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I'm stumped....but then this is literally the first engine I've gone into this much depth on.
Background:
Briggs 286707-0441-01 12.5 HP I/C Quiet engine that slept in a flood for a year. I grabbed it, drained the oil and fluids etc....replaced the carb with a chineasium one and it fired up and ran but SMOOOOOOKED like crazy. I also rewired it and new starter solenoid etc....but that's not really an issue with this part.
SOOOOOO
I decided on a learning experiment(I was only into it $200 at this point)
Decided to do rings and in order to do this.....CRACK open the case.

SO....I did. Drained oil, separated the crank case, etc. It was dirty mess in there but cleaning it all out of all the crude made me feel GREAT.

I slipped the piston out, honed the cylinder until 95% of the marks were not noticeable by finger touch. installed the NEW rings on the piston ensuring the ring gaps were 1/3 piston away from each other.

I should say that I removed the governor assembly and the camshaft which had the bottom valves fall out and I didn't catch which was which.....so assembled in revers and matched the little "o" of the Crank and the Camshaft to align timing.

Now after it's ALLLLLL back together I stick it back on the tractor assemble everything and go to fire it....1/4 crank and then stops.....WAAAAAAY to much compression. remove the spark plug, cranks over and over without problem.....spark plug back in....no crank.

I do my research....find out there is a "compression relief" on some Briggs engines.....I POUR over every parts diagram and manual I can find without fining anything associate with a relief on this engine, no little mechanism on the Camshaft at all.

So.....I didn't check the Valve clearance or lash etc as I didn't remove the head from the block.

What am I missing, and this will be the third time I've pulled this engine apart...lol Any help is appreciated as this is an old engine from a Husqvarna LTH-125 tractor.

THANKS!!!

I slipped the piston out, honed the cylinder until 95% of the marks were not noticeable by finger touch. installed the NEW rings on the piston ensuring the ring gaps were 1/3 piston away from each other.

So.....I didn't check the Valve clearance or lash etc as I didn't remove the head from the block.
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What kind of hone? What type of stones? What grit? Did you put a 45 degree crosshatch pattern on the cylinder? Never seen someone hone a cylinder with the head on.
If i were to take a SWAG at the problem i would say you have oil up past the rings causing hydro lock. Take the head off and see if you have oil in it.

it's an L head or flat head, not a OHV engine. I had the head off the cylinder but didn't remove the cylinder from the block only removed the piston from the cylinder and then honed it. I used medium stones on my power drill. Sorry I don't know what the different terminology are for things(head, head cover, valve cover, etc.) I removed the "valve cover" to show the combustion chamber, top of the piston and 2x valve tops).

I hadn't noticed any oil on top of the piston but did add a little to the rings before reassembly. If I were to guess it would be like less then a 1/4 teaspoon total on the cylinder walls and rings.

I have some issue with the compression relief on it I think I just can't figure out what that entails and how to fix it.....I may end up just disassembly and discarding the entire tractor at this rate....it is only a project without any reason lol

I plan on pulling the engine apart again and seeing what I can figure out just wanted to ask here to see what others have encountered.

If you removed the crankshaft and the camshaft, you probably dropped the lifters. When you reinstalled them you may have switched them around, changing the valve clearance. No matter what you do you will have to remove the valves and reset the valve clearances. Many DIY mechanics try to just switch the lifters, but 90% of the time they still have to reset the valve clearance.

Lets start with getting the terminology straight on an L head engines. The head is the part with the spark plug held on by 8-9 bolts. The valve cover is on the side of the engine with two 1/4 or 5/16 headed bolts and should have a rubber hose between it and the air intake side of the engine. You have to remove the valve cover to check the valve clearances and to remove the valve springs to grind the valve stem to set the valve clearances.

As far as compression release this engine may not have a mechanical release. More like a modified cam lobe that holds one of the valves open longer than it should allowing compression to bleed off before firing. This is a constant release happens every other engine revolution

excellent and thank you.
Yes when I pulled the camshaft out the lifters fell out....actually more then once. they appeared to be the same length and size so I didn't really think much of it and just stuck them back in the way they came out. Is it possible that something else was stuck up the hole on the one that keeps the valve slightly open? I remember seeing a little "cap" type thing but couldn't figure out where it came from and it may have been from a different engine or something.

I'll pull it apart again and do the valve clearances......what do you do if you grind them down too far? lol I guess you learn a lesson and replace them.

This being my first foray into the world of small engine rebuilding it's been fun(and aggravating) to deal with a unit that was completely flood damaged. The oil looked like swamp water even after draining it out 2x.

Hopefully I can get it going again, I am having issues with the Hydro drive in it not wanting to do anything after my shitty attempt at a fluid change but that's another problem after the engine runs...lol

my god I love those guys....their videos make me laugh!

Grinding valve stems to adjust valve clearance by a DIY can take 15-30 minutes, if he has the patience to do it slowly. Get them to the low end of the tolerance (.004” intake .009” exhaust) and then reinstall with springs. I grind a little, then push down hard with my thumb and measure clearance hold tight as I can. When I reach low end I install. Usually I have to remove and do it again. May take a few try’s but patience is your friend. You must make sure the end is flat and square or your gap will be wrong. This manual may be of some help. https://drive.google.com/file/d/0B6NaqjIxWV1ycG8wd0s3Z2Q2X00/view

thanks all, I'm feeling more and more like I can get this thing running again and well. I've had luck with another tractor rebuild I did and hoping this one goes well too.

Sounds like just another person using a flex hone to do the work of a rigid hone. Just makes things worst.

If the cylinder is either ovaled or tapered (usually both) a flex just makes both these worst. Besides if you were able to hang a finger nail on grooves the cylinder should be rigid hone to .020"over as there is no .030 piston supplied anymore. If you got go over .020" then the engine is a basket case. I have seen cylinders tapered that only clean up within the last .002"

As for valve clearance on L-head (side valve) engine I always grind for the max clearance spec as the these engines tend to close up valve clearances over time. This is so I don't need to redo the valves as often. Right the opposite with OHV engine where I do the minimum settings.

There was nothing that hung a nail on, just some glazing from the engine sitting with old oil/water in it. the cylinder wall was clean when I finished and the new rings seemed to seal well, when I installed them on the piston and then into the cylinder id didn't appear to have any ovaling to my eye and again the rings seemingly were contacting the walls well. it was a pressure hone I used, a $25 one from local Canadian tire store.

I'm no technician and this is only the second time I've repaired a lawn mower engine, first one was on a OHV Briggs that had a broken push rod which runs like a champ now

minor update on this. I just pulled it out again and started working on this "winter" project.
both valve clearance were 0.00 I couldn't fit anything between the tappet and valve with the engine at TDC.

I've curious now though about how this might effect my slow turning over problem? it seems like there is too much compression in the engine and that the cam lobe relief is the problem, I would think that a 0 gap would mean a bigger lift meaning loss of compression rather then the other way around....maybe I'mma missing something?

Thoughts?

Couple of questions. When you rotate the flywheel by hand do the valves open and close properly? When you checked the clearance were the rocker arms snug against the valves and pushrods? The last time you set the valve clearance, are you sure the locking set screw was very tight? Finally, have you pulled the head and checked the valve faces and seats? Sorry, but it will be hard for me to state possible causes until I have a better picture of what you have going on.

Thanks for the reply!
it's a Briggs L-Head, with the side Valve cover off and the top of the head removed to expose the Piston and valves I rotate the engine and the valves go in and out as normal as the piston cycles though it's stroke. The rocker arms were snug against the intake valve stem, on the exhaust it was .004 I believe. I adjusted Intake to .005 and Exhausts to .006 I believe. I don't know what the "locking set screw" is and there was no screw in the valve area that I can identify. I cleaned up the lip and seats for the valves and lapped them in prior to setting the clearances above.

Sorry, I thought I read you have an OHV engine, L-head changes everything I posted. Two different questions now. How did you adjust the valve clearance last time? How did you lap the valves and how long ago did you do this service? I need all engine numbers, model, type and code please.

This is my first time adjusting the valves.
I removed the valve springs, removed the valves, cleaned them with wire wheel, cleaned up the seats with emery cloth. Once everything looked clean...
I lapped them in with lapping compound and a lapping tool but doing the quick back and forth in my hands and rotating 1/4 turn and repeating.

It appears I have a good seat now. then I pushed them in with my thumb and checked for clearance with a feeler gauge, adjusted to the lower end of the specs I found, I think .005 intake and .006 exhaust.

I've yet to put the machine back together now after doing this part. I'm having problems getting the Exhaust valve spring and retainer in place, it has the 2x half circle lock bits for it and my make shift spring compressor I made isn't working well for it.

Don't to check the valve guides especially the exhaust. A worn exhaust valve will cause one to smoke like a freight train.

Also hopefully you used a ridge hone as flex hone only breaks the glaze and make things worst if the cylinder is ready ovaled and/or tapered. Plus if the cylinder needed honing it is possible that cylinder worn to a point that over sizing is required.

I used a flex hone...I think. the arms were not rigid, there was nothing in the cylinder that looked bad, nothing that was pitted, gouges, nothing to catch a finger nail on or anything. it seems to seal well with the new rings installed, but also seems to build compression to the point of limiting the machine from turning over, I'm hoping that the valve adjustment will help and the machine will at least turn over well now.

the guides seem to be a good snug fit, no play in the valves when installed, and a seemingly good fit overall.

I'm not expert though....lol

Guy used a flex hone. He doesn't have a machine shop at home so lighten up on the poor fella' LOL

That large HP engine must have some form of compression release.

Like some mentioned but funky wording. Open the valve clearance gap to the widest, in spec value. Example an EX valve specs out at 0.004" to 0.008" gap. Set clearance at 0.008". As one said above, gap will shrink over time and operation.

Too late but when honing or boring, you need to scrub the crap out of the cylinder when done with HOT soapy water and brushes. And do it again and again until a white paper towel stays white on a bore scrub. Think hospital clean here.

slomo

Noted, I'll keep that in my records for the next(if ever) time I do it. I have to fabricate a spring compressor so I don't buy yet another tool for a 1x build. I thought I had it done but the one I built didn't' work on the exhaust valve spring. with that I'll pull it apart again and reset the clearance to max rather then min settings, I wasn't sure which to do so went with the minimum, but after thinking it does make sense that the gap closes over time to to simple wear on the stem.

More to follow once I get it all back together.....

Can anyone confirm if on 286707-0441-01 12.5hp Briggs engine has a compression relief built into the Crank/valves? Ie does the crank keep one of the valves open slightly to bleed off the compression to allow the engine to rotate to start? when I rotate the engine clockwise by hand, there is a point where both valves are slightly open(ie about 1/10 the way).....normal?

Not confirmed but a 12.5hp engine would either pull the rope out of your shoulder or stall a starter easily. Thinking it must have one. The more intelligent guys on here can verify your question. We have a great team of people on here.

slomo

So just a random update on this.
Everything is all back together and still the problem persisted....
So I started looking deeper.

I found one problem was the main drive belt is way too tight, and it binds on 2 of the "keepers" and just doesn't allow the machine to turn over. I loosened the belt off a bit and it started to turn over better for sure.

Curios thing now....it seems as if fuel is spitting out of the carb intske side.

Still no start but some headway.

Hoping the large issues are compete now and on to a dirty carb or something similar.

Will need a longer belt for sure as the one I have is way too tight it seems.

I should also mention that i think the starter is dead, it still turns over the starter on the key, however the stsrter does not engage the flywheel to turn the engine over.

This has been quite the project, never again will i attempt this type of mower repair....lol

If the starter spins over, but does not push the bendix gear up, you either have a weak battery or a bad bendix drive.

So I took the starter off and apart.....I found that 1x bush was disconnected, and another wire came apart from the brush when I touched it. these were on the "neg" end of the starter. Tried bench testing both before and after I thought I fixed it and nothing, no spinny spin. I'm hoping that my Epoxy fix works after taking it apart again. I did have some smoke exit the starter when it was turning over and feel it's not getting enough juice not to turn it over. It is entirely possible the battery is on it's way out, however I hooked my car up to the battery via jumper cables and it didn't do anything different.

Chasing gremlins on this amazing learning experience. haha

Main issue that I found with the "slow" turning of the engine was the belt I bought was too short. I believe the replacement for this tractor was a 82 2/3" belt when the original belt was a 84 1/3" belt or something in that range. Some people think size doesn't matter but it definitely does with a belt like this. The part number from Husqvarna's website matched up and I bought the belt locally(months ago) not realizing that somewhere along the lines the original P/N was superseded by an updated shorter belt. Original one for the tractor was loose feeling, new one was terrible to get on and in place and was SUPER tight. Now I'll have to figure out the proper length to run and change the belt.

Who knew that working on old Tractors would be more interesting and complicate then my old car?

I'd leave the belts off until I got the engine running smoothly. No point in putting a load on at this time.

The plan is to leave the drive belt off until it runs well.

Everyone likes updates right? RIGHT? well here is what happened I think.

The drive belt being too tight on the machine and binding made excessive friction and would not allow the engine to rotate enough to start. Due to my not being aware of this fact it pushed the starter beyond its normal capacity and eventually fried 2x brush wires. It was not apparent at the time as the starter was still engageing…..just not enough to pop the gear out and connect with the flywheel.

Removed the starter and disassembled it to see lots of corrosion and the damaged brushes. I thought about replacing the mech with new but it was a week away and $30 ish bucks so in the meantime thought I'd attempt a fix. Tried my had at solder, I suck and it never held. Second attempt I had some epoxy and used it, making sure to get a good connection between the wire and the brush as this was the main point. After a day of curing I assembled the unit and bench tested to great satisfaction it almost spun off the table.
Installed on tractor and with some starting fluid it banged to life and ran really well once it was going.

Next was the driveability. In forward......nothing...….reverse.....nothing. Remembers that I "changed the oil" in the Hydrostatic system....thought well....maybe air in there......maybe not enough fluid.

Tried both, added about a half liter of fluid to the system and noticed a lot of bubbles and air coming out.....let it sit for a good 10 mins running in neutral until there was a white foamy looking stuff at the top.

Installed everything and not is goes forward well and slowly in reverse......like I can push it faster in reverse not....haha

all in all not a bad project to go from sleeping for a year with water in the carb/gastank and being bashed around in a flood area to driving around my driveway.

thanks again everyone for your help, I learned a lot and am glad I did this learning project. Next up to find a longer drive belt, sharpen the blades and install the deck.

now all I need is the proper driver belt for the machine, even though I bought the proper one from the Husqvarna dealer here it is much to tight it appears and jams against the belt keepers on the idler pully part.

What's the model number of the mower?

You bleed the air out of a hydro by jacking the back of the mower so both wheels are off the ground
Then you run the engine as SLOW as possible to avoid frothing the oil ( white foam )
With the bypass valve open you run forward then reverse quickly changing for about 10 minutes.
Then close the bypass and do the same .
It can take a very long time to get all of the air out.
As the oil level drops you keep topping it up.
Hydros are he only thing where I measure the lubricant to the specified amount and keep working the pedals till all of it goes in .

Model number is LTH125
I went to the Husqvarna dealer, asked for a belt and they gave me the one that matched the parts list.....it runs and drives now but I had to take the idler pully off as the belt was way to tight to run with it on.....even with it not on there I cannot remove the belt easily and the clutch brake doesn't work at all and only way to slow the mower is by the main drive by sliding the handle into neutral.

belt that it says it needs 532140294, which seems to be 82.5" and I have read somewhere that the belt needed is closer to 84-85" but cannot confirm. Tractor is OEM pulleys/etc so no changes there etc.

Weird one.

when I look at my manual I have listed 532141416 drive belt which seems to be a 83 3/4" belt?

Ideas of "which" belt is correct for this mower so I can finish this off.....