Yamaha f115 1000 RPM Miss

[patbalmos]

2005 Yamaha has a miss at 1000 RPM or below. It does not do it all of the time and it seems to run fine in the upper rpm range. Primer bulb is hard, Just had injectors cleaned, Cleaned VST 50 hours ago, Checked TPS voltage with multimeter and test harness, Tested low pressure fuel pump, Checked both fuel filters. Everything seems tight. What's next? check fuel rail pressures? I need some ideas.

 

[BaileysBoat]

Re: Yamaha f115 1000 RPM Miss

Are you using ring free?

I would do a compression test and de-carbon, then look for an vacuum leak using propane.

Are you getting full power and reaching normal WOT rpm?

 

[patbalmos]

Re: Yamaha f115 1000 RPM Miss

Yes full power and normal wot rpm. No ring free used. Motor has 50 hours on it since a rebuild, so it should have no carbon build up. Yes I have done a vacuum leak test

 

[patbalmos]

Re: Yamaha f115 1000 RPM Miss

I ran a compression test today top cyl was a little low at 135-140. All other cylinders were 150. What kind of gauge can i adapt to measure fuel pressure? and where can i get a screw on schrader adapter to hook it up?

 

[multimech]

Re: Yamaha f115 1000 RPM Miss

Question: Did this start to occur around the time it was rebuilt?

Those compression numbers are near being a problem. Do a leakdown on the cylinders instead of a compression check. It is far more accurate.

My guages are all shop tools sent by the different manufacturers, I will check the special tools book to look for the shrader adapter for you.

 

[patbalmos]

Re: Yamaha f115 1000 RPM Miss

Yes I will try and do a leakdown test tonight the compression of no 1 does bother me. The motor has run great up till now after rebuild.