QuestionQUESTION: I have honed & re-ringed a 28 series 11.5 hp B&S ride on mower engine and have the following problem.
As the engine warms up it seams to generate too much pressure in the crankcase and blows oil into the air cleaner through the breather.
This results in white smoke, eventual drop in revs and oil pooled in the carby.
The breather has been replaced before the rebuild.
I have not ground or reset the valves as the engine has had only 140 hours of running time.
Could this be the problem.
Thank you for any help you can give me.
ANSWER: Positive crankcase pressure is caused by an air leak. The first places to check our the oil fill tube and the dipstick seals. Next would be the oil pan gasket and oil seals on the crankshaft. Any gasket surface can cause this. Also check if there is a pulse line coming from the crankcase to the fuel pump be sure that pulse line is in good condition and there is not a leak at the nipple. I hope this information helps.
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QUESTION: Thankyou for your suggestions.
I will pull the engine down again and replace the crankshaft seals, oil pan gasket(I have already replaced this) and if I can source them the dip stick seals.
This engine does not have a fuel pump but from your description I gather that I am looking for any way that air can get into the crankcase.(cracks etc)
While it is apart I will also check the ring end gap.
Could you please give me an idea of what this should be.
I think the rings are still ok as the engine seems to have compression and increased horse power.
Thankyou again for your assistance as the grass is getting long.
AnswerI do not have specific engine specifications. I leave those to the manufacturers if you do not have an engine service manual and want to just look at one I suggest your public library you could even make copies of the pages. Or go to Briggs & Stratton website and search your particular model type and code. I think you will find a list there.
