Export thread

I have a 2013 Troy Bilt Pony 42" lawn tractor with the Briggs and Stratton 17.5 engine. It does the thing where when i turn the key it turns a little stops at compression turns a little more stops again at compression, etc. If I take the spark plug out and turn the key it turns over normally. The battery is good and every thing I've learned by googling and watching youtube videos says to adjust the valves. I've adjusted both valves to .004 as one youtuber suggests, and to .004 intake and .006 exhaust as others say ). I've tried both settings several times and keep having the same problem when I put the spark plug back in and turn the key.

both the intake and exhaust enter and exit near the top of the valve housing so I'm not certain which valve is which. One video I watched which was for riding mowers in general and not Troybilt Pony said the exhaust valve is the one that is on top and the intake valve the bottom one - is this correct?

I do notice a sulfur / rotten egg smell when I try to start it - does this help diagnose anything ?

I'm at a loss - any suggestions on what I might be doing wrong or whether it might be a problem other than the valves like the solenoid or something would be greatly appreciated. :confused2:

I work on my own cars when they need repaired (have done head gaskets, brakes, etc.) but this is the first time I've tried to adjust valves.

Briggs vertical are intake on top. All of them.

You watched the vids and turned the flywheel so they were at the right position when you made the adjustments ??

Briggs single cylinder vertical OHV engine use a crossflow head, Which means the intake is on the bottom. If you are sure you have the valves adjusted correctly, then while turning the flywheel slowly watch for the intake valve/ bottom to bump off seat slightly just before TDC compression. You could have a situation where the flyweight on the camshaft is broken and the compression release no longer works, and will require replacing the camshaft.

I always thought you were supposed to set them 4 to 4? I'm sure I'm wrong though, And do you think it could be the compression release on the cam? More thane likely not, but sometimes the spring will come off and the CR won't work... But it does sound like something in the head/ valve mechanism.....:smile:
ILENGINE, it shouldn't require replacing the entire cam, just the comp. release. It is riveted in on most engines. But in some cases people just go ahead on put a new cam in, it's a lot simpler.

I did 4 over the summer this year. In all cases the decompression mechanism was in about 10 pieces laying in the sump of the engine. On some engines the valve clearances are .004-.006 for both on others it is .004-.006 for intake and .005-.007 for exhaust. So most people will just say 5 and 5.

Briggs doesn't normally offer just the decompression mechanism as a replacement part.

"ILENGINE, it shouldn't require replacing the entire cam, just the comp. release. It is riveted in on most engines."

Let me know where to get the parts.

Walt Conner

Boudreaux In Eunice La. said:

Briggs vertical are intake on top. All of them.

Click to expand...

??

Walt Conner

Tinkerer200 said:

"ILENGINE, it shouldn't require replacing the entire cam, just the comp. release. It is riveted in on most engines."

Let me know where to get the parts.

Walt Conner

Click to expand...

Walt is that a statement or a question. I am slightly confused by your post.

I use pro parts direct.com, they have the ACR but need to call for avaliabilty .... I know cub cadet (kohler) makes the ACR for their cam.

I AM JUST GOING OFF OF WHAT I HAVE SEEN ON MOST LAWNMOWERS Cam wise.

ILENGINE said:

Walt is that a statement or a question. I am slightly confused by your post.

Click to expand...

Me too, i think he's saying " Good luck finding one"..??

Scrubcadet10 said:

I use pro parts direct.com, they have the ACR but need to call for avaliabilty .... I know cub cadet (kohler) makes the ACR for their cam.

I AM JUST GOING OFF OF WHAT I HAVE SEEN ON MOST LAWNMOWERS Cam wise.

Click to expand...

the one that they list on their website for the ACR is for the Courage single. I replaced one of those this summer, and then had to go back in and replace the cam gear because evidently it was slightly warped causing the ACR to hang up and not work sometimes. The compression release on the camshaft in this guys case is pushed through the cam gear and then pressed into the rotating counterweight with a halfmoon part of that same pin that acts as the compression release. There are no rivets that hold it attached.

The weight gets broken around were the pin in halfmoon shaped, and ends up in about 4-5 pieces, the rotating pin normally will be 2-3 pieces and then the spring is found damaged sometimes and not others.

pull up a picture of the briggs 793880 camshaft and you will see what cam he has in this engine that is possibly the cause of his start issues.

Oops I stand corrected. I don't know why I had a L head stuck in my brain.

I guess it's all the L heads Iv'e been working on in the last month.

Ilengine - could you or anyone else explain in a bit more detail how to determine if it's the compression release that is bad on my mower ? I should be able to replace the camshaft if that's what it is.

Also does the rotten egg/ sulfer smell mean anything, or is that just the battery trying to hard to turn the engine ?

Not sure about the smell, i'd try my best not to breath it in a lot. As far as i know, the only way to see if the compression release is bad, take the cylinder head COVER off, spin the engine over by hand, and the exhaust valve should just barely "bump" open after the intake......

Compression release should be on the intake for this engine. Bottom valve is closest to the compression release mechanism on the camshaft. Remove the valve cover, and the spark plug, Rotate the engine over by hand and watch the valves open and close. Just before TDC compression stroke you should see the intake valve completely close and then the rocker will tighten up and push the valve open just a few thousandths of an inch before it closes. Without that bump the compression release isn't working and then you get into replacing the camshaft.

I'm not sure about the 'bump' - maybe because i don't see it happening. One video i watched said if after adjusting valves engine still turns over hard tightening the valves a bit more would help release the compression, so i set both intake and exhaust at .002 to see if it did anything and I still had the same result - engine turns a little and stops, turns a little and stops. Would this suggest the compression release mechanism being bad to you guys ?
I'm looking at some videos on compression release mechanism to see if one might show the 'bump' so i'll know a little more what to look for.

That bump is about 1/8 inch of valve movement. Sometimes I will hold the rocker and turn the flywheel. Went the effected valve completely closes, and then shortly thereafter you can feel it tighten up the rocker, and have a slight movement before quickly releasing the tension on the rocker. I suspect that you are dealing with a broken release

ILENGINE said:

Compression release should be on the intake for this engine. Bottom valve is closest to the compression release mechanism on the camshaft. Remove the valve cover, and the spark plug, Rotate the engine over by hand and watch the valves open and close. Just before TDC compression stroke you should see the intake valve completely close and then the rocker will tighten up and push the valve open just a few thousandths of an inch before it closes. Without that bump the compression release isn't working and then you get into replacing the camshaft.

Click to expand...

Do you mean exhaust not intake, the compression has to go out the exhaust....

No I mean intake. the compression release mechanism operates the valve closest to the cam gear, and since the engine uses a cross flow head that puts the intake valve on the bottom of the head which is closest to the gear, therefore the compression release is on the intake valve.

On Briggs horizontal OHV engines the compression release is on the exhaust. Release mechanism next to gear. faces sump cover which on side shaft engines is under the muffler, but on Vertical engines with the cross flow head the intake is closest to the sump cover and the compression release next to the gear therefore opens intake.

Releasing compression via the Intake valve has been a long standing practice with B&S whether flat head or OHV. Not all of them but a lot.

Walt Conner

It took some turning of the motor by hand and watching the intake valve closely, but I did finally see it make the little 'bump' Ilengine said to look for. Should this mean that the camshaft and release mechanism is good ? I had the battery tested again just to be sure and it is good. Might the starter or solenoid starting to go bad cause this same problem, or is it still more likely to be the camshaft or valves ?

I can send you detailed instructions on adjusting the valves and a Service Manual if you contact me at address below, put in proper format and remind me engine model number and what you want.

Walt Conner
wconner5 at frontier dot com

I have a 17.5 HP 31C707 type 3346 G6 engine Code 110510ZD and have a question about adjusting the valves. I have a manual that came with it so it shows me the settings Intake clearance .003-.005" / exhaust clearance .005-.007"
First question is it better to set to the smallest tolerance or in the middle of the range?


I have read three ways to set the valves and not sure which to use.
One was to set TDC feeling in the spark plug hole to get TDC
Second was to set the valves when the TDC is returning 1/4"
Third and in many videos, is to rotate by eye and set each one when one is compressed and the other is loose, rotate and then set the other when it is loose.

Thoughts on how much it matters which is used for this engine?

Thanks

I just told you above how to get the right way.

Walt Conner

W.,
I sent you an email as requested.

I must have reset the valves 30 times to no avail and as a last resort decided to try to jump start the mower with my car battery. Sure enough the mower started right up, so my problem has been the battery all along... I had the battery tested twice at O'reilly auto and both time was told it was good. And I charged it quite a few times while adjusting the valves as well and had it tested after charging.

Just thought I would post what worked for me in case it helps someone else, because the valves are fairly easy to adjust. If you adjust them a few times to no avail, make sure the mower uses a 12 volt battery ( from what I understand about all modern mowers do ). Then see if it will turn over normally with a battery that you know for a fact is good.

P.S. - I'm not expert at repairing mowers but do most repairs on my cars. I've had a good dozen or more car batteries tested at auto parts stores - this is the first one I've had test goot that isn't good lol.

Thanks for the help guys.

P.S. - I'm not expert at repairing mowers but do most repairs on my cars. I've had a good dozen or more car batteries tested at auto parts stores - this is the first one I've had test goot that isn't good lol.

Thanks for the help guys.[/QUOTE]

This may be an indication that you problem is with the battery cable connections. Often the ground to frame is overlooked.

Walt Conner

Tinker please tell us your instructions on how to set according to his engine model....... I am curious