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An engine that's not been turned over in 4 years should be fine, but it depends how it's been stored. If it's been stored inside with a dry ambient temperature, then great. If it's been outside in all weathers, then you've possible condensation to contend with, etc. Basically you're going to have to service it.
First things first. New fuel. That means draining fuel lines and tank, including a new fuel filter on the engine. These Optis use specific DFI oil, so check levels. Conventional TW3 2-stroke oil is no use. Interesting link here on servicing the fuel pump:
Next battery. Put on trickle charge and check voltage. Could start first time, but might take a few attempts for it to kick into life. One word of warning, turn the ignition for only short bursts or you'll burn out the starter motor. The toothed belt should probably be changed too. Visual inspection is no use.
New spark plugs. Grease thread very lightly and don't over-torque when tightening. I'd be inclined to squirt a little DFI oil into the cylinder bores and turn over briefly without the spark plugs (use a rag to towel to stop oil spraying out). Check the cylinders with a torch to gauge condition.
Renew the impeller, new gear oil and lube the drive-shaft Lube the gear linkages too.
Run a length of strimmer wire into the tell-tale. Sometimes it may block with sediment if it's been sitting idle, especially after 4 years.
I'd also be inclined to check the thermostat. You'll need a new gasket. The thermostat can be cleaned with a soft bristle copper wire brush and lightly lube rubber with marine grease. You can test in a pan of boiling water to check it opens.
Connect up muffs, then start it over.
Sula
Eastern Thunder
Northern Exposure 5
BLACK PIG
Piglet
