[AT] Tecumseh too far advanced

Will Powell william.neff.powell at comcast.net
Sat Oct 16 23:32:52 PDT 2004


The engine is the newer type, OVM120-200017A not the type with the
ignition under the flywheel. 

We had just rebuilt this engine and I did not notice any compression
release mechanisms on the camshaft and the camshaft looked good....

But it does sound like a good theory. 

The on line parts list shows: CAMSHAFT ASSY. (MECH. COMPRESSION
RELEASE). 

I'm going to take a look in the parts manual....

Regards;

Will Powell (PA)



-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of Larry D. Goss
Sent: Saturday, October 16, 2004 6:32 PM
To: 'Antique tractor email discussion group'
Subject: RE: [AT] Tecumseh too far advanced

It depends on the model of the engine, Will.  On some of the older
engines, the whole ignition assembly under the flywheel could be rotated
around the crankshaft to adjust the timing.  Later models don't have
that capability.  I think the change in design coincides with Tecumseh's
use of electronic ignition.  The electronic ignition modules (outside
the flywheel) are not adjustable.  

It could be that the compression release mechanism is stuck.  If the
flyweight stays in the "out" position, or if the pin that goes through
the camshaft gets bent, or if the return spring breaks -- any one of
these things would cause the symptoms you describe.  As a matter of
fact, if the engine runs normally when it does start, then I would
suspect that your ignition is OK and that the problem is with the
camshaft.

Been there, done that!  I hate Tecumseh's!  I've pulled Tecumseh engines
apart and found that the whole compression release mechanism was a mass
of twisted sheet metal.

Larry 

-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of Will Powell
Sent: Saturday, October 16, 2004 8:53 PM
To: 'Antique tractor email discussion group'
Subject: [AT] Tecumseh too far advanced

Hello;

I have a Sears tractor with a 12hp Tecumseh engine. 

When I go to start it the spark is so far advanced that you can hear the
starter stop when ignition happens. Sounds like "wuh wuh wuh urh urh whu
whu whu urh".   Sometimes it starts, sometimes it doesn't....

Is there a way to retard the spark? Would it require an offset flywheel
key? 

Regards;

Will Powell (PA) 



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