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89 Yamaha moto 4 250 wont start

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Old Mar 10, 2025 | 09:16 AM
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Default 89 Yamaha moto 4 250 wont start

I just had to replace the cdi magneto. Pulled off the old one and installed the new one. It turns over but does not fire. I have spark. I have fuel. Did I inadvertently get the timing off?
 
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Old Mar 11, 2025 | 02:58 AM
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I have heard of the pulse coil wires being fitted backwards which throws the timing off. So long as the new stator is for the same model as the old one, that is just about the only way timing can be got wrong. If you think this may be your problem, connect them the other way round at the stator plug and see if the bike then starts.
 
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Old Mar 11, 2025 | 08:41 AM
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Default 89 Yamaha moto 4 250 wont start

Thanks, merryman. Actually I got it started. After reassembly, if wouldn't start so I pulled the plug to check for spark. I dropped the plug, picked it up and put it in the wire. I had spark but didn't notice it had landed on the tab and bent it almost closed. After another round of trying to start it again I pulled the plug and checked spark again and noticed the spark was small and weak. On closer inspection I saw the tab almost closed. I gapped the plug to specs and it fired right up.

Thanks for your help.
 
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