Rough Idle 115 Yamaha

[chmerr]

I just purchased a used 2001 115 yamaha with only 59hrs on it. I changed the plugs and the old one's were dirty but not too bad. The motor purrs like a kitten any where above 1500-2000. Below 1500 it is rough and around 1000 it really spits and sputters. Seems to run too rich at idle. Is this something I should mess with or let the mech. take care of. Any help is welcome.

 

[jim dozier]

Re: Rough Idle 115 Yamaha

Spitting and sputtering sounds more like a lean condition. Regardless, you can pin it down more, try choking it manually (is this a carb or EFI model) partway and see if the idle improves. If so, you can try richening the idle mixture screws 1/4 turn (here's where you need a manual-some screws unscrew to richen (bleed in fuel), and some screw in to richen (bleed in air)).<br /><br />If twiddling the idle mixture doesn't work you may need to rebuild the carbs with particular attention to the idle circuit orifices and the float valves which may be stuck open or shut.<br /><br />Also pull the plug wires 1 at a time (best to ground the loose wire) and check for any cylinders that aren't firing at idle. If the offending cylinder is attached to the fuel pump you may want to check the diaphragms in the fuel pump for leaks.