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2002 xlrta 50 yamaha

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kebees4

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I have a 50 hp 2 stroke that runs great until it hits 4100 rpm and then starts breaking up or misfiring. I took carbs apart and they looked great. Anyone have any tips to look for could you help me out?
 
Does it help to pump the primer bulb when this happens? Can you isolate a particular cylinder? How are all the coil grounds and primary connections? Is the tach original and set on 6 pole?
 
PBRMAN said:
Does it help to pump the primer bulb when this happens? Can you isolate a particular cylinder? How are all the coil grounds and primary connections? Is the tach original and set on 6 pole?
Click to expand...

I pumped the primer bulb thinking fuel pump and it didn't help. I switched to a new tank of gas to eliminate fuel. Tach in original and never been touched. I haven't checked ground wires. It has new plugs and don't know what cylinder is the one. It has always ran good and just started this.
 
See if you can isolate to a cylinder. Possibly a coil. If you find it is only one cylinder affected you can swap primary and secondary leads with another cylinder to see if the problem travels or stays. Otherwise you need to start diagnosing charge coil and pulser coils.
 
PBRMAN said:
See if you can isolate to a cylinder. Possibly a coil. If you find it is only one cylinder affected you can swap primary and secondary leads with another cylinder to see if the problem travels or stays. Otherwise you need to start diagnosing charge coil and pulser coils.
Click to expand...
What is the easiest way to do this?
 
Your model number is not one that I recognize. I assumed 2-stroke, in which case there are some other things to eliminate first. So, is there an F before the model number or no?
 
Go to your hardware store and buy some plastic fuse puller pliers. Tie off your boat really well to the dock and run it up until you hear it start breaking down. Pull plug wires and see if a particular cylinder seems affected. See what the spark looks like on all cylinders under load. Clean all your coil grounds and primary wire connectors.
 
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