Nytro,wont run fine

[Crisse55]

The nytro will start right up when cold,will idle fine for a few minute,after a few minute it will start to missfire,If i touch the throttle it will either rev fine or stall.After arround 5minute of driving it wont idle at all and if i keep driving it for about 20minute backfire are alot worse and i wont be able to start it back until i wait arround 30minute to let the sled cool down.i've changed the 3 ignition coils with brand new one,new plug,new gas,new gas filter,bypassed tors.When it wont start and i keep cranking the engine for like 20-30 sec i have a fuel smell from the exaust.
Compression test was 205psi-210psi-215psi.Fuel pump is working,the only code im getting is 81 and 81 is for the grip warmer,tps show 16-96 on diag mode.Sled has also 33,720 killometer(21k miles)

I bough it in summer and i've only seen it running for like 30 second,seemed like it was running fine,but it wasnt the case,i couldnt test drive it back there was no snow and snowmobile are cheaper in the summer.Paid 3200$ cad for it i've been trying to fix it for the past 3month and i cant figure it out.I would appreciate some help from here thanks you

 

[Norse]

Could be limp mode because of the grip warmers. Happened to a friend of mine last season.

 

[grizztracks]

Crank sensor could be heating up and failing which causes a poor idle. On some engines I've been able to run cool water on the sensor and the idle smooths out.

 

[Crisse55]

Where is the crank sensor located?

 

[grizztracks]

back left side of engine. You can see it to the left of the oil filter.

 

[Norse]

Any luck?

 

[Sno-Xr]

Id like to know too, as Im having a very similar issue with mine. It will act up after only a minute of running, or after 15 minutes!?! Very persistent, but very random at the same time!
Searched for rub throughs, tried a used regulator/rectifier, unplugged hand warmers and headlights, ohm'ed the stator, unplugged the stator......ive stripped this thing down more times than a 5 dollar lap-dancer over the last week!! Figure it out and let me know!
Seriously, good luck

 

[Sno-Xr]

Crank sensor could be heating up and failing which causes a poor idle. On some engines I've been able to run cool water on the sensor and the idle smooths out.

Grizz, would the crank sensor act up as quickly as a 60 seconds of cold start running? Or would this be more of a warmed up situation? Also, would the sensor cause the random codes to pop up....mine is mostly the hand warmer code, but has also thrown the low oil icon a few times.
Mine also seems to drop voltage at the battery when it is acting up. It will go from 14ish down to battery voltage of around 12.8V Ive disconnected the stator and still had the warnings and codes kick on with a fully charged Battery.....so Im somewhat confident its not the stator. Really thinking mine has a short causing a major voltage draw somewhere.

 

[Crisse55]

I sent my nytro at the yamaha dealership and they couldnt find the problem,Stator was good,cdi was good,valve were good,coils were good too....Im still facing the same problem,They told me if it was the crank sensor the sled wouldnt fire up and the sensor would throw a code when it stop working.Mine act up after one minute or two and get worse and worse until it backfire and wont start for like an hour

 

[Sno-Xr]

Thats not what I wanted to hear!! You were supposed to have the solution to the problem so I could get my fixed! Haha
Good luck, and i will let you know if I come up with anything

 

[grizztracks]

I sent my nytro at the yamaha dealership and they couldnt find the problem,Stator was good,cdi was good,valve were good,coils were good too....Im still facing the same problem,They told me if it was the crank sensor the sled wouldnt fire up and the sensor would throw a code when it stop working.Mine act up after one minute or two and get worse and worse until it backfire and wont start for like an hour

Crank sensors don't always completely fail. They can be bad but still work well enough to sense the engine position and allow it to run. There have been many reports of a failing sensor causing a poor running engine. It's not a cheap part but if the dealer can't help I'd be looking at changing it out to at least eliminate it as the cause of your issues.

Here is a video of a Harley that came to me last summer that wouldn't idle when warm. Ended up being a failing crank sensor.
(Sorry for the poor video, I was trying to record and test it myself)

 

[grizztracks]

Grizz, would the crank sensor act up as quickly as a 60 seconds of cold start running? Or would this be more of a warmed up situation? Also, would the sensor cause the random codes to pop up....mine is mostly the hand warmer code, but has also thrown the low oil icon a few times.
Mine also seems to drop voltage at the battery when it is acting up. It will go from 14ish down to battery voltage of around 12.8V Ive disconnected the stator and still had the warnings and codes kick on with a fully charged Battery.....so Im somewhat confident its not the stator. Really thinking mine has a short causing a major voltage draw somewhere.

multiple codes being displayed quite often ends up being a wiring issue. When I've seen it happen it's usually a ground issue and more than once it was the ground splice connector burnt. I always go to those connectors first. The last one I worked on with a splice problem started as a hand warmer issue then progressed to no lights and troubles restarting the engine.

 

[Sno-Xr]

multiple codes being displayed quite often ends up being a wiring issue. When I've seen it happen it's usually a ground issue and more than once it was the ground splice connector burnt. I always go to those connectors first. The last one I worked on with a splice problem started as a hand warmer issue then progressed to no lights and troubles restarting the engine.

This is definitely the direction that I have been lead, but having a hellavu time finding a problem with any of the wiring. The ground blocks Ive found all look great. Ive even pulled the spider and added dielectric to each to help keep them looking good. Ive added a ground from the battery to the frame and another from the frame to the motor. Ive stripped the sheathing from several feet of the harness including many of the common rub thru areas!
Stumped!

 

[grizztracks]

Sno-Xr, how old is the battery? I've seen batteries check ok but still have issues that cause running problems.

You can also check the resistance of the crank sensor. I'd check it cold and hot.

 

[grizztracks]

Pulling the stub shaft and checking to see if the reluctor gear slipped my also be a good check to at least eliminate that as a cause. The crank sensor reads off of the reluctor and if it slipped the ignition timing will be off causing the engine to idle and run poorly. We've been seeing this more and more lately.