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Hi all, I have a small problem. My motor starts fine, and runs great until 4100 RPM. At 4100 or above it runs for a few seconds and then dies as if it is out of fuel. I let of the throtel for a few seconds and as lond as I do not go above 4000RPM she will run fine all day. There is half a tank of last years fuel mixed with half a tank of freash fuel. The fuel/water filter is brand new. Any help will be greatly apreciated. Email me back at capj66@adelphia.net Thank you.
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capj66,
Your motor could be going into "rpm reduction" due to overheat condition, but this should be accompanied by your audible alarm. The alarm buzzer could be bad.
You should have a thermo switch mounted in the cylinder assy of both banks that closes at around 180 degrees. I have seen them go bad and close much sooner (130). This will give you an audible alarm and the motor rpm will be automatically reduced by the ignition control until the overheat condition goes away and the thermo switch opens back up.
You can test the alarm by disconnecting the wire between the switch and the power pack ignition, turning on the ignition (do not start motor) and momentarily grounding out the wire to the power pack. This should set off the alarm. If not, then the alarm buzzer/wiring is bad.
You also can test the thermo switches by placing them in water with a thermometer and heating the water and measuring the continuity of the switch with a digital multi-meter. Should close around 180 and re-open again around 160. A Yamaha shop manual explains all of this - get'cha one at yamahapubs.com
Good luck,
Ken K -
You have two fuel pumps on that motor. It kinda sounds like one is bad and one fuel pump alone has a hard time keeping up with a V-6 appetite for gas at high rpm settings. Other than that the carbs may need a cleaning out. Without taking the carbs off the motor you can unscrew the main jets and inspect them for gunk or clogging. The main jets are those brass bolt looking things at the bottom sides of each carb bowl. Inspect the O-ring seal on each jet for deterioration, cracks or otherwise messed up O-ring. If that O-ring is damaged you'll get flooding above mid-throttle settings. Berryman's Chemtool spray (Walmart) is a great carb cleaner to use.
Mike......... Miami, FLComment
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