piston slap

seattle##gs · Nov 23, 2018

One winter I put the Atlas away after using all summer. When I brought it out next summer and started it up one piston began to make a lot of racket especially while warming up. As the days went by it increased so I fanally had to pull the cylinders off. One piston was noticably worn. So now I am running into the same problem with an A65. The motor was rebuilt by a reputable shop about a year ago and ran well. This year it has developed the familiar harsh whacking sound. How does this happen all of a sudden?

motorson · Nov 23, 2018

My Commando did that in one day by running the timing too far advanced.

Fast Eddie · Nov 24, 2018

Maybe you’re running too rich and washing the bores?

seattle##gs · Nov 24, 2018

perhaps...but my main question is why it seems to develop almost overnight. The A65 has a #3.5 slide

Fast Eddie · Nov 24, 2018

Good question. I don’t know...!

kommando · Nov 24, 2018

seattle##gs said:
but my main question is why it seems to develop almost overnight

Its called human perception, there is a threshold below which you ignore and above you take notice.

For clearances in bearings its typically 3 thou, so until there is 3 thou of wear you cannot feel it, above 3 thou you think the world is coming to an end

Fast Eddie · Nov 24, 2018

That makes perfect sense to me.

eskasteve · Nov 30, 2018

I experienced this same issue years back, probably in the early to mid 80s. Perfect runner when stored, piston slap after a year and a half of storage. I'd oiled down the cylinders and drained all of the fuel so it was stored properly. I shut it down immediately and pulled off the top end. The two compression rings on the right hand side were gummed/stuck in the grooves. Since the barrels were off I did a quick hone and put new rings in. Didn't touch that motor again. I sold the bike about 20,000 miles after the ring thing and I know that it ran well for another 10,000 miles when the new owner attacked it with all kinds of hop up parts.

seattle##gs · Dec 8, 2018

I wonder if pourinf some solvent down the cylinder maybe some gasoline and run the pistons up and down a few times would loosen the rings and get them working again. However, this bike ran without smoking and went down the freeway untill the battery fell to 10.5 volts.

Bernhard · Dec 10, 2018

seattle##gs said:
I wonder if pourinf some solvent down the cylinder maybe some gasoline and run the pistons up and down a few times would loosen the rings and get them working again. However, this bike ran without smoking and went down the freeway untill the battery fell to 10.5 volts.

Don't you mean Redex?- it sometimes works, but if the rings are heavily gummed up or engine worn it will not work.

oldbeezer · Dec 10, 2018

seattle##gs said:
I wonder if pourinf some solvent down the cylinder maybe some gasoline and run the pistons up and down a few times would loosen the rings and get them working again. However, this bike ran without smoking and went down the freeway untill the battery fell to 10.5 volts.

I don't know if it is still available but Chrysler made a product (we called it "can o' rings") made just for stuck rings. Poured it down the carb...........

Bernhard · Jan 11, 2019

oldbeezer said:
I don't know if it is still available but Chrysler made a product (we called it "can o' rings") made just for stuck rings. Poured it down the carb...........

I don't know this produce but I would like to try some Berryman 0116 B-12 Chemtool Carburetor/Fuel Treatment and Cleaner, but I am in the UK and shipping costs are prohibitive.
any body know of any carbon cleaner available in the UK.
I have included the web site :

piston slap

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