Stator test

tor*p*do

Squarenose FTW
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NW NC
Ski would start up on reduced power, like 1 cylinder, eventually fire off and run ok. Occasional fail to rev up. Does this with MSD and OEM CDI.
The charge coil is putting out 28 volts, where normal should be 30 to 50. All other readings in spec.
Have I found the cause?
 

OCD Solutions

Original, Clean and Dependable Solutions
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Rentz, GA
What meter did you take that reading with? Stator and CDI readings have to be taken with a Peak Voltage meter to match the specs in the service manual. A regular meter will only be able to capture part of the signal and would show a lesser value. Even a Fluke 87 with true RMS is going to show a lesser value than a PVA.

I use a PVA from Amazon for all my readings. Great build quality for the price.
https://www.amazon.com/Electronic-S...=gateway&sprefix=peak+voltage+,aps,387&sr=8-2

Peak Voltage Adapter.jpg

Here's some more reading on the subject.
https://www.go2marine.com/productcenters/electrical/2-dva-explained.pdf
 

OCD Solutions

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A weak Stator could cause what you are describing, I'd just want to quantify your readings before throwing money in that direction. If you do have a PVA, test the output of the CDI itself to see what it's putting out. I have attached an excerpt from the service manual detailing these testing procedures, the tools to use and the readings to match.

Anytime I hear of intermittent spark or spark on only one cylinder, my focus usually moves from Stator and CDI to coil wires, plugs, fuel, carbs, etc.

Since these are wasted spark ignitions, if it can fire off even one cylinder, you've already proven that everything is working up to the coil at least. My next step would be to determine if it's an open or shorted plug wire, a bad plug, low compression or intermittent fuel delivery.
 

Attachments

  • Yamaha Peak Voltage Testing.pdf
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tor*p*do

Squarenose FTW
Site Supporter
Location
NW NC
I am using a Fluke 23 iii meter with a HOLD button.
After battery being charged all night, charge coil at 30 volts. But not using the HOLD. Will try again this evening.
Coil ohmed out correct. Occurs with both MSD and 61x CDI.
I have a fresh coil I can try. Have new plugs in ski.
Will read through attached documents. Thanks!
 

OCD Solutions

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That article was written by John from Jetski solutions so you can be sure it’s damn accurate and written to use tools available to most people, like your Fluke.

The stuff I posted was straight from the manual. John’s is all real world findings.
 
ocd has a great post here which shows the stator stupidty...I have a 96 Superjet. The ski has been lovingly maintained, but would bog after 30 minutes...you could set your watch-it would stop hitting, then run...raggedly, but never stalled. The problem was gradual until it became constant. Fuel pressure OK. Carbs...rebuilt....fuel pump....rebuilt....all lines, valves, one way, etc, replaced..temp sensor replaced..still started easily, ran great till hot, and poop......finally decided it was time to replace the 20 year old crank seals, so got an SBT shortblock (hold the flames please, ski is stock, sbt was good to do business with and the engine is solid) and sure enough, ran better, till a half hour and poop. The only part of the ski not rebuilt was the stator...Jet Ski Solutions did the wiring harness, but their test and ours showed the stator in tolerance and to be fair, JSS only tests at room temp and they tell you that.

With great gnashing of teeth, took flywheel off (lots easier with engine out, but oh well) replaced Stator, end of all problems -- The Cause of the problem was once the stator got hot it went out of tolerance, and was no longer charging the coil properly-once hot, resistance changed, and voltage dropped, knocking the whole system of whack. OCD has a great post where he heats the stator and it goes out of tolerance. We were able to show it as well in my case...we took the stator, ran it to 250 degrees in the oven, and boom ! way out of tolerance. Visually, the new stator was snow white, and mine was a dead leaf brown...

Other than the fact the stator is work to get to, it's not too expensive and still available OE. (jetmanic, of course)

Three seasons and 150-200 gallons later, thanks to this forum (jetmaniac spotted my dead stator visually from some posted photos, no less !!!) for all the help, and ski runs great.

Here's the prior thread - you can see I had a lot of friends here help out.

---TL DR excerpt----

The new-in-a-bag Yam stator tested at 540 ohm.
Spec, per the manual, is 497.7 to 608.3
The old Yam stator tested at 528 ohms-JSS was correct in "tested OK" and they state they don't temperature test.

The new coil was a snowball white, while the old coil has some discoloration. I intend to unwind it to verify insulation failure. In the future, a visible discoloration may be a fail symptom....

To check the coil, it was placed in the oven....and run up to 300 or so degrees, slowly, as to mimic what happens with the engine.

At 265 measured degrees, the coil resistance went up to 718 ohms. As it cooled, the resistance dropped. After a minute it was down to 695, and continued to drop as the coil cooled.

This "in spec" while cold but "out of spec" when hot is the same thing OCD showed in a post where he set up his ignition test rig, the coil fired OK at room temp, until he warmed it to 180 degrees using a heat gun, where the output voltage of the coil then dropped enough not to fire the CDI and plugs properly. This is exactly the same thing (ohm's law) we observed, even though we were testing resistance and he was measuring output voltage. The increase in resistance would decrease the output....and the 20% change agrees with his experiment.

http://www.x-h2o.com/index.php?threads/twenty-years-on-one-engine-sorta.184018/#post-1939334
 
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