I don't understand electric stuff

Okay, I'm new to the forum, and there seem to be some intellegent people on here. I bought an '83 xj750. The carbs were discusting and there were other small thing wrong with it. I rebuilt the carbs, and now I have no spark at the plugs....... I replaced the battery, ignition coils (one of the wires were burnt through), and the starter relay switch. I got the workshop book and started going throught he troubleshooting steps. Is there any other fuses besides the ones under the seat? I can't figure out what to do next. Please help!!!!

 

there is a cut out switch on the kick stand, worth a look.

 

There are several components. I'm concerned about the burnt through wire but let me give you an overview

On the left side of your bike on the end of the crank case is a cover held by 4 screws. Behind it is the pickups. This is the non adjustable timing As the engine spins the magnet passes the pick up coils and sends a signal to the TCI. The TCI is behind the left side plastic cover and is an electronic ignition device. The TCI then "fires" the coil.

So you have changed the coils - hopefully with known good parts. With the burned wire I would suspect the TCI could have been damaged. You can open it and check for obvious burnt traces or components.

You can debug the TCI a bit by metering the input from the pickups as you spin the motor with the starter and similarly the output. If you get input and no output the TCI is bad.

Hope that helps some...


EDIT: I of course assumed the starter is spinning - no spin - no spark. If your starter is not spinning then as wiz said there are several switches to consider.....

 

I have to go to a field training exercise for a couple of days, life of a soldier, but when i get back I'll check the pickup. Oh, and yes starter spins and motor turns fine. Thanks for the help.

 

I don't think the motor turns over if the kick stand switch or neutral switch safety devices are enacted. But the TCI is definetly worth a look. I took my pickup cover off last week and cleaned the pickups. I'd check all the wiring from battery straight through to the plugs again. Maybe the plug wire was not the only one that burnt. Make sure you have a full battery. My bike seems to be pretty picky about that. How do you know you do not have spark? Did you hold the plug to the motor while starting? You can get a plug wire tester from sears for a couple bucks that shows you if there is power in the plug wires. At least you'd know the coils are good.

 

I don't think the motor turns over if the kick stand switch or neutral switch safety devices are enacted. But the TCI is definetly worth a look. I took my pickup cover off last week and cleaned the pickups. I'd check all the wiring from battery straight through to the plugs again. Maybe the plug wire was not the only one that burnt. Make sure you have a full battery. My bike seems to be pretty picky about that. How do you know you do not have spark? Did you hold the plug to the motor while starting? You can get a plug wire tester from sears for a couple bucks that shows you if there is power in the plug wires. At least you'd know the coils are good.

 

You should also check to see if you've got power to the coils. The TCI breaks the ground side, but the hot side (red/white wire) should show ~12V+ when you're ready to crank over the engine. If you've got power then the problem is somewhere with the TCI/Pick-ups. No power would indicate a bad fuse or wiring to the ignition coils.