URGENT HELP Please!! 25 yamaha

[speedmo]

Hi<br />I've a 25 Yamaha outboard made in 1990. Well Its a two stroke model as you can guess.<br />4 days ago my dad prepared the gasoline oil mixture as extra rich 2% oil and now The problem is, motor is running on only one cylinder for the past two days. I've replaced the plug cables and found out that both of the cables are capable of bringing electricity but the lower cylinder is not running.<br />I've also changed the plugs and no difference!<br />Please give me your valuable ideas.

 

[Backlash]

Re: URGENT HELP Please!! 25 yamaha

When you say the cables are capable of bringing electricity, do you mean you have spark to the plugs when cranking the engine? How did you determine that "the lower cylinder is not running?" A little more info will help us help you. <br />Backlash

 

[speedmo]

Re: URGENT HELP Please!! 25 yamaha

Well, I did the following experiment to determine the prob.<br />--I unplugged the old plugs and put on the new set. Later on I crancked the engine and found that the lower piston's plug was not working. (the upper plug has some carbon dep. on it)<br />--After Putting on the plugs I took the upper plug cable and put it on the lower plug and observed no response! I also took the lower plug cable and put it on the upper plug and engine worked.<br /><br />I know my explanation is confusing but at the end I found out that lower plug is not working although the cable brings electricity. <br /><br />I need your thoughts..<br /><br />thank you

 

[Backlash]

Re: URGENT HELP Please!! 25 yamaha

Hi Speedmo,<br />I'm a little thick this morning....so I'm still a bit confused You need to check the spark to each plug and I'd suggest the following procedure to do it. Remove both plug wires, remove both spark plugs (optional...just makes it easier to crank the engine over), insert a screwdriver or something similar into one spark plug wire boot and hold the shank of the driver close to the engine block, have someone crank the engine and observe the spark jump from the screwdriver to the block. There should be a crisp blue-white spark that jumps at least 1/2 inch. It's always a good idea to ground the other plug wire(s) when checking the spark. Proceed to the next plug wire and test it the same way. If you have good spark to one cylinder and nothing to the other, switch the coil (the spark plug wire comes out of it) from the good cylinder to the bad and run the spark test again. If the "no spark" condition moves you've got a bad coil. If not, let us know and we'll proceed from there.<br />Backlash

 

[speedmo]

Re: URGENT HELP Please!! 25 yamaha

Hi Captain Backlash,<br />Well I tried your way and found that both of the plugs are working fine. Each cable is sparking at least half an inch. And also they are capable of running the upper cylinder fine. But the lower cylinder is still silent <br />I'm gonna check the following:<br />-- Oil % in the fuel (still it over 1%)<br />-- If there is a prblem with the fueling..<br /><br />Please give me your ideas.<br /><br />Thank you.

 

[Backlash]

Re: URGENT HELP Please!! 25 yamaha

Good to hear you're getting a good strong spark to both plugs. You indicated that you have already changed the plugs (I presume you used new plugs)without improvement. Try taking the spark plug out of the lower cylinder, put the plug wire back on the plug, ground the spark plug to the block, crank the engine and check to see if you're getting a spark at the electrode. If you're getting spark to the plug but not to the electrode, you have a faulty spark plug (easy fix). By the way, you should be mixing your fuel at 50:1 which is the same as 2%. Let us know what you find with the spark plug.<br />Backlash

 

[speedmo]

Re: URGENT HELP Please!! 25 yamaha

Hi,<br />Well, I'm gonna check your solution in an hour and tell you the result but I believe that grounding is the main issue! Is there a correct way to check the proper grounding while putting on the plugs? I mean cleaning the plug or something?

 

[speedmo]

Re: URGENT HELP Please!! 25 yamaha

Hi,<br />I'm here with the latest updates.<br />I have to say that result is negative.<br />I've checked everything about spark plugs and come up a wierd solution.<br />As the motor is cranked it starts running with single cylinder and it hardly accelerates. But If I unplugged the fuel line entering the motorthe second cylinder awakes within 3 sec.! and the performance increases dramatically.<br /><br />Well I found a spare fuel line and replaced it and nothing changed. So its not an issue of fuel line!! I think It may have a vacuum prob. but have no idea about it.<br /><br />Waiting for your help.<br /><br />thanks

 

[45_red]

Re: URGENT HELP Please!! 25 yamaha

Sounds like a classic case of flooding. When you pump the primer bulb does it firm up?

 

[speedmo]

Re: URGENT HELP Please!! 25 yamaha

I'll check it soon. But I dunno what do ou mean by "flooding"? can you open it u a little bit,?<br />Sorry I'm a litle thick today.

 

[jim dozier]

Re: URGENT HELP Please!! 25 yamaha

45_red means that the engine may be getting too much gas or "flooded" with gas. Unhooking the fuel line allows the overich gas condition to temporarily go away and the engine picks up. This is most likely caused by a stuck float valve in one or more carburetors. As a temporary fix, try tapping on the bowl of the carburetor with a plastic screwdriver handle, sometimes that will free a sticking float valve. Usually however that is an indication that the carbs will need to be dismantled, thoroughly cleaned with immersion in carb cleaner, blown out with compressed air, and new parts (rebuild kit) installed with emphasis on replacing the float valve. You need to acquire a manual for this engine.

 

[speedmo]

Re: URGENT HELP Please!! 25 yamaha

Hi,<br />Today I dismantled the part which pumps the fuel from gas tank to engine. (well I really dunno the name of the part) Well this part has a vacuum hole in it and a diaphram positioned just over it. I figured out that the diaphram is teared off and will replace this soon. I believe that is the cause but we wil see soon.<br /><br />what do you think?

 

[speedmo]

Re: URGENT HELP Please!! 25 yamaha

any comments?

 

[jim dozier]

Re: URGENT HELP Please!! 25 yamaha

A leaking fuel pump diaphragm does 2 things. It won't supply an adequate amount of fuel to the carbs and since it is run off crankcase pressure you may be sucking air into the crankcase leaning out your air/fuel mixture. Either way it would cause problems and needs to be fixed.

 

[jim dozier]

Re: URGENT HELP Please!! 25 yamaha

A leaking fuel pump diaphragm does 2 things. It won't supply an adequate amount of fuel to the carbs and since it is run off crankcase pressure you may be sucking air into the crankcase leaning out your air/fuel mixture. Either way it would cause problems and needs to be fixed.

 

[jim dozier]

Re: URGENT HELP Please!! 25 yamaha

A leaking fuel pump diaphragm does 2 things. It won't supply an adequate amount of fuel to the carbs and since it is run off crankcase pressure you may be sucking air into the crankcase leaning out your air/fuel mixture. Either way it would cause problems and needs to be fixed.<br /><br />Sorry speedmo there was a glitch on the forum posting this afternoon. Wish my ATM acted like that.

 

[speedmo]

Re: URGENT HELP Please!! 25 yamaha

case solved, problem is the faulty regulator that I mentioned.

 

[Backlash]

Re: URGENT HELP Please!! 25 yamaha

Glad to hear the problem is solved.......but what regulator..........?<br />Backlash

 

[speedmo]

Re: URGENT HELP Please!! 25 yamaha

A leaking fuel pump diaphragm was the problem