Cylinder crankcase /engine block seals???

Boilermaker

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I have never had my 1978 Johnson 115HP engine apart, but would imagine that there would have to be some sort of seal between cylinders in the lower end, to keep pressure pulses separate for cylinder charging. (If I'm wrong>>>please tell me)<br />How can you tell if these seals are bad/leaking??? Can you tell without a teardown?? I would imagine that it could be a cause of rough running, weak throttle responce & all around lower power. <br />I always read about checking the compression, and cleaning the carbs, ect... But have never heard anyone suggest a problem with lower end seals??? Do they never go bad??? Are they just a figment of my imagination??? <br /> :confused: :confused: :confused: <br /><br /><br />Thanks for any help.<br /> :cool:
 

Dhadley

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Re: Cylinder crankcase /engine block seals???

I think you're talking about the seal rings between each cylinder on the crank, right?
 

Basscat 1

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Re: Cylinder crankcase /engine block seals???

One sign of a bad seal ring is that the engine may "pop" back through the carbs.<br />If you pull the intake off, you can see the seal rings that Dhadley is talking about, but you probably cant tell much unless its broke.
 

Boilermaker

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Re: Cylinder crankcase /engine block seals???

I NEVER had a multi cylinder 2 cycle apart, but figured there MUST be isolation between cylinders lower end to get the air/fuel charge pulse right.<br /><br />Are these soft seals, and do they slowly wear out??? Would years of the engine sitting unused cause them to dry & leak???<br /><br />Is popping through the carbs the only sign? Just wondering if a worn/leaking seal would cause loss of torque or HP???<br />Thanks<br /> :cool:
 

Walker

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Jun 15, 2002
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Re: Cylinder crankcase /engine block seals???

The ring seal between the cylinders are similar to piston rings. You can't see them unless you split the cases. I'd say if you had a bad ring seal then you lost lubrication somehow and you probably have more damage than just the ring seal.
 

walleyehed

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Re: Cylinder crankcase /engine block seals???

When assembling the case halves, it's common practice to turn the crank after torqing case-halve bolts to make sure crank seal rings have not pinched the crank.<br />I "can" tell you needle bearings from an upper cylinder /piston assembly can cause a few issues on their way down!!!<br />The rings used to come in 4 sizes of wall thickness, now they have 2...If it's tighter than .0015, install the thinner seal.<br />For the seal to go bad, you would have to be experiencing too much crank end-play, or something has worn to the point the crank can move around it's axis(Wobble)
 

Basscat 1

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Re: Cylinder crankcase /engine block seals???

Actually, you can't see the rings if you remove the intake, you can just see where they ride on the crank between the cases. (I had a blonde moment)<br /> If there was a problem you might be able to see a broken ring by just removing the intake.<br />As Walker said, you have to split the cases to see the rings.
 

Dhadley

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Re: Cylinder crankcase /engine block seals???

I've seen motors with them cracked and it still ran fine. We actually took apart a motor once - for other reasons - and one was missing. It still ran OK as far as the seal was concerned.<br /><br />If your motor is spitting back thru one carb its sucking air or too lean. It probably isnt the seal ring.
 
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