Fixing Briggs and Stratton lawn tractor

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PaulD wrote:

Does your tractor have an hour-meter? The repair manual for your engine says that the heads should be pulled and combustion chamber deposits removed every 100 to 300 hours. Has that ever been done for your engine? If it's 13 years old, I imagine it's due.
Mine is just completing its sixth mowing season and has 180 hours on it. I haven't pulled the heads yet.
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Rich256 wrote:

Re-read his post. It's the other way around. He said there's a "puff" but "little or no suction". Could be a broken valve spring.
A broken valve spring could make that valve open during the power stroke when he is turning the engine, thus no suction. During the compression stroke, the pressure pushes the valve closed and he feels the compression. Just a working hypothesis. On this engine, the valves are oriented in the horizontal direction and are driven directly from the camshaft.

With the right tools maybe.
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Ether Jones wrote:

Yeah, I got it turned around but I don't think that makes a difference to what I was saying. That is that a stuck open valve would not produce what he saw. But pulling the head would confirm if it is a valve problem.
And yeah, pulling the head is usually easy, as long as you don't have to remove a bunch of other stuff to get at it. And he thought it would be easy. All I ever used is a socket wrench or even an open end wrench. Come to think of it that is all I ever used to pull the head on a car engine but there usually was a lot of stuff to remove before I could get to them.
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Rich256 wrote:

I don't recall anyone postulating that a stuck-open valve might cause the symptoms Paul described. A broke valve spring might, though (on theoretical grounds - I've never had the pleasure of actually witnessing the symptoms of a broken valve spring).
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Ether Jones wrote:

Again I agree. Just that if the head is easily available it is a quick way to eliminate the problem of a broken valve. I have seen both broken and stuck valves.
I can't see that really being related to the starter problems. But I can't see the starter problem having anything to do with the original problem of the engine running rough and then dieing either!!
My thoughts keep going back to something electrical. What kind of ignition does that engine have?
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This is an older tractor. I am thinking that some thing caused the tractor to stall out. Then when my son tried to get it going again he shot the starter, that may have been on its last legs anyway. It is possible that the two problems are related, but they might not be.
Rich256 wrote:

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PaulD wrote:

This may be the most likely scenario. A "casacading" failure, of sorts, instead of a single failure causing both symptoms.

Well, it doesn't owe you anything, after 13 years, I suppose.

Right. There are very few single failures that would cause both symptoms. The only one I could think of was a valve problem. You have some qualitative test results which tend to support this hypothesis ("slow" cranking & different puff/suction behavior between the two spark plug holes), but without quantitative measures it's not very conclusive.
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I pulled the cylinder head on the side where I was not getting suction. Neither valve is broke or sticking. I thought the intake valve could use a little cleaning. Otherwise, I cranked through the various cycles and the valves moved properly through each cycle.
I think I will pull the cylinder head on the other side just to do the standard maintenance of removing carbon and to visually compare the two sides.
I'll make some calls on Monday to see if someone can test the starter. I did try jumping directly from the battery to the starter and this did not resolve the cranking issue. At this point, I am fairly convinced that the starter is bad.
I learned from my son that he had accidently been cranking the engine while the blades were engaged. The engine will not start when the blades are engaged. This may very well have contributed to stress on the starter. Ether Jones wrote:

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At least you have that area cleared. And something that should be done every now and then.
And of course we still wonder if there could be two problems. The starter should not have any connection to running rough. Now without getting started you can't get back to that problem either.
And I would be concerned about that little battery. I expect all that testing would be running it down. You really should have a little charger to keep it charged. If you don't already have one it is a good investment. For it I would go for one that has a 2 amp mode. I like those that have both 2 and at least 12 amp modes. Since I charge RV batteries I also look for a "smart charger".
Does the battery have caps? That is can you check the state of charge with a hydrometer?
PaulD wrote:

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Not that old. I have an edger I bought in 1963. Still works great. Especially after I switched to Mobil 1 oil. Only thing I ever did to it was replace the spring on the throttle.
Now you have us all curious and hope to hear what the solution is. I keep coming back to the electrical system which could be related to both symptoms. Not getting enough voltage to the starter. I was wondering what type of ignition system it has. That is electronic from the battery or Magneto.
PaulD wrote:

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Rich256 wrote:

What single electrical cause do you have in mind, specifically, that would cause both slow engine stalling AND slow cranking, that hasn't already been ruled out by the tests that Paul has conducted?

Starter is getting 9.5 volts under load. That should be enough to crank the engine, no?

Magneto, with either an electronic module or breaker points. I think Paul's engine has the electronic module instead of points.
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Ether Jones wrote:

I really don't know. It sounds rather low to me. With a small engine I would expect the battery voltage to be a bit higher. And I wonder what he calls slow cranking. Maybe it is still fast enough that it should try to start. I would jumper a big car battery to just be sure. Hard to guess from here not seeing and hearing what it sounds like.
If I could feel how difficult it is to turn over by hand I might get different thoughts.
At this point I know I am just throwing out wild ideas. Trying to reconcile the problem running with the crank problem and keep coming back to electrical.
A magneto system would not be affected by the battery. Yeah, I would expect it would have the module. When did they come out? 30 years ago.
I know from experience with them you can test the spark system by holding the wire and turning the flywheel by hand!! Not that I ever did that intentionally but I was close enough to the wire that I got bit. Should know better too because I have gotten bit more times than I should have but fortunately not by really high voltages that I have worked with at times (30,000 volts on Radar Transmitters). But with that you might not be around to tell about it later on.

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I bought a new starter and installed it. The tractor started right up. I mowed our lawn. My son mowed the neighbor's lawn. No problems. So I guess whatever caused it to stall out initially will remain a mystery. I would like to thank everyone who gave advice. The advice was very helpful and I learned alot. For the benefit of the archive, here are some additional things I learned along the way. 1) I checked the local B&S service dealers for a new starter. Their prices were very expensive, almost so expensive that it would not be worthwhile to make the repair. I found a dealer on EBAY who was selling an after-market replacement for a fraction of the cost of the B&S with a one-year guarantee. I emailed him and he was also willing to sell a B&S replacement part at a much better price than local dealers. Since this was an older tractor (13 years old), I went with the after-market which was about 50% cheaper than B&S.
2) The Briggs and Stratton repair manual says to remove the flywheel to get to the starter. I was able to easily remove and replace the starter without touching the flywheel. Maybe there are some versions of my engine model that are put together a little differently. For mine, however, messing with the flywheel would have been pointless and made the job much more difficult.
2) I ended up removing both cylinder heads to check the valves and engine condition. While they were off, I cleaned the carbon deposits. I particularly noticed some carbon deposits around the valve seals. Although the deposits were not preventing the valves from closing may have interefered with an optimal seal. WOW, cleaning made a huge difference. The egine went from sounding tired and missing fairly frequently to sounding like a brand new engine. Doing this standard maintenance was definitely worth the time. If someone else does this, however, just make sure you have the manual for the bolt tightening sequences and torques. paul_d snipped-for-privacy@yahoo.com wrote:

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PaulD wrote:

Thanks for the informative update. And you were correct all along that your main problem was the starter. And it could be that the carbon was causing some of the running problems. A tiny leak there can make a huge difference in performance.
As for tightening the head bolts, the main thing is to bring them all down slowly and evenly. Keep going around slightly tightening a bit at a time. What torque did your manual specify?
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PaulD wrote:

This may have been why the engine stalled in the first place. Then the old and tired starter gave up the ghost when your son cranked it a lot in an effort to restart the engine with the blades engaged.
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