12 PRO TOP END BOG

Hansen13 · Feb 18, 2019

The famous bog has finally come across my wife's sled, after me putting on 3500 miles before she took it over. It runs, idles, low and mid range are great, but once you hit WOT it revs up then falls on its face and won't pick back up. Sometimes feathering the throttle helps but mostly not. Here's what I've done:

Compression check - Good (just rebuilt beginning of season)

Tested fuel pressure at pump - Constant 58 psi throughout all throttle ranges

Remove Power Valves - Cleaned, ensured port holes were free and bellows we not torn etc

Checked TSS -Even bypassed it for purpose of elimination process

Checked Grounds - Good

The ONLY thing I haven't done yet is check the TPS setting, I have to pick up my tester tool from my buddy today. My next step is to test the TPS, potentially an EGT probe? I'm also thinking of grabbing a new fuel line, it's putting out good pressure from the pump but maybe filter is causing restriction. Sled has never caused major issues since I've owned it, so anything else that people can think of let me know. I'm not leaning towards injectors until a last resort just because it could use a new fuel line anyways and I have some spare parts including a EGT probe to try as well.

Rush600guy · Feb 19, 2019

I'm having the same issue, just did a motor swap and I know for a fact the TPS is completely off... messed around with it a few times, adjusting it by hand, and the sled started, idled, but died with WOT.
Tried to redneck check it last night but I'm swimming upstream with all the different ways people say to check it (w/o a Polaris tool), hopefully tonight.
If you're gonna be replacing the fuel filter I would highly suggest you clean the 3,500 mile injectors too while you're down there... pretty easy to unbolt the fuel rail and injectors pop out easy. I used brakeclean, straw to a tire stem w/o valve core (fits perfectly over the injector and holds some good brakeclean pressure), and tapped the + to a 12vdc so not to burn out the injector's coil, and should squirt out the other side. Rotate injector 180* and squirt out the other direction. easy enough, then make sure not to over torque the two 8ft lb fuel rail bolts.

Hansen13 · Feb 27, 2019

I cleaned the power valves, checked fuel pres, and swapped out the ethanol switch. Cleaned everything right up good.

Rush600guy · Mar 1, 2019

fixed my TPS and runs all better, but still boggin in the top end too.
People I'm talking to keep asking me how my clutch is... how's yours?

MNboosted · Mar 2, 2019

Same issue

Sorry to hack I’m fighting the same issue
My 12 pro will hit 8250 and then drop to 6600 rpms,
New voltage reg, stator, coil packs, swichted ves solenoid, cleaned valves. Also had dealer re calibrate the tps. I have 670 miles on the sled.
Going to try egt probe tomorrow from my turboed sled to see if that helps
Thanks for the info and help

05rmksteve · Mar 2, 2019

Have you replaced the motor mounts and check your clutchs. Springs, rollers, weights, is it binding, belt deflection.

live2beel · Mar 2, 2019

MNboosted said:
Sorry to hack I’m fighting the same issue
My 12 pro will hit 8250 and then drop to 6600 rpms,
New voltage reg, stator, coil packs, swichted ves solenoid, cleaned valves. Also had dealer re calibrate the tps. I have 670 miles on the sled.
Going to try egt probe tomorrow from my turboed sled to see if that helps
Thanks for the info and help

Try a different fuel pump if you have one. Replaced everything like you, and it was my fuel pump.

MNboosted · Mar 3, 2019

Sorry to hack

Last night it woukdnt let get over 6800-7000 rpms. Ran great for about 15 miles then this happened. Plugs are little moist but brown and new yesterday.
So I swapped fuel pump from turbo sled = no difference
Pulled clutches out went through them again, made sure they moved freely. Also swapped secondary, pulled some weight out of it and still won rev over 7000.
In mn running 68g tried 64 and 70 but no difference.
Running out of ideas ecm, injectors?
Any help would be great.

Rush600guy · May 2, 2019

Anyone figure it out?

Mine is all good, till 7,200 rpm.
My RPM gauge goes haywire, sounds like the track or clutch starts skipping with big vibration, and the engine will just rip yo the rev limiter w/o any additional speed increase - right before it bogs/retards itself.

My case doesn't seem to me like it's anything motorwise, more like track and clutch. I know my speed sensor is due for a replacement.

Any ideas would help.

sledhed · May 2, 2019

Rush600guy said:
Anyone figure it out?

Mine is all good, till 7,200 rpm.
My RPM gauge goes haywire, sounds like the track or clutch starts skipping with big vibration, and the engine will just rip yo the rev limiter w/o any additional speed increase - right before it bogs/retards itself.

My case doesn't seem to me like it's anything motorwise, more like track and clutch. I know my speed sensor is due for a replacement.

Any ideas would help.

Had something similar happen a few years back, ended up the chaincase tension adjuster had broken and allowed enough slack in the chain that it would skip under pressure... if chaincase tensioner is okay I would check the driveshaft and jackshaft bearings for excessive wear or play. And of course make sure the track is tight enough. Tension the track to Polaris specs for now to make sure there is no ratcheting, you can always back it off later once you eliminate that as a possible problem... could be a lot of possibilities based on your description. But that is my list... and the clutching / broken springs / rollers / helix can do strange things too.

Rush600guy · May 12, 2019

sledhed said:
Had something similar happen a few years back, ended up the chaincase tension adjuster had broken and allowed enough slack in the chain that it would skip under pressure... if chaincase tensioner is okay I would check the driveshaft and jackshaft bearings for excessive wear or play. And of course make sure the track is tight enough. Tension the track to Polaris specs for now to make sure there is no ratcheting, you can always back it off later once you eliminate that as a possible problem... could be a lot of possibilities based on your description. But that is my list... and the clutching / broken springs / rollers / helix can do strange things too.

That's good to know actually. When I got this sled from my friend it had a cracked chain case, he gave me a replacement, and just yesterday I was replacing it's bearings. I'll recheck the chain tension soon, there isn't a set torque for that is there, if I remember in the book it says hand tight... ?
I'm gonna replace all my track bearings soon, noticed they're all pretty shot, hopefully I find everything else wrong down there. Other than that yeah I'm over due to fix my clutching... added some power with v force reeds, AAEN fat pipe/muff, billet head, big intake, big stator, pistons, and doing a light porting.. as it sits she's a torque monster and appearantly loves to destroy my track-parts.

Tunneltwister · Jul 24, 2019

When is the last time you changed the fuel filter...? If it hasent been changed then it may not have enough flow on the top end...

sledhead_79 · Jul 24, 2019

05rmksteve said:
Have you replaced the motor mounts and check your clutchs. Springs, rollers, weights, is it binding, belt deflection.

What Steve said. Clean clutches and belts, you’ll be amazed.

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12 PRO TOP END BOG

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