Xj900f spark

Okay. I have had spark but no compression and have swapped engines. I tested the engine prior to moving over.
The starter works and turns the engine over but no spark on any plug.

I have 12v at the coils and have tried two ic both I think are good.

I am obviously getting something wrong but can’t think what.
What I have tried
New fully charged battery
New spark plugs
Different coil
Different ic
Cut the black and white safety wire
Bypassed the neutral switch
I have gone through the fault finding. I think! And am really stuck.

any help would be appreciated




i

 

Do you have the original fusebox?

 

I do not

 

I have now tried direct connections between the IC and the coils. No difference.
I get 12v on both sides of the coils - not sure if this is correct.
I get no OHMS across the coils, but this is the same for all four of the coils that I have.

Very close to just giving up :-(

and am concerned that I am now making things worse!

 

https://xjbikes.com/forums/threads/xj900f-ignition-problems.131518/

 

I

I am getting no sparks on 1 - 4 so these are not the problems.

I think (maybe wrong!!) that:
1) The pickup is not working
2) Both coils have failed
3) The IC unit has failed

My confusion is:
1) How do you test this??
2) Why would both coils fail?
3) I have tried two IC with same result

As I said it was working prior to engine swap

 

Do the same for the primary resistance but put meter leads on wires going into coils.

 

I don't think you are making things worse. Follow the tests above. I think your coils pickup and ignition are fine bike was running before. Its annoying l know been there but it will be something simple that is stopping it starting.

 

Are you using resistor plug caps and resistor plugs, you cannot use both as far as I know? Try your old plugs and see what happens. Has ignition fuse blown, just throwing in ideas you never know, it is simple faults that stop engines most of the time. Pinched wire on frame when you were installing replacement engine? Even with a new battery if the voltage drops below 10 volts when pressing the starter button you will have no sparks. TCI transistors don't work below that voltage. Car battery and jump leads you could try too just to check.

 

Thank you.Your suggestions are really helpful

Update"

coils test
It is quite odd I have the same readings on both coils - 26k on secondary and 4 on primary. Obviously, the readings are well out of spec. Do you think it is worth buying new coils?

battery
volts are not dropping below 10
but i have added a car battery in case

i cant see any pinched wires


still no joy...

 

You can fit Honda CB750 coils. Strange as the bike was running before. You can change the coils but are you getting a good connection between the handlebar and the right hand switch, the latter grounds through the handlebar.

https://xjbikes.com/forums/threads/cb-750-coils.88468/


Do you have a spare digital multimeter to double check the resistance figures you got? When you press the starter wiggle wires at the handlebar switches, key switch, TCI, coil input wires, double check jumper wires etc. You want to make sure it is not something like a faulty wire before buying parts.

 

Finally --- worked it out ! I must have strectched the cable from the pickup! it was broken where the 2 earths go into one...

Thanks so much for the help

 

Just goes to show again its usually something like that. Makes sense as all four plugs were dead. Splendid result.

 

Thanks again