Valves

[Dave9354]

I have a b&s engine model 12s902-01-bi. Will not start. Cord snaps back sometimes. I noticed that the intake and exhaust valves are opening at the same time. Should this be happening? If not, what would cause this? The flywheel key is not sheared. Also got a backfire when trying to start. I would appreciate any help. Thank you. The only other number is 10060962. It is from a craftsman power washer model 580.752310.

 

[mechanic mark]

Post complete model xxxxxx, type xxxx, trim xx & code xxxxxxx numbers please. Thanks, Mark

Small Engines - » Valve Specifications–Briggs and Stratton

www.small-engines.com

 

[cpurvis]

Intake and exhaust valves opening at the same time?

Should this be happening? No.

Could this be happening? I really doubt it. I'd have to see it for myself.

 

[Dave9354]

Post complete model xxxxxx, type xxxx, trim xx & code xxxxxxx numbers please. Thanks, Mark

The only other number is 10060962

 

[Dave9354]

Post complete model xxxxxx, type xxxx, trim xx & code xxxxxxx numbers please. Thanks, Mark

Post complete model xxxxxx, type xxxx, trim xx & code xxxxxxx numbers please. Thanks, Mark

12s902-0142-b1. Sorry did not have complete number.

 

[ILENGINE]

Intake and exhaust valves opening at the same time?

Should this be happening? No.

Could this be happening? I really doubt it. I'd have to see it for myself.

There is a point where the intake and the exhaust will overlap with one opening and the other closing right at the top of the exhaust stroke, but just before intake. And that overlap is normal.

 

[cpurvis]

Yes, I know that.

The OP said "I noticed that the intake and exhaust valves are opening at the same time."

The key word is "opening" which means (to me) that both valves were moving in the same direction at the same time.

That, I'd like to see.

 

[ILENGINE]

Yes, I know that.

The OP said "I noticed that the intake and exhaust valves are opening at the same time."

The key word is "opening" which means (to me) that both valves were moving in the same direction at the same time.

That, I'd like to see.

Have seen it happen once. The camshaft on a 5 hp Briggs horizontal had moon shaped. Don't know how the cast metal camshaft had bent in the middle without breaking I will never know.