Not pulling vacuum?

[relative4]

Hi, I'm working on a 2006 Craftsman self-propelled push mower with a B&S 122T02-0824-E1 engine. It came in as a no start. Sprayed some carb cleaner in, fired up & died. Ordered a new carb, no help. Must be a defective carb. Ordered another, no difference. Rebuilt the OEM carb, no help. Made sure the primer is working; doesn't matter how much gas I prime in the venturi, the only thing that gets it to start is spray down the throat. It'll keep running as long as I keep spraying. Old spark, new spark plug, no difference. I figured maybe the exhaust valve isn't closing and it's not pulling vacuum. With the spark plug removed, I can see the valves. I removed the reel and operate the crank manually, and the valves seem to operate normally, but of course I can't be sure they're sealing well. If the rings are worn, would that prevent the cylinder from pulling enough vacuum to pull in mixture?

What are my next steps? Thanks!

 

[Scrubcadet10]

I would check that the intake manifold doesn't have any cracks in it. I had a similar issue with a tank mounted carb version and the manifold was cracked.

 

[relative4]

Thanks! Pulled it and checked OK. Also the gaskets at both ends of the manifold are good.

 

[slomo]

Thanks! Pulled it and checked OK. Also the gaskets at both ends of the manifold are good.

What Scrubcadet10 is getting at is you need to spray something flammable around possible leaking areas, checking for vacuum leaks, engine running.

If you spray fire juice and the engine fires off for a short period, there is a carb or fuel delivery issue. On a 15 YO mower, I would flush the tank. Make sure you have fuel flow AT carb inlet hose.

If the rings are worn as you describe, it wouldn't try to run on spray juice.

I would pull the head. Might have an exhaust seat floating around where it shouldn't be. Also check valve clearances. While you are there, per ALL engine manuals, clean carbon from cylinder areas AND dirt, oil, bugs and so on off the engine cooling fins all the way around the cylinder. Floating exhaust seat will cause low to no compression.

Test the compression. You need, air, fuel, spark and compression. Go back to the basics.

slomo

 

[StarTech]

That is an old L head so I would be thinking the valve clearances have zero out.

 

[relative4]

Compression tested at 65 PSI. Is that normal for one of these?

 

[slomo]

Compression tested at 65 PSI. Is that normal for one of these?

A Briggs will run on that. Should be around 115'ish PSI on a good sealed up engine. Check valve clearances and pull the head for loose exhaust valve seats.

slomo

 

[slomo]

That is an old L head so I would be thinking the valve clearances have zero out.

Zero out meaning they are not the issue or could of closed up to 0 lash?

All these OPE engines require valve lash checks. Unless you have some larger cc unit with hydo lifters.

Just didn't understand the zero out comment.

slomo

 

[Scrubcadet10]

L head clearances get tighter... until zero. or .000"

Intake Valve Clearance 0,005 - 0,007 in
Exhaust Valve Clearance 0,007 - 0,009 in

 

[StarTech]

L head clearances get tighter... until zero. or .000"

Intake Valve Clearance 0,005 - 0,007 in
Exhaust Valve Clearance 0,007 - 0,009 in

I even seen a few with negative clearances.. Yes I said negative clearance; otherwords, the valves were being held slightly open even when they should fully closed.