hi,
after just over 500 miles since the restoration of my 61 a7 the number of oil leaks seems to be getting greater.(my dad told me if it dont leak oil theres none in it!) ,but i am sure it never had all these leaks in the first 100 miles!.i have had the timing cover off a number of times to reseal it,also put sealant around the dynamo to timing case gasket many times ,but it still leaks.
So one time i cleaned all the oil off the engine and frame and went for a quick ride,just enough to warm it all up.got home put it on the center stand and checked for leaks ,just saw two one from the dynamo gasket again! and the other one seem to come from some where middle of the crankcase under the dynamo,or at least i thought so.
These leaks soon stopped within a few minutes? why i thought the oil would still be warm and thin? Oh by the way i forgot to say it never leaks when cold and parked in the shed.
So i came to the conclusion it must be forced out by excessive crankcase pressure,so reading the old bsa service sheets i read some where that if the crankcase breather had any play it would result in a very oily engine.
So this weekend off came the timing covers and checked the breather .......yes there was some play in the breather ,about 0.4mm sorry for the metric guys .looked in my gasket set and found the next thickness of cork washer ,fitted that but was so tight i could hardly turn over the engine!
Well i had no gasket material of the thickness i needed ,measured the cardboard that my full gasket set came on 0.4mm hummmm worth a try, so cut a ring of cardboard to fit under the old cork gasket ,refitted everything and went for 10 mile local run ,stopped half way to check for leaks.....none! and when i rev the engine a slight mist could be seen coming from the vent hole in the crankcase just behind the primary case.
When i got home checked again no leaks! no sure how long the cardboard will last but at least it proved it was a problem with the crankcase breather .Although still trying to work out how the bloody thing does what it does and why the little play can make all the difference!
If any one could explain the workings of the crankcase venting (in simple terms please) just for my own piece of mind it would appreciated!!!.