B crankcase pressure

[primer gray A]

rebuilt motor on a 51 B now it seems to build up with fuel in the crankcase and will ingnite, smoke will come out of breather. are the compression rings on wrong. how is the fuel getting past the pistons? thanks in advance

 

[RobMD]

Start off with the basics. You're probably in bad need of fuel system repair - jets in the carb may be squirting fuel instead of vaporizing it into a fine mist. With the tractor off, gas can bypass the needle valve in the carb, and flood the engine slowly, or overnight.

Regardless of the amount of blow-by, you should be BURNING fuel, not dumping it all in the cylinders. Look at the fuel system and check for a good blue spark while you're at it.

Do a compression check. The only way you're going to know a quality rebore and piston fitment is to check it. You could also do a leak-down test by putting a specific PSI air in the cylinders.

You don't know what you've done wrong mechanically unless you rule out other predisposing factors and tests.

 

[c.seydel]

Had fuel in my crankcase but no smoke or blow-by. Was my cutoff on the sediment bowl leaking and pushing fuel into the crankcase. Shut off the fuel and drain the carb, check carb in the morning to see if full, if so you know where its from.

 

[Mike M]

Check for the carb. float and/or needle and seat leaking which will fill up the cylinders and crankcase.

I had bought a late B once that the story goes once in awhile it would have a crankcase explosion that would blow the valve cover gasket.
Upon inspection and tune up I noticed that # 1 cyl. the piston was rotated the wrong side up so that the notch made to clear the spark plug area was not lined up with the hole. Took the rod loose spun it around so the top of the piston was up and sold it and never heard anymore about it ? The guy I sold it to did come back later for an antifreeze leak. Luckily the head just NEEDED retorqued as it was pretty loose.

 

[johns48jdb]

if your getting that much gas in there its diluted your oil. it will have to be changed or your in for more troubles. fix the problem first. adjust the screws down a lot on the carb and turn it up only enough to make it run ok. probably need to change your plugs. the only champions are still working for me, but most people like the 3116 autolite.