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This is a carb engine it has 115 compression on all cylinders. The vacume on one bank is too low to operate the fuel pumps. Motor ran fine the day befoe then the next day on crank up it started this condition. Ideas as to where too look? Someone said the cylinder lower skirts could be scored not allowing vacum but still have compression. Seemed odd but worth asking about.
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there are rings that seal the combution chamber on a 2 stroke, but the crankcase has seals on the ends of crank shaft, seals between the cylinders on the crank shaft, reed valves, and possibly recirculation check valves that may cause sealing problems .
How did you check this vacuum? -
I would check re circulation valves, I chased that monster on my motor, turned out 4 of them had failed , bad production batch , simple test , then move on if it checks out okComment
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I found 3 of the 4 on my c40 bad alsoComment
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Im not sure. It has been at a five star yamaha repair shop for two weeks chasing the problem. I couldnt understand how the lower skirts could score and cause a vacume problem but still have good compression. I will be picking it up today. Y'all have given me a very good advice.Comment
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its cause the tech is chasing ghosts while the rest are twaking wabbits.
that pump needs PRIMARY compression as well as a small amount of vacuum to operate.
trust me if secondary compression is fine the piston is not damaged.
however a FREAKING model number MAY aid in identifying WHAT 225 hp Yamaha is being discussed.Comment
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always remember, mechanical issues do not come and go.
always remember that a two stroke carbed motor has to have both primary and secondary compression.
primary and secondary compression is a function of piston rings.
the skirt just helps stabilize the piston.Comment
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