Signs of faulty pv servo

fourbarrel

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I have seen over the years a few threads with sleds having similar issues as what I'm about to post.I have even posted one but never figured out the problem so here goes again.I have a '98 that has been converted over to 2000 electrical with the 300 watt mag,wire harness,headlight,carb rack w/tps and regulator.The sled had been working fine for the first few years after I did this conversion but for the last 2 or 3 I have been plagued by a weird stumbling issue.What is happening is the sled will work great down low and even mid throttle but when I get into the upper rev range it seems to hit a certain spot and then the engine will fall on its face with a dull monotone out the exhaust and won't climb in rpms at all.Once the revs drop it'll pick back up until it gets to the same spot again in the rev range.Seems to happen around 7000 or so.Clutches are spotless and have new brass bushings in the primary cover as well as the helix,and the others are still good.The tors is hooked up but working fine plus I know what it acts like when it activates and it isn't the TORS.I have checked and replaced the fuel filter and it's good,the wire harness is wrapped in loom and has been checked for rub throughs prior to wrapping.The carbs are cleaned regularly and they have oem fuel lines just replaced a few years ago.Float setting is 14mm if I remember right because that was what I half suspected as the problem,but upon reflection it doesn't act like the engine is starving for fuel it's more like an electrical issue.I have checked the TPS setting and believe it is properly adjusted but mabey the TPS have a fault in it?But something I wanted to ask of you all too was what does a faulty serve act like? I'm wondering if the servo isn't closing off the powervalves at high rpm not allowing the engine to rev like it should? Is there a way to test the windings of the electric motor to see if there's a flat spot or open in the circuit? I am grasping at straws with this problem because everything I have changed makes no difference.
 

That does sound liked a weak pv motor.You could put power too it and see if it starts too back the pully off from full pull after a couple min. Or unplug it put some visegrips on the pully full pull and go out and try it. Weak stator does funky stuff to.
 
The servo idea just occurred to me yesterday and I'm just grasping at straws with this but you make a good suggestion with unplugging it and locking it open to try it.The only access I have to another servo is the one on my '01 and I really don't want to start swapping parts back and forth just to narrow down this problems cause,especially when I'd have to take the cables off and readjust them all twice.I have ohmed out the mag but I may do it again just to rule it out.I do have a spare one here to swap in so surely sooner or later I'll narrow this down.
 
Well I powered up the servo and readjusted the slack in all 3,didn't seem out but did it anyway.Left the power on and the spool wound to full stroke and never moved at all so I don't think there's anything wrong with the electric motor.Our snow was decimated Saturday night by rain so I can't even try this thing out to see what,if any, difference was made.I will be taking a pair of vise grips with me when I do get to try it again and lock the spool open to see what happen if the original issue still persists.
 


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