No compression

[Ron]

I have a Briggs engine on a push mower with no compression. Flywheel key is fine. Took the head off to watch valves. Shouldn’t at some point as the piston comes up, both valves should be closed. I have a video but don’t know how to post it. Maybe I can send it in an email to someone to check it out.

[hanz63]

Sounds like you may have an exhaust seat come loose and holding the valve open?

[KE4AVB]

Yes they should both fully once every other cycle that is if the camshaft is rotating. IIRC there were some engines with plastic crankshaft timing gears that would break.

If a L-head (side valve) engine they get to where they will not fully close simply because wear. Other things like stuck valve or missing retaining clips can also be a problem too. I had one valve last year that completely worn the retaining tip off so of course the valve never closed.

[Ron]

I suspect mower is only a couple years old. Looks in very good shape. Mower is a husqvarna HU725AWD. No model stamped anywhere on engine. It’s a 725EX. Only thing I see is a sticker on the plastic gas tank that has engine serial number 16 0321 58 60265. How do I look up parts? It is an L-head engine. I also suspect plastic timing gear but I’d like to see an ipl.

[KE4AVB]

Based on the serial number given it is a 128M02-0120-F4. From there you should be able to look-up the parts.

IPL says it is a metal one but looks a little flimsy.

[Ron]

Thanks. For future reference, how were you able to figure out the model with the serial number?

[Ron]

Would you believe, I got the exact same Husqvarna mower in for service and the model number (that KE4AVB provided) is on a sticker above the muffler on a plate that in the past had been stamped. Anyone, other than a B&as engineer, would know at some point that would come off.

[KE4AVB]

I have never like stick on stickers for engine or mower info. I have got lucky a few times as the equipment had been in the shop before the sticker went AWOL.

[Ron]

I see also according to IPL the timing gear is metal. What all is involved in replacing it or opening it up to see whats wrong? Engine out. remove sump and it should be pretty much visible?

[KE4AVB]

Yes you need to open up the crankcase. Download the service manual from the download section under Briggs Service info.

File name > 01_270962 Single Cylinder LHead