Sled idles perfect, but won't rev past 3000 RPM

[steyan]

This one has me scratching my head. Here's what's up:

• 2008 Polaris RMK 600 with carburetors.
• Sled will start and idle perfectly. But, as soon as I give it gas - up to where the clutch is about to engage - it will die. It's just like I turned off the key - It's not a carb issue - I verified that it's losing spark. Also (the sled has electric start) the battery is not getting charged. Voltmeter on the battery with sled off is 12.4 V, when idling, the voltage goes down to 12.2 V.
• Headlight and cluster gauge lights would flicker on/off/dim, but after a lot of tinkering, that problem has seemed to stop.

Here's what I've checked and/or replaced:

• Voltage regulator - I suspected this first since battery is not getting charged. Bought a used one on eBay - no change
• Stator - measured resistance across all the connections - within spec, but I replaced it anyway with a used one from eBay - no change (kinda' expected that).
• Kill switch/throttle safety switch - I unplugged this, then tried again but saw the same behavior
• Checked all connections/grounds/wires/etc. (including the brake light wire - one post said to check that). No issues to report.
• This sled has a throttle position sensor, however I don't have the tool to check it, but I assume it's working fine. In one test I unplugged the TPS, then tried to start it. It started and idled for just a second, then stopped. So, I plugged it back in.

What else should I check? What am I missing? Thx for any help you can offer!!

 

[JakeVIII]

I have a similar issue with a 2002 Polaris Trail Touring. Two carburetors, 550 fan engine.
It idles and starts great. But when I go wide open with the throttle it sticks at 3000 rpm and won't go any higher.
Carbs were rebuilt, no change.

For what it's worth, I'm not running a battery at all and I'm having those problems.
This machine doesn't have a throttle position sensor.

 

[retiredpop]

This one has me scratching my head. Here's what's up:

• 2008 Polaris RMK 600 with carburetors.
• Sled will start and idle perfectly. But, as soon as I give it gas - up to where the clutch is about to engage - it will die. It's just like I turned off the key - It's not a carb issue - I verified that it's losing spark. Also (the sled has electric start) the battery is not getting charged. Voltmeter on the battery with sled off is 12.4 V, when idling, the voltage goes down to 12.2 V.
• Headlight and cluster gauge lights would flicker on/off/dim, but after a lot of tinkering, that problem has seemed to stop.

Here's what I've checked and/or replaced:

• Voltage regulator - I suspected this first since battery is not getting charged. Bought a used one on eBay - no change
• Stator - measured resistance across all the connections - within spec, but I replaced it anyway with a used one from eBay - no change (kinda' expected that).
• Kill switch/throttle safety switch - I unplugged this, then tried again but saw the same behavior
• Checked all connections/grounds/wires/etc. (including the brake light wire - one post said to check that). No issues to report.
• This sled has a throttle position sensor, however I don't have the tool to check it, but I assume it's working fine. In one test I unplugged the TPS, then tried to start it. It started and idled for just a second, then stopped. So, I plugged it back in.

What else should I check? What am I missing? Thx for any help you can offer!!

It sounds like your TPS may be faulty. You can check it with a volt-ohmmeter. Unplug the wiring connector on the TPS. Set your meter to ohms. Connect the black lead of the ohmmeter to the TPS pin where the black wire of the wiring harness was (it will be one of the outside pins). Connect your red lead of the ohmmeter to the middle connector of the TPS. Move the throttle lever slowly and see if the resistance changes in an even manner with no momentary opens (dead spots). An analog meter works best as it is easy to see if the needle moves evenly.

 

[steyan]

I'll take a closer look at the TPS - thx for the info!

 

[steyan]

TPS checked out ok - there was a smooth change in ohms while squeezing the throttle.

Also, today after some more tinkering I was able to get more RPMs before it would die - but it still dies. Gonna try a different ECU next.

 

[RHODESIE]

i don't think you can unplug the throttle safety switch an expect it to function properly. try removing the switch from the throttle block and tape it in the compressed position. if the ecm does not see that the switch is compressed and it reads higher voltage from the tps it thinks the throttle is stuck.
it will kill the spark then.

 

[zilla]

On a stand or the ground ? Either way ?

 

[steyan]

On a stand - I haven't tried riding it.

 

[TDR]

Sounds like TSS. It will limit rpm to just below engagement.

 

[steyan]

Figured it out - I replaced the ECU with a used one on eBay. Now it runs perfect. Thx all for your ideas!