Help Rider with Bent intake Rod

carpsteveMay 24, 2014

I have a briggs and Stratton 20 hp engine 31P977-0575-E1 OHV on a craftaman rider. Just bought from somebody claimed only 40 hours or so on engine and has sat for few years. First time mowing with it there was some white smoke coming from exhaust not too bad figured it would clear up with more driving. This time finished lawn seemed to be smoking more just about got it put away and it began sounding like it was backfiring loudly would not restart let it sit for a while and tried again did not want to turn over much seemed like too much compression. Pulled plug cranked for 10 seconds or so and put it back tried again still same problem cranked then stopped like it was getting full of compression. pulled bolt on flywheel to check flywheel key it is fine. pulled head looks like new head gasket cant see any problems with it. Piston and cylinder full of oil and carbon build up intake rod is bent. Should I replace intake rod and try again or does engine need more work. How is the oil in the cylinder and what steps should I take from here? Thanks for any help.

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Smell the engine oil for the presence of gasoline.
How long did the tractor sit after you fill the gas tank before you tried to start it?
If it sat a day or so since filling the tank before you ran it, it is possible the carb has leaked fuel into the engine.
Gasoline in the crankcase will cause copious amounts of white and blue smoke out the exhaust.
The bent push rod may have been caused by by the intake valve having stuck in storage and letting the push rod fall out of its pocket and get trapped on the edge of the rocker arm when the engine was cranked.
But those are 2 separate issues that need to be determined, and solved.
The sticky valve is best addressed by running some Sea Foam additive in your gas tank along with some Marvel Mystery Oil and Stabil fuel stabilizer.
The carb leaking fuel can be handled by rebuilding the carb and replacing the needle valve and seat, and check the float to make sure it is sound.
I also always advise folks to install a manual, inline fuel shut off valve and learn to use it to absolutely prevent a leaking carb from ever drowning the engine again. But you must remember to always keep valve turned off EXCEPT while you have the engine running. Engine off, valve off, no exceptions, no excuses.
Yes, the intake push rod should be replaced, and the valves need to be checked and adjusted properly.
Improper valve adjustment on a Briggs OHV engine will cause the compression release feature to be ineffectual, and the engine will be hard to crank.
If you smell gas in the oil, make all your repairs and change the oil and filter (if it has one) before operating the engine again.

    Bookmark   May 24, 2014 at 10:23PM
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Thanks for the help mownie I did install a fuel shutoff valve after the first time I ran it because it seemed to get flooded easily and the valve was shut off for since I ran it the week before. I had ran it for about 30 minutes before it started getting loud and backfiring. I will take all the steps you suggested and try it out. Unfortunately I don't think im going to be able to get parts until at least Tuesday. One question I have is can I turn the flywheel with the head off and the flywheel key in place and get the piston to tdc, to clean the carbon off of it, with out causing any timing.problems

    Bookmark   May 25, 2014 at 9:20AM
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Yes, you can turn the flywheel with the cylinder head removed and timing will not be affected.
You should be aware that the flywheel retention bolt needs to be torqued to 110 foot pound (using a torque wrench) before returning the engine to service. Failure to do so risks shearing the flywheel key.
If you can manage to, post a few photos showing the combustion side of the cylinder head and the deck of the cylinder block (where the head joins to the block).
A photo of both sides of the head gasket might help in determining if the head gasket has failed.
You said "pulled head looks like new head gasket cant see any problems with it", but I would like to see that for myself if you can arrange it. :^)
Since we obviously can't see it in person, photos are our next best thing.

    Bookmark   May 25, 2014 at 10:58AM
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Thanks for all of the help. Here are some of the pictures

    Bookmark   May 25, 2014 at 1:09PM
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pic 2

    Bookmark   May 25, 2014 at 1:11PM
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pic 3

    Bookmark   May 25, 2014 at 1:12PM
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pic 4

    Bookmark   May 25, 2014 at 1:13PM
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pic 5

    Bookmark   May 25, 2014 at 1:15PM
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pic 6

    Bookmark   May 25, 2014 at 1:16PM
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pic 7

    Bookmark   May 25, 2014 at 1:18PM
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I don't think the oil smells like gas right now however I checked the oil immediately after it stopped running and did think that I smelled gas. I did change the oil after the first time mowing and it seems to be low on the dipstick now but did not seem so low when it was hot. thanks again for the help it is so nice to have someone who knows a lot more about engines helping me.

    Bookmark   May 25, 2014 at 1:22PM
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OK, pictures are adequate to tell me that that head gasket has probably not been recently replaced, and I also do not see any overt signs that the head gasket had failed.
2 other numbers you need to post are the engine Code number, which will reveal the build date of the engine, and the full, technical Craftsman Model number (on a decal on the frame under the seat) which will give an approximate year of build for the tractor.
That engine has more than 40 hours on it.
At this point in the game, it is somewhat of a toss up between a recently failed head gasket, and gasoline in the crankcase oil. It might even be a combination of the 2 problems because gasoline leaking into the crankcase must first make its way into the combustion chamber (where it then leaks past the piston rings to get into the oil). Liquid gasoline standing on top of the piston creates a "hydrostatic lock" condition when the engine is cranked. This severe shock loading of the head gasket can cause the head gasket to blow out.
Head gaskets on these engines tend to always fail by blowing out into the push rod gallery, because that space on the gasket perimeter has the least clamping force holding the gasket in place.
Head gaskets that fail gradually, or are continued to be run after failing nearly always show signs of "combustion etching" (aka "fire erosion") in the gasket remains and to the head or block. I do not see any such erosion on your head gasket, so if it did in fact fail, it may have failed at the time you first got the engine to run.
That is a lot of "unknowns".
I think if it were me (careful with that) I would be replacing the intake valve stem seal and cleaning up the valve and the intake plenum in the head, because all of the gunk you see on the piston and head are the result of oil burning.
Oil consumption is often due to worn and leaky intake valve stem seals.
Worn piston rings can also cause oil consumption, but contrary to popular belief, piston rings are not the most likely culprit.
Only a proper leak down test of the cylinder with the correct equipment and compressed air would disclose piston ring wear, and I don't think you are to the point of resorting to that right now.
Replace the intake valve stem seal and clean up the head.
Clean off all the old head gasket material from head and block.
New head gasket.
Replace intake push rod.
Perform a PROPER Briggs & Stratton valve adjustment.
Add some Sea Foam to the fuel and some Stabil and Marvel Mystery Oil is helpful to combat the stickiness factor on the intake valve stem/valve guide induced by ethanol in today's gasoline.
Do all this and run the engine. Expect to see some smoke for maybe up to a couple of hours after you get it going.
It will take a little run time to completely burn all the residues out of the exhaust system.
It can also take a few hours of run time to get the piston rings back into good shape where they can inflate properly in the ring grooves. The Sea Foam in the fuel will help to clean out the varnish that has undoubtedly built up in the piston ring grooves over time.
If this does not give you a working, smoke free engine, we can revisit the issue later.
Keep us posted.

    Bookmark   May 25, 2014 at 2:10PM
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engine code is 060523za
craftsman model 917.287080
I am going to follow the steps you have told me to and I will keep you updated Thanks again

    Bookmark   May 25, 2014 at 3:54PM
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OK, engine build date 2006, May 23.
According to the copyright date of the Craftsman owner's manual. the tractor appears to be a 2007 year model.
So, roughly 7 years old. AVERAGE annual use of this type lawn equipment is around 50 hours or so.
And without a working hour meter in place, the hours can be whatever a seller wishes to say.
I personally would hazard to guess the engine might have 300 to 400 hours or more on it, but that is really a guesstimate.
While you are into this project, take the sheet metal shrouding/duct work off the engine and give it a good cleaning under there. This is even more important considering the alleged long period of storage.......mice just love using the spaces under the sheet metal for nest site and food caches..........and they will pack the spaces full of grass and stuff. This material blocks the flow of cooling air from the fan which will lead to catastrophic overheating of the engine.

    Bookmark   May 25, 2014 at 5:24PM
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thanks for all the help. I have taken all the steps you recommended the tractor seems to run ok but still smokes when moving throttle up or down and smoke's quite a bit especially under load and mowing on hills. seems to be whitish grey smoke any suggestions i'm not sure what to check next possibly rings or warped head? just my guess i'm far from a mechanic. thanks for any help

    Bookmark   June 27, 2014 at 10:50AM
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On the push rod issue, do use a new replacement. While it might work on that engine, my attempts to straighten bent push rods on larger engines have ALWAYS failed. The repaired rod bent again very quickly.
And do verify that the valve and rocker arm work freely before installing the new rod.

    Bookmark   June 27, 2014 at 11:41AM
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Regarding the smoking:
An engine that was stored for an extensive time under less than ideal conditions, and without the proper preparations for long term storage..........might have some issues with the piston rings not being able to move freely in their ring grooves on the piston. (aka "stuck rings")
If that is why the engine is smoking, it may require a little longer run time to get the rings freed up.
The Seafoam might help in that respect.
It might also be that the crankcase breather valve is stuck or defective.
You did use a new head gasket, right?

    Bookmark   June 28, 2014 at 10:28AM
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Yes, on the new head gasket. I will keep running it with the seafoam and checking oil. I will keep you posted thanks again.

    Bookmark   July 1, 2014 at 7:09PM
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