My Tractor Forum banner

1 - 4 of 4 Posts

·
Registered
Joined
·
32 Posts
Discussion Starter #1
First off I would like to say that this is an awesome forum and very informative!!! I have a Bolens st120 with a 12hp briggs and stratton engine (model 281707 Type 0127 01 Code 87082711). The motor will crank and crank and crank but will not start. I know I'm gettin fuel and spark but compression is around 35psi. Also I noticed gas is blowing OUT of carb. I started out by makeing sure flywheel key was ok, which it was. So I pulled the head off to check valves and found that Intake valve was black and nasty. I cleaned best I could with carb cleaner and turned engine over by hand and saw that valve almost looks as if it sits one side then the other. But when I shine light in, it seems like valve is seating ok but valve could be bent right? Can anyone please try and help with any suggestions? I'm gonna go nuts here! Thanks guys Brian :banghead3
 

·
Registered
Joined
·
1,683 Posts
I would lap the valves and reset the valve lash before replacing stuff. Also would run some Rislone or Mystery Oil in there for a bit. It's possible that something got gummied up in there. If the problem re-occurs....then go to the serious stuff....
 

·
Registered
Joined
·
32 Posts
Discussion Starter #3
can you explain lapping? Just starting out with learning small engines and not exactly sure what that is. thanks
 

·
Registered
Joined
·
704 Posts
can you explain lapping? Just starting out with learning small engines and not exactly sure what that is. thanks
You'll have to take the keeper off the valve (compress the spring first of course), then using a gritty paste for lapping valves ( you can get this at any auto parts store) smear a little on just the surface of the seating area of the valve. Move the valve back and forth on the seat while applying pressure to the valve. Go about 5 strokes back and forth, lift the valve slightly, 5 strokes, spin it 90 degrees, 5 strokes, lift it, etc. until you can see a shiny ring that is complete and even all the way around the valve and the seat. Wipe it off each time you check it and be sure to not get ANY on the valve stem where it goes into the guide.

Check your valve guides for play while you have it out. If the valve moves aroung alot you'll need new guides. These will need to be installed by someone who has a press and a reemer. You might be able to get them knurled if they are not too bad.

If you can find one, they make a hand crank valve lapper with a suction cup on the end of it. This tool will save you alot of time and finger pain.
 
1 - 4 of 4 Posts
Top