John Deere L100 17HP Briggs and Stratton

[dj098]

I have a JD L100 Briggs and Stratton 31f777. After heaps of trouble shooting I've determined it won't start due to a valve issue. When I opened the housing the exhaust valve was off the rocker. Fixed it, started ran for 2-3 min and struggled then engine stopped. Opened cover and valve loose again. Fixed it and now it will run briefly for 10-20 seconds then starts to miss and the engine dies. Usually the valve is loose again. It seems this time I finally got the valve to stay sitting at .005 best I can tell - but it won't start.

Does anyone have any ideas of what would cause the valve to continuously come loose and then / or other ideas that would cause this issue?

Things I've done - new fuel, new filter and flows fine, new fuel line. Starting fluid makes no difference. New spark plug. New oil.

 

[Forest#2]

Is the push rod bent?

I would suspect the valve is sticking in the guide and or the valve guide has moved or is moving in the head due to valve guide seizing on the valve stem. Sometimes the stud that is holding the rocker arm will start coming out of the head. You can compare the top of the rocker stud to the other stud.

Symptoms are pointing towards a bad head.
You might remove the valve spring and make a close inspection of the valve and guide. Compare the exhaust guide location to the intake guide.
Run the piston up to top before removing the valve springs. The valve springs on the OHV's are weak enough that you can do this by just pushing on the springs by hand. Keep the ex and intake parts separated. (do not mix them up)

 

[dj098]

Is the push rod bent?

I would suspect the valve is sticking in the guide and or the valve guide has moved or is moving in the head due to valve guide seizing on the valve stem. Sometimes the stud that is holding the rocker arm will start coming out of the head. You can compare the top of the rocker stud to the other stud.

Symptoms are pointing towards a bad head.
You might remove the valve spring and make a close inspection of the valve and guide. Compare the exhaust guide location to the intake guide.
Run the piston up to top before removing the valve springs. The valve springs on the OHV's are weak enough that you can do this by just pushing on the springs by hand. Keep the ex and intake parts separated. (do not mix them up)

Is there any fixing that or is it a completely tear apart engine so much you might as well replace it kind of repair? The rod seems fine.

 

[bertsmobile1]

When overheated the head becomes soft and the valve guides start to slip inside the head
So they need to be staked or even pinned or the head replaced
Now that is the fix for the valves then you have to find out why it was overheating in the first place which is usually debris accumulated under the blower housing restricting air flow.
When it suddenly happens early in the season it is often because things have been nesting under the blower housing over winter .

 

[Forest#2]

Like bert says:

We do not know your mechanical limitations but;
First you need to inspect the head as described or if not a mechanical tinker/piddler and repair stuff yourself it's a trip to the repair shop with the engine still on the machine so a good small engine mechanic can test. (lots of you tube info about your engine as to how to do this)
If you can remove and replace stuff yourself and find you have a bad head you will need a complete replacement head and a new head gasket and do the proper torque sequence. If the cooling fins/shrouds are clogged it will do it again.
New heads are pricy and complete used heads are more reasonable on fleece bay.
Them Briggs 28, 31, 33 series engines are prone to all kinds of failures, such as what you are seeing plus camshaft failures. Little bit of TLC such as keeping the cooling fin shrouds clean helps but even new engine can bite the dust at any moment. Cleaning the cooling fins, deck and complete tractor only requires about 5 min's TLC after each dirty condition of run time using a air compressor or leaf blower. I tell some guys this TLC stuff and it just seems to go into one ear and out the other and when I see a repeat customer ignoring such I tell them to go buy new. (their neglect of TLC maintenance is mainly why I have lots of salvage stuff for parts, but in your case a new Briggs engine of your model can flame at any moment, but little bit of TLC is also a good thing.
Also no need in checking with JD for Briggs parts. (the parts will be quite expensive over the JD parts counter, due to the grn/y colors)

Summary: You have to weight the odds yourself but installing a replacement engine on a worn out tractor is another thing to consider.

Don't hurt the messenger.

 

[dj098]

Like bert says:

We do not know your mechanical limitations but;
First you need to inspect the head as described or if not a mechanical tinker/piddler and repair stuff yourself it's a trip to the repair shop with the engine still on the machine so a good small engine mechanic can test. (lots of you tube info about your engine as to how to do this)
If you can remove and replace stuff yourself and find you have a bad head you will need a complete replacement head and a new head gasket and do the proper torque sequence. If the cooling fins/shrouds are clogged it will do it again.
New heads are pricy and complete used heads are more reasonable on fleece bay.
Them Briggs 28, 31, 33 series engines are prone to all kinds of failures, such as what you are seeing plus camshaft failures. Little bit of TLC such as keeping the cooling fin shrouds clean helps but even new engine can bite the dust at any moment. Cleaning the cooling fins, deck and complete tractor only requires about 5 min's TLC after each dirty condition of run time using a air compressor or leaf blower. I tell some guys this TLC stuff and it just seems to go into one ear and out the other and when I see a repeat customer ignoring such I tell them to go buy new. (their neglect of TLC maintenance is mainly why I have lots of salvage stuff for parts, but in your case a new Briggs engine of your model can flame at any moment, but little bit of TLC is also a good thing.
Also no need in checking with JD for Briggs parts. (the parts will be quite expensive over the JD parts counter, due to the grn/y colors)

Summary: You have to weight the odds yourself but installing a replacement engine on a worn out tractor is another thing to consider.

Don't hurt the messenger.

Lol I like the tag of don't hurt the messenger! I just bought the mower used a couple years ago, I've maintained it well e.g cleaning, oil changes etc. But God only knows how much it was abused before. So with that I had to toss it as it was like $400 but it's sounding like the cost is going to be pretty high of it's the head. I'll probably cave and take it to a shop knowing this info and see what they say. I've definitely reached the end of my mechanical knowledge when it entered head gaskets and rods. I was just really hoping someone would be like - no you're an idiot just adjust valves this way lol. But also good to know I'm not crazy, valves can be adjusted and move if something else I'd broke deeper.

 

[kody1234]

There are some good videos on you tube that can help you out,good luck.

 

[kody1234]

There are some good videos on you tube that can help you out,good luck.