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post #1 of 5 Old 06-22-2019, 09:45 AM Thread Starter
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G12 loses power

Have a G12 that starts and runs good for 20 minutes to half hour then loses power and sometimes won't run. It will restart after sitting for a couple hours then same sequence. Checked gas flow, adjusted carb, cleaned engine fins, and no change. What else should be checked?
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post #2 of 5 Old 06-22-2019, 10:24 AM
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Re: G12 loses power

It could be the ignition coil is failing after it gets hot enough..next time it stalls ,check right away to see if it has spark...if it has points,a failing condensor can do it also..

Could be vapor lock if any of the fuel hoses or carb,fuel pump get hot enough to boil the gas into a vapor too..check the fuel flow after it acts up..old hoses may have inner linings that are loose from ethanol and can restrict flow of gas when they get warm...

The valves might not have enough lash,after they heat up they expand and might stay slightly open enough to make it lose power and eventually stall..this is probably the least likely cause but it can happen..


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post #3 of 5 Old 06-22-2019, 08:31 PM Thread Starter
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Re: G12 loses power

Stupid question maybe. But can I try an automotive coil on it to see if it works of not? Or is it that specific?
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post #4 of 5 Old 06-23-2019, 01:12 PM
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Re: G12 loses power

I would drop the bowl on the carb and clean it. Next, clean the points. See if it recurs.

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post #5 of 5 Old 06-24-2019, 07:42 AM
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Re: G12 loses power

Pick up an in-line spark tester so you can verify if you're losing spark or fuel when it shuts off. If you have spark than you may be losing fuel pressure when it gets hot, if you don't have spark than the coil is breaking down when it gets hot. If you're losing fuel pressure than I suspect your fuel pump is failing or you have an issue with vapor lock. Gravity feed the carb to see if the problem goes away. If the issue is resolved than replace the fuel pump. If you have no spark than replace the ignition module, it's specific to that engine so you can't just use some random off the shelf part.

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