Re: 70 hp 1980 johnson fule
Re: 70 hp 1980 johnson fule
A reed valve is basically a hole covered by a flat piece of metal, attached to the intake manifold, opened by crankcase vacuum to let air/fuel in from the carburetor, closed by positive crankcase pressure so the air/fuel mixture can be passed to the cylinder when the intake port opens.
There's a set of these behind each carb. When they wear out or break & can't close completely, fuel blows back out the carb instead of going into the cylinder.
Go to
http://shop2.evinrude.com/Index.aspx?s1=fnafup8n36j6ketdot8r235tm5&catalog_id=0&siteid=1
Select "Johnson" in the dropdown box, then select your year/hp/model #. The picture below is from the "Intake Manifold" chart.
If a piece of a reed has broken off, you need to find it before it gets sucked into the cylinder and blows up a piston or something.
They aren't that tough to get to, just pull the carbs & manifold, but you want to make darn sure it's not just a leaky carb before you tackle 'em. A bad reed will literally spit gas back out through the carb, as opposed to say, just pooling in the throat.
If you take the carb off and shine a light into the hole you might be able to tell if something is lodged in there, or if there's any obvious deformity. I don't believe you can really inspect it without pulling the manifold. I don't believe you can re-use the manifold gasket, btw.
Handle the reed cages with care -- don't push on the reeds with fingers or anything else, if they get bent, they're toast. Held up to the light, you shouldn't be able to see through 'em -- it's ok if you can just see light peeking though, but there's shouldn't be any gap.
If you don't have a repair manual, I highly recommend the factory service manual. You can get one at
www.marineengine.com
