Oil seal leak Clamshell help.

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am I missing anything, the oil seals on clamshell stihl saws simply slip onto the crank shaft? When the crank rotates, the metal rubs on the rubber seal right? This seems strange, what is stopping the rubber wearing out so quick from friction? Especially that it has to hold pressure!

Anyway have a leak where the crank meets the seal... am I doing
Something wrong?

FAC613BA-8411-4962-B83E-17678C8A2C52.jpeg
 
That's why the crank is highly polished for the seal and seals do wear out. They will last alot longer than you might think. How many saws from the 60s are still running with original seals?

How much air pressure are you using?

Chris B.

Using 5-7 psi, held fine until I turned the crank then it started to leak haha. How well do farmertec oil seals hold up?
 
am I missing anything, the oil seals on clamshell stihl saws simply slip onto the crank shaft? When the crank rotates, the metal rubs on the rubber seal right? This seems strange, what is stopping the rubber wearing out so quick from friction? Especially that it has to hold pressure!

Anyway have a leak where the crank meets the seal... am I doing
Something wrong?

View attachment 764958
Is that a new seal?
 
Using 5-7 psi, held fine until I turned the crank then it started to leak haha. How well do farmertec oil seals hold up?

Correct testing but I don't like aftermarket seals. They seem to have an bad rep for lasting. I am pretty sure that OEM engine seals have a different design lip to resist both pressure AND vacuum which regular generic oil seals wont. Sometimes Stihl offers a gasket kit which includes the seals for less than the cost of just the seals.

BTW, It is hard to tell from your photo exactly WHERE the leak is coming from. The leak may be coming from the pan gasket material and NOT the seal itself. I have seen several of those. Either way you have to tear the whole thing apart. You won't know until you pull the engine out of the housing (or use less soap/pressure to blow smaller bubbles!).
 
It's hard to tell from your wording and the picture what you did. The seals slide onto the crankshaft and are then enclosed by the two halves of the shell which is then bolted together. Sealant is applied to both halves of the shell surfaces before fitting the seals into their seats and closing the shell. Make very sure the seals are perfectly aligned and seated before you bolt it up. Also be sure the springs don't dislodge when you slide them on.
 
Correct testing but I don't like aftermarket seals. They seem to have an bad rep for lasting. I am pretty sure that OEM engine seals have a different design lip to resist both pressure AND vacuum which regular generic oil seals wont. Sometimes Stihl offers a gasket kit which includes the seals for less than the cost of just the seals.

BTW, It is hard to tell from your photo exactly WHERE the leak is coming from. The leak may be coming from the pan gasket material and NOT the seal itself. I have seen several of those. Either way you have to tear the whole thing apart. You won't know until you pull the engine out of the housing (or use less soap/pressure to blow smaller bubbles!).
Aftermarket seals will indeed have the proper lip for both pressure and vac. If it’s made for a specific 2 stroke motor, it won’t work at all without them.
 
Hey guys thanks for all the info! just an update for everyone!

So I split the case to change the gaskit maker (I used the wrong type before so cleaned it off and then applied dirko)

Slipped the seals on the crank and put sealant between the case halves and around the seal pockets and greased the inside of the seals and the crank. The leak is from the clutch side and appears to be where the seal meets the crank shaft. The OEM seals are worth it if the saw was worth it, but it’s old and beat up so just got some farmertech ones to try first?
 
Hey guys thanks for all the info! just an update for everyone!

So I split the case to change the gaskit maker (I used the wrong type before so cleaned it off and then applied dirko)

Slipped the seals on the crank and put sealant between the case halves and around the seal pockets and greased the inside of the seals and the crank. The leak is from the clutch side and appears to be where the seal meets the crank shaft. The OEM seals are worth it if the saw was worth it, but it’s old and beat up so just got some farmertech ones to try first?
Should be fine, vac pressure test and run It!
 
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