8hp Briggs - won't run right after rebuild


Old 08-22-06, 11:46 AM
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Join Date: Feb 2006
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8hp Briggs - won't run right after rebuild

My Troy-built Chipper vac has an 8hp Briggs with a unique crankshaft that has the normal drive on one end and has a pulley drive off the recoil end to drive the wheels.

I use it quite a bit, and awhile back the chipping flywheel sheared off the crankshaft clean.

I bought a new crankshaft from Briggs, took it all apart and put it back together. I'm usually a pretty good mechanic - but I had no instructions to put it back together...

So I started it up, and it runs, but really rough, and it has no power.

It acts like I got the timing messed up, but I'm sure I lined up the timing marks correctly. A mechanic buddy said he had the same thing happen one time and it was something to do with the valves not seating correctly after the rebuild.

I'd hate to have to take it apart again - but it wouldn't be the first lesson learned the hard way...

Any ideas?
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Old 08-22-06, 01:44 PM
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If timing is in question that would be my first place to start. You can check valve timing by only removing the head and insure that both valves are seated when the piston is at TDC.

I have had briggs that only sheared the flywheel key just enough to have the same symptoms. Usually tho it will sputter and backfire if this is the case.
Old 08-22-06, 07:06 PM
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A quick check of cam timing is remove the cyl head (if a valve in block) & rotate the piston to top dead center exhaust. Now rock the crank back & forth & watch the valves. They should be in "overlap" (both open slightly) @ t.d.c. exhaust.
Old 08-23-06, 04:34 PM
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I think the flywheel key would be the first place I'd look. If the flywheel wasn't tightened sufficiently, or has oil/grease on the area where it contacts the crankshaft, it has probably sheared partially.

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