850 Khaos low rpm issue

[stevo313]

Looking for help diagnosing a low rpm issue. Have a 2021 Khaos 850 165 2.75". Sled ran absolutely mint last year with no issues. Did all preseason regular maintenance. Fresh fuel as was stored with pretty much all fuel drained. Put new bushings in primary weights, checked and cleaned secondary and everything looked good. Only other thing I did for this year was put on the SLP picnin'r can, otherwise everything else is stock and exact same as last year. Went out for first ride this year and the sled would only sometimes pull 8000+ rpm. most times it would flop down to just over 7000rpm. Went to change the plugs and apparently I had put ones in with the stupid screw on top and they both pulled off and stayed in the plug caps. Was able to get those out and put in fresh new plugs with the solid tops but sled still ran the same. Thought maybe the plug cap connection wasn't that great and it was arcing in there. There was a bit of black soot on top of the new plugs when I checked them later. Sled never threw any codes or check engine light.

My thoughts on possible issues are;
-Plug caps are actually ruined now from bad connection
-New SLP can creating a bad back pressure issue. Hard to think that this would be the cause as SLP been in the game for a while and should know what they are doing. Lots of people running this with no problems
-Exhaust valves not opening all the way. Maybe bad relay. Dealer doing exhaust valve relearn for **** n giggles
-Bad fuel

Any thoughts or anyone experience similar issue and was able to find the cause?

Thanks

 

[TRS]

How does your primary spring look?
Sacked out, broken?

 

[caper11]

Put the stock muffler back on.

 

[Sheetmetalfab]

Check your new primary weight bushings to make sure they swing free.

Tight belt deflection?

Primary cover installed 60 degrees off from the arrow?

Stretched EV cable?

 

[stevo313]

How does your primary spring look?
Sacked out, broken?

Everything in the primary & secondary checked out

 

[TRS]

Check the slack in your throttle cable.
Push the flipper to the bar(not running of course) you should hear an audible click from the throttle stop on the TB. If not thumb push the cable towards the bar while holding the flipper at WOT. If you have slack you can adjust it with the cable adjuster. I adjust mine to where you here the audible click.

 

[G-Force]

Could try the stock can again, but I run that can on mine, and sled runs mint. Not affiliated in any way, but if you feel like there's performance left on the table, try TRS's clutch setup, its pretty dang good !

 

[TRS]

Did you get it figured out?

 

[stevo313]

Did you get it figured out?

Not yet. Only codes that were on it was 13 overheat codes. But this may mean we are on to something as I watch my temp super close and to have it throw that code 13 times, meaning it went over 185F that many times is fairly peculiar as i never let it get even close to that. The other problem is we don't know when those codes were thrown as they could have happened last year and it didn't show any codes when i rode the other weekend. My dealer cleared the codes, stock can is back on and I'll be taking it out this weekend to see what happens.

 

[TRS]

That has been an issue with the temp sensor. That may be your problem.
False readings to the ECU.
There was a whole thread on it.


https://www.snowest.com/forum/threads/another-‘19-850-heads-up.453477/

 

[stevo313]

That has been an issue with the temp sensor. That may be your problem.
False readings to the ECU.
There was a whole thread on it.

https://www.snowest.com/forum/threads/another-‘19-850-heads-up.453477/

So I see you dealt a lot with the temp sensor issue. Other than displaying wonky temps on your guage, did this affect how your sled ran. I read through that thread and did not see where anyone said their sled was running crappy like mine did. Thanks

 

[Murph]

So I see you dealt a lot with the temp sensor issue. Other than displaying wonky temps on your guage, did this affect how your sled ran. I read through that thread and did not see where anyone said their sled was running crappy like mine did. Thanks

Yes. If the sled reads low temp it will fatten up fuel, oil, and retard timing

 

[Murph]

Went out for first ride this year and the sled would only sometimes pull 8000+ rpm. most times it would flop down to just over 7000rpm.

When it "flops down" to 7000rpm, does it have an audible change in the exhaust note?-- does it sound flat? If yes, your exhaust valves may be sticking. Pull your valves and see how dirty they are. If need be, clean them and the E-VES chamber.

7000rpm is also the medium position for the exhaust valve. Sometimes if the ECU doesn't like one of the values it sees from a sensor, it will command the E-VES valve to the middle position-- limiting rpm to about 7000.

 

[TRS]

So I see you dealt a lot with the temp sensor issue. Other than displaying wonky temps on your guage, did this affect how your sled ran. I read through that thread and did not see where anyone said their sled was running crappy like mine did. Thanks

Yes, rpm would fall off and it would be intermittent. You can’t always catch the temp change on the gauge.
It may throw an over temp, or cold reading.
Murph has some good info as well.
We did make a resistor test plug that allowed you to see if the sender was the culprit and I still pack it to get out of the back country when they completely fail.

 

[tdblakes]

So I see you dealt a lot with the temp sensor issue. Other than displaying wonky temps on your guage, did this affect how your sled ran. I read through that thread and did not see where anyone said their sled was running crappy like mine did. Thanks

My '19 had a bad temp sensor. It would flake out at full throttle periodically, the temp on the gauge would go crazy for a split second (flash Eng Cold) and the sled would fall on its face or bog down. I caught it on video to show the dealer. Replaced the temp sensor and the issue went away.

 

[stevo313]

When it "flops down" to 7000rpm, does it have an audible change in the exhaust note?-- does it sound flat? If yes, your exhaust valves may be sticking. Pull your valves and see how dirty they are. If need be, clean them and the E-VES chamber.

7000rpm is also the medium position for the exhaust valve. Sometimes if the ECU doesn't like one of the values it sees from a sensor, it will command the E-VES valve to the middle position-- limiting rpm to about 7000.

I guess the audible thing is a tough one as yes it technically sounded "flatter" but it was also only running at 7000rpm vs 8000+ which sounds different regardless. But i would say it did sound a bit "flat", almost muffled. And on occasion it would pull strong and hold 8000+, sometimes it would go to full rpm and flop to 7000, and sometimes it would only go to 7000. I am heading out this weekend and I am going to try and get my hands on a spare temp sensor so that if it does it again, i can just swap it in the field and see if that fixes it.

 

[stevo313]

My '19 had a bad temp sensor. It would flake out at full throttle periodically, the temp on the gauge would go crazy for a split second (flash Eng Cold) and the sled would fall on its face or bog down. I caught it on video to show the dealer. Replaced the temp sensor and the issue went away.

I'm definitely going to keep a closer eye on the temp if it acts up again this weekend as previously i was only really looking at the rpm and never thought to or noticed the temp being screwy.

 

[TRS]

Start it up at home and wiggle the wires on the sensor while someone watches the gauge. You will be able to tell if it’s a wire problem at least.

 

[stevo313]

Start it up at home and wiggle the wires on the sensor while someone watches the gauge. You will be able to tell if it’s a wire problem at least.

I tried that and it did nothing but good call

 

[Sheetmetalfab]

I tried that and it did nothing but good call

So it’s probably the sensor then.