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Smoking 912 - and I don't mean fast


tej

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My 912 has developed a bad habit, it smokes. As I was mowing last evening I noticed that there was a good deal of smoke coming from a small vent on the left side of the engine (Kohler), from just below and in front of the air filter. I am assuming that this is not good news. Any ideas as to what to do now? I think that I am losing power as well. Help.
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TimH,
I don't know anything about your engine, but if the tube
that's spewing the smoke is a crankcase vent, then it
sounds like you have a case of blow-by. This usually
means that the compression ring is damaged or worn,
thus allowing some of the compressed air from the cyl.
to enter the crankcase. This also is supported by the loss
of power. However, before tearing your engine down,
make sure your oil isn't just overfilled. I just
remembered that could cause smoke from the vent too,
but probably wouldn't effect the power too much.

Good luck,
Greg
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Greg is correct, too much oil can cause a problem, so can excess fuel from a leaky carb. Fills crancase. Most likely is exce3ssive blow by in the cylinder. In normal operation these engines should pull a crankcase vacuum of about 15 to twenty inches of water, using a water manometer. Whe the cylinder leakage is bad you get pressure instead. and it comes out the breather located in the valve chamber. Check to see that the reed in the breather is functioning. Most likely I would bet you'll need an overhaul. While you are at it you should consider a bore job if its bad, ring are just throwing good money after bad. In most cases. Mike the cylinder, if it shows over.004 wear I would forget about a ring job. THat's my 2 cents worth, and its free, so you may want to value it acccordingly. Al GOOD LUCK
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TimH, One more thought on the smoke. If the rings are worn the engine should have been using oil and smoking bluish white from the exhaust. If this problem just started the rings could have become stuck from carbon in the engine. You could pull the head and check for carbon. I don't know about Kohler but some of the engines have a taper boarded cylinder. If the rings stick this could cause blow by at the lower end of the stroke. If the rings are stuck they could be cleaned. When re-installed the gaps in the rings should not line up or they will blow by. If you put in new rings you should ream the ridge. These are only my thoughts and may be total wrong. Worst case scenario, probably not your problem, if the engine was low on oil to the point the oil got hot enough to smoke. As the bearings got hot and swelled up the motor would lose power. If run long enough the bearings would swelled to the point they couldn't turn the rod would break and goodbye engine. Tim
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Karl_Brandt
Tim from my experence you probally have an engine that is tired. I would bet you have wear on the clyinder and rings which allow blow by the piston causing presure in the crankcase. As some one said you should have vacumn in the crankcase and not presure. The best way to check is with a water manometer or air test the cylinder. This will give you a percentage of leak by and let you know exactly where the leakage is coming from. I have tore down several engines and find most of them with several hours are wore out of round and need to be bored to seal back up. Also you will find the crank shaft will be out of round and some wear on it. It lives now due to the decrease in compresion due to laakby. If you put in a new piston and seal the clyinder the rod might not hold the increase in load.
In short figure the engine needs a complete overhaul. It will be expensieve but should give you several years of added life to the engine. Hope this helps
Larry
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  • 3 weeks later...
It would appear that the motor is tired ,no question that it can be repaired...for the right amount of CASH anything can be fixed...!
I would price out a complete rebuild/overhaul,and also a short block....and remember the short block will have a warranty....!
And depending on the mechaical ability of the owner this is a good project for a "shade tree mechanic"....
Good luck Jim L.
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