[AT] OT- Briggs and Stratton valve clearance

Stephen Offiler soffiler at gmail.com
Fri Jun 24 09:28:32 PDT 2016


I'm curious to hear how this turns out once you've got it fixed.  Here's an
engine that ran until it got over-revved until it quit, and now there's no
compression and a valve problem.  Unfortunately, this isn't the same as
normal wear and it might take more than a valve clearance adjustment to fix.

SO


On Fri, Jun 24, 2016 at 9:33 AM, <k7jdj at aol.com> wrote:

> Thank you for the good replies.  The valve springs look OK, maybe weak but
> not broken.  I may get some new ones.  Yes it was starting and running OK
> when I loaned it out.  I am going to look closer at the seats and valves
> and will report back.  It probably ran at WOT until it quit running.
>
> Gary
>
> Renton, WA
>
>
> -----Original Message-----
> From: Cecil Bearden <crbearden at copper.net>
> To: Antique tractor email discussion group <at at lists.antique-tractor.com>
> Sent: Fri, Jun 24, 2016 3:22 am
> Subject: Re: [AT] OT- Briggs and Stratton valve clearance
>
> I would make a bet that the high speed and that vibration was a big
> factor in the valve recession.  Also, that cheap unleaded gas will give
> you a lot of valve seat recession.  I use only the super unleaded no
> ethanol in my small engines and ATV's.  My wife & I use about 12-15
> gallons a week in our ATV's checkiing cattle etc..
> Cecil in OKla
>
>
> On 6/23/2016 9:49 PM, Dennis Johnson wrote:
> > Gary,
> >
> > Valve wear like what you describe are common on Brigg's engines. I have
> seen it several times. Not sure of the exact wear mechanism but my guess is
> that 3/4 of the wear is on the valve, and the other 1/4 is on the hardened
> seat.
> > When you get  Brigg's that losses power when hot, that is the first
> thing to check.
> >
> > Thanks,
> > Dennis
> >
> >
> > Sent from my iPad
> >
> >> On Jun 23, 2016, at 9:23 PM, John Hall <jtchall at nc.rr.com> wrote:
> >>
> >> Maybe if that engine was built for leaded fuel, the lack of the "cushion
> >> deposit" the lead used to leave has allowed for the seats and valves to
> >> hammer themselves to the point you lost clearance?
> >>
> >> John Hall
> >>
> >>
> >>
> >>> On 6/23/2016 8:45 PM, k7jdj at aol.com wrote:
> >>> Not a lot of traffic so I thought I would post a question about a 70's
> vintage  5 HP Briggs engine.  The engine is used on a plate compactor so it
> is subject to extreme vibration.  I made the mistake of letting someone
> else use it and got a report that the engine was running extremely fast and
> you couldn't adjust the speed.  Quick check and it was obvious the throttle
> plate had fallen off the shaft.  Not an easy fix but after a lot of bad
> language I was able to reinstall with a new screw.  The engine would not
> start.  It would try but just would not run.  I checked the compression and
> it was zero.  Pulled the head and discovered the intake valve was not
> closing completely.  Exhaust was OK but probably doesn't have enough
> clearance.  These valves are adjusted by filing/grinding the valve stem.
> Not a big deal but I can not figure out why the valve clearance would
> decrease.  I can't imagine there can be enough valve/seat ware to reduce
> clearance nor the valve stem growing !
>  l!
> >   o!
> >> ng!
> >>>   er so what am I missing?
> >>>
> >>> Gary
> >>>
> >>> Renton, WA
> >>>
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