Motorcycle Repair: 1987 yamaha pw 50, yamaha pw 50, 2 stroke motors

Question
good spark carb clean and working. the oil injection
thing,what can go wrong with that or can it be deleted or u
think another reason it wont start?  thankz   darrin

Answer
Darrin, I don't know a lot about a PW Yamaha 50, but I do recall that they had an unusual handlebar switch to KILL the engine, I think.

For the engine to run, you have to have:
Fuel... metered at the right amount at the right time
Spark... Strong spark at the right time. CDI system modules can go sour.
Compression... at least 100psi I imagine.

http://www.cmsnl.com/yamaha-pw50s-1986-1987_model9235/partslist/ for illustrations of the parts on this bike.

Don't blame the oil-injection for non-starting issues.

With 2 stroke motors, they can seize their pistons, break rings, suck oil in from the transmission side of the crankcase, suck AIR in from behind the magneto seal. Seized pistons/rings will lower compression drastically, causing non-start issues. Remove the exhaust pipe and look at the condition of the piston as it moved back and forth past the exhaust port.  Or pull the cylinder head and check for any signs of scoring or deep scratches from seizures/ring breakage.

Bill MrHonda Silver