Thoughts on fixing a B&S engine cheap

 
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gaw
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Post by gaw » Fri. May. 29, 2020 9:06 am

I am wondering if anyone else has done this or something like it and how did it go?

I have a 27 year old Dixon ZTR mower, it is not my only mower but it has been pretty reliable through the years and as long as it works I continue to use it but I won’t be sinking big bucks into his machine. A couple weeks ago I turned it off as usual when finished using it. A week later I go to start it and it cranks with incredible ease but won’t start. It seemed obvious that there was no compression. A head gasket is cheap so I figured I would take the head off to investigate. Yesterday I did this and it revealed the intake valve seat was popped out and stuck under the valve, nothing looked marred up or damaged so using a punch I carefully drove the seat back into the block and punched on the aluminum next to it to try and stake it in place better. The head gasket was also leaking a bit by the exhaust valve. This is a 12 HP Briggs & Stratton vertical shaft L head, old school. How long will this cheap fix last? My guess is between ten minutes and ten years. BTW this engine has about 500 hours on it.


 
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Rob R.
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Post by Rob R. » Fri. May. 29, 2020 9:22 am

It is anyone's guess. I think if you did a good job staking that seat in place it may stay there for the remaining life of the engine.

 
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Post by Sunny Boy » Fri. May. 29, 2020 10:36 am

Rob R. wrote:
Fri. May. 29, 2020 9:22 am
It is anyone's guess. I think if you did a good job staking that seat in place it may stay there for the remaining life of the engine.
This.

Without pictures of the fix, only you can say if it will stay put. However, there is no force to push the seat out other than if the valve face sticks to the seat over the long offseason. And the easy way to prevent that is dump some Marvel Mystery Oil in the gas - enough to really get the exhaust smoking white - and shut it down after fogging it with that for about a minute.

That's a decades-long proven method used to prevent sticking valves and piston rings in expensive marine and antique engines when prepping for long-term storage.

And it only cost pennies everytime you do it. ;)

Paul

 
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Post by Rob R. » Fri. May. 29, 2020 11:08 am

Paul, do you mix the MMO right in the fuel? Or just spray/drizzle it into the carb?

I have had good luck with marine fogging oil, and draining the bowel of the carb.

 
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Post by Sunny Boy » Fri. May. 29, 2020 1:15 pm

Rob.
Always in the gas so that it also cleans and protects the entire fuel system from the gas tank on into the cylinders.

Just draining the carb bowl can let in moisture and lead to corrosion, and sticking restrictions/jets. We never drain carbs and leave them empty. The gas will evaporate on it's own leaving the oil in the MMO coating everything in the carb, fuel pump, and fuel lines. And it will protect metal gas tanks.

Some of the marine engines would also get fogged-out by pouring additional oil into the carb, but you have to be very careful how much gets poured in, or it can damage a piston. Plus, spark plugs often become oil fouled from an excessive amount of oil and would need to be cleaned or replaced next season start up.

Paul

 
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Post by coaledsweat » Fri. May. 29, 2020 3:23 pm

If it has compression and runs, I'd say your all set until the next great adventure.

 
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Post by titleist1 » Fri. May. 29, 2020 3:28 pm

I have found that if I brag about the cheap fix that got me running again it will last 10 minutes....

If I keep my mouth shut it lasts until I forget exactly what I did to fix it the last time. :what:


 
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Post by Rob R. » Fri. May. 29, 2020 3:30 pm

The fogging oil I have used is in an aerosol can.

I had the same thoughts as Paul for a long time about the carb sitting dry, but I got tired of cleaning the green disease out of idle jets. I had problems with it despite using ethanol free gas, stabilizer, MMO, and other products. The manual for my John Deere lawn mower says to drain the bowl prior to storing the engine for over 30 days, so I started doing it for everything and have not had an issue since.

Carbs made with high quality brass do not have this issue, but the modern China stuff certainly does...and that is what was giving me issues. I would be willing to give MMO another try, but I think I need to use a stronger mix.

 
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Post by freetown fred » Fri. May. 29, 2020 3:34 pm

G, ya done good-- just keep runnin the old btch, she'll let ya know when she's done!!!!!!!!!!!!!!!!!!!!!!!! LOL

 
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Post by gaw » Fri. May. 29, 2020 4:05 pm

It will be put together and run and I’ll see what happens. The head gasket is about $7.50 on Amazon and now the gas tank is dripping so I need a rubber grommet for that, another $2.50 so for ten bucks we will see.

I have never had a small engine like this loose a valve seat or any type of mechanical failure. All other L head Briggs were small push mower size and the mowers were shot before the engine ever died. I spoke to the guy who sold me this mower new and he said that he has seen several L heads loose valve seats and once they do it they eventually do it again. When you work on those engines as a business may be you see it often. He knew I wasn’t going to sink money in it and he didn’t think it was a good idea to. He also knew I was not going to buy a new mower from him either so I assume he was being honest.

Every time I get gas for my small engines it is 93 octane Shell, why Shell? Because it is the closest and usually the cheapest. All gas is treated with ½ oz of Sta-Bil per gallon and all 4 stroke gas gets ½ oz per gallon Mystery Oil. I never had any problems with bad gas. Fall maintenance consists of turning the engine off after the last mow and spring maintenance consists of starting the engine before the first mow. This engine had been running several hours this year before this happened and one week later it popped that valve seat probably upon cranking it.

Thanks for the feedback and I’ll update how it goes. For ten bucks I have to at least see what happens.

 
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Post by D-frost » Fri. May. 29, 2020 4:15 pm

Gaw,
Been there, done that, still running.......
Those old 'made in the USA' B&S are pretty tough...........now if it says'made in china,..........say a prayer!!!!!!
Cheers

 
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Post by cabinover » Fri. May. 29, 2020 4:28 pm

I had a Kawasaki horizontal on a walk behind that did just that, popped the seat out and hung the valve open. The seat sometime in it's life had cracked as well. I now wish I'd have thought about staking the seat back in, that motor ran well with very little compression.

What popped the seat out? A backfire believe it or not. Good luck with your motor, it'll be fine.

 
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Post by Sunny Boy » Fri. May. 29, 2020 4:48 pm

Valve seat inserts can pop out for various reasons. Most common is that it wasn't that tight a press fit to begin with. mass production has it's range of tolerance and that may have been at the loose end of the range with a small end of the range insert pressed into a large end of the range seat.

Plus, rust can stick parts together, so any rust on the valve face and seat over the winter can make them stick. Add to that, an aluminum head has much more expansion/contraction than the steel seats and years of expanding and contracting can change how tight the inset is in it's seat. Then, add years of the insert pounding in the aluminum when it's hot and not as hard. It's what engineers call a cascade failure - bunch of little things come together as the cause.

I deal with aluminum heads on air cooled aircraft style engines. The early ones had brass seats. When the gasoline industry started switching to leaded gas in 1930 the brass seats developed chemical reaction erosion problems. So in 1932 the engine manufacture switched to steel inserts. No more seat erosion from the lead in the gas, but the steel seat expansion was different than the brass and those sometime come loose. Not all, but just the few that were at the looser end of production tolerance limits.

So how do we fix those ? We stake the aluminum around the seat with a machinist punch to tighten the grip of the aluminum head again...… just like Glen did.

Paul

 
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Post by Freddy » Sat. May. 30, 2020 1:31 am

You are set to go! I predict you'll not loose that seat again. <fingers crossed>

 
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Post by gaw » Sat. May. 30, 2020 7:26 am

Yes fingers will be crossed. I'm waiting for the head gasket from Amazon, I always choose free shipping because I'm cheap that way and I don't believe in paying for Prime :D


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