Too much compression?

[StarTech]

Sir you are wrong I’ve been to many schools and replaced many of these so unless you have a picture to prove your correct then you are not.

Look IL is right about the 310000 series being a cross flow head of sorts. The intake port and exhaust ports are about the same height; therefore, intake port must cross over downwards (about 30 degrees) to the intake valve. Now the exhaust valve does have a straight shot at the exhaust port. Either way the paths are not a prefect criss cross but is very close. A true criss cross flow it is not. The old L heads the intake valve is always on top (magneto side) and the exhaust valve is on the bottom (PTO end).

As far going to schools I haven't been to a single small engine school in my life.

One advantage of this head design is the less fuel waste as all ACR vented fuel mixture is to the intake, One drawback is there is no way to fully clamp the head gasket in the area where the intake is crossing over leading to lots blown gaskets.

Now IL is wrong about the only Briggs 19 hp engines with the ACR on the intake as not only the 310000 but the 210000, 280000, and 330000 series also uses the same camshaft and head design. So far the most common ACR failures on these camshafts I have seen is only on the 310000 and 330000 but the camshaft is the same one in all four series. I just replace two 21hp 793880 camshafts this month alone.

 

[Scrubcadet10]

Dunno, just watched a video by EReplacement parts.com and they said the bottom valve is the intake... Which if it's on the bottom, it gets bumped.
Unless I've been adjusting valves on intek engines wrong for years.

 

[bertsmobile1]

I can't remember the last OHV engine I worked on with the ACR on the exhaust
I will hazard a guess that ones again it would be an EPA regulation to prevent unburned fuel being emitted from the engine thus compression release shifted to the intake.

 

[StarTech]

Kawasaki v-twins have the ACR on the exhaust valves.

 

[ILENGINE]

Look IL is right about the 310000 series being a cross flow head of sorts. The intake port and exhaust ports are about the same height; therefore, intake port must cross over downwards (about 30 degrees) to the intake valve. Now the exhaust valve does have a straight shot at the exhaust port. Either way the paths are not a prefect criss cross but is very close. A true criss cross flow it is not. The old L heads the intake valve is always on top (magneto side) and the exhaust valve is on the bottom (PTO end).

As far going to schools I haven't been to a single small engine school in my life.

One advantage of this head design is the less fuel waste as all ACR vented fuel mixture is to the intake, One drawback is there is no way to fully clamp the head gasket in the area where the intake is crossing over leading to lots blown gaskets.

Now IL is wrong about the only Briggs 19 hp engines with the ACR on the intake as not only the 310000 but the 210000, 280000, and 330000 series also uses the same camshaft and head design. So far the most common ACR failures on these camshafts I have seen is only on the 310000 and 330000 but the camshaft is the same one in all four series. I just replace two 21hp 793880 camshafts this month alone.

I didn't say that the 19hp was the only series with the cross flow head which is what Briggs call it. that was jamesds016 that said that. I knew all the single cylinder ohv engines which I should of clarified at the vertical engines, and not the small horizontal version of those engine. I knew that the 28-31-33 all used the same camshaft and have had ACR failures on all three. Haven't looked into the 210000 series so not sure about that one. Just haven't have camshaft failures on that series for my own experience.

 

[hlw49]

Some times the cam lobes or gear can slip and cause it to kick back and not start. If it is the compression release most of the time you can turn the engine backwards by hand until you come up on compression. This way you have one full turn with no compression and the engine will start. But if the cam lobes or gear have slipped and it kicks back you will know it, really kicks back hard.

 

[hlw49]

Haven't followed this threat and this may already been addressed but valve lash can cause kick back as well.

 

[GroundFisher66]

IL, I think I see why the ACRs are failing and it is a design problem. Even when the ACR is fully retracted the pin is still loose enough to be constantly bump by the tappet rocking the pin until it breaks off sending the ACR weight flying across the engine. It is just like you bending a piece until it breaks. And sometimes it takes out the governor while at it along other damage. The last two I did use aftermarket camshafts ACR had damage the governor too. THe next to last one actually snag the cylinder a little, lucky it was just a nick.

Great info! I am having exactly the same problem. In addition, the ACR weight probably messed up my governor, because the engine runs at a substantially higher rpm now and has a higher rpm when idling. Thanks for the information.