17.5 briggs gave up

dahyippur · Oct 3, 2017

I have a craftsman lt-1000 (917.272673) with a briggs 17.5 engine which was running fine, but now it cranks and never fires. Here is what I've checked so far:

drained and refilled the oil
plug is sparking / tried new plug
flywheel key is intact and aligned
tried a different carb / sprayed carb cleaner into spark plug hole
adjusted the valves / push rods look fine / air is blowing out the spark plug hole

sometimes i get a little flame near the intake but it never really fires up.
really appreciate any suggestions, I'm stumped

Ronno6 · Oct 3, 2017

Check the muffler to see if mud dobbers may have plugged it up.....(or, any other obstruction..)

Boudreaux In Eunice La. · Oct 3, 2017

Your head gasket may be blown.. You are not getting enough compression possibly. Usually an engine will run with a bad gasket but yours may be bad blown.

When you said flame out the exhaust that is a dead giveaway. The gasket will look good from the front side. The back of the gasket is where you can see it. It will be in between the cylinder wall and valve rod valley.

Hope this helps ~!~!

dahyippur · Oct 3, 2017

sorry i should have been more clear, sometimes i get a quick flare up near the carb, like a weak backfire. I actually replaced the head gasket a few months ago when it started smoking like a fog machine. the muffler is also new and very clean

Boudreaux In Eunice La. · Oct 3, 2017

Same thing. You should not be getting a backfire if you checked the head for flat and the cylinder. Also torquing the head to specs.

I have seen them go out in a week ~!~!

Tinkerer200 · Oct 4, 2017

First thing I would do is locate and disconnect the "Kill Wire" at the engine. You say the pushrods "look" fine, are they actually working when you turn the flywheel? Do both move equally?

Walt Conner

dahyippur · Oct 4, 2017

the pushrods aren't bent or anything and they're hitting both the rockers. tried pulling the wire off the ignition coil (kill wire?) nothing changed, and the valves are moving nicely. When i hold down the key gas just builds up inside the carb and starts sputtering out the top =[

bertsmobile1 · Oct 4, 2017

Have a close look at the valves.
They are the same length, have the same springs and the same guides.
Thus they sit at the same distance off the head floor.
The should appear to be at identical heights.
Not uncommon for the inlet seat to get loose or the inlet guide to get loose then the inlet does not effectively close so when the charge ignites, it flashes back through the open valve and into the carb.

Boudreaux In Eunice La. · Oct 5, 2017

dahyippur said:
sorry i should have been more clear, sometimes i get a quick flare up near the carb, like a weak backfire. I actually replaced the head gasket a few months ago when it started smoking like a fog machine. the muffler is also new and very clean

Oops I misspelled it I mean't Intake. Sorry about that........

Boudreaux In Eunice La. · Oct 5, 2017

I agree with Bert........... We are on the same page now. Since I mean't intake for exhaust. I was typing exhaust a few minutes to a friend of mine right before I posted.

A loose valve seat or a intake seal will do that like Bert said. It almost has the same effect as a blown head gasket.

Bert will back me up on a gasket going out quickly..

17.5 briggs gave up

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