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Simplicity Sunstar fixer
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Discussion Starter · #1 ·
Hello, Don't know if this is the right place to ask but my Sunstar Engine has been spewing oil for a while now and I cannot seem to fix it. Was coming out of the breather and down the front as well as out the crank seal. Got a new top gasket and now that stopped.
Last fall I replaced the 2 head gaskets.
Reading the Kohler engine manual and it says the crankcase should have a vacuum when operating. It actually has positive pressure and blows out the oil dip stick tube (when stick is removed).
Checked the cylinder compression and both read 100 PSI while cranking.
I ordered a cylinder leak down tester to help and it will be here in a couple days.

Checked the breather reed and it is okay. I blew some air down the breather ports while it was open and no restrictions seemed there.

The engine runs great and has no power problem operating the 60" mower deck.

She drips constantly and runs thru 1/2 quart of oil in an hour and a large puddle under as it drips off the front in the garage.

Well that's about all I know, so any ideas?
Thanks in advance.
 

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How many hours are on it? Could be blow-by. I have a sunstar 18hp but i am not where i can look at it. Make sure the crankcase breather is not plugged.
 

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Simplicity Sunstar fixer
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Discussion Starter · #3 ·
It has 1384 hours. To check the crankcase breather not being plugged, do I just apply compressed air to the rubber tube that comes up into the air filter area by the carb to see if free flowing?
 

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Senior Tinkerer
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1,588 Posts
I know you said you replaced the head gaskets, but his sounds like a head gasket problem (assuming your breather valve is OK). The Command heads are known to be subject to warping. If one or both of yours were warped, a new head gasket might not help. Don't know if you will be able to pick this up in a leakdown test? Also, with 100# compression, I doubt very much you are getting any significant blow-by.
Gerald
 

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Simplicity Sunstar fixer
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25 Posts
Discussion Starter · #7 ·
A couple things I neglected to say earlier:
1. When I replaced the head gaskets I did check for warping on the engine with a straight edge and looked good
2. When I checked compression one side spark plug was a good tan color, the other side was black and carbon fouled. I mean it was full of small chunks of carbon. Don't know why it should have worked.
3. When reading the Kohler manual it said there should be 160 PSI in the compression check. That seemed high to me but I am not a small engine guy.
Thank you for your help so far. I will do the leak down test as soon as it arrives and post back my findings.
 

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Father Deerest
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2,794 Posts
I have a 50/50 shot of being correct but I'll put it all on red and say the right side cylinder (#1) is the one that is fouled. Order the new version head gasket set with the steel ring and valve seals. Take apart the heads soak the valves and head in paint thinner or charcoal lighter fluid using a junk cake pan, use a green 3M pad to remove the carbon from the valves and the head with a smaller brass brush. Lap the valves, re-assemble with new seals and gaskets and that SHOULD fix the problem, not an absolute guarantee but I had a Ferris zero turn and most Commands doing the same thing.
 

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Simplicity Sunstar fixer
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25 Posts
Discussion Starter · #9 ·
Received the cylinder leak down tester and followed the procedure, this is what it indicates:
1. Both cylinders show in the "green" for leaking by the piston rings. I later confirmed that the cylinder bores are like new.
2. The right side cylinder (#1) was leaking by and out the exhaust. There was a small air flow thru the crank case breather tube and carburetor. Held my hand over the muffler out put and it would build pressure.
3. The left side cylinder (#2) has a similar air flow out the crank case breather tube and carburetor. No discernible exhaust leak.

So I pulled the engine and removed both heads. Found the #2 exhaust valve does not seat. Much carbon keeping it from sealing.
Neither head gasket showed blow-by but one tore during dis-assembly. Will replace both anyway.

What do you think about wire brushing the valves and seat areas and lapping a bit? Or take to an engine repair place to perform a valve job?
 

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I would clean the valves and seats good and lap the valves. After lapping put the springs back on and put some gasoline on top of valves to see how good they seal
 

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Simplicity Sunstar fixer
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Discussion Starter · #12 ·
Well I cleaned up the valves on a wire wheel and ran a wire wheel on a drill motor all around the head. Then seated the valves by lapping them in as best as I could. Re-assembled with new head gaskets. New oil filter and oil.
I was going to replace the front output seal (that I put in last year) when I noticed there was plenty of room to add a new seal on front of the old one. So why not ! I added the seal and it fit nicely. Instead of reinstalling the spark plugs I headed to the local dealer and got 2 new ones. They were nothing like the ones that I took out. I don't remember replacing them since I owned it. The depth was much longer and the heat rating much hotter. I had to run a tap to clean out the threads so it could be seated. I did check the specs on the plug depth and the new ones were correct.
Put everything back as it should, reinstalled the motor and fired it up. It ran very good but does have some smoke coming out of the exhaust. noticeable but not terrible. Cut the grass for an hour and checked the motor and there were no oil leaks!
Think I'll see if the smoke gets worse before getting back into the tear down again.
Thanks for the help.
 

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Father Deerest
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2,794 Posts
Where you pushed the new seal in there is a hole that the old seal may now be covering. Yoiu can see the galley from the oil filter to the side of the bearing boss and on the other side you can see the oil exit hole into or through the crankshaft to rods and then to the rest of the oil system. The seal should only be pushed in flush with the outside of the block. This ic the rear (PTO) side cover from a Kohler CH25
031.JPG
 

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Simplicity Sunstar fixer
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Discussion Starter · #14 ·
Thanks for the seal information. Could this be a reason for pressure build-up in the crankcase and pushing oil out gaskets and seals?
 
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