Loss Of RPM, Wet Plugs, Twitching Servo Motor

SRX_700

SRX_700

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Not sure if these are all related, but my PTO cylinder seems like it is not firing correctly, especially at high RPM. When the motor is first slightly warmed up, it will hit 8,500 a couple of times and then once warm, does about 7,800 - 8,000. PTO plug (see below) looks dark and wet. My servo motor also stops half way when it open and closes with or without cables attached. PV's clean and adjusted. Couple of things comes to mind here.

1) Weak PTO Coil
2) Needle and seat leak at PTO cylinder
3) Poor compression (could not check)
4) Weak Stator

I am leaning towards coil but want to make sure before I buy a new one. If it was leaky needle and seat, wouldn't WOT use of most of the gas? Leaky needle and seat would affect low to mid range more. Also a weak stator would affect all 3 cylinders, correct? What coil does the Servo Motor get it's signal from? I replaced plug and cap on PTO clyinder which did not fix the issue.
 

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The first thing i would look for would be chafed wires under the engine and near the cdi and handle bars. Chafed wires raise all kinds of hell with these things. also it doesn't cost anything to look and rule that out.
 
Thanks Steve,

I have had the wires checked and fixed under the steer pad and all along the steering rod. Nothing else electrical is funky at the moment. Everything works, except for PTO Cylinder. Also took the coil off to check wires and connections. It looked good.
 
ok i was trying to address your servo problem i had a similar problem ran good until completly warmed up then fell flat rpm loss ended up being wires under the engine chafed
 
Servo twitching might be a result of the wire underneath the motor. The twicthing isn't affecting my performance, however. I can live with the twitching, the wet plug is another story.
 
Yes 3 weeks ago. I did not inspect needle and seat for wear as I did not have my punch with me for the float pin.
 
I tried taking #2 coil off after I took #1 off but TORS switch on the carb was in the way. Bit of a PITA to take them off. Is it easier to take the rack off? Don't want to take carbs off to get to them. After taking the first one off, I decided it was just easier to buy a new coil and put it on. Still thinking it might be leaky needle seat. The clue might lie in the servo twitch with regards to having a defective coil. Don't know enough about it though.
 
unscrew the sp plug boot from the other 1 or 2 and put it on the one thats not firing good, see if the problem then moves to another cylinder.

when you say the engine runs good till warm thats a good sign of a stator.
the servo is operated via the cdi box not a coil, but if the stator is weak, so is the signal coming from the cdi box because it would be low on voltage. usually twitching of the servo is cables adjusted too tight or the wire harness under the motor is chaffed.

obviously youll start off switching the spark plug boots around if that doesnt fix it, then the next logical and free spot is to pull harness under engine, (if its never been done it needs it any ways), then look into the stator.
 
mrviper700 said:
unscrew the sp plug boot from the other 1 or 2 and put it on the one thats not firing good, see if the problem then moves to another cylinder.

when you say the engine runs good till warm thats a good sign of a stator.
the servo is operated via the cdi box not a coil, but if the stator is weak, so is the signal coming from the cdi box because it would be low on voltage. usually twitching of the servo is cables adjusted too tight or the wire harness under the motor is chaffed.

obviously youll start off switching the spark plug boots around if that doesnt fix it, then the next logical and free spot is to pull harness under engine, (if its never been done it needs it any ways), then look into the stator.
Click to expand...

I did put a new boot on PTO cylinder and plug was still wet. I tested Ohms and it was at 5K for the new boot so I know it was within spec. I also cut back wire to get a fresh connection but that also did not help. Seeing that servo motor twitches without any cables attached tells me that the wire harness is chaffed or the CDI box is kaput or the servo motor is shot. Is this correct?

All my other electrical items runs great. Thumb warmer, grips warmers etc. get very hot, even with high beams on. Doesn't that need a good stator to produce the energy?
 
well, your next free step to finding the problem is the wire harness, remove and inspect.
 
also i no you said you cleaned your carbs but i would go thru them again and make sure the fuel screws are set to spec you have to take the airbox out to get to the wires under the engine anyway so your right there.
 
Bought new plug boot and coil so I will try that next Monday. Could a loose main jet also cause this problem?
 
Needle in seat in my experience makes for a no fire at start up because it's flooding. Never had it effect any sled at open throttle.
Loose main jet....never had the pleasure...yet. lol
I'd pull the harness as suggested. All root electricity is starts at your stator, but your harness is the least expensive thing to check and is a well known problem. Throwing parts at it wont fix the harness if it is rubbed.
I do hear your point about it ONLY happening when it gets hot. Chaffing should act up randomly and coils are bad either hot or cold. I've never seen it both ways until it calls it quits.
I'd be inclined to borrow some known good parts. It's a quick swap. If it works, your riding.
I've had to leave my sled elsewhere in the past, so I get what your up against.
Dont really want to head north just to work on it all weekend.

If you do get out, try to head where the road runs are short. They took a beating with the sun today.
 
So bought new cap and ignition coil ($78 bucks later) and for sh*ts and giggles, I decided to test for resistance.

Spec. for plug cap is 5k, I get 4.84 k at 68 F.
Primary coil resistance spec is 0.38 - 0.46, I get 0.9.
Secondary coil resistance spec is 5.8 - 7.0, I get 6.37 so that is fine.

Should I be concerned about the other 2 being out of spec?
 
Is this a 98-99? If yes swap plug wires around. Center to pto/pto to center for example. If problem follows to center then its either Cap,plug wire,coil. If it stays in PTO than its a carb/compression or exhaust problem. 00 and newer has 3D ignition and cant move plug wires around like that.
 
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