Briggs 16.5 hp OHV - No compression, but not all the time

sflem849

Well-known Member
Not sure if I can talk about fairly new engines, but I'll try it.

I was given a Ranch King with a 16.5 hp Briggs OHV engine. Not sure what exact model it is bc the cowling tag is gone. It doesnt have compression on half of the motors cycles (if that makes sense) When you turn it over by hand you can feel it get hard to turn and then easy, then easy, then easy, then hard. If I understand my 4 cycle motor technology properly it should have compression twice and no compression twice in the cycle.
I then pulled the valve cover to investigate. I was expecting to find a c clip off a valve or something. Nothing really seemed out of the ordinary. The top rocker arm seemed to have a lot of play, but that is all I really saw.
Any thoughts on what the problem may be?
 
Pull the valve cover and I bet you will find the INTAKE PUSH ROD is broken. DO NOT buy a aluminum intake push rod to replace. Buy the exhaust push rod. It is the same length and the guide plate will not wear it like the aluminum one. The aluminum push rods break where the guild plate wears the push rod.

Kent
 
Is the intake the top one or the bottom one? I actually pulled the valve cover already. The top one seemed a little fishy, but nothing obvious.
 
If the push rod is not broken, try setting the valve clearance. Intake .002 to .004 inch. Exhaust .004 to .006 inch. I set them at .003 and .005.

Kent
 
I forgot to add to what the action of the valves. If not working you might have a broken cam. On later Briggs engines the cam gear is not a solid disc. I can at time break easily.

Kent
 
I charged the battery and got it to turn over. It turned over pretty hard. From some of my research this helps support the valves being out of adjustment (not that I doubted you) I guess one of the valves opens up the compression release and they don't want to start when out of adjustment.

I played with my gooseneck trailer tonight rather than this mower so I didn't get the valves adjusted. I will try and do that tomorrow night. I will be waiting on trailer parts anyhow... :(
 
First my ignorance, I assume the 16.5 is a single cylinder? If so yours is working correctly as you discribe it.

The strokes of a 4 cycle engine are
1. Intake
2. Compession
3. Powe
4. Exhaust

Each taking 180 degrees of rotation so every other turn you have compression. You can google "4 cycle engine" or similar to get the wordy answer to how it works.
 
(quoted from post at 10:37:51 04/11/11) First my ignorance, I assume the 16.5 is a single cylinder? If so yours is working correctly as you discribe it.

The strokes of a 4 cycle engine are
1. Intake
2. Compession
3. Powe
4. Exhaust

Each taking 180 degrees of rotation so every other turn you have compression. You can google "4 cycle engine" or similar to get the wordy answer to how it works.

That's true. There shouldn't be much/any resistance on the exhaust stroke because it is all going out the valve.

I haven't set the valves yet because I have been working on my MD. That project should be done pretty soon. (and my feeler gauges are in the shop with the MD) I have to get the Briggs running ASAP because the grass is getting pretty green!
 

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