Cannot get Spark

Hello everyone. As the title suggests I cannot get spark on my 1985 Yamaha 750 Maxim-X (Xj750X). The engine is currently mounted onto a go kart and I have built my own custom wiring harness for it. The engine currently does turnover with the starter motor. Here are the things that I have checked:

- Continuity through every wire
- Made sure the grounds are ok through the frame
- Checked tci wiring
- Checked Primary coil and secondary coil resistances
- Checked pickup coil resistances
- Check Spark Plug resistances
- Checked stator resistance
- Made sure that battery is charged
- Made sure that 12v is getting to the coils


If anyone knows what I should test for next or what the problem might be please let me know.
Thanks.

 

How did you wire the TCI?
Did you use the minimal diagram from this site, or draw your own?

Are you planning on riding the go-cart?
Is your life insurance paid up?
Can I have a go?

 

The wiring I used for the Tci is attached.
The Wiring diagram that I used is also attached.
My life insurance is .... well its there lol
Its gonna fly

 

That's not showing the whole diagram. The closeup of the TCI doesn't show the power feed to the TCI, or any of the ground and safety wires.


EDIT: Both diagrams are showing up now.

The XJ750-X really isn't an XJ in terms of the TCI.
It's an FZ750 engine, so the TCI is different. I'm not sure that the minimal diagram for the XJ TCI will work.
If I'm wrong, someone will be along shortly to correct me

 

Heres the wiring diagram i used

 

I think the go-cart gods are trying to tell you something!

 

Do you know where I could find a Fz750 minimal diagram and diagram for the tci

 

I don't have a minimal diagram but you may be able to refer to the full Maxim X Diagram:

On the right hand side is the TCI and I believe it needs to have two grounds on the output side. The one that is supposed to be functional but not used on your cart is the Black and White one that completes a ground when the side-stand and clutch switch complete the circuit as it comes from the factory. You may have to wire that up as a "Dummy" ground so you can get spark.

Tony

 

Thanks so much xHondaHack this really helps. Ill let you know when I get spark

 

Don't worry about spark, I want to hear when you get it aloft!

 

When you get it going please post a video.

Strongly recommend a minimum 3-point harness, when you hit that power band ain't no telling what that cart will do!

 

Does anyone know if the coils have to be grounded to the frame to get spark?

 

So the coils are mounted to the frame and the tci is wired according to the diagram and still no spark. I'm starting to think I blew the Tci because I had it wired incorrectly before. Anyone do tci repair? Or know if I could buy a cheap universal cdi online and convert it? Thanks

 

I had the same or kinda the same problem with mine. I checked everything as you have done, one thing are you getting spark to the plugs? If you are as I had done I checked the compression and found that I was avg. 50-65 psi. From this I found that I had three bent valves and three broken guides.
Just a suggestion

 

What do you mean by are you getting spark to the plugs.

 

doesnt the black white wire cut the tci if side stand is put down while in gear?
the black white wire has a bullet connector close to the tci to disconnect it to test side stand switch.
disconnecting it bypasses the safety switches on a non X .

to xjforlife do you have 12 volts at the tci should be the red white wire?

 

rebilding tci instructions and parts list on www.xjcd.org

there is a company that rebubuilds them in england very expensive to just have them look at it.
company in NZ sells after market ones. not cheep

maybe someone with an X can test it in their bike for you

can you post a photo of your wiring diagram that you used ? the photo you posted is not complete.

 

your pick up coils are wired wrong there should only be three wires at the connector not 4

or not in 4 positions of the connector
the brown and black wire go to the same point at the tci you show them in 2 different locations

 

This is the wiring diagram I am using currently and this is way I have the tci wired up.

 

The connector coming off the pickup coils only has three connections, like you said, and I currently have that connector plugged into the slot circled on the picture below. Is this correct? I also took the time to open up my tci so I have attached pictures below of the inside if you want to have a look at that. If you see anything that looks bad please let me know. Thanks, Anton

 

do you get 12 volts at the tci should be red/white wire to feed voltage to it?

hard to tell from photos but it looks like the row of caps have holes in the tops and D9 looks funny at the solder joint.
the 2 links below deal with repair of tci and proper parts to buy and replace all are available online www.digikey.com
but I would only do this if I were sure the tci was dead its a big job
TCI Repair

Replacement TCI Transistors

 

As in if the plugs are connected to the plug wires and the plugs are grounded outside of the engine do you see spark across the electrode when the engine is turned over. This is a poor mans way of verifying that you have spark to the electrodes.

 

It doesn't verify that the spark plugs are any good though

 

true but it verifies that there is spark to the electrodes. How strong the spark is unknown-blue is better then orange.

 

I am getting no spark at all when I do that test. That is my main problem.

 

My bad didn't fully understand your problem.

 

Was this issue resolved?

 

Looking at the pics I would say yes that is correct. I don't have the 750x, but the labeling on those pins P1, P2 make sense for the pickups as with other Hitachi TCI's.

It would be nice to see a picture of the wires connected to the TCI to see if we agree with the hook-up. I am not sure if you have moved wires around within the plugs, but I know the pictorial of the connectors can be a bit confusing.

Should go something like this if it is similar to the older TCI's, but I would double / triple check the supply voltage before applying power:

6 pin connector using CCA labeling:
C1 orange wire to low side of coil 1
C2 grey wire to low side of coil 2
B red/white wire to kill switch +12V
E black wire ground
SW black/white wire do not connect (unless Yamaha changed this from the earlier versions a ground here will disable TCI)

4 pin connector using CCA labeling
P1 orange wire to pick-up coil
P2 grey wire to pick-up coil
P1e black wire to pick-up coil common return. Note on older versions P1e and P2e are electrically the same.

It would really be nice if someone with an X would supply a photo of the TCI with the connectors installed to verify wire color location.

Do you know how you had it wired? Swapping supply voltage would likely be the worst thing that could happen and would probably damage the internal components. It is hard to tell, but do those capacitors have holes as XJ550H suggested.

 

Hi all, sorry I haven't been on this thread in a while, I've been super busy with other projects. So I bought a new battery ( to spec of course) and I charged if fully, hooked it up to the engine... And only got 11.41 volts to the tci. So I'm beginning to think that my custom wiring is bad and has too much resistance. Please tell me your thoughts.

 

Hate to ask this but did you ohm out each wire end to end? I mean did you make sure that none of the wires in the new harness were bad? A lot of work but if you are completely wiring a different bikes harness into a new frame and engine, you might want to check that. Chasing electronic gremlins is tricky sometime but can be rewarding in the end. Stick with it.

 

I ohmed out each wire end to end. It was painful but worth it.

 

And what did you get as a result? Happen to find any wires that were bad?

 

That should be fine as there is some loss in the ignition switch, kill switch, fuse and wiring.

Did you get a new TCI? You suggested earlier you may have blown it with a mis-wire. Are you certain of the wiring to the TCI? You posted this earlier, showing the pick-up coil going to the 6 pin connector. It looks like they should attach to the 4 pin connector per all the drawings I have reviewed.



Still hoping someone with an X ( @Timbox or @dowski68 ) would post a photo of the TCI connectors and wiring to ensure you have that right.

 

Will do that later on today...been busy with other things.

 

he could start a conversation with them just by clicking on their name to ask directly

 

Keep it open so others can use this as a trouble shooting tool.

 

Okay, here we go.....





While you are there and anyone else that might have a X, the three wire connect on my bike was heat fried.

Got that all fixed up and hope it holds with solder and new connectors.

Hope this helps.

 

Ok so after alot of trouble shooting I have determined the following things:

- All the wires in the wiring are working
- The battery I am using is working great
- The wiring to the tci is correct

After ruling out all these things, I am thinking that parts of the tci are broken, because of a wiring mishap that most likely broke the tci.

 

I would guess there is a way to test the TCI or IC ignition, someone will be along shortly to help you with that. I would guess you can find a used one on line as well.

You ARE making progress and I would guess leaning a lot along the way. Just stay with and it will pay off great dividends in the end.

 

The only way to test a TCI at home is to swap it into a running bike.

 

Hi all, after months of testing and trouble shooting with the wiring, I am pleased and excited to say, SPARK HAS BEEN ACHEIVED! I ended up buying an new tci and then when I swapped that in and used the wiring for the tci that was given to me , it sparked right away. Thank you all, I couldn't have done it without your help. There will be a video in a week or two of the kart running and driving, so stay tuned!