How could an exhaust valve possibly be so far out that it doesn't let
exhaust gas escape and the mower run, cut grass and work perfectly
fine when it does start. Sometimes it would spin over and then start.
I don't know how you'd test it without some kind of test jig. Even
if it spins up under no load on the bench doesn't mean much because it
has no load against it.
It doesn't take much. Maybe only a hundredth of an inch. It just
lowers the compression when it's turning that slow. My one that has the
same problem I can start by clicking the key off and on and stopping it
at top dead center. From that point it will have enough speed built up
to make it past that point again and hopefully fire. One of these days
I'll fix it, I have to remove the valve to do it.
If the exhaust valve never opens the compessed air just pushes the
piston back down and the intake valve opens again - the compression
pressure NEVER gets significantly higher than if the valve was opening
Remove the spark plug(s). Does the starter moter go like it should?
If so, I would think the motor doesn't have enough oomph to get past the
compression. Just guessing, the spark plug is not firing when it should.
On May 24, 7:16 am, firstname.lastname@example.org wrote:
A non sealing carb float flooding the cilinder? Take out plug see if
its wet and turns over and check oil for gas in it. Bypass the battery
and hook the positive to the starter and clean something for a good
ground, a bad connection or battery might be found, but a newly
purchased starter could be a rebuild, not new and worthless, once my
car mechanic went through about 4 , then he just bought a new one. So
I gues not enought volts, bad starter or flooded motor.
That has nothing to do with the starter failing to spin the engine.
I posted that I had connected both the lawn tractor's own battery and
a fully charged car battery directly to the starter with car jumper
cables and the starter would only move little and NOT spin the engine.
Yes, the new one could be bad, except that after the "valve
adjustment" by Sears, the new starter does start the motor. The only
problem he now has is that he says sometimes it doesn't start it
immediately, ie the starter still hesitates at least some of the time.
I'm wondering if there is another problem in the starter circuit, eg
bad cable, solenoid, etc, that was not delivering full current to the
old starter and eventually over time caused it to fail. With a new
starter, maybe it's on the same path, but the starter still works most
of the time, but is still marginal because it's not getting full
power? Since it's not mine and I didn't get to try any testing with
the new starter, really don't know at this point.
Bad solenoid can cause that as can loose or corroded cable connections,
even the key switch. Another cause can be a clutch that is dragging or
not fully disengaging or the mower deck clutch and binding of the
flyhweel itself because of a misplaced cowling cover.
On Mon, 24 May 2010 08:21:49 -0700, trader4 wrote:
That's how I normally start my mower anyway :-) I get tired of those
crappy little batteries.
Bad ground between engine and starter seems unlikely (but maybe worth a
check that your ground from your battery wasn't connected to a bolt on
the engine which was painted).
Did you disconnect the normal positive line to the starter (from the
mower's solenoid) when you tried these tests? If not, maybe there's a
short to ground somewhere in the solenoid or wiring (or even something of
low enough resistance to cause problems).
If you can turn the engine by hand, I can't see a reason why a *good*
starter shouldn't be able to turn it over, too. The sort of symptoms
you're seeing do sound like a bad starter, though (my old mower one was
the same, and sometimes I'd have to rotate the starter by hand a few
degrees just to get it to spin when power was applied) - I suppose
there's the possibility that Sears gave out a bad starter, but it seems
On May 24, 8:16 am, email@example.com wrote:
I agree, bad valves are not a cranking problem. Bad timing can "stop"
a starter but usually it continues to crank after the plug fires.
When you say you hooked the positive up to the starter terminal you do
mean the terminal directly on the starter? Both cables? To insure
that a bad connection is not the culprit you need to clamp the
negative on the starter preferrably like where it bolts to the block.
Then hit the positive terminal directly on the starter. And make
completely sure you are using battery that you know will crank a car.
If there is any doubt, use a car. Make sure the clamps on the battery
are well dug into the lead of the battery terminals.
After it quit cranking did the lead spark when you took it off? If
it's not sparking then check all your other connections and try
again. A battery tester that also shows cranking amps would be handy
for this problem.
Yes. As I described, I hooked the jumper cables from both the lawn
tractor battery and a 1 year old car battery that came right off a
battery tender from my garage. In both cases I connected the
negative to a large bolt right on the motor close to where the starter
is bolted on. I held the positive cable jaw firmly against the
starter connection bolt. Got a good spark with initial contact, then
only a little bit of rotation. Exactly the same results as turning
Yes got a good spark both on connection and removal.
On May 24, 8:16ï¿½am, firstname.lastname@example.org wrote:
On some models, if the battery isn't at FULL voltage, you will exhibit
these problems. Check battery voltage. They should be at least 12.8
Another thing to check is the belts that go to the crankshaft pulley.
If they are not completely loose when the clutch is disengaged or the
mower deck is disengaged, they may be grabbing. This may be just
enough to cause your symptoms.
You know, that's an excellent suggestion. I just assumed that with
the mower in neutral, no blades engaged, that the engine was free to
spin. Never considered that something it's CONNECTED to could be
holding it back.
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