Low RPM checklist

[Ron Burgandy]

Is there a checklist to run through to check rpm issues? running 70 weights w/ gold spring in MN. Can't get over 7900 rpms. usually 76--7700 rpms on backshift. Pulled 8250-8300 before?

So far...

New Pro engine mounts
New Belt
New Injectors
New throttle bodies
TPS adjusted a dozen times
Clutching inspected.
Compression checked.

Everything done by the dealer under warranty except motor mounts... they are more in less throwing in the towel cause they don't know what else to do. My next step is calling polaris customer service.

 

[maurfello]

Is there a checklist to run through to check rpm issues? running 70 weights w/ gold spring in MN. Can't get over 7900 rpms. usually 76--7700 rpms on backshift. Pulled 8250-8300 before?

So far...

New Pro engine mounts
New Belt
New Injectors
New throttle bodies
TPS adjusted a dozen times
Clutching inspected.
Compression checked.

Everything done by the dealer under warranty except motor mounts... they are more in less throwing in the towel cause they don't know what else to do. My next step is calling polaris customer service.

It's not listed so I have to ask, did you change your plugs?

 

[Sheetmetalfab]

Egt probe

 

[Ron Burgandy]

It's not listed so I have to ask, did you change your plugs?

No...they were given a clean bill of health at the dealer but now that i have the sled home I can throw some fresh ones in.


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[Ron Burgandy]

gonna check warm/cold compression tonight. dealer said it was good but...


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[eyefish123]

Had the same issues as you since last year and did many of the same things plus had Indy Dan balance clutch and finally figured out last week it was the EGT probe. Got my RPM back. Happy, Happy, Happy!!!!

 

[Ron Burgandy]

i'm gonna test the resistance of my probe as I don't have one around to swap. dealer told me 76 ohms at 1600 degrees is spec, does anyone know what EGTs are at when it's warm and at idle? 1600 seems crazy hot to test it at. i doubt they even get that high.


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[Sheetmetalfab]

i'm gonna test the resistance of my probe as I don't have one around to swap. dealer told me 76 ohms at 1600 degrees is spec, does anyone know what EGTs are at when it's warm and at idle? 1600 seems crazy hot to test it at. i doubt they even get that high.


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Tell your DA dealer to loan you a known good one........

 

[Ron Burgandy]

Tell your DA dealer to loan you a known good one........

ya tried that. they are a super small dealer and don't carry much for parts. They weren't to interested in scavenging one of another sled either. Dumb service I know but they are 5 miles from my house and the next dealer is 1.5 hrs away so i go there. Only option is to buy a non returnable new one at $180


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[Teth-Air]

Pulled exhaust valves after cold compression was 95/105. Found a bunch of brass filings. Was concerned. Took to dealer, they did warm compression test at 110/110. Also found exhaust valve bushings completely shot and this is were the brass came from. They replaced the exhaust valves and my I re-tested compression. Cold now 120/120 and hot 110/110?? Exhaust valves must have been hanging up??

Can't explain otherwise.

 

[Ron Burgandy]

well i borrowed an EGT sensor and threw it in, pulls 8000 consistently now. would still like to see 8250 but feels way better. atleast i'm in the power band now. still have an erratic idle from 1700-2000 though.


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[Spaarky]

power valves are pretty common culprit. stretched cables, broken cables... bunch of things.

 

[PISTONPETE]

Starting to see crank seals here out east.

 

[Ktmsx350f]

just because mounts are new doesn't mean they are tight lots wear around the rubber and with new ones are still loose seen it a few times. belt deflection is polaris spec is loose set it trace in the air belt as tight as it can be with out rotating the track all the time. Exhaust I have had 6 ggb cans and 2 others cause 300-500 rpm loss all were fixed with a good quality exhaust or stock. EGT probe. Power valves.

 

[TRS]

Before you go digging into your sled, try a can of sea foam in the tank.
It’ll take 50-90 miles, it has worked on the mule twice.
The sled would run best at 3/4-7/8 throttle. If you would pin it from there, rpm would drop. If you backed off from wide open throttle it would pick up rpm. We checked everything.
After a can of SF, throttle response was back and the drop in rpm was gone. Peak rpm was back.
Give it a try. Cheap and easy.

 

[snobyrd]

Pulled exhaust valves after cold compression was 95/105. Found a bunch of brass filings. Was concerned. Took to dealer, they did warm compression test at 110/110. Also found exhaust valve bushings completely shot and this is were the brass came from. They replaced the exhaust valves and my I re-tested compression. Cold now 120/120 and hot 110/110?? Exhaust valves must have been hanging up??

Can't explain otherwise.

I had same issue, pol just ordered a complete exhaust valve system under warranty.
Brass fillings, low rpms, stuck at 6500 rpm at one point.

 

[AKFULLTHROTTLE]

Yes first thing to check is EV system completely. Check cable then pull them out to inspect. Clean them while your in there.

 

[JMCX]

The Cat guys figured out their exhaust temp sensor is the same as used in Dmaxes. Does anyone know a cheaper source for the Axys ?

 

[snobyrd]

My dealer told me, pol is now starting to see jackshaft bearing failure on high millage sleds, this info came from pol warranty staff.

 

[AdrenalineAddict]

My solution was motor mounts and new pistons and rings. The rings were flaked terribly. I am sure my running compression was down a bit. I got 200 rpm's back, went from a max in any condition of 7,900, it now spins 8,300 down the trail and 8,100r's all day on the hill. They might only make good power for roughly 800 or 900 miles. I think I might run 120:1 premix as added insurance from now on.