Briggs and Stratton 17.5 valve adjustment help

[ILENGINE]

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.

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.

 

[Boudreaux In Eunice La.]

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.

 

[indyyy]

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 ?

 

[Scrubcadet10]

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......

 

[ILENGINE]

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.

 

[indyyy]

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.

 

[ILENGINE]

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

 

[Scrubcadet10]

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.

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

 

[ILENGINE]

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.

 

[Tinkerer200]

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