98 yamaha troubleshooting

[2dwaves]

hi guys new to the forum.
have a 1998 yamaha 2stroke that has the throttle and shifting lever on the outside and you have to manually mix the fuel. the motor will jump up when you throw it in the corner.. but falls on its face within a couple of seconds .. seconds. plugs are good and i tried pumping up the ball and that does not help.. cleaned the carbs (2 ) they look look spotless ,, compression is 105 in both cylinders.. really need help or a way to troubleshoot farther.. engine idles and runs slow like a dream??? thanks guys
Tony

 

[Mas]

Re: 98 yamaha troubleshooting

What horsepower and what boat?

MAS

 

[2dwaves]

Re: 98 yamaha troubleshooting

thanks Mas
it is a yamaha 40 ..does not have oil injection.. and is on 17 foot flat bottom skiff...the motor wants to run. but falls on its face in a couple of seconds..after you jump on it..plugs good,good gas, carbs clean,pump up the bulb doesnt help. idles great, runs slow great, just something not quite right,,hits WOT for a second then bogs down...linkage all going where its supposed to ( I think ). where else would you start looking? fuel pump or electrical??
thanks Tony

 

[cousinabe]

Re: 98 yamaha troubleshooting

while bogging down, does pumping the primer ball help?
if so, could be a bad fuel pump.

 

[2dwaves]

Re: 98 yamaha troubleshooting

seemed like it kinda helped a little once or twice but nothing consistant..now if i pump the ball it doesnt help at all ?? it will pump up solid but wont help.

 

[cousinabe]

Re: 98 yamaha troubleshooting

i just re-read the entire post and i guess i failed to see that you already pumped the ball... duh.
have you tried with an auxillary fuel supply/tank?

more history... when did it last run right?

 

[2dwaves]

Re: 98 yamaha troubleshooting

just purchased it ..the lady I baught it from said it was doing this..fuel tanks are good.. good oil mix .. cleaned the carbs ( thats what I thaught it was ) engine looks spotless and has been maintained..how can I check the electrical?
Tony

 

[2dwaves]

Re: 98 yamaha troubleshooting

right after I cleaned the carbs I ran it WOT. it jumped up and ran great for about a minute then I had to shut it down for a no wake zone and do some work.. ran it slow for the rest of the day ( idleing).. next time I took it out agian shoved it in the corner.. starts off hard then falls on its face.. and thats what its been doing ever since?????
Tony

 

[cousinabe]

Re: 98 yamaha troubleshooting

what is the model number off of the port bracket.

 

[Mas]

Re: 98 yamaha troubleshooting

Is the throttle plate horizontal at WOT?

MAS

 

[2dwaves]

Re: 98 yamaha troubleshooting

yes the carbs are opening completely.. I will get the model number tonight..
I think im pretty mechanical but this one is eluding me thanks guys.. how can I check the electrical.. maybe see if a coil is breaking down or if the timing is correct? maybe the stator??
Tony

 

[2dwaves]

Re: 98 yamaha troubleshooting

hi guys model number is C40PLN1 OR C40PLNT i think its a 1.. sure could use some advice on troubleshooting guys thank you
Tony ps seriel number is 335648 if that helps.

 

[cousinabe]

Re: 98 yamaha troubleshooting

get a spray bottle of premix, while it's acting up see if spraying some fuel/oil mix into the carbs help.
if that helps, sure sounds like your carbs are still fouled up. I would go through them again. clean out the jets, etc.
http://www.boats.net/parts/search/Yamaha/Outboard/1995/C40PLRT/CARBURETOR/parts.html