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Advice needed on B&S Engine

GBertolet

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I am working on a 18.5 hp B&S OHV engine on a Craftsman tractor. It belongs to a relative. The pressed in valve guides keep working forward, to the point they interfere with the valves closing. This is the third time this has happened. The last time it was the exhaust valve guide. I didn't tear the engine down yet, to see if it is the same guide or not. Same symptoms as before, no compression and backfires. I have to go pick it up, and take it to my shop.

I drove them back in previously with a wood block and hammer. They seemed tight going back in, but apparently not tight enough.

What is the proper procedure to permanently lock these in place? Stake them, hi temp epoxy, set screw, or some other method?
 

Termitebuffet

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I am working on a 18.5 hp B&S OHV engine on a Craftsman tractor. It belongs to a relative. The pressed in valve guides keep working forward, to the point they interfere with the valves closing. This is the third time this has happened. The last time it was the exhaust valve guide. I didn't tear the engine down yet, to see if it is the same guide or not. Same symptoms as before, no compression and backfires. I have to go pick it up, and take it to my shop.

I drove them back in previously with a wood block and hammer. They seemed tight going back in, but apparently not tight enough.

What is the proper procedure to permanently lock these in place? Stake them, hi temp epoxy, set screw, or some other method?
Might not be "correct" but I'd put a bit of the thin loctite...wicking grade I think it is ...and stake it good....

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MACHINE

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I am working on a 18.5 hp B&S OHV engine on a Craftsman tractor. It belongs to a relative. The pressed in valve guides keep working forward, to the point they interfere with the valves closing. This is the third time this has happened. The last time it was the exhaust valve guide. I didn't tear the engine down yet, to see if it is the same guide or not. Same symptoms as before, no compression and backfires. I have to go pick it up, and take it to my shop.

I drove them back in previously with a wood block and hammer. They seemed tight going back in, but apparently not tight enough.

What is the proper procedure to permanently lock these in place? Stake them, hi temp epoxy, set screw, or some other method?
Fixed a vanguard the other day the exhaust valve seat had fallen out .

If you could cut a c clip groove somehow that would work

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Moparmyway

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I am working on a 18.5 hp B&S OHV engine on a Craftsman tractor. It belongs to a relative. The pressed in valve guides keep working forward, to the point they interfere with the valves closing. This is the third time this has happened. The last time it was the exhaust valve guide. I didn't tear the engine down yet, to see if it is the same guide or not. Same symptoms as before, no compression and backfires. I have to go pick it up, and take it to my shop.

I drove them back in previously with a wood block and hammer. They seemed tight going back in, but apparently not tight enough.

What is the proper procedure to permanently lock these in place? Stake them, hi temp epoxy, set screw, or some other method?
Are you sure that the guide isnt too tight to the valve ?

I’ve had HD Sportsters, B&S, even a Kohler or two do the same thing.

I suggest that you mic the valve the get a good broach or reamer thats going to give you between 0.002-0.004 clearance on your exhaust valve to guide.
Intake should be between 0.001-0.003
 

scrubcadet10

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Staking them would probably be the next best thing.
The engine isn't getting too hot? Or overheated previously?
Usually overheating moves the guides.
 

GBertolet

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I am to pick up the tractor this week. When I get it apart, and examine it more closely, I can determine the best fix from the suggestions offered.
 

FergusonTO35

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Green Loctite should work, although of course you would want to try the other suggestions first. I imagine you could likely get some good used heads for cheap also.
 

GBertolet

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I have green loctite (290). But would it withstand the heat?
 

FergusonTO35

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Far as I understand it will, you may want to check with the manufacturer to be sure.
 

Al Smith

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I've never had the guides come loose but have reseated a few valve seat inserts .You basically dimple the counter bore and pound them back in and punch around them to deform the metal .
 

GBertolet

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It was the exhaust valve guide again. It advanced inward until it stopped the exhaust valve from closing. I removed the guide, degreased it, and the hole, and put hi temp sealer on it, and drove it back in with a hammer and block of wood. It was really tight going in. I can't see how it keeps moving forward, but it does. I also staked the heck out of the hole, inside of the head, supposedly keeping it from advancing inward again. The engine started right up, and runs fine. I hope that this was the last time I have to deal with this.

I am attaching a photo of the sealer I used. It costs $30 for a small bottle. I used it previously to help hold an intake valve seat, that kept coming out, on another B&S engine. I had to aggressively stake that also, adding the sealer, as it kept coming out, again and again.
 

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scrubcadet10

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Yep, 99% of the time it's the exhaust guide that moves.
Since the head is aluminum and the guide is cast iron (most likely) the softer metal expands faster and lets the guide slip.
 

Al Smith

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I'm not exactly an expert on B and S specs but it might be a thing they make a slightly over sized guide for repairs .If so you might be able to heat the head and freeze the guide causing a heat shrink fit .I've got the manual for flat heads but not for over head valve engines .I'll see what that says in the next few days .Thee might be something on the net for that matter
 

Jimmy in NC

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Tarryl on YouTube has a video drilling and tapping the head. He shows inserting a Ball Bearing into a drilled dimple in the guide then a set screw with loctite. Next one I see I will try it on...

Moving guides is common. Normally from a dirty motor not cooling or a mouse nest.
 

KennyWinCT

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I've done the Tarryl trick too. The Head kit is about 140 shipped on Amazon. For a guaranteed repair I'd replace the head, that is if the machine isn't too roached out that it isn't worth the investment.
 

Larry B

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I fix them by driving out the guides and then slide them over an old valve chucked in a vise and then use a center punch and hammer to upset the outside of the guide with about 30 or so punch marks. Then driving the guides back in the head. Should take some serious driving. If the valve is tight in the guide after installing Briggs sells a reamer or you can carefully use a drill bit NOT in a power drill to ream it. Some type of Locktite or JB weld wouldn't hurt but i have never used any. As far as i know Briggs does not spare out the guides.
 

stretch5881

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Briggs suggests replacing the heads. Pppffft!!! Why don't they just suggest replacing the engine.
Easiest, quickest way for me, is to tap the guides back in, reach in with a wire feed and put a little weld on 2 sides of each guide.
 

KennyWinCT

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Easiest, quickest way for me, is to tap the guides back in, reach in with a wire feed and put a little weld on 2 sides of each guide.

That'll work too!
 
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