2-stroke 90hp: check valve orientation in crankcase cover

dandreye

Petty Officer 2nd Class
Joined
Oct 19, 2007
Messages
141
Hello All,

In my 3-cyl 2-stroke carbed Merc 90hp made in 2000/01 there are 3 tiny metal check valves each with a nylon ball inside. They reside in black plastic holders installed in the crankcase cover (each at the corresponding crankshaft bearing).

Can someone please confirm which way their single hole must face and what exactly they do as the piston goes up and down? Seems like we put 2 of them the other way round by mistake and those 2 cylinders don't work. Everything else looks perfect (brand-new ignition, good compression, etc.).


Many thanks in advance,

Dmitriy
 
Last edited:

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: 2-stroke 90hp: check valve orientation in crankcase cover

Dmitriy,

The check valves should allow flow away from the crankcase... They are there to bleed off excess oil that gathers in the bottom of crankcase in each cylinder....

Chris........
 

dandreye

Petty Officer 2nd Class
Joined
Oct 19, 2007
Messages
141
Re: 2-stroke 90hp: check valve orientation in crankcase cover

Thanks a lot Chris - we're going to give it a try.

Dmitriy
 
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