DET issues 2015 pro 800

PSI 800 · Aug 21, 2017

I am hoping that there is a gearhead out there that can help me as my dealer is out of ideas. I have a 2015 Pro 800 with an SLP pipe, PCV, Bikeman air box mod, SLP intake kit, Vforce 3 reeds and RkTek head with stock compression domes. I run 91 octane fuel with Lucas Oil octane boost from the same gas station as everyone else. All of this was put on from new and worked great with no issues first year and a half. Then it would DET both cyls and shut down at WOT every once and awhile. Didn't matter if I was pulling a hill or ripping across the lake. Now it is much worse, every ride out and a few times a ride, still at WOT though. It is very random though as I can pull the same hill 5 times and it will only do it once. The sled is not over heating or over reving as I keep an eye on that. We have programmed in the latest map from SLP for my altitude which is 0-6000ft, tried another PCV that we know works checked the TPS and it still does it. The only thing that has helped is we turned on the Ethenol map in the Polaris ECU. Pulling my hair out as this usually occurs at the wrong time on a hillside. Please help me enjoy hill climbing.

richracer1 · Aug 21, 2017

Try loosening it and torquing it again. It's torque range is 144 - 192 in/lbs (I'd stay on the low side of the torque range) DO NOT use any kind of anti-sieze or lok-tite.

Also, make sure the exhaust is not hitting anything, especially under high load. I've heard of the Det sensor registering a "knock" that came from the pipe hitting the bulk head/cross member. This could be from sacked out engine mount bushings.

ripnit · Aug 21, 2017

Wrist pin hole in RK Tek pistons.....Everyone can flame me but there is/was a problem.

Reg2view · Aug 21, 2017

If you forget the boost and mix in a couple of gals of race or AV gas, is it gone? That would easily tell you if it's something other than det or pre-ign itself, like the sensor, mounts, pipe knock, etc. Unless the ethanol map is retarding timing, it's just adding fuel, which will help with pre-ign, but not det. Don't know the 15's, but once upon a time the eth map would just add 5% fuel. And you even get that race fuel perfume...

Sheetmetalfab · Aug 22, 2017

ripnit said:
Wrist pin hole in RK Tek pistons.....Everyone can flame me but there is/was a problem.

It's just rk tek products in general.
Detonation kills motors.......

gtwitch · Aug 22, 2017

Miles/time on sled ??? Don't forget to check the fuel filter and possible replace as this can cause a lean issue that leads to DET!! I had this happpen this last season. Also check fuel pressure because either filter or pump can cause fuel flow problem.
gtwitch in wyoming

TRS · Aug 23, 2017

Have you checked your plug wires and caps? If they are shorting, they will throw the det sensor.

PSI 800 · Aug 23, 2017

The sled has around 1800k on it. I have ran a few tanks without the octane boost and the same thing happens, I have also ran chevron 94 octane and the same thing. I have changed out the fuel filter and it didn't make a difference. How do you check the motor mounts? When the sled does die it says DET on the screen and when the dealer checks the codes DET is what comes up. Thanks for the help Guys. WINTER is coming.

simnil · Aug 24, 2017

I have a completely stock 2015 RMK 800 and I have the same problem. Once i a while the DET-light will come on and the engine dies.
It can take very long WOTs sometimes and DET out after a short pull another time, no logic at all....... Very small difference in altitude where I ride, 0-1000m, (0-3000ft-ish) and 90% of all riding is between 250-750m altitude.

I had the pipe heat shield hitting a mounting bolt for the Skinz front bumper, fixed that but no difference.
Changed the rubber support under the pipe to a slightly higher one as I thought the pipe would touch the chassi sometimes... no difference
Had a "severe" but intermitent rattling noise, turned out that the mag front engine mount hat come loose from the chassi. Bolts had come out approx 8-10mm but were held in place by the float plate. Fixed that, no difference..... (even had my dealer tear down my engine to check if everything was OK and the engine looked like new inside)
Changed fuel filter, no difference....
Removed the Fire n Ice engine supports... No difference, (so I put them back again)

I'm running out of ideas!!!

Speed Shop Inc. · Aug 24, 2017

Internal motor issue is more than likely. The lower rod bearings flatten out on those things, so it could be that very easily.
Could also be caused from piston slap from too loose of clearance, also a common problem with stock pistons.
And if it had wossner pistons used in aftermarket piston kits, they did have problems with the wristpin holes egging out.
I would suggest taking the motor completely apart.
Especially if it keeps getting more common for the det light coming on. Whatever is wearing out is wearing more and more and likely something could let go.
We have replaced many pistons and cranks due to these issues.

simnil · Sep 12, 2017

Mine has done this since new, and nothing funny was discovered when the cylinders were taken off for inspection last year. (I'm pretty sure my dealer did check the rod bearings as good as possible without lifting the crank out at the same time)

RoostinRyan · Sep 14, 2017

So is it actually saying "DET" on the screen? Might be a dumb question but I thought my sled was detonating half of last season. I found the culprit the throttle safety switch in the throttle block. The way I was pushing the throttle under WOT wasn't fully pushing the button down. I ended up putting a pin in the oblong bolt hole which is now pushing in the TSS switch all the time. Problem gone. I should mention that mine is an RMK not a PRO so Im not entirely sure if they have similar design of the switch but Im sure they do. It about made me pull my hair out but ended up with a bunch of upgraded parts in the process of trying to find the culprit. Good luck.

Sheetmetalfab · Sep 14, 2017

ryanlinger said:
So is it actually saying "DET" on the screen? Might be a dumb question but I thought my sled was detonating half of last season. I found the culprit the throttle safety switch in the throttle block. The way I was pushing the throttle under WOT wasn't fully pushing the button down. I ended up putting a pin in the oblong bolt hole which is now pushing in the TSS switch all the time. Problem gone. I should mention that mine is an RMK not a PRO so Im not entirely sure if they have similar design of the switch but Im sure they do. It about made me pull my hair out but ended up with a bunch of upgraded parts in the process of trying to find the culprit. Good luck.

All you needed to do was tighten your throttle cable slack.
This forces the tss pin to fully compress before throttle plate opening.

Disabling the tss can make for some hairy stuck throttle situations.

Hope you run a tether.

Fyi i pulled the guts out of my tss to nueter it completely.

simnil · Sep 15, 2017

ryanlinger said:
So is it actually saying "DET" on the screen? Might be a dumb question but I thought my sled was detonating half of last season. I found the culprit the throttle safety switch in the throttle block. The way I was pushing the throttle under WOT wasn't fully pushing the button down. I ended up putting a pin in the oblong bolt hole which is now pushing in the TSS switch all the time. Problem gone. I should mention that mine is an RMK not a PRO so Im not entirely sure if they have similar design of the switch but Im sure they do. It about made me pull my hair out but ended up with a bunch of upgraded parts in the process of trying to find the culprit. Good luck.

Yep, it says "DET" when it shuts down. And it shuts down completely, it doesn't just go into limp mode and keeps on running. It has to come to a complete stop and be restarted with the rope.

Sheetmetalfab · Sep 15, 2017

simnil said:
I have a completely stock 2015 RMK 800 and I have the same problem. Once i a while the DET-light will come on and the engine dies.
It can take very long WOTs sometimes and DET out after a short pull another time, no logic at all....... Very small difference in altitude where I ride, 0-1000m, (0-3000ft-ish) and 90% of all riding is between 250-750m altitude.

I had the pipe heat shield hitting a mounting bolt for the Skinz front bumper, fixed that but no difference.
Changed the rubber support under the pipe to a slightly higher one as I thought the pipe would touch the chassi sometimes... no difference
Had a "severe" but intermitent rattling noise, turned out that the mag front engine mount hat come loose from the chassi. Bolts had come out approx 8-10mm but were held in place by the float plate. Fixed that, no difference..... (even had my dealer tear down my engine to check if everything was OK and the engine looked like new inside)
Changed fuel filter, no difference....
Removed the Fire n Ice engine supports... No difference, (so I put them back again)

I'm running out of ideas!!!

When i get det I approach it like so.

Egt sensor or wiring connection

Stuck roller in primary clutch. (Yes even if new) overev makes hard det in midrange.

Loose or rattling small pieces/ pipe/ motor mount.

Leak down test of motor

Injector testing / fuel filter

Plug wires check for loosening

Of course the standard things.
Water in fuel?
Old fuel?
Low octane?
Tight stinger aftermarket silencer at low elevation?

Last is pull the whole wiring harness and go over it with a fine search for rubbed wires.

PSI 800 · Sep 22, 2017

Thanks for all the suggestions to check on my sled. I think I may have found the problem which makes complete sense as the issue has progressively gotten worse. I tore into my sled and started checking all the ideas, took the knock sensor off and tested with a voltmeter and it showed the same result as one my dealer had so I cleaned the threads and retorked as suggested , took my pipe off and noticed that it had been hitting the bulkhead so then I checked my motormounts and they are shot. Thinking back it makes sense that the problem is more than likely due to the mounts as the problem slowly got worse which would be as the mounts got worse. Just hard to believe that the mounts are that ****ty as the problem started after about 1.5 yrs. Fingers crossed and now waiting for snow to find out if that was the problem. Thanks again everybody. Happy sledding to all

gtwitch · Sep 24, 2017

In earlier posts on the DET issues , I found,, in my case, that DET was being caused and actually DETing because of a fuel filter being neglected/overlooked and causing lean conditions and DET. Replaced fuel filter and DET has not happened since (happened early/mid season last winter ).
gtwitch in wyoming

radtulz · Sep 25, 2017

my 13 pro with similar upgrades was haunting me with this similar issue. SLP stage 3 with mtntk fix kit. Only at WOT, and not all the time, it would act likeit was running out of fuel, or over fueling. If i back out of the throttle and pin it again, it wouldnt always repeat the fall on its face feeling. Multiple re-maps on pcv, fuel filters, fuel press tests, injector flow tests, diff mufflers, cleaning of power valves, more or less trick fuel, more weight in clutch, nothing would get rid of it. Ran flawless, except at WOT when you really needed it. I finally narrowed my issue to my power valves not moving. I removed valves and reinstalled them in a spare set of cylinders i have. I applied air press to the feed hole in the cylinder and blocked vent holes on diaphram, and i could not get valves to move. Ive had them apart for cleaning multiple times, but after closer inspection, I was missing the super tiny feed hole in the housing that was totally blocked with carbon. It was so blocked, I thought they forgot to drill the passage from factory. After clearing the passages, retested in spare cylinders and wow, valves moved like theyre supposed to. Ran 20 times better after that.

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