DIYbanter - View Single Post - Engine in John Deere Snow Thrower 522 Cannot Run without Choke

E Z Peaces

hr(bob) wrote:
On Dec 14, 4:05 pm, E Z Peaces wrote:
Jay Chan wrote:
One additional question: The Tech Manual from John Deere asks me to
make sure the engine is running at 3600 rpm when the engine is set at
high-speed mode. I am under the impression that we don't want the
engine to spin too fast and burn itself. That's why we want to keep
its rpm to not more than a certain limit. This means I need a
tachometer. But tachometer seems to require seeing or touching the
spinning part of the tachometer in order to measure the rpm.
Unfortunately the engine is fully enclosed, and I cannot see the
spinning part of the engine. Is there any tachometer that doesn't
require seeing or touching the spinning part of the engine? Can we
measure the rpm by timing the number of sparks that the spark plug
makes?
Where grass wasn't heavy, I used to throttle my mower down to reduce
noise an save gas. Now my mower has only one speed.

I think manufacturers have found that engines that can't be run slow
have fewer warranty claims. Keeping the RPMs up can mean better
lubrication and cooling.

It also sounds like the throttle spring is crazy in its operation.
The throttle spring should keep the throttle closed and the control
should work against the spring to open the throttle. That seems to
not be what the original poster described. ALso If the carburetor
has really beeen cleaned , then an air leak beteen the curburetor body
and the manifold or the manifold and the main engine block is suspect.

Bob Hofmann

The opening and closing at 60% choke makes me think the problem is an
air leak. With 80% choke it gets a good no-load mixture. With 60%,
it's too lean, so the engine slows and the governor opens the throttle.
With the throttle open much wider, the air leak matters much less.
The mixture is better, the engine speeds up, and the governor closes the
throttle. Then it's too lean. Vicious cycle.