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Riding Mower Engine Problem


Gorrillasnot's Avatar
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08-20-06, 08:41 AM   #1  
Riding Mower Engine Problem

It's a Simplicity 5116 Special with a Briggs and Stratton 656cc 16HP I/C cast iron twin cylinder. Model 402707 Type 0141 01 Code 84042612.

I purchased the mower used and this makes the second season I've used it to mow about a half acre of lawn.

It has been cold natured ever since I've owned it, but would run fine after warming up for 10 minutes or so. Then towards the end of the first season it wouldn't run smooth unless I left the choke part way out. Also when I would shut the engine off after mowing, maybe 2 seconds or so after the engine stopped spinning it would make a loud bang that sounded like a backfire through the muffler.
Another problem it's had since I've owned it is if I'd shut it off while it was warm it wouldn't start back up until the engine cooled off for an hour or so.

The first few uses this season was like the last, but then it started to loose power and seemed like it was running on 1 cylinder. I thought maybe the plugs were going bad so I replaced them, but it didn't help.
I mowed a couple times with it running like that.
It sounded like it would run on 1 cylinder then both, then back to 1.
Then the next time I mowed with it I got about half way done and the thing started losing power real bad and finally the engine quit.
I pushed it to my neighbor's house who works on mowers quite a bit and explained everything to him and he said it sounded like a problem with the electronic ignition(don't remember exactly what he called it).
So I left the mower with him and a couple days later I went back to check on it.
He said he did a compression check on it and 1 cylinder had 100psi and the other had 30psi. He said most likely the engine had bad valves and/or valve seats on the cylinder with 30psi and he could fix it for around $200, but the machine shop wouldn't guarantee the new valve seats.
He also said he got it running again by fixing the carburetor, but it was still running fairly ruff and that I could use it until it quit again.
He said I should look for another engine or another mower in the meantime.

The next day I picked up the mower and started mowing with it. I got almost finished when it ran out of gas.
I filled the tank and tried to start it, but it wouldn't fire. I figured it wouldn't start since I'd always had problems with starting it while it was warm.
I let it cool off for about an hour and a half and tried again, still wouldn't start. I waited a few minutes and tried again, still nothing.
I kept doing this for a while and then I noticed a little smoke coming from the wire that goes to the starter, so I stopped and didn't try starting it again for about a half hour. Then when I went back to try to start it again it still would only click.
I put jumper cables to it from my car and still it just clicked.
Then I pushed it into the garage and put the battery charger on 2 amp and let it charge over night.
Tried to start it the next morning and again it just clicked.
The clicking noise sounds like it's coming from the solenoid under the seat near the battery.

Does it sound like the engine is most likely shot?
Do you think I burnt up the starter or solenoid? (is there a way to test them?)
I checked the price on a replacement engine and it was over $800 Ouch! I only paid $200 for the mower to begin with. Heck I even had the engine replaced in my car and it didn't cost quite that much.
I've checked around locally and on eBay and there don't seem to be very many good used Briggs and Stratton twins that'll fit my mower. Are there any other manufactures of 16HP twin or single cylinder engines that would fit my mower?
I've seen rebuild kits for my engine for under $200, but cant afford to pay someone to do the work. Could a guy thats rebuilt small block Chevy engines handle a job like that or would it be over his head?
Or should I just chuck the whole thing and save up for another used mower?

Sorry for being so long winded and I appreciate any help or advice you all could give.

Thanks

 
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08-20-06, 09:49 AM   #2  
You likely do, in fact, have a valve seat problem on the cylinder that's low on compression. The thing I'm worried about now is if the engine is seized. Can you turn the engine over by hand, via the flywheel? To do this, first pull each spark plug out (to eliminate compression) of each cylinder head. The smoking of the wires may be due to the starter not being able to spin the engine over and you are overheating the starter circuit. If you can spin the engine over by hand and the oil is full and in good condition, you likely have a corroded start circuit wire, hence the clicking noise you hear, being the solenoid. Check all wire ends (six [email protected] the starter, [email protected] the solenoid, [email protected] the battery and [email protected] the other end of the battery ground cable) for corrosion and clean and resecure them. As for the possible valve train issue, if you've been around engines before, and it appears you have, then you can do this job. Pull the suspected cylinder head off, turn the engine over by hand until one valve is full open, take a probe of some sort and see if the corresponding valve seat is loose, do the same with the other valve. If one is loose (likely the exhaust valve seat), you'll need to remove the valve cover in order to remove the valve from the cylinder. To best do this you'll want to remove the intake manifold/carburetor as a unit and if you do this be sure to take a photo (for possible future reference) and make a drawing of where the governor/throttle links and springs go. Next, you need to tap the seat in place, reinstall the valve and be sure you have a minimum of .004-.005" clearance between the valve and tappet. If not gradually grind the valve stem in order to obtain this clearance. Now, reinstall the valve and spring and be sure to have the valve at full closed. Take a light hammer and tap the valve lightly (in order to ensure the seat is seated squarely and fully). Using a center punch and hammer, you will now stake-in the seat with eight marks around the circumference of the seat in the cylinder material (aluminum) just to the outside of the seat. This will peen the aluminum material in towards the seat and, hopefully, keep it in place. Next, take a flat punch (about 3/16" +- pin punch and tap each stake mark flat. You'll now want to buckle up the engine using new gaskets (head, intake manifold (2) and valve cover). For less than $15, I would highly recommended you buy the Briggs service manual for this engine, part number 271172. For this and all the parts you need, see your local Briggs shop. Good luck and let us know.

 
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08-20-06, 10:48 AM   #3  
Thanks much for the reply and info.
I can place the palm of my hand on the screen looking thing attached to the flywheel on the top of the engine and easily turn the engine even with the plugs installed.

I had the oil changed 6 days ago when the neighbor worked on it to get it running. Just checked it to make sure it was full and clean and it looks good.

With the engine turning easily by hand with the plugs installed does that still point to a bad valve seat or something worse?

Will try cleaning all the connections in the starting circuit, but if that fails is there a way to test the solenoid and starter individually?

thanks

 
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08-20-06, 03:24 PM   #4  
Azis
I'm not all that familiar with Simplicity and the wiring will be of theirs and not briggs. Assuming the solenoid is seperate from the starter, you can test it or the starter alone.

Easiest usually just to listen for and find where the click is coming from.
Personally I like to begin at the starter as this saves checking lots of wires and connections and finding them in good condition only to find the starter bad. You can use another battery or jumper from the one on the mower. With cables attatch a good ground to the engine. Be careful of fuel lines and or fumes as the next step can cause sparks. With the - of battery jumpered to the engine, connect a cable to the + side and briefly but firmly touch it to the lug on the starter that the wire from the solenoid connects to. If you get it to turn the engine then the starter is good.
If you solenoid is mounted somewhere on the frame and is bad you should be able to hear and feel it click. Should be two Hot leads attatched to the solenoid. One leading to the + side of the battery, the other to the starter. The solenoid is just a relay and needs to close to transfer battery power to the starter. You can momentarily do the same by jumping the lugs on the solenoid with a screwdriver or the like. If you still get a click then you may have a shorted wire in the circuit between the solenoid and starter, not allowing enough current to reach the starter to turn the engine. If a wire was smoking, it could be as Puey mentioned overheating from the current such as holding the key to the start position while nothing seems to be happening. It could also be that a wire is shorted and in contact with ground which will also cause excessive current to flow and heat the insulation on the wire.

The engine should not turn over by hand very easily. When spinning it slowly as you mentioned, you should be able to feel when a piston is coming up on compresion, slowly continue to turn it until you feel the most resistance then quickly and cleanly, let go. I should have enough resistance to slightly spin the engine backwards a small amount. Spin it around and check the other piston the same way.

Do hope your solenoid matches somewhat the one I described, however if not the same theory will still apply.

 
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08-20-06, 04:07 PM   #5  
I tried jumping the starter straight from the battery, bypassing the solenoid, which is mounted under the seat in the battery compartment and nothing happened.
I then took the starter completely off the engine and attached the ground of my jumper cables to the starter and touched the positive to the terminal on the side of the starter. Immediately I noticed smoke coming from the bottom of the starter. Starter shot.

I'm going to check with a nearby shop tomorrow to see if they have any decent used engines, otherwise I think I'll tear into the engine and see if I can fix it.

thanks all for your help.

 
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08-21-06, 01:17 PM   #6  
Checked with a nearby mower repair shop today and they said it would cost $600ish for a new engine plus exhaust and labor.

Quote on new starter was $125.

$60 per hour labor to repair my engine which they said if it was just the valve seat it would be about 2 hours.

So I think I'll get a starter off eBay ($45) and see if I can fix the possible valve seat problem myself.
Anyone know a good source for gaskets for my engine?

thanks

 
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08-22-06, 04:36 AM   #7  
$45 for a starter? I'll bet it is used! Also, be sure it is for a Briggs Twin Opposed, not a V-twin or a single cylinder Briggs. For the gaskets needed, I'd buy them at your local Briggs shop. Just bring along your engine numbers and they'll set you up with what you need. And, by all means, you can do the valve seat trick, if needed, but be sure to remove the cylinder head (actually, you should remove both) and have a look at each combustion chamber, even before ordering any parts. If you have a scored cylinder then you'll have to reassess the value and costs.

 
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08-22-06, 12:27 PM   #8  
I asked my neighbor which side of the engine had the low compression and he said if I was facing the front of the mower it would be the right side.
I popped off the head and found the exhaust valve seat dangling loose.
The upper right hand half of the metal the seat fits in looks in decent shape, but the lower left half is wallowed out.
The intake valve and seat looked in decent shape. I rotated the engine to open it and tried to wiggle it to check the guide and it seemed nice and tight.
When I did the same to the exhaust valve I could slightly wiggle the valve.
Would JB Weld be strong enough to hold the seat in or is fixing it myself a lost cause?

The starter I'm thinking about having rebuilt if I can't find a good used one locally.

I've included a picture of the bad guide at the link below.

Thanks

http://i20.photobucket.com/albums/b236/phatTweaker/08-22-06_1457.jpg

 
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08-22-06, 01:19 PM   #9  
Azis
Standard reference of left and right is from the operators point of view, so I am guessing you are refering to the left side.

I dont think it would be recomended to try and bond the seat in, among other reasons tolerances are fairly tight already and any bonding agent will affect that. I can't really tell from the photo, but peening as Puey mentioned in his previous post would be my recomendation.

Also on the starter if you can find a rewind shop, they may be able to rebuild your old starter or have a rebuilt one and may give you something for your old core, usually for about half the price of new.

 
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08-22-06, 02:57 PM   #10  
It's hard to tell by the picture, but the lower left part of the seat hole is pretty much gone. With the seat centered and held in place by rotating the engine until the valve makes contact with it, there's probably about an 1/8" gap between the hole and the seat on the lower left. I think the gap may be to big to use the hammer and punch trick.

My neighbor that works on mowers said that a machine shop can fit an oversize valve seat in the hole then machine it to fit the valve.
He also said I should take the other head off and check the seats and have both heads checked for warpage. Said it should cost about $150.

Does that sound about right to you guys?

thanks

 
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08-22-06, 04:34 PM   #11  
Azis
As I mentinoned in the beginning I am not that familiar with Simplicity but it is sounding to me like much more time and money than I would personally put into a used $200 mower unless it was some high end make that the rest of the mower was in pretty good shape. If I were going to be into one that deep I don't think I would do so without going a bit further and rebuilding or at the very least checking out the rest of it. Lot of course depends on how much value you place on your time since it is your own equipment.
My experience is in aviation maintenance so I would have to do my own homework as far as prices. Cheese and Puey have been doing this a lot longer and I think much more qualified to give you a better answer or opinion.

I wish I could be more hopefull for your situation but thats just my honest opinion.
Best of luck!

 
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08-23-06, 09:34 PM   #12  
Wow, it must have run a long time with the seat loose. I don't think I've ever seen one that loose in the block. The JBweld won't fix it. Peening would do it if the fit were better, but in your case, I personally would say the engine's toast, put it out with the "parts engines" and stick another one on it. IF you can have an oversized seat installed, chances are the machine shop will want you to bring an empty block....no crank, pistons, cam, valves, etc... So, you are looking at a total disassembly, the machine shop charges, a starter, gaskets, and since you're totally disassembling it, you really should put it back together with new parts, like rings, possibly pistons and rods, probably a new valve, and whatever other parts show signs of wear. The top rod usually shows the worst signs of wear on these engines, and is usually the one to break. Check it well. Then you have time cleaning the engine, cutting the ridge, honing the cylinders, reassembling, and reinstalling it. Then, you still have a used-but-rebuilt engine for close to the same price as a new one, especially if you count your time.

If you stopped using the mower when the engine first started showing signs of a problem, it probably would have only cost 6 bucks for a head gasket and 4 bucks at the hardware store for a center punch, and maybe an hour of your time.

I don't mean to smash any hopes of fixing it, lol. It can be fixed, but you'll want to think about how much do you fix it and if there's enough value in fixing it to warrant it.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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