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Discussion Starter #1
Check this out..... Engine is getting fuel, valves are not seized or busted. I looked and the flywheel key appeared to be in place, is it possible the coil is malfunctioning? This is a single cyl 12hp powerbuilt briggs.


 

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Have you checked the valve lash. (per the service manual) Set when 1/4 past TDC, etc.

I seen a puff of smoke up front. What is the compression? them are know for leaking head gaskets.


What does it do if you try to rev the engine?

Do not run it very long with the air cowling off. (it will overheat)
 

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Discussion Starter #3
Have you checked the valve lash. (per the service manual) Set when 1/4 past TDC, etc.

I seen a puff of smoke up front. What is the compression? them are know for leaking head gaskets.


What does it do if you try to rev the engine?

Do not run it very long with the air cowling off. (it will overheat)
yes yes i know the cover I ran it for 20 sec etc.....

I was running fine and then it died.... So I finally got it to start and this is what it does. I have replaced many OHV single head gaskets so I could check that out....

I can check the valve lash yes, but looking at it by eye it wasnt really loose or tight which is concerning to me....
 

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set valve lash first, run the engine , is it better or worse ??? If worse pull the head, the sparkplug can't burn the fuel and oil mix, BTW did you try a new sparkplug ??? Is the float bowl clean ??? The coil could be failing , but what is the airgap set at ???

My 2 cents, Jim
 

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Discussion Starter #5
set valve lash first, run the engine , is it better or worse ??? If worse pull the head, the sparkplug can't burn the fuel and oil mix, BTW did you try a new sparkplug ??? Is the float bowl clean ??? The coil could be failing , but what is the airgap set at ???

My 2 cents, Jim
Thanks for the reply, yeah first thing I did was change the plug & try multiple other plugs. I checked the gap on the coil quickly but I need to verify with feeler gauge.

I didnt open the carb yet because its a nikki & they have those idiotic gaskets that dont like to be taken apart more than 1 time.

I will try setting the valves.

I also noticed at some point i did replace that coil with an amazon china coil, that is kind of why I suspect it.
 

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Sounds to me like metal against metal rather than a misfire. Maybe you have coil touching flywheel or as mentioned a rocker hitting a push rod.
 

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Watch the video close toward the valve cover and you can see intermittent smoke puffs. Look like maybe oil smoke, but ????

Wonder if the smoke is a hint. The engine w/o the air cowling is running cool so this smoke is not being produced due to a oil leak onto a hot engine.

He indicates it done it all at once, no warning when it quit.
 

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Sounds like the choke is closed !...too rich a mixture...
Agree.

He needs to look under the air filter cover with the engine not running and see if the spring loaded choke rod it returning when the throttle lever is moved from fast to slow. that is type carb that gets choke applied when the throttle lever is a max throttle.:tango_face_wink: (and also make sure the choke is not applied when the engine is running)

Don't know why it would happen all at once unless a choke return spring broke.:tango_face_surprise
 

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Discussion Starter #11
OK I didnt have much time tonight, but I swapped the coil to another known good coil and it runs the same.. I checked the choke and it is working properly, no difference if it is on or off.....

Guess I am checking the valves or pulling the head tomorrow cant think of anything else.
 

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OK I didnt have much time tonight, but I swapped the coil to another known good coil and it runs the same.. I checked the choke and it is working properly, no difference if it is on or off.....

Guess I am checking the valves or pulling the head tomorrow cant think of anything else.

no difference is the choke is full on????:tango_face_surprise suspect
 

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Discussion Starter #13
So took everything apart and it seems head gasket is ok, I cleaned up the piston, flywheel looks ok. The only thing I noticed is the little brass part in the bottom of the carb was dislodged. So It was kind of loose, so I put a little rtv around the edges and hopefully it will stay put... I couldnt restart the engine because I need to wait for the new head gasket.....
 

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So took everything apart and it seems head gasket is ok, I cleaned up the piston, flywheel looks ok. The only thing I noticed is the little brass part in the bottom of the carb was dislodged. So It was kind of loose, so I put a little rtv around the edges and hopefully it will stay put... I couldnt restart the engine because I need to wait for the new head gasket.....
The jet was the problem. It was running rich and chugging.
The jet will work installed either way but the correct way to install is from the top. That way it can not fall out ans sit in the bottom of the bowl like it was doing.
You have to use a drill bit or something to slide it in to make sure it is not sideways and push it into the hole so o-ring seals it.

I find them all the time in from the bottom and I believe some even came from factory this way.
 

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Discussion Starter #17
The jet was the problem. It was running rich and chugging.
The jet will work installed either way but the correct way to install is from the top. That way it can not fall out ans sit in the bottom of the bowl like it was doing.
You have to use a drill bit or something to slide it in to make sure it is not sideways and push it into the hole so o-ring seals it.

I find them all the time in from the bottom and I believe some even came from factory this way.

It can only install one way.... but yes it wasnt quite sitting in the bottom of the carb but it was way loose... hopefully when I get the new head gasket I can just put it all back together and its solved... and yes I hate nikki carbs, worst design of all time.

 

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Discussion Starter #18
just following the thread up, I put that piece back in the nikki carb and the issues are solved. So changing the head gasket was for the **** of it...
 

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It can only install one way.... but yes it wasnt quite sitting in the bottom of the carb but it was way loose... hopefully when I get the new head gasket I can just put it all back together and its solved... and yes I hate nikki carbs, worst design of all time.

No, it can certainly be installed two ways . You can push it in from the bottom which is the wrong way in my opinion and the way that allows it to possibly fall out or you can turn it over and push it in from the top sliding it down the hole in the middle of the plastic that the brass tube will fit in when you slide the carburetor bowl onto the top of the carb. This way it's being held in place and gravity is also holding it down. Either way it's still fits in the same hole with the O-ring stealing around the outside circumference in the same spot but it can never fall out when you put it in from the top and create the condition you had which was extremely rich running.
 

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Here is a screenshot from the website mentioned a couple of posts above that mentions how to install the seat the best way from the top. So often when I pull them apart I find a seat pressed in from the bottom. I believe many even came from the factory this way but it's not the best way.
 

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