Briggs and Stratton L Head - Low Compression

Hi All,

I was hoping that someone having experience in repairing B&S L Head Engines could provide some insight on my issue, before I decide to just scrap this engine for parts.

I have a Husky Pressure Washer with a B&G L Head Engine. The Engine Model is the 10L902-0010. Pretty much a standard B&L L Head Engine. The cylinder is low on compression, around 80psi. It runs very, very rough......not to the point that it stalls, but very poorly. Changed plugs and still did not resolve.

Background Info - Purchased for $25 at a local online swap sale. Ran ok for about 5 min, discovered it needed a new pump. Purchased for around $70. Purchased new carb (kit w/ diaphragm and all), new air filter, sparkplug, and fresh engine oil. Started running funny, realized sparkplug hole was stripped. I definitely did not do this, so purchased another head on Ebay for $10. Inspected cylinder and seemed ok. No knicks or pitting. Piston looked ok with normal carbon buildup. Intake manifold looks ok. Did not disassemble, but no signs of cracking.

The head gasket looked ok, but not sure how to tell if its 100% ok? Wondering if this is the main issue? I see they are very inexpensive, around $5 on Ebay. I'm definitely willing to take the risk for that amount.

I don't have any sort of leakdown testers, so I won't be able to tell where the air is coming in at? I'm thinking its got to be sucking air somewhere.

I don't mind taking the head off again if someone needs to see a picture of the head gasket.

Any suggestions on where else the problem is? Or am I right and thinking the head gasket is not ok?
 

AVB,
 
Not sure what you mean by my spec (type) number is wrong.  This is the model # of the B&L Engine.  I have the parts diagram right here in front of me.  I can even show you a pic off the engine.
 
I will tear off the head again and look at the valves. From what I remember, they seem ok.  Do you need pics if I post?  I'll also remove the intake manifold and inspect.  Looks ok from the top, of course you can't see the bottom side.

AVB,
 
You are correct, it was a mistype.  It is a 10L902-0110...........which doesn't make a huge amount of difference.  All these L Heads are basically the same.  Just trying to figure out where this air leak is coming from if that's what I have.

That gasket is a large part of your problem, replace it and properly torque the bolts but before you do remove the breather and check the valve clearances. 80 psi with a leaking gasket tells me they are excessive, the compression release is not working which will kill performance

AVB,
 
I agree with you.  I'll start by replacing this gasket tomorrow when it comes from Amazon.  Hopefully this will resolve all of the issues I'm having.  If not, I guess I'll look to the valves next, but as I mentioned, looks like they are seating properly.  There is no wiggle in them at all when they are fully seated.
 
Not sure how this gasket failed....but I did buy it used so no telling how well/not well it was taken care of.  I've never had a pressure washer blow a head gasket before.

gibbywmu
 
If not, I guess I'll look to the valves next, but as I mentioned, looks like they are seating properly.  There is no wiggle in them at all when they are fully seated.
 

Why not remove and inspect the valves while the head is already off?
How can you tell if they are seating good without removing and inspecting them?
 
At the bare minimum have you checked with a feeler gauge and checked for the "compression relief bump" AVB mentioned?

AVB, I worded that poorly. I meant to say that excessive valve clearance would kill performance and render the compression release ineffective. Even a new engine would normally have 75 psi  cranking compression. 80 sounds odd especially with that leaking head gasket.

80lbs doesn’t seem low to me.
Head gasket help any?

Guys,

So we have some life.  My mistake.  It was a new carburetor, but somehow when I installed it, the diaphragm was not right.  I pulled it off and sure enough, it had a hole in it.  No worries as I had a spare diaphragm.   Installed, engine ran great right away!  (No pump on).  Now, here's where the trouble lies.   When I installed the pump (this is a brand new Annovi Reverberi pump, the same style that are on my other 3 pressure washers), it start to run for about 1-2 seconds, and shuts off immediately.  Its like with the load of the pump on, it can't handle it.  Shuts off right away.   I turned the water supply off, disconnect the hoses, and fired up again.  Runs perfect with no water supply.  Only let it run for a couple seconds so the pump coudn't get damaged.

Now...........why with a new pump does the engine want to stall out immediately if it runs fine w/out the pump on?  What am I missing here?

Roy,
 
Sounds like it by the symptoms right?  This is a brand new pump.  Now, I did install a new carb and had issues as I just discovered.........due to a diaphragm not being installed correctly.   I did remove the Unloader Valve on this AR pump, and its brand new.  Still has white grease on the spring.  Definitely not the unloader valve.