[SEL] Piston slap ????

[Elden DuRand]

I've experienced the same oddball knock at cranking speed and found that it was caused by (as someone else has said) the little end of the rod clacking against one of the wrist pin bosses as the rod moved slithtly side to side.

In my case, it was on the little engine I recently built and I traced the problem to a very small misalignment of the rod journal on the crankshaft.  I fixed the problem by moving the crankshaft slightly so as to give a little more side clearance on one side of the little end of the rod.

Take care - Elden
http://www.oldengine.org/members/durand 

> -----Original Message-----
> From: sel-bounces at lists.stationary-engine.com
> [mailto:sel-bounces at lists.stationary-engine.com]On
>  Behalf Of Graham
> Harris
> Sent: Tuesday, January 13, 2009 09:55 PM
> To: sel at lists.stationary-engine.com
> Subject: Re: [SEL] Piston slap ????
> 
> 
> Gday Tom
> 
> I've noticed a similiar problem on my Sundial 
> 4HP, an Oz built horizontal engine, closed 
> crankcase, 5" bore, thrott gov. All bearings 
> tight (i.e. good) and no slop in a good bore, and 
> fresh rings. As it coasts to a stop (use the 
> magneto stop button) I get a audible knock from 
> the crankcase at < 100RPM till it stops and a 
> small fore-aft rocking. The knock is not coming 
> from anywhere on the transporter.
> 
> Interested to hear suggestions you get, wondering 
> maybe if being a throttle governed engine, and 
> the butterfly almost closed, the (very good) 
> compression could be doing it? Sounds just like a 
> loose big end or gudgeon, but not in my case. It 
> is really weird. What make is your engine?
> 
> 
> Graham in Oz
> 
> 
> 
> Got a question for you guys.  I'm working on an 
> engine and it has a knock in it and you only hear 
> it when the engine is coasting down really slow 
> but the slower it gets the louder it gets.  The 
> noise is coming from the cylinder and it has been 
> sleeved so that rules out egg shaped cylinder.  
> Only thing that I can come up with is piston slap 
> but I've taken a piston and rod out of an 
> identical engine here and it does the same thing 
> but the other engine doesn't make the noise and 
> it's pretty irritating noise and is pretty loud.  
> You can't hear any loud knocking when the engine 
> is running at a decent speed but only when slowed 
> down to under 100 rpm that the noise starts.  Any 
> ideas or suggestions are appreciated
> 
> Thanks
> Tom Winland
> Ohio
> 
> 
> 
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