Riding mower engine issue

danrob123(7)November 28, 2012

Hey guys, I am new to the forum so please go easy on me. I recently purchased a very nice Huskee rider for $100.00. The reason for the ridiculous price is that the engine does not sound right. It has a 17.5 h.p. briggs & stratton ohv engine, and when started it sounds exceedingly loud, and just not right. Upon close examination, (and removal of the breather)I discovered that the extra sound was coming through the carburetor. I can literally feel the exhaust coming out of it. My first thought was it has to be coming back through the valves, so they must be burnt(or at least the exhaust valve) I removed the head, and turned it on its side and poured a little gasoline in it, and sure enough, I had leakage. I removed the valves from the head and cleaned them up, and re-installed, and re-tested. This time no gas leaked past the valves, so I re-assembled everything, and adjusted the valve lash per Briggs & Stratton specs. The problem still persists with no change. My next thought was the muffler could be in some way plugged, causing back pressure so great that it would push the exhaust valve open and come back through. I disconnected the pipe from the muffler, made sure that it was clear, and installed it pointing up, instead of into the muffler. When started, it still had exhaust shooting out of the carburetor. I looked at the flywheel key, and it appears to be o.k. I have fixed many a lawn mower in my time, but I have never run across anything of this nature. Any suggestions? or has anybody seen this before? Thanks in advance for any help you may be able to offer.

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One more thing, it starts easy, but does not have the power it should. Hope this helps.

    Bookmark   November 28, 2012 at 11:34AM
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You didn't post the Model & Type of the engine, although it's likely a 31 series.

I've heard mention of "some" Briggs engines having a bad cam shaft where the lobe wore down.
You might remove the valve cover and see if BOTH valves have a similar amount of travel.

    Bookmark   November 28, 2012 at 12:00PM
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Thanks to bill_kapaun who hit the nail on the head the first time. The exhaust valve is not travelling anywhere near the distance that the intake valve is. Obviously this is causing a lot of the exhaust gasses to remain in the cylinder, and then leave through the intake valve when it opens. He also guessed correctly that it was a 31 series engine. Thanks Bill.

    Bookmark   November 28, 2012 at 2:40PM
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It does indeed sound like the cam has gone bad.

Walt Conner may have some input on this when he see's it. He's my "go to" guy for Briggs.

    Bookmark   November 28, 2012 at 3:05PM
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I have nothing to add to what Bill said though I do wonder were I am to "go to". :)

Walt Conner

    Bookmark   November 28, 2012 at 4:48PM
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That's the reason I never get lost,Walt, 'cause everybody tells me where to go,LOL!!

    Bookmark   December 3, 2012 at 9:27AM
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Update, I found a bad engine with a good camshaft in it for $20.00. I changed it out, and it started right up, and runs beautifully. It will be back on Craigslist soon, but not for $100.00. Thanks again Bill.

    Bookmark   December 16, 2012 at 8:20PM
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