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Compression on 1964 sportwin 9.5 model 9422s

I'm getting 70 and 65 after 3 pulls.....motor runs really rough , has new coils , points, condensers plug wires,plugs, cleaned carb twice...seems like mixture screw doesn't make much change when idling..... Idles spluttering
 
Dave117 said:
I'm getting 70 and 65 after 3 pulls.....motor runs really rough , has new coils , points, condensers plug wires,plugs, cleaned carb twice...seems like mixture screw doesn't make much change when idling..... Idles spluttering
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This is where you should be looking. If the low speed screw isn't making a significant difference, you have a problem in the idle circuit.

At the very least, you need to pull the low speed screw out, then shoot some carb cleaner into the passageway where the screw was. Follow up with a cautious blast of air to remove the excess carb cleaning fluid.

I have a 1966 9.5 that developed a slightly rough idle (after 2.5 years of silky smooth idling). The above procedure fixer her right up.

CMOS
 
These motors are susceptible to under cover exhaust leaks which affect normal operation. See if it runs differently with the cover removed.
 
Try Bobby's advice, these motors will not run in a testing barrel with the cowling on. I also drill some additional holes under the carb to enhance fresh air intake, make about 4 or 5 at 3/8 inch diameter. Still a problem? Look to see if oil is spattered around the inside of the cowling at flywheel level. Replace the upper crankshaft seal. Occasionally the lower crank seal may fail too (same part number but much bigger job)....depending on how much ethanol it has been exposed to. It has great compression.....not the problem. If that doesn't repair it I will buy you a new motor. Thanks Tim
 
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