Yamaha Big Bear 350 won't start


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Old 01-30-09, 06:57 AM
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Yamaha Big Bear 350 won't start

I have a 98 yamaha 350 big bear that won't start. Prior to it not starting it would just shut off without any warning. It would start pretty easily and then have no problems for a while. I checked to see if there was a clogged fuel line and it is ok. Air cleaner looks ok too. I have yet to pull the plug wires and check for a spark. I am leaning toward this though as to the being the problem. Do these machines have spark solenoids or something and where are they. If anyone has links to repair manuals it would be appreciated. thanks fitzy67
 
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Old 01-30-09, 11:11 AM
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It could a coil or CDI box. Both have been known to cause problems. The spark is the first thing to check. Pull the plug wire and put in a known good plug, ground that to the engine head and crank it. You should have a bright blue spark. Anything else is prone to cause trouble.

If no spark you have the coil, CDI box, stator, and a few other things as possibilities. Usually a bad coil won't start back up until it cools a little. CDI boxes, though, do just about what ever they want.

To find the coil, just follow the lead wire back from the spark plug.
 
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Old 01-30-09, 04:12 PM
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No spark,

I pulled the plug boot off and tested it with a spark tester and had no spark. I now have the coil off. How do I test to see if it is the coil or the other parts you mentioned?

Originally Posted by marbobj View Post
It could a coil or CDI box. Both have been known to cause problems. The spark is the first thing to check. Pull the plug wire and put in a known good plug, ground that to the engine head and crank it. You should have a bright blue spark. Anything else is prone to cause trouble.

If no spark you have the coil, CDI box, stator, and a few other things as possibilities. Usually a bad coil won't start back up until it cools a little. CDI boxes, though, do just about what ever they want.

To find the coil, just follow the lead wire back from the spark plug.
 
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Old 01-31-09, 06:22 AM
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You would need an ohm meter and the resistance values for that coil. A lot of times the coil gets a break in it and loses the continuity through the windings. Just checking through the two leads for continuity will often tell you if the coil is dead.

The resistance through a coil that shows no break is a little iffy at best, though. When cold the resistance may be within specs, but as the windings heat up during service that resistance goes up and the coil fails. That type of diagnosis problem can exist with any electrical component. Equipment designed to load the electrical component in testing works the best.

In small engines a common way to check for a failing coil is to replace it with a known good coil - either used or a new one kept back for that purpose.

The CDI box testing, I can't help you with. I have yet to use or see a method for testing those things. My view on it is with the expense of the part involved someone on the parts supply end should be obligated to provide that testing.

The stator and signal coil can be checked with an ohm meter (same drawbacks apply). Those specs should be in a service manual, if not, call a parts supply for those resistance values.
 
 

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