yamaha g2 no compression

Thimmesch1

just bought a non running 1992 Yamaha g2 4 stroke ,no compression.
took off valve cover and found one of the pushrods loose from the rocker arm and excessive clearance for valves. turns out that the upper valve train is not getting any oil and the rod holding the rocker arms have worn allowing the excessive valve clearance. tightend the valves and now it runs great.
is there any way to backflush the oiling system for the rocker arms/springs?
or why is it not getting oil on the top end?

BGW

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Mike Mac

Take off the steal tube going up the back of the motor (one bolt) blow through it, push a piece of wire through it, soak in solvent, what ever. Then, blow air through the fitting there at the back of the block. To do this, you need to remove the oil fill cap, hold a rag over the oil fill tube,( to prevent oil from coming up through the fill tube, and splashing all over you. (Then I'd change oil before you run it again.) Anyway, replace short oil hoses with 5/16" fuel injection hose, and it should be ok!! I'd also check that upper rocker galley is getting oil after running 5 or so minutes! Hope this works!!

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smallblock450sl

Like Mac said and also check the "check valve" coming from the valve cover. It's a one way valve, so you should be able to blow thru it, but not suck thru it.

sho305

Might just be goo, it takes 1 qt of oil but a lot of people never change it. Iirc oil is supplied from that line behind the head to the top of crankcase that Mike says to clean, the other line on the flywheel side is the pulse line for the fuel pump pretty sure it comes up to the top with the valve so it stays flushed out or oil in it will make the pump stop. The last line is for fumes to go to the airbox and can stink if not hooked up.

Thimmesch1

thanks guys.
will do this afternoon.

Thimmesch1

good call it was the check valve in the tube to the fuel pump.
ordered a new one.
Thanks guys