Does this engine have a compression release built onto the cam? With head off spinning engine over, both valves will fully open but neither will crack open. 2001 Murray Riding mower with 12.5HP Briggs and Stratton Engine. The engine is not OHV.

 

Well, there WAS a forum called precise engine repair, but when I went there, they said that the founder retired and dropped it.

However, there was a link to a new one run by some of the old members. McAfee didn't like it, but I took a peek and it looked OK. I think that McAfee was worried because it could be hacked.

Somebody there could probably answer your questions -- or possibly Ckal will see your post.

There's also a small engine section on mytractorforum.com that might be helpful.

Good Luck,

hj

 

Thanks for the info. I did a bunch of googling on the subject of my question and came across so many different answers, which makes it really hard to tell which ones to believe. So I figured I would try here instead of one of those other forums. I figured the guys here would all give the same answer instead of mix answers. If i dont have any luck here I will try the tractor forum.

 

I have a repair manual on the L-head B&S engines.

Post the model number and serial number of the engine, and I'll look up the specs.

Looking at the manual, it says:

Checking Compression Release (Mechanical Yoke Type)
Mechanical yoke type compression releases use a spring loaded yoke (2) at the exhaust cam lobe (1) to open the exhaust valve during starting.
When engine starts, centrifugal force causes the yoke to overcome spring tension and swings away from exhaust tappet returning engine to normal compression, Fig. 8.

To check, move yoke away from face of cam gear and release. Yoke should return to compression release position without binding or sticking.

Model Series 111200, 111900

This cam gear has a mechanical compression release on the exhaust lobe plus Easy-Spin® (1). In the starting position, the actuator cam (3) moves the rocker cam (2) so it will open the exhaust valve at the same time as the Easy-Spin® lobe opens the intake valve. When the engine starts, the actuator cam moves down and the exhaust valve operates normally.

The manual then lists the steps to check the mechanical compression release.


With the above (from the manual) I suppose there is a compression release.

IHTH.