UK xj 4ko 1982 no spark

I have a xj 650 4ko UK was fine then started intermittent no spark fault i started bike every day before this happend checked every wire/ switch put new coils on and it still won't spark but I can get a spark if I remove pickup case and run a screwdriver across them or unscrew 1 screw from each pickup and rotate it slightly further away from pickup . This bike has no side stand switch and pickup is within ohms range new battery coils pls help I know some wiring is different from us spec bikes but I have tried everything in my knowledge apart from stick it in a shop but I feel I can't let this beauty of a bike beat me

 

This is a strange anomaly. It would appear that altering the signal from the pick-up makes the TCI function. The TCI does have a built in feature that causes it to go into shutdown mode if no signal is appearing at the pick-up coil. This is done to protect the ignition coils if the key is left on for an extended time and the bike is not running. You can see this occur when the key is first turned on and either the orange or grey ignition coil wire will be low for about 3 seconds, and then switch to battery voltage.

I would check the voltage at the TCI 4 pin connector by back probing the R/W and B wire while the starter is engaged just to verify that the TCI has the intended voltage to function properly.

What reading did you get here? Also, remember to check them to chassis ground as they should be isolated from ground.

 

Thanks for the quick reply I'm getting battery voltage at tci I will go try while turning her over I'm getting round about 700 ohms at pickup plug be back shortly with outcome thanks ppl

 

Got good voltage at tci when push start button dips a small amount but still no start I'm pulling more hair out every day

 

And nothing to chassis ground?

Which was how much? And was measured by back probing at the R/W and B wire at the TCI? I ask this because issues with grounds could make a difference if perhaps you put the positive lead on the R/W wire at the TCI and the negative lead on chassis.

And did you check the voltage at the ignition coil orange or grey at power up (key to ON) to see if one of those lines goes low for about 3 seconds? Note, whichever line is switching you should see a spark on that set of plugs; orange 1 & 4, grey 2 & 3.

 

Just because it's so common, I have to ask; what is the battery voltage at rest, and what does it drop to when starting?
Just because the battery is new does not mean that it is good.

 

I had it hooked up to car just in case battery was at fault not been the whether for out working on bike but the pickups are isolated it drops about 2 volts at tci when I hit the starter button. the orange and gray are battery voltage all the time with coils plugged in and very low with them unplugged thanks for ur help I'm going off a Haynes manual that illustrate wrong colour wires and relays in wrong place

 

So, some more of the basics before blaming the TCI:

Battery voltage must be above 9.5V when the starter is engaged to supply sufficient voltage to the coils to produce a usable spark. It is best to measure it, and not assume it is OK just because the battery was just charged, replaced, or jumper cables from an external source are connected. Measure the voltage by attaching the meter leads to the battery cables on the bike (not the battery post) just to ensure good connections exist.

Check the spark with a known good plug, preferably a new one. Best method is to disconnect one spark plug and install the new spark plug in that location while placing the threaded grounded part of the spark plug on the aluminum head. The remaining four original plugs are left in to maintain the load on the starter. Crank the motor and look for spark. Note these bikes don't produce a very strong spark so try to do this with minimal lighting, and definitely try to avoid bright sunlight when checking.

If there is no spark with a known good plug and battery voltage is above the minimum requirement then time to check the ignition coils, ignition coil wires, spark plug caps, and pickup coils. You mentioned you have new coils, but did not mention new wires or caps.

Start by checking the ignition coil secondary resistance from spark plug cap to spark plug cap on cylinder 1 & 4, then 2 & 3. Simply push the meter leads up into the respective caps where they contact the metal terminals. I believe the UK bikes are very similar, so look for a reading of about 21K +/- 10%. This will be 11K for the coil, and approximately 5K for each spark plug cap giving you the total of 21K. If the reading is out of spec (usually on the high side), then separate the spark plug caps from the ignition wire by unscrewing them, and check each component individually; coil with wires for 11K and caps for 5K .

Once secondary ignition coil resistance is verified, check the primary side. This can be done by removing the respective TCI connector (4 pin) and measuring from the orange to red/white and grey to red/white. Look for a reading of 2.5 ohms +/- 10%.

Next move to the pickups. Measure these by removing the respective TCI connector (6 pin) and measuring from the orange to black and grey to black. UK bikes per the Haynes manual are spec'd at 650 ohms +/- 10%. You have already verified these, so good to go there.

This is a little bit concerning but not knowing exactly what you were doing here. Anyway, if you were just starting the bike and not riding, repeated starts with enrichment can foul spark plugs. So if you haven't already, a new set of plugs may be in order just to start with the simple things first.

 

Iv done 200 miles on the bike it pulled really strong but did fail to start some times now it just won't fire up at all I very much appreciate your help iv not been at it last fue days stripping a Chinese import for spares for the wife's bike

 

Just to update everyone I got the bike sorted it was bad soldering joints on tci unit sparking as normal thanks to all one happy Yamaha owner

 

Wow nice find, that was some digging to check and re-solder the joints on the TCI. Well done.

 

3 weeks with no spark does crazy things to a man just the headlight to go back on after I spent ages re wrapping my loom