SX/SXi/SXi Pro 750 sxi little/no spark - Must be stator...?

[Iowa750sxi]

‘95 750 sxi stopped running mid-season last year and when I finally dug into it this year I found that I had no visible spark across the spark plug and minimal lighting of the bulb in the inline spark tester. I tore into the e-box and discovered that it had standing water inside. Cleaned it all out, replaced the ignition coil and the starter relay, and cleaned all of the electrical connections. Put it all back together and I can occasionally get a single small spark that jumps the spark plug gap, but it’s basically just as bad as before.

Have ruled out start/stop switch by testing stop switch for infinite resistance and checking with a spare start/stop switch just to be sure.

Next part I am considering replacing is the stator. However, when I tested the stator coil resistances, I got the following values that all appear to be within spec.

Blue to Green: 511 ohms
Purple to Red: 413 ohms
Brown to Brown: 1 ohm

Given the expense of rewinding/replacing the stator and the hassle of installing (need to remove Factory Pipe (wet), I’m curious how likely it is that this is really the problem. Is there something else that could be wrong with the stator that the coil resistances wouldn’t reveal? Would I gain anything by disassembling everything and visually inspecting the stator?

 

[wmazz]

Can you build a simple electronic circuit? If so we can make a
peak voltage tester for the stator and CDi.

It will help if it you enclose it in a plastic project box and had an
extra set of leads for the MM. Don't want you to get shocked
while testing.

If not ACV testing is more reliable than resistance/ohm testing.


Bill M.

I am assuming you have a digital multi-meter, if not a cheap
MM from Harbor Freight will work.

 

[wmazz]

Resistance testing isn't very reliable. If I was still a mechanic, I would not
rely on those specs to order parts.

Your Purple & Red ohm test is at the bottom of my specs (410 to 530)

Ac voltage testing is more reliable than ohm testing, but it doesn't test the
CDI.

My Ac voltage specs are:

(1). Fully charged battery, spark plugs torqued, plug caps grounded to head
or E-box.

(2). Tether in place, and all wires still connected.

(3). AC pick-up coil test. Green and blue wires w/mm set to acv (.5 to 2.0 acv).

(4). Exciter Coils, Red and Purple is a 2 part test. It is important to note which
wire and positive or negative mm lead is used despite being a ac volt test.
(a). - lead to purple, + lead to red (8 - 12v ac)
(b). + lead to purple, - lead to red (75v ac)


But the Peak Voltage Test is the best test, and there are Kawasaki specs for it.


Bill M.

These specs were developed using the Kawasaki analog MM special tool. Results
should be the same with a Dmm, but I have always used my Kawasaki mm.

 

[Iowa750sxi]

Can you build a simple electronic circuit? If so we can make a
peak voltage tester for the stator and CDi.

It will help if it you enclose it in a plastic project box and had an
extra set of leads for the MM. Don't want you to get shocked
while testing.

If not ACV testing is more reliable than resistance/ohm testing.


Bill M.

I am assuming you have a digital multi-meter, if not a cheap
MM from Harbor Freight will work.

THANK YOU for responding, Bill!! This is exactly what I was looking for - a way to further test the stator instead of just replacing it.

Yes, I have built electronics projects and should be able to build whatever is needed. I have a DMM with a few sets of leads (and probably still an analog meter somewhere too). Do you have more info on how to build the peak voltage tester? More detailed plans and/or photos? I'd definitely like to go this route to test the stator and CDI.

 

[Iowa750sxi]

Resistance testing isn't very reliable. If I was still a mechanic, I would not
rely on those specs to order parts.

Your Purple & Red ohm test is at the bottom of my specs (410 to 530)

Ac voltage testing is more reliable than ohm testing, but it doesn't test the
CDI.

My Ac voltage specs are:

(1). Fully charged battery, spark plugs torqued, plug caps grounded to head
or E-box.

(2). Tether in place, and all wires still connected.

(3). AC pick-up coil test. Green and blue wires w/mm set to acv (.5 to 2.0 acv).

(4). Exciter Coils, Red and Purple is a 2 part test. It is important to note which
wire and positive or negative mm lead is used despite being a ac volt test.
(a). - lead to purple, + lead to red (8 - 12v ac)
(b). + lead to purple, - lead to red (75v ac)


But the Peak Voltage Test is the best test, and there are Kawasaki specs for it.


Bill M.

These specs were developed using the Kawasaki analog MM special tool. Results
should be the same with a Dmm, but I have always used my Kawasaki mm.

I responded to your other post about the peak voltage tester and I'll plan to go that route, but if that doesn't work I'll try the AC voltage test you described above. Thank you for taking the time to provide all of this great information!!

 

[kevbo]

The plug wires are solid core and they do break. Usually when I find a weak spark it was because the core wire broke and the insulation stretched making an internal gap. The symptoms are erratic running. It seems to always occur near the cap. Its an easy fix by pulling the cap and clipping the wire a little.

 

[wmazz]

The pdf instructions include the circuit so it can all be printed out.

Enclose the circuit in a plastic project box for safety. I epoxied the
leads to the box.

The instructions are for the 800, but they are for in common parts
with the 750.

Someone should take the peak voltage tester and make specs for it
using my ACV test as a guide line using known good components.

The same goes for documenting Yamaha ignition specs.

As I remember, Honda was the first to incorporate peak voltage testing
and then Yamaha.


Bill M.

You might need to ground the test leads before using it for another test.
That should drain the capacitor and prevent a shock (it has been several
years since I used this tester) just want you to be safe. BM.

 

[Iowa750sxi]

Thanks for the detailed instructions, Bill! I have the stuff I need on order and will hopefully be able to do the testing this weekend. Looking forward to better isolating the issue!