nytro stumble at idle

[rage man]

at the end of last season my 2009 rtx se had roughf idle an hard start would even shut off at idle an backfire sometime ran fine down the trail dads apex stared doing this 2 seasons ago an has gotten worse over time anyone have any thoughts ?

 

[09nytro]

I would pull air box out clean any oil out and try some new plugs first and check the wiring harness and plug for rub thou or corrosion

 

[sorenson1610]

What fuel are you using? Check plugs also

 

[dubla92]

Exhaust donuts.

 

[apexmcneil]

donut gaskets would make it do this becuase why??? back pressure?? Do the yamahas like back pressure???

 

[dubla92]

With blown exhaust donuts the scavenging effect of the exhaust is diminished and the engine does not "flow" correctly. The efi and general runability of the sled is set with a sealed exhaust system that scavenges correctly. As soon a the donuts start to leak a change in how the sled runs at idle and wot are noticed. Do a search on blown exhaust donuts and you will see a pile of complaints exactly like yours. No yamaha 4stroke idles or runs well with blown donuts. Many complain of backfiring and decreased power.

 

[raginyamaha]

dougnuts are a good place to start.... plug exhaust with rag while running and see if the engine dies. if it doesnt youve got bad dougnuts...

 

[rage man]

exhaust dounts are are all new like 500 km on them an there not leaking but this seem to star after i did the dounts i needed the extensions off the motor too an my 3into one was cracked i needed to buy one of thoes too an i drove it for quite abit before i replaced all this an bout 250km after that this started...

 

[rage man]

exhaust dounts are are all new like 500 km on them an there not leaking but this seem to star after i did the dounts i needed the extensions off the motor too an my 3into one was cracked i needed to buy one of thoes too an i drove it for quite abit before i replaced all this an bout 250km after that this started...

 

[upei93]

I wonder if your mid pipe or manifolds are cracked?? I'm getting a mid range stumble which got worst as the season went on and thats what i'm thinking is wrong with mine. I have the copper donuts and the rag still stalls it but I also have the excell header which is prone to cracking.

 

[bottlerocket]

TPS out of adjustment?

 

[yamadoo]

Idle stumble I would start simple fuel-?gummed up throttle bodies etc, plugs, make sure not simple first
My two cents

 

[nate007]

One other thing to check would be the idle system. First, listen for the stepper motor to run when you turn the key on as it sets the idle solenoid into position before starting it. If the stepper motor doesnt make any noise, start checking the wiring for corrosion, or possibly a bad idle solenoid.
Second, take a very close look at all of the hoses that are attached to the throttle bodies, as one of them couldve come off or have a cut/tear etc in it. The idle circuit adds air for idle operation behind the throttle blades, and if its sucking too much air when you open the throttle, the stumble could be caused by a lean condition as well. Might be best to pull the tank off to inspect from the engine side to allow for a better angle to look at everything.