Cub engine queston?

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smokinj

smokinj

Minister of Fire
Hearth Supporter
Aug 11, 2008
15,980
Anderson, Indiana
Cant quite figure this out. Had no issue with the cub until yesterday. It now runs rough at wot and oil leak seems to be coming from the top of the fly wheel housing(Oil leak started two weeks ago)But just now started to run rough? Runs fine at idle to half throttle.
 
Jags said:
Jay - did you do piston/rings/cylinder work on this engine?
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No but I got great compression and will smoke a little when first started. Spark plug is dry. Ran great when I put it away last Sunday.
 
Before suspecting the worst, I'd check the breather assembly. These get gummed up on those K301's, and can cause some of the issues you describe. In fact, are you sure the oil is not leaking from the breather, itself?
 
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Joful said:
Before suspecting the worst, I'd check the breather assembly. These get gummed up on those K301's, and can cause some of the issues you describe. In fact, are you sure the oil is not leaking from the breather, itself?
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No I didn't have much time to check. I ran through the simple stuff. Spark plug wires and coil. Then I jump on the deere and finish the lawn.
 
The reason I ask is that it sounds like you have blow by (coming out the breather). That is usually a sign of rings. Does the plug look nice and dark tan or is it sooty looking?
 
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Jags said:
The reason I ask is that it sounds like you have blow by (coming out the breather). That is usually a sign of rings. Does the plug look nice and dark tan or is it sooty looking?
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Sooty looking.
 
smokinj said:
Sooty looking.
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Yeah - you are burning oil. The higher the RPM the more oil it will pump. Check your breather to make sure it isn't just plugged solid (and it might be), but I hate to break the bad news, it sounds like it is time to pull the motor apart.
 
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Will painting it green and yellow help? ;)
 
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Jags said:
Yeah - you are burning oil. The higher the RPM the more oil it will pump. Check your breather to make sure it isn't just plugged solid (and it might be), but I hate to break the bad news, it sounds like it is time to pull the motor apart.
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The compression seems way to high and the lack of smoke seem that the rings are at least in ok shape wouldn't think?
 
smokinj said:
The compression seems way to high and the lack of smoke seem that the rings are at least in ok shape wouldn't think?
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Well...You would think so. It is possible for the oil ring to be shot, yet the compression rings are still doing their job. "Check the breather" is step number one.

Don't take me as the only voice of reason, hopefully we will hear from others, but K series Kohlers are about as simple as they get.
 
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Jags said:
Well...You would think so. It is possible for the oil ring to be shot, yet the compression rings are still doing their job. "Check the breather" is step number one.

Don't take me as the only voice of reason, hopefully we will hear from others, but K series Kohlers are about as simple as they get.
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I am not just throwing it out there. Rebuilding it not that out of the question. Wanting to repaint the whole thing anyways. I will check the breather and pull the head see whats up for sure first.
 
smokinj said:
I am not just throwing it out there. Rebuilding it not that out of the question. Wanting to repaint the whole thing anyways. I will check the breather and pull the head see whats up for sure first.
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Yep, see what kind of carbon is deposited on the head. A big build up of carbon can also cause pre-ignition at higher speeds.
 
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I don't think we've confirmed the breather is oiled up...could just be a failed seal.

If you were burning oil, it would smoke...a lot...and not just on startup. You might have a bad valve seal that make is smoke on startup. You might have a sooty plug because you are running rich. You might be leaking oil from the jug gasket and/or the crank seal. It might be running rough because you just now fouled the plug enough, or you might have a weak coil, or it might be starving for fuel, or....

That's a lot of mights. Figure out where that oil is coming from before you tear down the engine. Could be simple. Or it could be time for a rebuild.
 
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Another mention of the breather broke loose an old memory. I have actually had the internals on one of the breathers rattle loose. They do act as a one way valve, if this ain't working correctly, it can allow for leaks and actually cause weird stuff to happen.
 
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lukem said:
I don't think we've confirmed the breather is oiled up...could just be a failed seal.

If you were burning oil, it would smoke...a lot...and not just on startup. You might have a bad valve seal that make is smoke on startup. You might have a sooty plug because you are running rich. You might be leaking oil from the jug gasket and/or the crank seal. It might be running rough because you just now fouled the plug enough, or you might have a weak coil, or it might be starving for fuel, or....

That's a lot of mights. Figure out where that oil is coming from before you tear down the engine. Could be simple. Or it could be time for a rebuild.
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Oh yea....Best thing though about the 301 is the whole rebuild kit is under 75.00. Plus machine work probably another 50.00. But ti could just be a blown head gasket or clogged breather.
 
Jags said:
Another mention of the breather broke loose an old memory. I have actually had the internals on one of the breathers rattle loose. They do act as a one way valve, if this ain't working correctly, it can allow for leaks and actually cause weird stuff to happen.
Click to expand...

Gives me a good game plan.
 
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Ok got the head off. Iamb seeing wet oil spots on the gasket. Could this be do to over filling oil?
 
Well, you already got the head off, but I would've changed the plug and if no change, check the points. (gap and condition)

Pull the air filter

Check to see if it responds to carb adjustments

Plugged breather would likely produce smoke while running and oil leakage at the gov shaft.

But since the head is off, check the piston for any noticeable lateral play @ TDC.
 
Yep your right if I wasn't through this thing already. Its very strong so that's what made me pull the head right away. Going to have it milled and new gasket. Just make it stronger either way. I GOT A GUY FOR THAT. Not sure that it but pretty cheap.
 
MM's suggestion of points is another area I would look at. I have also had a couple of condensers go bad, too.
 
Jags said:
MM's suggestion of points is another area I would look at. I have also had a couple of condensers go bad, too.
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There is fresh oil on the head gasket.
 
Just re-read the OP, and realized I was focused on the oil leak, not the running rough. Yeah, those points are severely heavy duty, for such a small engine, but they don't last forever!

I wonder, have you checked your RPM at WOT? Sure you're not severely over-reving? That's easy to do, given the hokey governor / throttle stop setup they have on those old Kohlers.

Oil on the headgasket... don't assume it's rings. These Kohlers seem to suffer bad valve guides before rings. That said, I'd still be changing that breather and running with that, before digging any further.
 
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Joful said:
Just re-read the OP, and realized I was focused on the oil leak, not the running rough. Yeah, those points are severely heavy duty, for such a small engine, but they don't last forever!

I wonder, have you checked your RPM at WOT? Sure you're not severely over-reving? That's easy to do, given the hokey governor / throttle stop setup they have on those old Kohlers.
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That would make since. Everything was fine when I put it up. Change the oil and problems started. The governor is just pop over and over.
 
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