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:
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:
- Hard starting: Hard starting when cold or won’t start when cold
- 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.
- After it warmed up it won’t start but if it sits for an hour it’ll start again
- 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.
- Runs bad at lower rpms but runs good at higher rpms (Low speed coil going bad)
- Runs good at lower rpms but runs bad at higher rpms (High speed coil is going bad)
- Backfiring and just won’t run good
- Sled slowly loses power during the course of the day. Spark plugs keep getting richer/darker as the day goes on indicating weakening spark.
- 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.
- Weak orange or yellow spark
