[AT] Old test for a bad valve?

[Mike Sloane]

The only time you would see smoke coming out the crankcase breather 
(which is also the oil filler in many tractors) from a valve problem 
would be if the guides were badly worn. Normally, there isn't really any 
path from the valves to the crankcase. (Smoke coming out the breather is 
usually caused by worn or stuck rings.) If you have a bad exhaust valve 
or burned seat, when that piston sucks fuel mixture in from the intake 
manifold, it will also suck some air in from the exhaust manifold. So 
you will see the piece of paper sucked in towards the exhaust pipe once 
out of three "pops". Unfortunately, that won't tell you which valve is 
the problem, but you can usually pull the plug wires one at a time to 
see which one doesn't result in the engine slowing down (as much). Of 
course the best test is either a compression or leak-down test.

Mike

Cecil E Monson wrote:

>> I sorta remember that there is a simple test for a bad engine valve-
> 
> 
> -something like holding a piece of paper against the end of a tail pipe
> 
> (exhaust stack for a tractor).  Anyone remember the details?     John
> 
>     I've heard of it in regards to blowback out of the crankcase.
> In that case, the blowback from a bad valve would puff out of the
> oil filler tube. Don't know about the exhaust pipe test.
> 
> Cecil
> 

-- 
Mike Sloane
Allamuchy NJ
Email: (msloane at att.net)
Website: <http://www.geocities.com/mikesloane>
Blog: <www.mikesloane.blogspot.com
Tractor images: <www.fotki.com/mikesloane>
Work: none - retired

In America, anybody can be president. That's one of the risks you take.
-Adlai Stevenson, statesman (1900-1965)