P750 engine running on one cylinder (occasionally)
The problem could be everything from
pick-ups (quite rare)
incorrect pick-up clearance to flywheel (air gap)
pick up wiring (can break where it enters the engine cover. The pick-ups will measure the correct resistance if a wire isn`t completely broken which makes it tricky)
ground connection to CDI units
CDI units (quite rare)
wiring to the coils (kill switch, ignition switch)
coils
spark plug (HT) wires
spark plugs, incorrect electrode gap
carb synchronization
HT wires can age and if a coil has cracks in the housing it can be affected by temperature or humidity.
The most common problem though is the wiring with bad connections and old wires with copper rust.
Measure the voltage at the coils and CDI units (orange wire) and if it isn`t nearly the same as the battery voltage clean the kill switch and all electrical connections (specially the main ground connections) then do the wiring mod.
https://app.box.com/s/waxvk1l9g47phfybd6n9
One indicator of low voltage at the coils is if the dropped out cylinders kicks in when rpms are increased.
Electrical resistance of bad connections does increase with heat btw.
To rule out parts like CDI units or coils swap them from one cylinder to the other (one part at a time) then see if the problem shifts to the other cylinder. If the problem remains the same the parts swapped are ok and the problem is somewhere else.
If the issue remains check compression and valve clearances.
