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1988 Yamaha 350 moto 4 backfiring through carb


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Hello everyone. I have a 1988 350 moto 4 that starts and idles great. My problems is when I try to rev the engine it just dies. If i ease on the throttle it will rev but it sputters and will backfire through the carb. I have cleaned the carb and put in a new spark plug. I did notice the spark was orange and looked a little weak. Any help would be greatly appreciated. This thing has me ready to pull out the rest of my hair!

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Timing could be off, valves may need to be adjusted, you may need to clean the carb better. Did you make sure EVERY little passage was clear, how did the gaskets and diaphragms look? You might also check the coil wire for damage and make sure it has good contact with the plug boot. Also, check for any damaged or loose wiring in the ignition system, this includes any switches. Lastly, there are some direct resistance tests you can do to check the ignition components using a multimeter. If you don't have a repair manual, I would strongly recommend getting one, it will have all of the specs for the ignition tests as well as valve clearances and other critical info you will need to properly maintain your machine.

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