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Discussion Starter · #1 ·
I see posts and get asked all the time; "What are the common symptoms of a bad stator?". I wrote up a quick article relaying some of the most common symptoms of a bad stator. I also put it on my web site: Symptoms of a bad stator


One of the most common questions I’m asked is: “How does the engine act when the stator is going bad?” First of all let’s understand that most older (2000 and older) batteryless EFI ignition systems and carburetor engines have similar stators and can have similar symptoms. Some stators have 1 ignition coil and some have 2 ignition coils which include a high speed and low speed ignition coil. When you get to the “newer” stators (Primarily 2000 and newer in most models) a more common design contains 2 equally wound ignition coils that ohm out the same. Some stators have both the ignition coil and the trigger coil mounted on the stator mounting plate. The EFI stators also contain other coils on it that help power the fuel pump and injector coils. There are also windings for the lighting side of the stator. That includes providing the AC power for the lights, hand warmers and dash cluster lights. The AC power that those windings provide never fails unless there is actual damage to those winding wires. Just pulling the recoil to see if the headlight flickers means nothing. The AC power windings have nothing to do with the ignition coils on a stator. So, now that we know some of the differences and similarities in different year/model stators let me list many of the common symptoms of a stator that has gone bad or is going bad:


  1. Hard starting: Hard starting when cold or won’t start when cold
  2. Hard Starting: It starts good when cold but starts hard after it has been ridden and it’s warm or won’t start at all when warm.
  3. After it warmed up it won’t start but if it sits for an hour it’ll start again
  4. No spark. I have many diagnostic resources to help figure out what the exact root cause of a no spark condition but having a bad stator can be the root cause of a no spark condition.
  5. Runs bad at lower rpms but runs good at higher rpms (Low speed coil going bad)
  6. Runs good at lower rpms but runs bad at higher rpms (High speed coil is going bad)
  7. Backfiring and just won’t run good
  8. Sled slowly loses power during the course of the day. Spark plugs keep getting richer/darker as the day goes on indicating weakening spark.
  9. On a twin one cylinder fires and the other is weak or not firing. On a triple 2 cylinders are firing but one is weak or does not have spark.
  10. Weak orange or yellow spark
 

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Had Blaine rebuild 3 Stators for me. Switched my Mountain Cat 1404 from 2001 cdi to a 93. Sled was unquestionably faster, although only had it out once. Nice to know I have. a fresh stator that works as advertised, and 2 good spares! Thanks Blaine
 

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OK here's one for you Blaine. Sled is a 2000 ZRT 800/1004 and all electrics are stock except for a 2.58* flywheel key. While driving fast through trails the sled will shut off for about 2 seconds and refire. This will not happen on the lake at WOT or part throttle. This has been going on for about the last two seasons. The sled always runs great except for these quick on and offs. This will happen about two or three times in about 60 to 70 mile ride.
 

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Discussion Starter · #6 ·
OK here's one for you Blaine. Sled is a 2000 ZRT 800/1004 and all electrics are stock except for a 2.58* flywheel key. While driving fast through trails the sled will shut off for about 2 seconds and refire. This will not happen on the lake at WOT or part throttle. This has been going on for about the last two seasons. The sled always runs great except for these quick on and offs. This will happen about two or three times in about 60 to 70 mile ride.
If it shuts off totally like you're turning the key off and on then it could be an ignition switch issue or it could be a trigger issue. Whether it is the trigger itself, moisture in the connector or the trigger is on the very very edge of the maximum air gap for the raised rib on the flywheel to excite it. Could have a shorted wiring harness although most of the time when that happens it runs worse and worse. Check secondary coil connections (CDI to coils and the jumper wire) to make sure they are tight. I've seen a CDI before that had a frayed wire right where it came out of the cdi box and that caused an intermittent issue. 2000-2002 stators don't go bad very often. Likely not a stator issue.
 

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My thoughts exactly Blaine. I replaced the ign. switch just like you said. Switch wasn't cheap at $50.00 though. Won't be able to test it until next season though. Thanks.
 

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My sled did that and I too replaced the ignition switch and the pick up coil. Problem solved. Unfortunately I did both at the same time so not sure which one was the culprit.

My buddy had a 99 T-cat and had that same problem with a D & D silencer on it. He took it off and ran the OEM as was told and problem was gone immediately. So there are 3 things to look at.
 

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Discussion Starter · #9 ·
My sled did that and I too replaced the ignition switch and the pick up coil. Problem solved. Unfortunately I did both at the same time so not sure which one was the culprit.

My buddy had a 99 T-cat and had that same problem with a D & D silencer on it. He took it off and ran the OEM as was told and problem was gone immediately. So there are 3 things to look at.
Normally if the ignition switch or pick up coil/trigger is bad it acts like someone is turning the key on and off. It is a well known fact that putting an aftermarket can on an EFI motor is not a good idea and many times will result in it not running right.
 

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I will throw one other symptom into the bad stator category.

Engine runs fine but wont rev to correct RPM after one quick pass.

I have seen several stators in the last couple of years where the engine runs fine but wont rev past 7000Rpm's or 8000Rpm's regardless of what you do except let it cool off and then it will rev for one quick pass before back hitting a rev limit wall again. We finally diagnosed it on a engine dyno. I have seen this happen on both triples and twins now.
 

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I will throw one other symptom into the bad stator category.

Engine runs fine but wont rev to correct RPM after one quick pass.

I have seen several stators in the last couple of years where the engine runs fine but wont rev past 7000Rpm's or 8000Rpm's regardless of what you do except let it cool off and then it will rev for one quick pass before back hitting a rev limit wall again. We finally diagnosed it on a engine dyno. I have seen this happen on both triples and twins now.
And they ohm ed ok?
 

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Discussion Starter · #17 ·
And they ohm ed ok?
Cat lists ohm values with a +/- 20% variance. That's not true. If a zrt low speed coil on a stator ohms out at 455 it is "good" according to Cat's listed specs but thru my very extensive testing I know anything that ohms 448-449 and higher for an OEM stator is bad.
 

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Hi, So i messaged maybe you on youtube also but just in case that is not you here is my question.

I just did a total overhaul on a 2000 ZRT 600. Runs great at idle but when you try to trottle up it losses power, bad. I did the stator test and found the following. 17, 182 and a total of 203 when the diagonal is checked. What doe this mean? is it still the stator or somethjing else like a ground issue?
I appreciate the help.

Browny
 

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2000 zrt600? Those are the wrong ohms for a 2000 zrt600 stator.

Right, but could it be secondary to something other than the stator? You indicated that they fail with a higher number becuase of more resistance. What would a lower number be from? Grounding issue?

Browny
 
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