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Old 01-08-2020, 12:21 PM   #1
jdt162
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Default G14 Runs great when cold but then won't rev up

I have a Yamaha G14 gas 4 cycle golf cart. When I start the cart (cold) it will run great for about 5-10 minutes. After that, whenever I let off the gas and bring the RPM's down to where the engine shuts off, it doesn't want to rev back it. It turns over, it just won't rev it. If I press the gas pedal very gradually, I can sometimes get it to run again. Once (if) it gets back to full throttle, it runs fine again. I've already replaced the fuel lines and fuel pump but this didn't solve the issue. What baffles me is that it runs great when cold which would lead me to believe the carburetor is fine. It also ran great for the weeks prior to it having this issue so it's not like it was sitting for a while. If I let it sit for a little while, it will run fine again for 5-10 minutes and then the problem returns.
Before I replace the ignition coil, I wanted to see if anyone else had any suggestions. I've read quite a bit on this site for the past 2 years and I appreciate all the help so far. Thanks!
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Old 01-08-2020, 12:35 PM   #2
mozzer
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Default Re: G14 Runs great when cold but then won't rev up

Does it need choke to start when cold or is it starting & running with no choke from cold?

First thing would be to check the colour & condition of spark plug that will give an indication of whether mixture is rich or lean.

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Old 01-08-2020, 12:42 PM   #3
CP241
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Default Re: G14 Runs great when cold but then won't rev up

Carry an extra spark plug with you. When it dies, quickly pull the wire off and plug it into your spare plug, hold the plug against a valve cover bolt and crank the engine. Report back IF there is spark, and if there is, what color it is
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Old 01-08-2020, 03:44 PM   #4
jdt162
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Default Re: G14 Runs great when cold but then won't rev up

It starts WITHOUT using the choke. I will check the plug again but from what I remember it looked decent. Not wet black or whiteish at all.

Ok, I will pick up another plug and see what it does when switching it out hot. Thanks for the tip!
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Old 01-08-2020, 04:10 PM   #5
CP241
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Default Re: G14 Runs great when cold but then won't rev up

My initial suspicion is a failing ignition coil. Chances are when it gets hot you'll either have a weak white or yellow spark, or no spark at all
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Old 01-08-2020, 04:29 PM   #6
raydhd
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Default Re: G14 Runs great when cold but then won't rev up

Just bear in mind the G 14 has a fairly complicated ignition system consisting of the coil,the pick up and the ignitor. The ignitor is the "brains" of the system and somewhat expensive.
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Old 01-09-2020, 07:59 AM   #7
jdt162
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Default Re: G14 Runs great when cold but then won't rev up

Ideally the spark should be blue, correct?

I was not aware of the ignitor component but have since looked it up and you are not kidding on the price (almost $300!). What would be the symptoms of a failing ignitor?
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Old 01-09-2020, 08:40 AM   #8
slonomo
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Default Re: G14 Runs great when cold but then won't rev up

Quote:
Originally Posted by jdt162 View Post
Ideally the spark should be blue, correct?

I was not aware of the ignitor component but have since looked it up and you are not kidding on the price (almost $300!). What would be the symptoms of a failing ignitor?
Usually a failed ignitor (aka CDI) will not make spark at all. However, they are usually "potted" components and can be affected by heat. I have also seen them act up at a certain rpm range.

If you hare having ignition issues, first start with all the basics. Spark plug, coil, wiring, connections. If you cannot find the issue, the CDI is usually the suspect.

Beware of cheap ebay cdi units. They are known to be low quality, problematic, and often are not returnable. For CDI units, stick with factory parts.
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Old 01-09-2020, 09:14 AM   #9
CP241
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Default Re: G14 Runs great when cold but then won't rev up

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Originally Posted by slonomo View Post

If you hare having ignition issues, first start with all the basics. Spark plug, coil, wiring, connections. If you cannot find the issue, the CDI is usually the suspect.



One step at a time. Start simple and don't overthink it or just start ordering parts hoping it will work.


Yes, the spark should be fat and blue. Might be worth comparing the spark when the engine is cold (and runs) to what it looks like when the engine is hot and it dies.

Something else I've done that's been helpful, is hook a timing light up to the spark plug wire and run the motor. Don't worry about timing marks or etc. just watch the light flashing its pattern. run the motor until it dies and you can see the light flash get erratic or disappear completely. Sometimes this can be helpful if you've got one that runs and dies, but then once you stop you can hit the pedal and go again for a while.
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