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850 patriot will not rev past 8100

J
Feb 14, 2013
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Hello everyone, looking for some help.

I have a 19 850 that was built from the ground up, everything was gone through and replaced. Has an indy specialty long rod in it the whole nine yards. at the beginning of the season we got it running and noticed the rpms were 7950 @ 645 meters but we thought the rpms would come as the motor broke in which was not the case. So i have been chasing the issues for the entire season trying to get this thing to run proper. it makes ~8050 @645m and @ 6500m. I have 66grams in it for pin weight and i have tried pulling the magnets out all the way down to 63grams with no change in rpm what so ever. The sled has been in for multiple TPS/EV relearns and nothing has changed, Had a new wiring harness put in it, and a new voltage regulator, new Tmap,New water temp, tried different ecm's, new fuel pump, the whole nine yards. It will not rev over 8100. Im being told it something electronically holding it out, but the only three things i have not replaced is the stator/trigger coils, injectors,and EV motor. Everything else is brand new. There are no engine codes, i have been through the machine like 7 times looking for signs and I, along with everyone else cannot seem to figure out what is holding this engine from revving out.
Im hoping someone on here has seen this before or knows where the culprit could be? Im at a total loss here.
Keep in mind that i cannot get it to over rev on a stand @645m with no load it should be able to rev to the moon.
Any help would be greatly appreciated
 

Teth-Air

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I believe these motors pull timing when they sense something wrong. Not sure what sensor controls that though. Maybe pipe temp as I have seen mine drop suddenly to 7900 when loading it up for long heavy pulls. Very interesting to get others perspectives to get an idea how these things tick. I expect you have changed both pipe and can sensors?
 
J
Feb 14, 2013
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The can im running is the factory one.

I have tried replacing both pipe temp sensor and muffler sensor, none of which fixed my issue, ive been trying to tack down all of the ecm inputs but i cant find any literature on it. you would think if there was a sensor that was not happy you would get a code for it of some sort.
 

Teth-Air

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The can im running is the factory one.

I have tried replacing both pipe temp sensor and muffler sensor, none of which fixed my issue, ive been trying to tack down all of the ecm inputs but i cant find any literature on it. you would think if there was a sensor that was not happy you would get a code for it of some sort.
It may just be avoiding a code by backing down the power. Have you actually tried increasing clutch weight beyond 68 grams as it may be sensing too fast revving like trying to protect when a belt blows? Load it up and see what it does.
 
J
Feb 14, 2013
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It may just be avoiding a code by backing down the power. Have you actually tried increasing clutch weight beyond 68 grams as it may be sensing too fast revving like trying to protect when a belt blows? Load it up and see what it does.
Its weird that other stock pros will pull this exact same clutch set up beside mine, but this one will not. Ive cecked the temp sensors, the coolant temp sensor in new, tmap is new, that leaves the fuel return pressure and det. theres not much left for me to try....
I have no tried loading the weights up no, i suppose i could try that..
 

FriscoProx

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Nov 29, 2007
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Are you seeing this on the trail, or just the stand? You should be in the low 70's for weight at that elevation. You may be chasing a non-issue trying to rpm tune on a stand. Try putting Polaris 10-72 or 10-74 weights in with stock springs\helix and ride it to see what it pulls.
 
J
Feb 14, 2013
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I’ll put a set Boondocker weights on mine. They fixed all my problems. Also clean And grease spark plug cabs.
Ive tried putting other weights in it, didnt change anything
Can you swap clutches with your buddies?
I out al the stock clutching back in it other then the weights, so it should have over reved
Try your buddies fuel rail.
I have not tried this yet
Are you seeing this on the trail, or just the stand? You should be in the low 70's for weight at that elevation. You may be chasing a non-issue trying to rpm tune on a stand. Try putting Polaris 10-72 or 10-74 weights in with stock springs\helix and ride it to see what it pulls.
This is on the stand, on the trail, on the mountain, in my back yard, doesn't matter where it is. I just got back off the mountain and i seen 8150 once. I have put the stock clutching back in it, it doesn't change anything.
 
J
Feb 14, 2013
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Just any update, i got back off the mountain the other day, i tried playing with belt deflection to see if it would change anything. all i saw was 8150. Ive heard there was problems with temp sensors in the exhaust can at one point in time. i may try put a boondocker resistor in the harness for the can temp. maybe im not getting all the timing out of it. Im really at a loss on this one
 

summ8rmk

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I must first say, deflection does nothing beyond belt engagement. All the little bolt does, is control how close the secondary sheaves come together when the sled is stopped (or primary is fully open[disengaged]).

How does the sled perform?
When climbing does the track speed match ur buddies?
Does the track speed change when u change the clutching?

Do u ever hear it hitting the rev limiter?

Is it possible that there is a problem with the tach itself?
Maybe the RPM are changing but the tach is stupid and won't show above 8150?




Sent it
 
J
Feb 14, 2013
20
3
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I must first say, deflection does nothing beyond belt engagement. All the little bolt does, is control how close the secondary sheaves come together when the sled is stopped (or primary is fully open[disengaged]).

How does the sled perform?
When climbing does the track speed match ur buddies?
Does the track speed change when u change the clutching?

Do u ever hear it hitting the rev limiter?

Is it possible that there is a problem with the tach itself?
Maybe the RPM are changing but the tach is stupid and won't show above 8150?




Sent it
Yea im aware of how the clutches work, but im grasping at straws because ive literally gone bankrupt remplacing every part of this thing.
-The sled runs great right up until it hits its peak rpm..... then i feels like it runs out of legs.
-I have no paid attention to the track speed when climbing, because it will not make its full rpm therefore it will not make its full track speed either.
-doesnt seem to change when i had the stock clutching in it ground speed wise
- ive been trying to get it to hit the rev limiter but it will not.
- Ive got a video of this machine running 8300 before it was rebuilt from the ground up, so im going to say not likely.
 

summ8rmk

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You need to hook the laptop up to it and watch all of the sensor's while it's running to make sure that they are within their parameters

Sent it
 

Mentzel

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I had the primary clutch main bushing get sticky on my 2020 850 at 2700 miles.

Pull cover off primary clutch remove spring and make sure there is no binding as the sheave moves in and out to full shift (moving by hand.)

Should move nice and smooth. If not bushing is toast..
 

b-litt

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I was getting a similar rpm issue with a higher mileage sled of mine. It ended up being the the power valve bushings. If they are shot you will see bronze shavings all over when you take them apart. The slop was causing it to hang up at 7,900 rpm.
 

FriscoProx

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When it was rebuilt were the power valves disassembled from the cable, and if so was it re-learned? And possible that your PV cable is stretched and valves not fully opening.
 
J
Feb 14, 2013
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You need to hook the laptop up to it and watch all of the sensor's while it's running to make sure that they are within their parameters

Sent it
This is pretty hard to do without a dyno.
I had the primary clutch main bushing get sticky on my 2020 850 at 2700 miles.

Pull cover off primary clutch remove spring and make sure there is no binding as the sheave moves in and out to full shift (moving by hand.)

Should move nice and smooth. If not bushing is toast..
The clutch has less then 400 miles on it, and it been apart multiple times. its literally brand new
I was getting a similar rpm issue with a higher mileage sled of mine. It ended up being the the power valve bushings. If they are shot you will see bronze shavings all over when you take them apart. The slop was causing it to hang up at 7,900 rpm.
I had the power valves out when the new motor went it. i checked them over completely, other then carbon build up on removal they were like new. i cleaned them and put them in the new motor
When it was rebuilt were the power valves disassembled from the cable, and if so was it re-learned? And possible that your PV cable is stretched and valves not fully opening.
When it was built the power valves were removed from the servo and put on a bench. when the new motor went it the power valves were cleaned and placed back in service. I have measured the cable and it is in spec. i had the servo re learned multiple times. and ive measured how far the cable travels on the servo motor itself.
 
J
Feb 14, 2013
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Just another report on the bd muffler resistor. I did happen to see 8300 on the trail going up the mountain ONE time. whether or not that was the resistor or not i have no idea. once in the alpine in the wet heavy storm snow it was anywhere between 7950 and 8050 maybe seen 8100 once.

I tried to get it to sing on the way back down to see 8300 at the end of the day with no luck
 
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