1994 115hp v4 idle problems

scottoz

Seaman
Joined
Oct 26, 2003
Messages
53
Hi all - I just got this motor. It ran fine on old, and I suspect, lower octane unleaded. I put in a new high micron rated fuel/water filter seperator (CAV Delphi), new fuel line and fittings. It ran fine before I did all this. I then went and put a belly full of 98RON high octaine unleaded in and out I went. Ran beautifully cold and hot on the plane, but brought back to idle it missed every few seconds but did not stall. I have a feeling that the high octane might be responsible. To hedge my bets, has anyone used carby cleaner in fuel with any success?<br /><br />Cheers all :confused:
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 1994 115hp v4 idle problems

hello<br /> I dont knoiw about your side of the world but on our sied that motor is designed to run on 87 octane. 98 octane will actually reduce the power.you may have dislodged some trash which is now in the carb fuel bowels. if so you will need to get it out.leave the carb cleaner out of the fuel. it will cause more problems than it will cure. you may try turning all the idle mixture screws out by 1/8th to 1/4 of a turn. I assume this miss also sounds like a cough. if it does its called a lean sneeze :) :) <br /> good luck ,leave the 98 octane to the bench racers and airplanes and lets all go fishing
 

scottoz

Seaman
Joined
Oct 26, 2003
Messages
53
Re: 1994 115hp v4 idle problems

Thanks mate - 2 things; why would high octane cause crap to get in the carbs and secondly why would it be in the float bowls and not the idle jets?<br /><br />Cheers<br /><br />PS. Thanks for the assistance.<br /><br />PPS. Yamaha Australia has since e-mailed me and said leave off the high octane and that the high oct could be the cause of the problems
 

scottoz

Seaman
Joined
Oct 26, 2003
Messages
53
Re: 1994 115hp v4 idle problems

Rodbolt - I would appreciate you thoughts
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 1994 115hp v4 idle problems

Hello<br /> Gday mate<br /> or somethiung like that.<br /> I dont think the high octane broke anything loose. I think something may have broken loose while you were cutting/cleaning and messing with the lines. octane rating is a very misunderstood thing. basically octane is the ability of the gasoline to resist uncontroled burning called detonation.but the higher the octane rating the slower the fuel burns. the slower it burns the less power is availible for the same compression and piston speeds.remember we can control when the fire lights just not when it goes out. if the motor still coughs at idle move the fuel idle mixture screws counter clockwise 1/8 to 1/4 turn if it improves do it again.<br /> good luck and keep posting
 

scottoz

Seaman
Joined
Oct 26, 2003
Messages
53
Re: 1994 115hp v4 idle problems

thanks mate - i will give the idle mixture screws a go because when I started it cold yesterday it backfired and then ran with a distinct miss and cough. I just think that it is odd that it would be doing that when I haven't played with the mixture - I suppose it could well be a blocked jet, but I will deal with the easiest thing first.<br /><br />Cheers again.
 
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