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Compression release ?


Patch's Avatar
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04-18-03, 07:35 AM   #1  
Patch
Compression release ?

I have a 15.5 Hp, Tecumseh OHV riding mower that is hard to start. I was told that the compression release isn't working & I needed to adjust the valves. How pray tell do I do that?

 
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04-18-03, 11:41 PM   #2  
Does the engine turn part way and stop, then turn a little more, then stop, etc...? If so, you have been told correctly (assuming your battery and starter are good). Pull the valve cover off and adjust the valves using feeler gagues according to specs. You get the engine on top dead center, insert the correct thickness feeler gague between the rocker arm and the valve stem, and tighten the rocker arm until the feeler gague fits snugly. The intake valve should be the top, and exhaust on bottom if I remember correctly.


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04-19-03, 05:14 AM   #3  
Tcumcman
Adjusting Valves OHV155

Patch,

Follow Cheese's instructions for doing this. When you remove
the valve cover you'll see the adjusting nut in the center of
the rocker arm with a hex set screw in the center of it. Loosen
the set screw, turn the adjusting nut to adjust settings on
BOTH valves to .004, and then hold nut as you re-tighten the
set screw. If the engine continues to be HARD TO TURN OVER
after you've done this, you'll need a new camshaft (Part #
36533A, 36565 for base gasket). When this problem surfaces,
often it is misinterpreted as a battery or starter problem. The
resulting attempts to start with jumper cables, or with a
boost charger, can result in starter damage. Hope your starter
is STILL OK.

Tcumcman

 
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04-19-03, 02:36 PM   #4  
Tcumcman:
I believe the Tecumseh has a thin jam nut on the rocker arm bolt. The setscrew is on the B&S. Tecumseh has also had a problem with the magnites coming loose on the starters. I would take the spark plug out to see if the starter is OK first. If the starter is OK then adjust the valves. Sometime it is a little problem the get the valve cover sealed up after it has been removed. There is a "O"ring kit for that. The camshaft is the last resort.

LOL

 
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04-19-03, 04:42 PM   #5  
Tcumcman
Compression release

Roger,

Thanks for the information, Roger, I appreciate it. The model
we're discussing here is a larger OHV vertical than the one
you're describing. Also, the pal nut locking system was used
on the older style OVM, OVXL 120 engines which Tec ceased
production on in 1991. The "newer" style OHV engines have
NO O-rings, push rod tubes, and use a different locking nut
system. You are correct about the magnets inside the starter
housing coming loose on occasion. Tecumseh had a MAJOR
problem with that about 5-6 years ago, and we occasionally
will see this again today, but very infrequently now. This is
definitely an issue of "TOO MUCH COMPRESSION" and this
can only happen 2 ways. My experience, unfortunately, tells
me it will most likely need a new camshaft to correct this.

T-Man

 
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04-20-03, 09:23 PM   #6  
T-man:

I don't know about you, but around here, people have this uncontrollable urge to whack starters with a hammer when the engine doesn't want to turn, and end up breaking the field magnets. Then if the starter turns a tad bit and the broken magnets cut the armature windings all up it ruins the whole thing. That's ok though...My shop rebuilds starters too, lol! (when they're worth it).

Briggs had a few earlier OHV engines with compression release that had premature cam failure too. They have an updated replacement kit for them now.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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