Valve adjustment tolerence setting

[Kruzer]

I've got a 24 hp twin. It has about 200hrs on it. Bought it new and never been adjusted. On a tractor. Basic problem is it has a backfire through the muffler. It was hard to start too at times too. I opened the valve covers to check them. I did the set up, TDC and 1/4 past it. On both I could not get a 005 in. The 004 goes in but you have to really push it. According to the book, they should be set at 004-006. My motor is 445667. The rocker arms are tight with the 004. I noticed on videos around even with 004 you get a very slight movement. Should I see a very slight movement? Should I go up to 005?

 

[reynoldston]

You should feel a small resistant's in the feeler gauge. Better a little on the loose side then the tight side.

 

[Kruzer]

So i should go with 005 and still be within correct adjustments? Would valves become too tight on their own in some cases instead of loose?

 

[ILENGINE]

Valves can become tighter as they wear. Even though the spec is .004-.006 I don't think you would even know if they were .003. Sometimes to they rocker arms will tilt a small amount and make the clearance appear smaller then what it really is. so you may want to wiggle the rockers to make sure they are not tilting, and appearing to give a smaller clearance than what you have in reality.

 

[motoman]

IMO "screw-type"rocker valve adjustment is an acquired skill. Having to push (force) a feeler gauge thru says it is not at that feeler gauge thickness, but a thinner one. Describing the sensation of a feeler gauge passing thru a clearance so you can accept that value is tough- like describing the first time you balanced on a bicycle, but here goes...Forcing is not acceptable, but neither is looseness. The feedback through the fingers is kinda (IMO) like buttering your thumb/forefinger and sliding the selected gauge thru. If you pinch hard while passing the guage it's not just right, and if you just make contact while passing through -too loose. Also the sensation is different for the small contact on (my) Intek valve tip/rocker tip than say an overhead cam car where the contact patch is as large as the feeler gauge width. Now that this is crystal clear :smile: More blather...

IMO "trapping" the feeler gauge while tightening the rocker screw can result in over -tight clearance because the screw can actually dig in to the feeler gauge. Best tip I can think of is checking the clearance after tightening and being prepared to change the setting until correct. The "ball " type rocker IMO is tricky to tighten because it moves around. I have seen the youtube demos and the professionals have a lot of experience at this, but this is to encourage you not to get discouraged with this type of rocker adjustment. There are a number of hand held valve adjustment tools on the market which promise easy adjustment. I have not tried them. Patience and practice.

 

[mechanic mark]

I've got a 24 hp twin. It has about 200hrs on it. Bought it new and never been adjusted. On a tractor. Basic problem is it has a backfire through the muffler. It was hard to start too at times too. I opened the valve covers to check them. I did the set up, TDC and 1/4 past it. On both I could not get a 005 in. The 004 goes in but you have to really push it. According to the book, they should be set at 004-006. My motor is 445667. The rocker arms are tight with the 004. I noticed on videos around even with 004 you get a very slight movement. Should I see a very slight movement? Should I go up to 005?

For B&S engines it's 1/4" inches past tdc., not 1/4 turn. Post model xxxxxx, type xxxx, trim xx from engine. When you have valves adjusted correctly, you should feel a light drag with feeler gauge between rocker arm and pushrod. Let us know how it goes, thanks.

 

[Kruzer]

Thanks for the replies,

I just went thru the process. I got 004 to where it glides in with minimal drag. Ran it and rechecked. I still get a mild sputter through the muffler which is what the original problem was. Should I go with 005 or go in to a different direction?

 

[mechanic mark]

Thanks for the replies,

I just went thru the process. I got 004 to where it glides in with minimal drag. Ran it and rechecked. I still get a mild sputter through the muffler which is what the original problem was. Should I go with 005 or go in to a different direction?

Absolutely not, 0.004 is just fine. Remove & clean spark arrestor from muffler & give it a try.

Engine & Carburetor Backfire | Mower & Small Engine Repair | Briggs & Stratton FAQ

FAQ | Lawn Mower Safety Tips | Briggs & Stratton

 

[mechanic mark]

Thanks for the replies,

I just went thru the process. I got 004 to where it glides in with minimal drag. Ran it and rechecked. I still get a mild sputter through the muffler which is what the original problem was. Should I go with 005 or go in to a different direction?

Post model xxxxxx, type xxxx, trim xx from engine.

 

[Kruzer]

Post model xxxxxx, type xxxx, trim xx from engine.

Not sure if these are the numbers but they are off the valve cover
445677
type:0827
080318yg