No Start/Spark

Hi all. I have a 1982 Yamaha XJ 750 MAXIM I bought about a month ago now. I bought it with the guy saying it didn't have spark it lost it sometime last year he thought it was the wiring for the pickup coils. I have since replaced the pickup coils and the ignition coils, re-wired the bike cleaned and gapped the spark plugs. I have compression but absolutely NO spark I have power throughout the system even to the coils but when I turn it over nothing. No spark no start. I have absolutely no idea where to go from here. I only have the wiring for the very basics connected. No atari system, no safety switches, I haven't even got the kill switch wired in the system yet. After I replaced the pickup coils I had spark and the bike running for about 30 seconds before it died. I have no clue what to do next. Any help would be GREATLY appreciated. Thank you!

 

Does it have the original fuse box? Might have an intermittent connection thru one or more fuses if you do.

 

Another possibility is a bad TCI unit. That's more difficult to troubleshoot, unless you are lucky enough to be able to get your hands on a known good unit.

 

It does not. For the sake of simplicity while troubleshooting I only have a 20amp fuse for the entire ignition system.

 

As far as I can tell it's the TCI unit. Unfortunately I do not have another known working TCI on hand. I have only been able to find used ones online for a couple hundred bucks and as far as I can find there's no way to use a different unit due to timing issues.

 

Ya, $200 seems a little much. I would guess $80-$100 for a decent looking one.

Keep in mind that the unit on the XJ750J (82 Maxim) is used on several other models.

The part number is 5G2-82305. This unit is used on 81-83 750 Seca, 82-83 750 Maxim, and 82-83 650 Maxim.

Might take some patience.

 

Whatever you do, please don't just throw the old TCI in the trash - might be fixable.

 

Any ideas on how to fix it haha

 

I don't know exactly how to fix them, unfortunately. Electronic components are not my bailiwick.

I guess if somebody knows what they are doing, they can go in and test the various capacitors, resistors, flux capacitors, and whatnot and replace the bad ones.

 

Just read the thread....Make sure you have a really good battery when you start to play with the spark. The TCI will no even make spark from a weak battery. So that is the first trouble shooting you need to do.

Then check and clean the contacts throughout the bike. If the bike has been sitting for a while and been in the elements, you need to check the contacts. That means take your time and remove them, clean them and maybe even put some grease on them.

Fuse box, even though it might look like it is good, pls take the time to change it out to a small blade type. Chasing down spark issues before you take care of some the basic wiring maint might mean you are chasing your tail.

The plug wires might need to be trimmed as well. You can take the boots off and see if the wire is green or nasty. Trim a little off of each, I mean just enough to get to good copper and see if that helps the spark.

 

I am having the same issue with my 1982 xj750 seca but I only don’t have spark on the inner coil. I have good ignition coils, good igniter module and good pick up coils. I have spark on the coil pack for the two outer spark plugs but none on the inner. Still trying to figure out what the issue is.

 

Hi @Joshuagilhuis . Welcome to the party.

If the coils, caps, wires, etc. have all tested good then I would definitely suspect the TCI unit.

When I had a TCI unit go bad, that is what happened to me - I had a two cylinder engine.

 

Any tips on how to test the tci box?

 

Unfortunately, no, there is not a good way to test the box as a unit.

Short of opening the box and testing every component I don't know of a way to test the unit itself.

The easiest way to confirm that the TCI unit is the problem is to use a known good unit. Which is easy if one has a known good unit. Admittedly, it is tough if you don't.

 

I’ll have to look into to see if I can find a good one thanks for the info

 

Just a quick question for ya guys. I took out the Atari and replaced the speedometer and tachometer with an after market one could that play a role in the no spark on the one coil pack

 

Business idea for somebody: Rent out known good TCI units for people to test.

 

Before you go with the new TCI move some wires around. If you have good spark on one coil then either move the good coil to the bad coil location and see if the trouble follows. This can be done just be extending the wires so they can reach the other coil.

If you do this, make sure the spark plugs are out of the engine and only in the boots to check for spark. Could it be the TCI, sure, but trouble shoot all issues before you spend the $$.

 

Yea I plugged in the bad coil with the other wires and the problem did follow

 

Are you getting 12 volts at the harness connector that plugs into the inoperative coil? I had high resistance on mine.

 

Yea getting full 12 Volts and good signal out of the cdi. Tested the circuit with my test light

 

Well first I replaced both ignition coils then I replaced the pickup coils which gave me about 30 seconds of run time before dying from the same issue before I went through the entire harness even swapped Atari units still nothing then I ripped out the harness did just the most basic wiring to start the bike battery to starter solenoid ignition switch start button regulator/rectifier TCI coils I cleaned the connectors I needed to and still no spark I replaced the spark plug caps the only thing I can think of at this point is the TCI when I started this endeavor the battery was brand new and fully charged now after multiple attempts to start it the battery has dwindled down to 11 volts so when I attempt to start it after checking wire connections I use a battery pack to jump it and check the system to make sure everything is getting a full 12 volts.

 

I replaced the coil packs and pick up coils and replaced the tci box with a used one off eBay and still the same issue

 

Did you test it with a multimeter set to 20 volts not just the light?

 

Yes checked with a multimeter aswell

 

Is the tach working? And where is it connected?

And please start a new thread as it gets confusing to who is replying to what

 

I figured out the problem, I had the after market tachometer wired backwards which drew To much power which starved my one coil pack. So I rewires the new tach and it fired up right away