Slight miss at idle and slight power loss..

[ozkor]

Hi Recently my 1987 115hp Yamaha has developed a slight miss at idle. I noticed that at full throttle it revs out to about 4950 rpm where as it use to rev out to about 5100 rpm. Is something bad developing here - spark plugs were changed about 10hours running ago / 6 months. Where should I look for the problem or am I getting flustered about nothing. It sounds fine when running above idle - no miss that I can tell. Any comments would be appreciated thanks in advance.

 

[hondam]

There a lot of things that can cause 150rpm drop at WOT. If you want to ease your worries do a compression test and spark check.

What I do is I have a nice set of insulated spark plug wire pullers from MAC, I pull one boot off at a time and make sure I hear a difference in they way to motor is running after I pull one off. If you pull off a boot and there is no change in the way the motor sounds then it may not be running on that cyl. Just a little word of caution, I do get Zapped sometimes if im not paying enough attention.

 

[ozkor]

No worries I will give it a try and see if I can hear the change in the motor. Thanks