"We triple checked the timing last night and it is perfect,"

What timing? Did you check the flywheel key?

Walt Conner

Is there spark at the plug? Like Walt said, it could be the flywheel key; usually is, especially if you (embarrassingly) mowed over an immovable object.

***"will not start. It wants to so bad."***
By that, do you mean it acts as though it is going to start? but just can't seem to get going?
***"electrical wiring looks good"***
If your carburetor features a "fuel solenoid valve", does the solenoid wire have 12 volts DC (or will it light a test light?) when the ignition switch is turned to the run position?
If I am "guessing correctly" what you are implying, the fuel solenoid might not be activating to allow fuel through the main jet (and sometimes the pilot jet just WILL NOT provide sufficient fuel to start a cold engine). In this scenario, the pilot jet could be suppying "just enough" fuel to make the engine spin easily as if it wants to start, but not enough fuel to actually get it running on its own.
The other possibility that comes to mind is valve adjustment (I'm referring to the "engine valves" in the cylinder head). If you are not using the correct valve adjusting procedure (or do not understand how to adjust valves), the valves might not be seating (closing) properly and therefore the engine does not have sufficient compression to start up and run. It would, however, "spin very easy" and give you the impression that "wants to start so bad".

Forgive me if my terminology isn't correct, or if I'm a little slow. The "Mower Project" has been worked on by my husband and neighbor, and I'm not all that familiar with what's happening, or how the engine operates.
I know the flywheel key(if this is the same as the keyway that sits underneath the flywheel) is new, and in good condition. We replaced it as part of the project, because it was broken.
When I say timing, I'm referring the the marks being lined up on the crankshaft and camshaft, valves are in the proper position and opening/closing properly when the shafts are spun by hand (this is of course when the engine is sitting on the workbench).
When I say that it wants to start so badly, yes, I mean it really sounds like it's going to start, but just doesn't.
There is spark at the spark plug, we know that's good.
I'm not sure if there is a fuel solenoid valve. I will have them check tonight. Would this be a small peice attached to the underside of the carburator with a wire going into it, possibly from the ignition?

Ok, looking at a diagram on the Briggs & Stratton website, I see that our engine does infact have a fuel solenoid, and it's a small peice my husband kept questioning, although I can't recall why. I just remember he kept talking about the little price on the understide of the carburator.

***"Forgive me if my terminology isn't correct, or if I'm a little slow."***
You are doing ok, I just sometimes try to draw more detail out of a description. It is in the details where clues may be found.
***"When I say timing, I'm referring the the marks being lined up on the crankshaft and camshaft"***
Ok, that part is good.
***"valves are in the proper position and opening/closing properly when the shafts are spun by hand (this is of course when the engine is sitting on the workbench)."***
That statement may or may not be 100% true, depending on "how" the valve adjustment procedure was done. The simple fact that the valves are opening/closing when the shafts are spun by hand does not in itself "prove" that they are adjusted correctly. Detailed valve adjustment procedure can be requested if you are not sure.
***"I'm not sure if there is a fuel solenoid valve. Would this be a small piece attached to the underside of the carburator with a wire going into it, possibly from the ignition?"***
Yes, that is the fuel cutoff solenoid valve.

You all are awesome!
I'm feeling a little hope for the all consuming "Mower Project" already!
Do you happen to know where I can find these valve adjustment procedures?

Aww, shucks, that engine doesn't want to take the chance that you folks won't go out and hit the same immovable object again, so it isn't going to start, no matter what!

Rustyj14, thank you for your words of encouragement. And for the record, we didn't hit anything with the mower.

starrah3, click the link below and read down that thread until you find Walt's "cryptic" e-mail address. Using the proper format in your e-mail client, send Walt an e-mail asking for his instructions for adjusting valves on 31 series B&S. Furnish the entire engine model number, type and trim numbers as in your opening post.

Here is a link that might be useful: valve stuff

Thanks for the tip to contact Walt, but I got a mailer deamon for his "cryptic" email address. Maybe he'll pop up out here sometime.
Are you out there Walt?

:)

starrah3, I went back and took another look at the address Walt furnished in that thread. It has a "typo" in it.
Walt usually gives it as this, wconner5 at verizon dot net (I know that to be correct, so please try again using the correct "characters" for at & dot, of course).

Ok, so we tested the fuel solenoid, and it works. Talked to the neighbor, who stated that they never removed the valves, and he checked the adjustment the other day. I asked him about a potentially sheared flywheel key, and he states that the engine wouldn't turn the way it is if it was sheared. I also talked to someone yesterday at a mower repair shop, and he said that our engine doesn't have a low oil sensor, so that can't be it.
Is this correct? Can anyone think of anything else that could be happening? I fear we may be at the end of our options, and may be taking the mowe to a shop...which means all of the time and $$ we've already put into this thing might be out the window.
Thank you all for your help!

I had a similar problem on a Briggs flat head and it turned out to be a worn cam shaft. I would think it could be one of three things:

1. Valve adjustment.

2. Distorted flywheel key.

3. Worn cam shaft.

Ray

***"we've torn the engine down, replaced some goodies in there that were destroyed"***
Since the thread (and your efforts) seem to be meandering toward an impasse, it might be helpful at this point to "come clean" and reveal the circumstances that have led you to this point! Embarrassment begone! There are hardly any confessions we have not heard before, and the world continues to turn. Begin your story with the last time the engine "ran" before calimity struck (and any "pre-use" checks or "things" you may or may not have done). It will be helpful if you also tell what parts have been replaced. Sometimes, you must have ALL the pieces of a puzzle in order to put it together.
***"potentially sheared flywheel key, and he states that the engine wouldn't turn the way it is if it was sheared"***
Well, I haven't been able to hear (or see) "the way the engine is turning", so that means little except for what we might imagine. I can say that a sheared flywheel key might have no effect on "the way the engine is turning" other than to render the spark timing so "out of phase" that the engine turns freely, and unproductively, without being able to run. A sheared flywheel key will not cause the engine to "bind" or lock up, so if that is what the neighbor means by what he said, that is off the mark. Only rarely would a sheared (or partly sheared) flywheel key result in the spark timing being "advanced" enough to cause the engine to "kick back" (and make the engine stop or even turn backward during cranking). You must keep in mind that the flywheel key is soft and "shearable" by design. It is made that way to "minimize" the likelihood of of the significant inertia of the flywheel mass from twisting the crankshaft if something abruptly halts the engine. That remark takes us back to "what the heck happened to this engine in the first place"? I've seen some cases where the key got "knocked out of the keyway" when the flywheel was lowered into place. When the installer tightened the flywheel retention nut, it allowed the crankshaft to turn inside the flywheel, moving the spark timing beyond its intended "time". Removing the flywheel again revealed the key lying there with an evil grin (might have imagined that, but it sure looked that way to me). The "mis-leading thing" (to some folks) about a sheared, or absent, flywheel key is: If you check for the presence of a spark.......you will see that it has a spark. The spark just isn't occurring at the "right time". The simple presence of a spark does not mean all is well in the ignition system.

Ok, so it's confession time. So, my wonderful hasband changed the oil in our mower at the beginning of the mowing season (maybe April). Apparently, it takes a good amount of time for that oil to settle in to get a proper reading.(lesson #1) So, the oil was not filled completely when it was changed. We both mowed several time, never checking the oil. (lesson #2)
One day when my husband was mowing (up a small incline) the mower just cut off. The engine just stopped running. Not thinking anything of it, he started the engine right up again, mowed about 20 feet, and it cut off for good. (Of course we have 1/2 acre that slopes in 2 directions, and the mower is ALL the way at the bottom of the yard when it died). We pushed it to the shed, and that's where it's been ever since.
We started with the process of elimination with our neighbor. Bought a new battery, filled the oil, etc. Then, he checked the engine for compression and the needle didn't move...at all. Conclusion, we blew the motor due to low oil.
Since that time, they've taken the engine out, cleaned it, replaced all the gaskets, piston rod (shattered when hubby repeatedly tried to restart the mower, not knowing of course), keyway, got another new battery this week because we killed the other one by draining, recharging, draining and recharging again trying to start the mower.
The engine was taken off again to recheck the timing, valves, whatever they've been doing down there daily for the past weeks.
When you try to start the engine, it seriously sounds like it's going to start any second.
So, that's my story....sigh....

Well, at least we have some idea of what the catastrophe was. Now, that brings up more inquiry.
***"We started with the process of elimination with our neighbor. Bought a new battery, filled the oil, etc. Then, he checked the engine for compression and the needle didn't move...at all. Conclusion, we blew the motor due to low oil."****
He "checked the compression" BEFORE the engine teardown was done? OK, I can agree that the needle should not move at all, considering "the piston rod" was "shattered".
Did you replace the piston with a new one also?
What about the condition of the cylinder walls? Is/was there heavy "galling" or scoring in the surfaces of the cylinder?
Has "the neighbor" tried to take a compression reading since re-assembling the engine? or is he simply doing the old "finger over the spark plug hole test"?
It is also possible (but not a "given") that a valve (either one) got bent slightly when the "piston rod shattered". If the piston struck one of the valves (while the valve was open) during the brief moments of chaos after the rod began to break up, that valve could have bent enough to reduce the compression of the engine below the critical threshold. One way to check to determine if you have a compression deficit (and just what is causing it) would be to perform a "cylinder leakdown" test. The problem with that is: It requires a "% of leakage guage and the expertise to know how to do the test, and to evaluate the results. That would be something a well equipped and competent shop could do, not the average DIY guy. A typical DIY guy could rig up a "reasonable substitute" for a leakdown test IF....compressed air is available AND a suitable air fitting adapter for the spark plug hole can be obtained. To do this "test" the engine must be turned to TDC on the COMPRESSION stroke AND the engine crankshaft/flywheel must be held securely in that exact position (so that it can't react to the compressed air). After positioning and securing the crankshaft/flywheel, connect at least 60 PSI, not over 120 PSI, compressed air to the spark plug hole adapter fitting. If the engine is "good and tight", you should hear very little, or none, air escaping anywhere. To "listen for leakage", you need a short length of flexible plastic tubing, 1/4" to 3/8" dia. about 24" long (from home centers in plumbing supplies). Put one end of the tubing close to a good ear (not into the ear, just near the ear). Place the other end of tubing into the following locations on the engine. (1) Outlet of muffler or exhaust port. Air escaping here indicates a problem in the exhaust valve. Damage or adjustment problem. (2) Inlet to carb or intake port. If into carb, the throttle must be wide open. Air escaping here indicates problem in the intake valve. Damage or adjustment. (3) Insert the tubing into the open engine oil dipstick tube (hot down into the oil though). Air escaping here indicates problems in the cylinder, piston and rings, or both. Heavy galling and/or ovalization of cylinder, or both, are preventing the rings from "inflating" properly and therefore not providing sufficient compression. (4) Run the end of tubing all around the seam of the head gasket (between head and block). Air escaping here indicates defective or damaged gasket, block, head, or all. This is not a likely scenario as the leakage of plain compression (without compressed air) would be easily detected when cranking.
If,...... this engine is making good compression, and is "getting fuel", about the only thing left to question is the "spark timing". One more question. After all this cranking without starting, is the spark plug "wet with gasoline" upon removing it from the engine immediately after cranking??? If the engine is getting SUFFICIENT fuel to start, but still is not starting, the plug should come out wet with gas if you remove the plug as soon as you quit cranking. As I said earlier, it requires a lot more fuel to start a cold engine than to restart a warm engine.

***"(hot down into the oil though)"***
That should read: (NOT down into the oil though)
I just hit the H instead of the N. My bad!

Ok, yes, we replaced the piston rod with a new rod. The cylinder walls were "honed out"? I'm not sure how to spell it, but they were not in bad condition, but still "sanded" down to a smooth surface.
At this point, I believe the only compression test that has been done is the finger over the spark plug hole. They were talking about checking the compression with the tool they used before, but the neighbor wasn't able to make it down last night, so that hasn't been done yet.
I will take this info home with me. This gives me a lot of good info to go on, and I think it's very helpful, thank you so much!
I do have one other question, something that keeps coming up in my mind. When I was incharge of watching the valves open and close the other night while the timing was being set, I saw something that I found odd.
Let me see if I can explain this in correct terms.. when they were lining up the marks for the timing on the Timing Gear and the Camshaft, someone would have to push (fairly hard) on the Camshaft to keep the "teeth" from slipping out of the timing gear. Is it possible that the camshaft was bent when the piston rod broke? They could turn the timing gear about a 1/4 turn, and the teeth from the camshaft would slip out, and they would have to start again. I questioned it, but the neighbor said that when the casing went back on that it would pull that camshaft against the timing gear to keep the teeth together. Does that sound right???

***"teeth from the camshaft would slip out, and they would have to start again."***
If they had the engine tilted so that gravity was influencing the two shafts, they might have a tendency to come out of mesh. If the end of the crankshaft was resting on the workbench, that could cause the crankshaft to try to move. A bent camshaft would not cause the "easy spin" and wants to start symptoms you are seeing.

Well, we adjusted the valves (the correct way this time), and the exhaust valve won't hold it's position. When we turned the engine by hand, the rocker arm was wobbling all over, like we never tightened it. We made sure to tighten the locking screw. So, we did the adjustment again, the one on the intake valve never moved (checked the adjustment again to be sure), and we put the engine in.
Same thing, turning, and turning, and turning, but will not start. So, we took the cover off of the valves to make sure they weren't sticking, and the rocker arm for the exhaust valve was loose again.
Our thoughts...the valve was messed up during the terrible events that lead us to this project in the first place. We've weighed out the potential cost of hauling this thing to a repair shop, and all of the labor we'd have to pay to correct the valve issue, plus anything else that might be found, and the cost of a replacement engine. We're thinking replacement engine. It's a sad, sad day, but this project has become all consuming (literally hours every night, for weeks), and we're thinking it's best to just move on with our lives.
Any last thoughts on a simple (not so expensive) fix for a valve that will not hold it's position?
Thank you all so much for all of your help. Walt, that information you emailed to me was great, we followed it step by step, and it lead us to the crucial discovery of the faulty valve. Wish we had it weeks ago! Well, off to research a replace B&S engine to put into the shiny red mower that is a year and a half old! Like I said, sad, sad day!

starrah3, Walt Conner has mentioned (in other threads) that he has a technique for restoring (tightening and securing) the rocker arm pivot studs for a certain series of Briggs engines. It may be the 31 series. Looking at the Briggs IPL online, it seems that your engine uses a pivot stud with a "ball & pocket" type of rocker arm. It might well be worth checking with Walt about your "new" discovery before writing this engine off as hopeless. While your frustrations might be gnawing away at you, don't give up until Walt "pronounces it dead".

Hmm, I'm having a difficult time understanding this (not unusual for me). It seems to me if the rocker is "wobbling" on the rocker shaft, then the rocker bearing must be worn, in which case just the rocker arm itself needs to be replaced. I had to replace one in a Tecumseh that bent for some unknown reason.

Not understanding the exhaust valve "not holding its position" either. The valve has no other position to take other than fully seated to the valve seat when the rocker-to-valve clearance is adjusted to the correct tolerance (probably about 0.006" gap or so?).

If the adjuster on the pushrod end of the rocker is loosening with the locknut tightened, that is unusual and maybe the adjuster threads are worn/cross threaded in which case a new adjuster and locknut is all that would be needed. Or am I way off base?

"If the adjuster on the pushrod end of the rocker..."

CORRECTION: the adjuster would be on the valve stem end. The ball and pocket would be on the pushrod end. But you knew that. my bad

***"CORRECTION: the adjuster would be on the valve stem end"***
CORRECTION TO THE CORRECTION: The adjuster in this configuration is in the CENTER of the rocker arm. See image. {{gwi:331157}}

It seems very likely that the "Pivot stud" is loose or stripped in the head if the rocker refuses to hold its setting. (see Walt).

Correction noted. These are different than I had remembered.

Thank you again to everyone for all of your assistance. We had to take a hiatus from the "Mower Project" because it was driving us insane.
We've kind of sorta decided to go with a new engine, but I'm intrigued by this Rocker Arm Stud, or Pivot Stud. It's a $3 part.
If this part is stripped or loose, would that cause the engine to just turn and turn without starting? I'm thinking so, because as soon as the valve moves, it knocks that rocker arm out of adjustment. Does anyone know if this is a difficult part to replace, or if it's stripped, if it is even replaceable?

I'm also wondering too if it wouldn't more likely be something with the actual valve. Due to the circumstances of how the damage originally occurred, and the fact that the piston rod broke into multiple pieces, isn't it possible something could have hit a valve during the process?

***"the piston rod broke into multiple pieces, isn't it possible something could have hit a valve during the process?"***
Oh yes, it is possible that something could have hit the valve during the process. That "something" would be the piston. If the cylinder head was "off" the engine we you have been working on this engine, a bent valve should have been seen or noticed during the inspection of disassembled components. I'm not 100% sure of what your statement: "as soon as the valve moves, it knocks that rocker arm out of adjustment." Are you trying to tell us that after you adjust the rocker arm for that valve, and then rotate the crankshaft exactly 2 revolutions, the valve clearance will be different than what you set it to?? OR are you just saying that after you adjust the rocker arm to the correct specs, and then turn the engine just a little bit....the valve adjustment changes. The question here is: Are you actually turning the engine crankshaft through 2 complete turns after setting that valve, or or you just turning it a little?

Hi mownie.
The valve adjustment was changed after one complete turn of the engine. Well, not only changed, but the rocker arm was wobbling all over the place.
Last night we torn the head down, and the exhaust valve is not broken, but it's no longer straight. We put it a drill to rotate it against a while back ground, and the as it rotates, it's also mocing up and down, like it's warped or bent. So, we're opting to get new valves, rocker pivot studs, adjuster balls (they feel a little loose when they are screwed onto the pivot screws), basically a complete valve set and go from there.
I'm hoping if I order the valves for my particular engine, they won't need to be take to a shop to be "fitted?" I've heard that valves are generic, and need to be fitted to each engine. I need to do some research on the B&S website to see if the valve part numbers vary by engine model.
Thanks for all of your help! I'm certainly hoping that getting these valves replaced does the trick...there's really NOTHING else that has been checked, some things triple checked.

***"The valve adjustment was changed after ONE COMPLETE TURN of the ENGINE."***
OK, this kind of terminology is where details get sort of "blurry" or fuzzy.
While "One complete turn of the engine" is "sort of" a valid term, it is usually used (by most folks) to describe "one revolution" of the crankshaft/flywheel. The term is usually accurate enough to support casual conversation, but when the topic is specifically about the relationship between the crankshaft, camshaft, and the "valve train", it fails to present the neccessary details. In dealing with issues of valve adjustment, and the general condition of the valve train, you must not say "One revolution of the ENGINE (or any other number of turns of the ENGINE). You must count turns of the CRANKSHAFT/FLYWHEEL as this alone will tell whether you are actually getting the engine positioned correctly for checking whether the initial valve adjustment is "holding" or changing. The reason that it is imperative to say CRANKSHAFT instead of ENGINE is because 2 revolutions of the CRANKSHAFT are required in order to turn the CAMSHAFT 1 revolution. In describing the "Four stroke cycle engine" ONE TURN of the ENGINE is in reality, TWO TURNS of the CRANKSHAFT. If you position the crankshaft correctly for adjusting the valves, and then turn the crankshaft 1 revolution, and recheck the valve adjustment, NOTHING should have changed on the INTAKE valve of that cylinder, but the exhaust valve of the cylinder will have zero clearance (because the exhaust valve is still open). You will have to turn the crankshaft 1 more revolution to to return both valves to the same position where you first adjusted them. I know that you have subsequently removed the head since the last time you adjusted the vales and then "rechecked the adjustment", but can you clarify whether you were turning the crankshaft only 1 revolution, or the neccessary 2 revolutions, in rechecking the valve adjustment. It is also helpful to refer to the valves as INTAKE valve, or EXHAUST valve. The INTAKE valve has a larger diameter face, or head, than the exhaust valve.

You are lucky to have helpful neighbors. Most people would not have even considered doing such a major endeavor.

You have learned a lot. You certainly will have an enhanced understanding of engines for the future. :)

starrah3, by now you may have given up on the "project", but in case you still are pursuing a solution I will try to "cover" some of the points in your last post.
......................................................
***"adjuster balls (they feel a little loose when they are screwed onto the pivot screws"***
Well, they should "be free" enough to turn on the threads of the pivot stud, but they should NOT just "slide up and down" across the threads of the stud. Are the "set lock" jamb screws present (Refer to the "exploded illustration", one set screw per adjuster "ball")?
If the "set lock" screws are missing, the adjuster ball will simply "unthread" itself during engine operation.
........................................................
***"the rocker arm was wobbling all over the place"***
That one is a little hard to pinpoint exactly what you are "seeing". What you are describing sounds like the pivot stud is "loose in the cylinder head". If true, the stud might have "pulled the threads" out of its hole in the head. The repair procedure to "restore threads" is something that "can be done" by a DIY person BUT...If you do not already have the "tool kit" and the neccessary "inserts" to do this (and "most folks" DO NOT), you will be better off having it done in a machine shop or competent automotive shop. The thread restoring technique is usually called "Heli-coiling" or "Heli-coil insert repair". Heli-coil is just ONE trademark brand name and style of "insert style" thread restoration method.
...........................................................
***"I've heard that valves are generic, and need to be fitted to each engine"***
I certainly would like to have been present when that comment was offered to your ears. Generic? NO! Made to a "default factory standard or specification? Yes! In the case of your OHV engine, you will very likely be able to use the new valves "right out of the wrapper". The comment about "fitting to each engine", is only true in cases of "F-head" style engines, wherein "grinding the tip of the valve stem" is the ONLY way to affect proper valve lash adjustment (your OHV engine uses adjustable rockers to affect valve lash adjustment). Other instances where "custom fitting" of new valves might be required, would apply where the valve seat in the cylinder head was worn, cracked, or burned, and needed regrinding or replacement. I do not infer that your engine has a problem in the valve seats, so you should be able to just "pop in" a new valve and go. I do, however, suggest that you "check the contact pattern" of each valve and valve seat by doing a very light "valve lapping" procedure using valve lapping compound. Here again, you might want to relegate this to a competent shop (automotive or small engine type). Please post back with the "latest news".