Mysterious Engine Problem


Old 08-25-05, 12:05 PM
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Mysterious Engine Problem

I have a Briggs and Stratton 3.5 HP engine on my Murray Lawn Mower. It was smoking alot and I totally tore down the engine and put it back together and it doesn't smoke anymore, thankfully, and it runs fine.

However, now it won't start with the air filter attached. If I remove the airfilter and attempt to start it, it will start and run great. However when I place the filter back on while still running, the engine chokes down rapidly and totally stops running after about 45 seconds. I've tried a new air filter, I have put a few drops of oil on the filter like it suggests, but nothing seems to make a difference.

The Carburetor is non adjustable, no screws or anything to turn to adjust. There is a governor on the engine and I've tweaked it some, but even having the engine going full throttle makes no difference, it still chokes down to failure when airfilter is applied. .

Any ideas as to the problem?

Jonathan Tubbs
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Old 08-25-05, 07:02 PM
Join Date: Oct 2004
Location: USA
Posts: 255

Sounds like you have an intake leak. Look at the gasket that mounts the carb to intake or the intake to the engine block. Once replacing your filter; your carb is being starved of air or your filter cartridge is starving the carb of air.

God Bless,
Old 08-25-05, 07:06 PM
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Join Date: Jul 2001
Location: USA
Posts: 16,817
I agree...

There should be an o-ring that fits inside the carb where it pushes onto the intake tube, and a plastic ring that snaps in and holds the o-ring in place. If these are missing, you could have the problem you're having. These often fall out when the carb is removed.
Old 08-25-05, 08:25 PM
Join Date: Oct 2004
Location: USA
Posts: 255
I just worked on one of these with a hunting problem. The one I was working on did not have a full gasket; only an o-ring seal to the head. I am not sure if it should have had a gasket or not, (did not look it up) but I removed the carb for recon. However, after removing and reconditioning the carb I had the same problem. I removed again and added a (cut) gasket to the block/carb. That did it. No more intake leaks and it roared!

Hope this helps.
God Bless,
Old 08-26-05, 07:55 AM
Join Date: Jul 2002
Location: wisconsin
Posts: 140
I have a gokart with a 5hp tecumseh engine with the same problem. i will have to take a look at that intake.......thanks guys

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