measure voltage leaving ignition-switch, red/blk wire, key ON volts = 12.89V, instantly 12,89V (Vbat: 12.92V)

7. measure voltage going into kill-switch, blk wire, volts = 12.76V (Vbat: 12.82V)

8. measure voltage leaving kill-switch, blk/wht, kill-switch = RUN, volts = 12.73V instantly 12.73V (Vbat: 12.80V)

(Vbat Bttery voltage dropping quite fast here during measurements)
The same results with Charger hooked up Vbat: 13,86V

4: 13.86V
5: 13.86V
6: 13.80V
7: 13.78V
8: 13.78V

MAin observation: the voltage at the kill switch (blk/wht lead) was unstable, going up and down and eventually up to Vbat. I sprayed some contact cleaner and flicked the switch many times back and forth and suddenly the voltage at that node was stable. Tried to crank the engine and I now have a nice strong spark!! It is very late here now (half past midnight ), so I need to go to bed but will continue tomorrow and verify these results. I will change the battery as you hinted already :-) as the voltage dropped quite fast after recharge. Thanks a lot for all the help with debugging my bike !!! I think the blade is alive again :-)

 

Hey, good job!!! Kill-switch failure is quite common. Not sure why? Perhaps its location exposes it for corrosion?

I usually leave mine to RUN and use key/ignition-switch to turn OFF, or put sidestand down.

 

Hi Dannoxyz , Sorry to bring you in on this topic again... since last time I have assembled everything back again as it should but the engine does not start. Sparks are there, sometimes weaker sometimes stronger. I have tried a lot of tricks here but everything I do gets me back to square 1. Backfire and wet plugs, Some smoke coming out from the exhaust, The last thing I could see was that the battery died really quickly, Attached a booster to the battery but that died quickly as well. Could there be a short in the starter or something? I have new Spark plugs, coils, spark cables, pickup coil is within spec (Resisitance), Killswitch is ok, I am out of ideas... please help