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98 Yamaha 60 2/ intermitently dropping bottom cylinder

S

steve n

New member
As completed so far;
New fuel pump, checked all hoses
Removed and cleaned carbs
Replaced all 3 plugs and HT leads. Checked for spark - all creating spark
New fuel primar and tank.
Pressure on 3 cyclinders is 140. This drops to 120 following fault
New Battery

Hard to start - will not until fast idle is engaged
Runs fine for a short while then bottom piston drops out. Spark plugs in top 2 cylinder chared and black. Bottom spark plug oiley and "wet" rotated plugs identical problem occurs.
Bottom cylinder when first removed during visual inspection was clean, however the bottom carb clogged with petrol/water goo.
Have noticed problems with manual primer bowl, seems to be soft and did go flat once during sea trial. Clean dry petrol used, new tote tank installed.

When running on 3 good pickup out of the hole, very little smoke.

Engine hours approximately 112 engine in avergae to good condition, clean but had sat (with cowel on) for a period
 
Check to see if spark will jump a gap of 7/16" ( 8 MM ) on all 3 cylinders.-------Sounds like a weak coil.------------You can also put a timing light on the bottom cylinder and see how spark behaves.
 
Cool checked with timer all ok
Will look into 8mm gap
Am also replacing fuel pump as diaphragm may be leaking...

Awesome thanks for the help/guidance
Steve
 
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