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I just recently replaced the decompression assembly..
How did I get the timing marks off? There’s only one place it will sit and line them up..
Brand new at this.. was auto tech for 23 years..
These darn lawn mower engines kick my butt, it’s always something..
Could I be missing something here? Is it possible that anything besides the cam shat line up marks being off and besides a flywheel key that could cause this to backfire thru the carb..
To see if it would run without ruining A-N-O-T-Her spark plug, I installed a gas shut off on the fuel line, the used my brake hose line locks to close off the hose between the fuel filter and the carb and then cranked it into a rag until I was sure the carb was empty.. Installed a newish spark plug and primed it to see if it was fuel problem or no..
No it was too.. it spit fuel back up into my face, my Harley the floor.
Ole lady not happy..
Anything at all guys?

ThatOneGuy1968 said:

I just recently replaced the decompression assembly..
How did I get the timing marks off? There’s only one place it will sit and line them up..
Brand new at this.. was auto tech for 23 years..
These darn lawn mower engines kick my butt, it’s always something..
Could I be missing something here? Is it possible that anything besides the cam shat line up marks being off and besides a flywheel key that could cause this to backfire thru the carb..
To see if it would run without ruining A-N-O-T-Her spark plug, I installed a gas shut off on the fuel line, the used my brake hose line locks to close off the hose between the fuel filter and the carb and then cranked it into a rag until I was sure the carb was empty.. Installed a newish spark plug and primed it to see if it was fuel problem or no..
No it was too.. it spit fuel back up into my face, my Harley the floor.
Ole lady not happy..
Anything at all guys?

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There are other reasons it can backfire through carburetor. Have valves been adjusted properly? Intake valve could be damaged. Carburetor could have issues. Ignition coil(s) could be weak. Anyone care to add more potential causes?

Post the model, type and code?

Check the valve lash and set it at .003-.005 on the intake and .005 on the exhaust. Vlave lash is critical on the OHV Intek single cylinder engines, especially the intake valve lash. If too much it may not crank through on compression. I've even ran them at .002 with good results. Flywheel key partly sheared will cause the spit back. (but not need in going their yet.
When setting the valve lash by the book be sure you are on the compression stroke and then go 1/4 inch ATDC on the piston. You gauge this with the spark plug out and a rod or something in the spark plug hole to get the 1/4 inch past TDC.

It's quite common after installing new cam for the valve lash (especially the intake) to change during break-in sometimes after only 15-20 hours of operation and require a re-adjust.

If it's still spitting back through the carb set the intake at .005 and test

How was the engine acting before you took it apart?

Forest#2 said:

uIPost the model, type and [ISPOILE[/ISPOILER]code?

Check the valve lash and set it at .003-.005 on the intake and .005 on the exhaust. Vlave lash is critical on the OHV Intek single cylinder engines, especially the intake valve lash. If too much it may not crank through on compression. I've even ran them at .002 with good results. Flywheel key partly sheared will cause the spit back. (but not need in going their yet.
When setting the valve lash by the book be sure you are on the compression stroke and then go 1/4 inch ATDC on the piston. You gauge this with the spark plug out and a rod or something in the spark plug hole to get the 1/4 inch past TDC.

It's quite common after installing new cam for the valve lash (especially the intake) to change during break-in sometimes after only 15-20 hours of operation and require a re-adjust.

If it's still spitting back through the carb set the intake at .005

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Q

Forest#2 said:

How was the engine acting before you took it apart?

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31C7070603B1081205ZE/ also
917.289031.. but it was runnin ok ,it had gotten really loud and I was searching the web for answers or suggestions and an ole boy said that if my flywheel key was bad that it could cause it to run louder than normal..
So I pulled it in the garage to check the key and to adjust the valves.. after that it wouldn’t spin so I tore it down and replaced the cam shaft..
After I put it together it some how started for just a second or two and died., I noticed that my plug wire wasn’t even connected to the plug., plug was fouled so I put in mew plug and it hasn’t fan or even tried to run since..
I think I’ve answered and added the model..
This thing started out it was running poorly and was bogging down while mowing..
I found a gas cap seal had come apart, so I cleaned the whole fuel system including the carburator.. it was really loud after that and still bogged way down under load..
The Governor did appear to be working correctly so I started there and adjusted the gov with no help but I did find a very weak spring on the gov.. I replaced that and performance came back but it is still louder than all get out., I bought a new muffler and that was another fail.. then I talked to that guy and he also convinced me that my head gasket could be why it was so loud, so I found a bad flywheel key and replaced the head gasket and adjusted the valves which I did at tdc and then it wouldn’t turn over completely so I went after the camshaft which was fine but I replaced it anyways.. that’s when I found out about the valve being open a little from the decompression mech.. wss told that was prolly why I couldn’t crank it completely over..
So that’s the basic story not mentioning the oil change the new plug, fuel filter, and air filter..

The reason for the lack ACR action was because you adjust it at TDC and the intake lifter probably still sitting on top of the ACR pin. Briggs instructions say to set the vavles with piston down 1/4" pass TDC compression stroke. I still personally just adjust each valve with the opposite fully open. Also make sure you are setting the correct clearance as the intake rocker is lower one or the one closest to the PTO end of the crankshaft. (cross flow head design).

But since you been inside engine you might to go back in and double check everything.

StarTech said:

The reason for the lack ACR action was because you adjust it at TDC and the intake lifter probably still sitting on top of the ACR pin. Briggs instructions say to set the vavles with piston down 1/4" pass TDC compression stroke. I still personally just adjust each valve with the opposite fully open. Also make sure you are setting the correct clearance as the intake rocker is lower one or the one closest to the PTO end of the crankshaft. (cross flow head design).

But since you been inside engine you might to go back in and double check everything.

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When I adjusted the valves the last time I adjusted the intake with the exhaust valve open and then visa versa..
is there anyway that when I did the intake valve the it could have still been on the decompression mech..

ThatOneGuy1968 said:

When I adjusted the valves the last time I adjusted the intake with the exhaust valve open and then visa versa..
is there anyway that when I did the intake valve the it could have still been on the decompression mech..

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Also.. could I have tightened the flywheel to tight using my impact and ruined the new key I put in it for the flywheel?

ThatOneGuy1968 said:

When I adjusted the valves the last time I adjusted the intake with the exhaust valve open and then visa versa..
is there anyway that when I did the intake valve the it could have still been on the decompression mech..

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No the ACR only affects the intake as the piston approaches TDC compression stroke.

ThatOneGuy1968 said:

Also.. could I have tightened the flywheel to tight using my impact and ruined the new key I put in it for the flywheel?

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Should damage the key but could seriously damage the flywheel taper and cause it to becomes stuck.

Now here is example what to a smaller flywheel that tighten by an impact. The owner tried riveting it together which did not work.


And I had Briggs opposed engine that the flywheel was torqued on by impact that I had cut off due damaged taper.

StarTech said:

No the ACR only affects the intake as the piston approaches TDC compression stroke.

Should damage the key but could seriously damage the flywheel taper and cause it to becomes stuck.

Now here is example what to a smaller flywheel that tighten by an impact. The owner tried riveting it together which did not work.

And I had Briggs opposed engine that the flywheel was torqued on by impact that I had cut off due damaged taper.

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Well so far I’ve found out that somehow or another I sheared that new flywheel key.. that could be the answer to my problems.. no idea how it happened unless it sheared it before I put in the cam when it would spin to compression and then stop.. idk..

Okay there is two service bulletins that affect your engine. Not you must use the new steel key.

APSI 82 attached and APSI 89 too large to attach but here is two pages from it.

So my part number would be?? 796335??
Is that a Briggs number or ?

ThatOneGuy1968 said:

So my part number would be?? 796335??
Is that a Briggs number or ?

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So I’m told to put nylon rope in my cylinder on tech to torque flywheel bolt..
I am not gonna do that and break my piston at the wrist pin.. I don’t have a special tool for this.. any ideas??

ThatOneGuy1968 said:

So I’m told to put nylon rope in my cylinder on tech to torque flywheel bolt..
I am not gonna do that and break my piston at the wrist pin.. I don’t have a special tool for this.. any ideas??

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Yep, put nylon rope in the spark plug hole and you will be fine. I do it all the time.

The other alternative is to hold the other end of the crank
Easy to do if the blade is there

bertsmobile1 said:

The other alternative is to hold the other end of the crank
Easy to do if the blade is there

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That works as you being using the engine's PTO pulley or you can just use a large flat blade stuck in the flywheel ring teeth and held up against the ignition coil mounting stud. If I can torque 48M series flywheel to 140 ft/lbs using ignition coil stud then torquing the 31 series to 110 should be fine which I have also done here. Just make the ignition coil is mounted it stabilizes that stud.

I just did the 49M flywheel yesterday.

Thank you all who responded to my post..
Lawn mower is now running correctly, I ended up ordering and installing a new fly wheel key.. the motor ran wide open with no throttle control.. I set the Governor shaft and it idled down but still not much throttle control, which ended up being the throttle plate adjustment.. now everything is just fine..
And the loudness has also went away, it seems the flywheel key was the culprit of all that exhaust noise..
All is well that ends well..