All is not lost. It's not necessarily time to buy a new tractor. Listen to tomplum and Mr. Walt Conner. Their knowledge and expertise enabled me to repair my Briggs 15hp OHV, 28U707. I had a broken intake push rod. In addition to recovering the other half of your push rod, it is important that you check your valve guides. One or both may have worked out from the head casting. You can do it. Good luck!

I'll definitely get out there and check the piston travel when I can. I'm not sure how confident I feel about splitting the engine to find the rod, but I've come this far and the next option is to sell it "as is" so not much to lose I guess. The high revving sounds like the governor went also, so I'm assuming that's something I would have to replace too if I'm able to recover the push Rod. Thanks for the quick responses.

Actually on this engine it is more likely that the screws came out of the carburetor throttle shaft vs a failed governor. One step at a time as they say.

So I spun the piston and it's still going up and down. Intake valve is also moving too, however i also found both lash caps had fallen off.

Well like Tom says, check that the throttle plate is still attached to the throttle shaft. Are you saying that the steel push rod has broken in two.?

Walt Conner

Yes the push rod broke in two. Feels like aluminum if I'm not mistaken. I was able to retrieve the half that is sticks out and contacts the rocker arm, but the other half is nowhere to be found. Assume it fell internally somewhere. Since I'm not entirely familiar with all of the parts, I'll most likely post a video when I get a chance of what happens when I move the throttle. That seems easier than trying to describe in words. Thanks for all the responses, great forum.

So I'm not sure if I captured in the video what you guys were looking for, but here are a couple videos nonetheless, hopefully somewhat helpful. Both show the throttle linkages as I'm moving the throttle lever. Sorry for the shakiness.

https://youtu.be/GaluGJQ9y2E

https://youtu.be/RcQ6ihXnsD8

"found the exhaust valve push rod was snapped in half."

" Are you saying that the steel push rod has broken in two.?"

"Yes the push rod broke in two. Feels like aluminum if I'm not mistaken."

It is important when asking for help to try to post accurate information. I asked if the steel push rod broke because you said the exhaust push rod broke and the exhaust push rod is steel, never heard of that. The INTAKE valve push rod is aluminum and will break about an inch down from the rocker arm where the push rod rides on a plastic guide and wears it thin which is why I recommend reversing the intake valve push rod when doing a valve adjustment

Walt Conner

I guess I could have been wrong in saying that it was aluminum although that's what it felt like. It was the bottom valve where the broken rod was, which I always thought was the exhaust valve.

Eric , bottom valve is the intake , push rod is alluminium , much more likely to fracture as Walt mentioned . Steel push rod normally only bend in this Small Engine Application . Did you confirm the Throttle shaft butter fly and screws ?

Thanks so much for the info. All this time my thinking was reversed on which valve was which. So yes, it was the aluminum push rod on the intake valve that broke in two. That makes more sense.

In terms of the throttle shaft butterfly and screws, can you be a little more specific? I'm trying to learn some of this on the fly and unfortunately am not familiar with all the part names and locations yet. I posted a couple video links above of my tractor, but I'm assuming what you're looking for is not in the videos. Thanks again for all the help.

You might benefit from a Service (Overhaul) manual for your engine. I can send you one IF you like at address below, put in proper format and remind me engine model number and what you want.

Walt Conner

wconner5 at frontier dot com

Great, email sent. Thanks.

Yes Eric , Walts Manual upload will clearly illustrate the Parts list for your unit , so you can better undertand the position or location of the particular part .

Sorry it's been so long since I posted an update, I haven't had a chance to get out to the tractor until today. Some good news and some "I'm not sure if it's good" news.

Good news. I pulled both valve rocker arms off, as well as the bolts that hold them to the engine. I slid the metal plate off over the exhaust valve push rod (the one that's still intact), shined a flashlight in, and wouldn't you know it, the other half of the broken intake push rod was sitting right there in a pile of oil. I was able to fish it out too, so if nothing else, seems like great news that is isn't banging around somewhere else in the engine.

The "I'm not sure if it's good" news, is that I unbolted the carburetor, and looked at what I think was the throttle plate you were referring to. It looks like the screws are still in. I'm attaching some pictures of what I'm seeing. Let me know if anything is sticking out to you guys. Not sure what else to look for as the cause of the high revving . Until then at least I can order a new push rod now that I recovered the other half.

I suspect your thought is correct and the governor is up for re-election. If there were no abnormal noises- it may be worth a look. No big parts investment.

Yep , I put my Money on Tom.s Suggestion :)

After looking at the service manual, I'm having a tough time determining if this is something I have to pull the engine to inspect/replace. Just trying to figure out if this is something within my capabilities to do. Thanks.

Check that the governor arm is tight on the governor shaft coming out the side of the engine, IF it appears to be, try a static governor adjustment per manual anyway. If all is well with both of those and all linkages are connected, then it is necessary to remove the sump to see what the - - - - is going on.

Walt Conner

Yes, the engine comes off, gets laid on its top and the pan comes off. What's the worse that can happen. ;) Drain all the oil, disconnect the throttle cable, harness, fuel line, lower pulley / clutch, remove the air filter, dipstick and 4 mounting bolts. If your wife isn't home, put a piece of cardboard on the kitchen table and remove the sump and oil pump goods (if applicable) and there ya go....

"If your wife isn't home, put a piece of cardboard on the kitchen table and remove the sump and oil pump goods "

You think you have trouble now.

Walt Conner

ROFLMBO !!

"If your wife isn't home, put a piece of cardboard on the kitchen table and remove the sump and oil pump goods "

You think you have trouble now.

==========================================================================

The dishwasher will clean these parts up nicely!

Haha yes the wife would LOVE to find that on the kitchen table, although we have 3 boys under 4 so the mess may blend right in.

One other (probably unrelated) question before I dive in to a governor adjustment and possibly crack it open: After the most recent valve adjustment and carb cleaning done on the tractor, (before the intake valve push rod broke and left me where I am now), whenever I would lower the throttle all the way down to slow (turtle), it would always just shut off, and never idle at a low RPM. I don't know if these issues are related in any way, but it only started happening after the valve adjustment and carb cleaning.

Hey Eric. Keep up the good work. You can do it. Consider all the knowledge you have gained!

Your engine shutting off as you throttle down may be due to the carb cleaning. Fuel flow may have been improved, altering your fuel/air mix. This may necessitate an adjustment of your carb idling screw.

I

Low speed can be relative on small engines. It could also indicate a problem in the carb. Just be clear that there is nothing different about the throttle link IE binding after the carb RnR.

So after a long while, I ordered and installed a new push rod on the intake valve, adjusted the valves, and started the tractor. Started up great and sounded good, so I drove it a little bit, engaged and disengaged the blades (which worked fine). When I disengaged the blades and went back down to idle, the engine started revving high again. I tried to lower the throttle, but it didn't make a difference, the engine stayed at the same high speed. Does this still point to a governor issue? Good news anyways is that the engine isn't blown...

Update: On Saturday I decided to try a static governor adjustment and also tune the mixture and speed adjustment screws on the carburetor. I was really just trying to exhaust my options before calling someone to replace the governor, which seemed increasingly like the culprit.

When doing the governor adjustment, there didn't seem to be excessive play in the governor arm, but I adjusted it using the recommended method anyways.
I also screwed both the idle mixture screw and speed screw all the way in , and then backed out a 1-1/2 turns.
I had every intention of fine tuning the idle mixture screw once I got the tractor started, but once I fired it up, it sounded great, and the speed was perfect at idle. No more high revving.

I mowed the yard and it was great. The throttle adjustment worked fine, and it runs better than it ever has (knock on wood). I guess a new battery, spark plug, fuel filter, valve adjustment, carburetor cleaning and governor adjustment will do that. :-) it's been a long road but hopefully this is the end of it for now. Just in time to pick up fall leaves with the bagger. Was not looking forward to raking here in New England. Thanks again for all the great help here. You guys are a great resource of knowledge.

Also as a cheap plug: Not being very mechanically inclined, a valve adjustment was very confusing to me at first...compression stroke...top dead center...etc. Yes, very easy concepts, but for someone who doesn't spend a lot of time around engines, some of it is a little foreign. I tried following a lot of methods to get the engine on the right stroke, sticking a screwdriver in the spark plug hole to find TDC, etc, but was never fully confident that I did it right. Even after following those methods, the engine would start, but still didn't sound great.

For any novice out there trying to do a valve adjustment on their own, I highly recommend following the instructions in this video. The guys are really goofy, but know their stuff. Some may not agree with the method, but it worked better than anything I tried.