I have a 2006 660 with 1200km and recently the red reverse light flashes when I'm at top speed in high. Has anyone had the the same problem? I have asked 3 different yamaha dealers and they claim they never had that problem before.
Keith, your friends machine likely needs the idle mixture screw turned out 1/4 of a turn. Run the warmed up machine a few times. If the backfiring continues then repeat the 1/4 turn until it quits. If the total adjustment is more than 1 turn complete turn then the pilot jet needs cleaning or the float level needs adjustment.
On yours, I would pull the spark plug and check the color of the insulator. If it is white or light grey then you are running lean, which makes more power, but too much heat. Ideal color is light brown or tan. If the insulator is black then your rich, but I would leave it alone as you are not suffering from lack of power and the rich condition will help the engine run cooler, thus avoiding the Griz 660 studdering problems.
Keep in mind that some engines just make a bit more power than others. My stock non HO Sportsman 500 beats every stock 500HO sportsman I have raced; my engine is tight where it needs to be and loose where it needs to be.
The flashing light does not put the machine in a limp mode so don't sweat it too bad if the spark plug color is good. The light indicates you are hitting the red line, but these engines can handle more than the red line if they are loaded and it is not for long period of time.
Have not had much to do w/Yamaha....On that 2004, Do they have a electronic throttle positioner & I am guessing mikuni slide carb ? I had a similar problem on a different brand. I fixed, But don't want to go off in wrong direction until I find out answer to my question.
I'm going to tag on, Tweaker mine grizz does the exact same it stumbles in the mud in reverse there is no throttle it stutters like its bouncing off the limiter just by touching the throttle sometimes even after it is out of the mud you have to keep "burping" the flipper so it will "catch" then it's good lots of power it has always done that it sure is a PITA. I always thought of bypassing the limiter and put it on a toggle switch so i can have the reverse light but I just haven't yet, just to see if it would help. I choke it when it's cold but it seems to do nothing always got to be on the gas until it warms up then it will idle by it's self all day long.
Oh and mine is bone stock engine wise
If it does this only in diff. lock then you are on the rev limiter.