Bike won't start due to carbon build-up

[road runner]

This carbon thing sounds like BS to me <_< . Sure it's possible, but very unlikely. You should be able to run at 3500 RPM all day, because it's injected so it should be at the correct mixture. If it's like mine it's lean not rich. I agree running at higher RPM may keep it cleaner, but I don't think you can hurt anything by running it at whatever RPM you want. If there is carbon build up it may be from a sensor not working making it go to rich, or a stuck thermostat keeping it too cool. I've never seen carbon keep a valve from seating, unless it had many miles and the valve seat was way to big, but I have seen the rings stick from what they call coking. As Ionbeam said Yamaha sells ring free to combat this.

It may be down on compression from a mechanical failure like a burnt valve, or a bad CCT let it jump time and bend a valve. I'd do a leak down test to see where the leak is before tearing it down.

Good luck and keep us posted.

 

[HaulinAshe]

Have the dealer perform a basic compression test on each cylinder and record the results. If at all possible, I would insist on being present. Unless you have two or more cylinders reading extremely low (100 psi or less), I'd call BS and get my bike out of there.

 

[charismaticmegafauna]

Have the dealer perform a basic compression test on each cylinder and record the results. If at all possible, I would insist on being present. Unless you have two or more cylinders reading extremely low (100 psi or less), I'd call BS and get my bike out of there.

From the OP:

...The mechanic did call me and tell me that my compression was down in the 60 range and should be at 200.

 

[Bustanut joker]

I might have bought into the carbon build up line of **** thirty years ago when "leaded" gas was available..

 

[JimNtexas]

Yamaha will honor the warrenty, call ther 800 number before you talk to the dealer again. No way can they bail on the warrenty for such a BS reason.

Or better, get a second opinion at another dealer.

Could this be a ground spider issue?