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50 hp yamy carb problems

Z

zimnucks

Contributing Member
Ive got a 50 yamy 4 stroke and the carbs are doing my head in , ive cleaned them 3 times and still the motor is not running on all 4 cyl at idle . If I spray ether into the intake she fires up so it has to be carbs , anybody got an online manual or the specs for these carbs ?
 
With engine idling use an insulated plug wire pliers and remove one wire at a time untill you find the cylinder that does not change the idle when the wire's pulled. That is the problem cylinder. Does it have a carb for each cylinder?
 
I thought I had similiar problem with my 50hp 4 stroke 2000 model. I adjusted the idle and mixture screws until the motor idled smoothly again. The only thing is I can not get it to idle at 800rpm now. it is more like 1000
 
Even though you've cleaned the carbs several times, it's easy to overlook a small port that could still be clogged. When you cleaned the carbs, did you use carb cleaner and then blow everything clean with compressed air? If you have strong, steady current going to the plugs and electrical system otherwise OK, then it pretty well has to be a carb or fuel delivery system issue. When you sprayed ether into the carbs, it would have increased the RPMs and perhaps given you the impression that it smoothed out. Also a worn crankshaft bearing can cause a crankshaft wobble that generally shows up as rough idle and goes away at higher RPMs.
 
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