Test your stators when they are cold because after they are warm it can be hard to tell if you have a dying stator. This becomes even more critical when drag racing…why? Because when you have a marginal stator, one that may be weak or slowly dying you don’t run your sled long enough to get the stator warm enough to cause catastrophic failure, it won’t start after shutting it off or at least get it to the point where you know for sure it is a bad stator. In essence you unknowingly can “limp” a bad stator along due to only running it for a few minutes and then shutting it off and letting it cool back down not even knowing it while thinking that you may have a bad carb, bad plug, tether connection was bad, bad key switch ect…
Case in point: This past weekend my buddy Ron Hunyady was at the Davison, MI nonsanctioned fun race. His 1st run of the day the sled ran pretty good and was slightly over revving so he hda to add more weight to the primary. Over the course of the rest of the day he experienced a slight miss at times, the sled slightly back fired when he started it up one time. One time it barley started (He was up at the starting line when that happened so I didn’t hear it). By the end of the day he had taken 40 grams of weight out of the primary trying to get it to rev to 8600 rpms but it was only revving up to 8100 rpms. I had a suspicion that the stator was going bad on it but he thought it was a bad tether connection. There was no way around it… he was losing a lot of hp as the day went on as evidenced by having to remove a lot of primary clutch weight. I couldn’t really check the stator properly because it was always hot/warm and never really let to cool off because of constant test runs, adjusting the tether, thinking that one cylinder was rich so it was jetted down and the jetting was rechecked by starting it on the jack stand ect…so it never was left alone for a couple of hours to cool down.
How do I know stators that measure slightly over the specs are bad: I have tested more than a ½ dozen stators where the low speed coil tested 455, 460, 465 ect…when cold when the spec is 450. Every single stator that measured over 450 ohms was bad. Some of them wouldn’t start, some would start but the sled was a pooch and some started, ran decent for a ½ hour to and hour and then died..but after 10-15 minutes they cooled off enough to allow the sled to start again. This last batch of stators..the ones that run “ok” but after a while they die but after they cool off you can start the sled again…are the most frustrating to racers because your sled may show a few signs of the stator dying like it did for Ron on Saturday but you’re not 100% convinced it is the stator because the sled still starts, it misses a little bit, the EGT’s are close with maybe one cylinder slightly lower ect…long story short a marginal stator can drive you NUTS! I measured Ron’s factory stator yesterday and the low side stator coil was 488 ohms…which of course equals a bad low side coil on the stator. In his instance as described above, it was never run long enough to totally die or cause the sled not to start. The continuous starting, short runs and allowing it to cool gave the internal coil wire time to cool off and retract giving it just enough output so the sled would start and run the next time the recoil was pulled. If he had been trail riding more than likely after a period of time it would not have started after stopping.
Also, Ron didn’t have one of my rewinds in his sled that day…he has 2 or 3 of my stators but he had them in other motors that day. He said that he’ll never run another factory stator at an event again. I don’t claim to be the best but I’ve done a lot of testing, taken my lumps and learned a lot over the past couple of years and believe that I have a very good rewound stator process.
Case in point: This past weekend my buddy Ron Hunyady was at the Davison, MI nonsanctioned fun race. His 1st run of the day the sled ran pretty good and was slightly over revving so he hda to add more weight to the primary. Over the course of the rest of the day he experienced a slight miss at times, the sled slightly back fired when he started it up one time. One time it barley started (He was up at the starting line when that happened so I didn’t hear it). By the end of the day he had taken 40 grams of weight out of the primary trying to get it to rev to 8600 rpms but it was only revving up to 8100 rpms. I had a suspicion that the stator was going bad on it but he thought it was a bad tether connection. There was no way around it… he was losing a lot of hp as the day went on as evidenced by having to remove a lot of primary clutch weight. I couldn’t really check the stator properly because it was always hot/warm and never really let to cool off because of constant test runs, adjusting the tether, thinking that one cylinder was rich so it was jetted down and the jetting was rechecked by starting it on the jack stand ect…so it never was left alone for a couple of hours to cool down.
How do I know stators that measure slightly over the specs are bad: I have tested more than a ½ dozen stators where the low speed coil tested 455, 460, 465 ect…when cold when the spec is 450. Every single stator that measured over 450 ohms was bad. Some of them wouldn’t start, some would start but the sled was a pooch and some started, ran decent for a ½ hour to and hour and then died..but after 10-15 minutes they cooled off enough to allow the sled to start again. This last batch of stators..the ones that run “ok” but after a while they die but after they cool off you can start the sled again…are the most frustrating to racers because your sled may show a few signs of the stator dying like it did for Ron on Saturday but you’re not 100% convinced it is the stator because the sled still starts, it misses a little bit, the EGT’s are close with maybe one cylinder slightly lower ect…long story short a marginal stator can drive you NUTS! I measured Ron’s factory stator yesterday and the low side stator coil was 488 ohms…which of course equals a bad low side coil on the stator. In his instance as described above, it was never run long enough to totally die or cause the sled not to start. The continuous starting, short runs and allowing it to cool gave the internal coil wire time to cool off and retract giving it just enough output so the sled would start and run the next time the recoil was pulled. If he had been trail riding more than likely after a period of time it would not have started after stopping.
Also, Ron didn’t have one of my rewinds in his sled that day…he has 2 or 3 of my stators but he had them in other motors that day. He said that he’ll never run another factory stator at an event again. I don’t claim to be the best but I’ve done a lot of testing, taken my lumps and learned a lot over the past couple of years and believe that I have a very good rewound stator process.
