16.5 single cylinder popping and missing greatly

[mr.farmall]

16.5 hp single cylinder vertical OHV 3100 series Briggs & stratton on a Husqvarna zero turn mower. 31E877 1502-G1
The engine is burning a lot of oil, about 1/4 cup every 2 hours. No oil leaks. The plug is continually fouled, and is cleaned often. It has run ok in the past, but now it is starting to miss-fire and it has to be hard on the engine and fly wheel, with a big 3 inch piston and having a large and heavy flywheel When it miss-fires and then pops it creates quite a strain on the whole system, sounds like it is going to break the flywheel loose. (it does require a steel key in the flywheel.)
I have checked the flywheel key and the timing, it looks good. The carburetor has been cleaned. The fuel pump is working and the fuel shut off solenoid is work correctly.
The compression is about 90 psi. I got a leak down tester and it shows 40% leakage on the gauge. I hear no air noises in the carburetor intake nor the exhaust, but I do hear a substantial air hissing through the oil filler hole.
The engine has been serviced a lot. This engine runs fine for a while then begins to running poorly and has needed work since the beginning, more work than all of the other equipment all put together. It's only 4 years old. I'm very disappointed with it.
What I could use your advice and expertise with is the following;
1. Should this engine just be replaced with something like a twin cylinder about the same size?
2. What kind of problems would that create, mounting, electrical, fuel, etc.?
3. Should I try to replace the ring set? If the cylinder walls look good.
4. Could the miss-fire be from one of the safety switches, like the seat, going bad? and if so , how would you test for it?
Thanks for any help.

 

[ILENGINE]

Ten to one says you have a blown head gasket. Pull the head and take a look. Will be blown between the cylinder wall and the push rod cavity.

 

[bertsmobile1]

16.5 hp single cylinder vertical OHV 3100 series Briggs & stratton on a Husqvarna zero turn mower. 31E877 1502-G1
The engine is burning a lot of oil, about 1/4 cup every 2 hours. No oil leaks. The plug is continually fouled, and is cleaned often. It has run ok in the past, but now it is starting to miss-fire and it has to be hard on the engine and fly wheel, with a big 3 inch piston and having a large and heavy flywheel When it miss-fires and then pops it creates quite a strain on the whole system, sounds like it is going to break the flywheel loose. (it does require a steel key in the flywheel.)
I have checked the flywheel key and the timing, it looks good. The carburetor has been cleaned. The fuel pump is working and the fuel shut off solenoid is work correctly.
The compression is about 90 psi. I got a leak down tester and it shows 40% leakage on the gauge. I hear no air noises in the carburetor intake nor the exhaust, but I do hear a substantial air hissing through the oil filler hole.
The engine has been serviced a lot. This engine runs fine for a while then begins to running poorly and has needed work since the beginning, more work than all of the other equipment all put together. It's only 4 years old. I'm very disappointed with it.
What I could use your advice and expertise with is the following;
1. Should this engine just be replaced with something like a twin cylinder about the same size?
2. What kind of problems would that create, mounting, electrical, fuel, etc.?
3. Should I try to replace the ring set? If the cylinder walls look good.
4. Could the miss-fire be from one of the safety switches, like the seat, going bad? and if so , how would you test for it?
Thanks for any help.

Answers to your questions
1) Can be done , get better power delivery not cheap not easy, bigger single will be easier.
2) bolt holes have the same centres , you can swap over your old alternators so no connection problems other than lengthening the wires, Custom control wires are easy to do custom exhausts are not so easy
3) always try the easist / cheapest first and check things before you jump in. Every day people come to this list having spent $ 300 + on new parts when all that was needed was an adjustment.
So ask first , check second & buy last, Pull down on Sunday so you can get your replies Monday get parts Wednesday and have yourself back on te grass by the weekend.
I will go with Ilengine as blown head gaskets ar a big problem on this model and about 1/2 day amateur fix once parts are in hand. Replacing rings will blow it out to a 2 day job and introduce a lot more chances of creating problems that you did not have in the first place.
4) not usually a safety switch generally just kills the engine stone dead. You check by undoing the cut out wire on the coil which removes all of the controls INCLUNING SHUTTING DOWN THE ENGINE ( get the hint ).
An oil fouled plug will cause a miss , popping and even an engine destroying backfire through the carb.

5) Do not ever even think about replacing the alloy shear key in the flywheel with a power transmission steel key no, no , no, never ever.

 

[mr.farmall]

Ten to one says you have a blown head gasket. Pull the head and take a look. Will be blown between the cylinder wall and the push rod cavity.

Just how many engines have you worked on over the years????? I'm amazed at your knowledge!
once again you pointed to the problem. It appears the head gasket was damaged right were you stated, between the push rod section and the edge of the cylinder. I have attached some photos just to make sure.
1. the block with the gasket in place.
2. the head, without the gasket of course.
3. the block with the gasket removed
4.the gasket, Block side.
from the markings on the block, I can see dark streaming marks were the gases and oil passed through and carbonized on the block. I would imagine it passed oil into the piston on the intake stroke as well.
I'll get a new gasket tomorrow and go from their.
any other suggestions?the valve lashing was intake= 6/1000 and exhaust = 8/1000. I'm not very knowledgeable about the stem seats or seals.
Thanks Rex

 

[bertsmobile1]

Before you replace the head lap it on a sheet of glass with some fine wet & dry paper oiled.
Check the block carefully it may have gone hollow where the gasket was leaking.
Home owners have difficulty facing the block but a little Davcon Alloy paste will go a long away if it is not flat.

 

[mr.farmall]

Answers to your questions
5) Do not ever even think about replacing the alloy shear key in the flywheel with a power transmission steel key no, no , no, never ever.

Thanks for all the good info Bertsmobil1.
It just makes since what you said about the engine kill wiring. remove it at the engine and all other kill switches become inoperative! good advice for testing it out.
Just a word about the flywheel key, it is designed to have the steel key that's in it. I had one of you engine killing backfires that destroyed the flywheel. It cracked and split right at the flywheel key. It was an expensive fix. the key that it required was a steel key. I tried to use one of the alloy keys in its place, but it sheared on the first start up of the engine in less than a second. That steel key is what the parts store ordered and sold to me when they looked it up. Maybe it's some type of steel/ alloy mix because it's much harder than the regular keys and it sticks to the magnet on the flywheel. Thanks for your concern.

 

[ILENGINE]

Clean the mating surfaces off real good. even using fine wet dry paper to smooth the head if needed. Valve clearances should be .004-006 for intake, but I like to run on the narrow side for the valve with the compression release. That thing is sensitive enough to excess clearance without giving it any to play with. and .005-007 for exhaust. middle of the road is fine there.

As far as number of engines I have worked on over the years, I wouldn't even know where to start counting. I overhauled my first briggs engine off o fa tiller at age 8. It sometimes isn't the number of engines that I have worked on, It is more the situation of I tend to get the, what I call problem children in the shop. those are the engines that are hard to track down the problem. And the ones where the customers bring it in, because there were referred by another shop. Or I am the 5th repair shop it has been to because nobody else can fix it.

I almost thought about telling you guys my age, but I think I will let you guys guess. I am having a birthday next week, so I think it would be fun to see if you guys can guess how old I am.

 

[Michael72]

Clean the mating surfaces off real good. even using fine wet dry paper to smooth the head if needed. Valve clearances should be .004-006 for intake, but I like to run on the narrow side for the valve with the compression release. That thing is sensitive enough to excess clearance without giving it any to play with. and .005-007 for exhaust. middle of the road is fine there.

As far as number of engines I have worked on over the years, I wouldn't even know where to start counting. I overhauled my first briggs engine off o fa tiller at age 8. It sometimes isn't the number of engines that I have worked on, It is more the situation of I tend to get the, what I call problem children in the shop. those are the engines that are hard to track down the problem. And the ones where the customers bring it in, because there were referred by another shop. Or I am the 5th repair shop it has been to because nobody else can fix it.

I almost thought about telling you guys my age, but I think I will let you guys guess. I am having a birthday next week, so I think it would be fun to see if you guys can guess how old I am.

59 ish

 

[Mikel1]

72 :biggrin:

 

[bertsmobile1]

Thanks for all the good info Bertsmobil1.
It just makes since what you said about the engine kill wiring. remove it at the engine and all other kill switches become inoperative! good advice for testing it out.
Just a word about the flywheel key, it is designed to have the steel key that's in it. I had one of you engine killing backfires that destroyed the flywheel. It cracked and split right at the flywheel key. It was an expensive fix. the key that it required was a steel key. I tried to use one of the alloy keys in its place, but it sheared on the first start up of the engine in less than a second. That steel key is what the parts store ordered and sold to me when they looked it up. Maybe it's some type of steel/ alloy mix because it's much harder than the regular keys and it sticks to the magnet on the flywheel. Thanks for your concern.

Don't know what you got sold buy the shear key is designed to do just that,
Shear when something jambs the PTO so as to avoid damage to the engine,
If the key shears too easy the the flywheel is not done up tight enough.