Re: Failed piston (skirt)

You'll probably never find out, but probably old age?

Dear Adrian,

not unheard of, depending on the type of piston you have. Some early types had a horizontal slot below oil ring at front and rear of piston which caused a weakspot. You can see which I mean if you look on Norvil website under tech Talk / Anything else / pistons.

Post a picture so we can see what type you have and where it cracked

Good picture, that looks like the weak type that is not reccomended any more; now you know why - another component on the list is any conrod with a D within a circle stamped on it.

So depending on your engine's damage it's rebuild time. If like me you have engine with no sump filter then bits of piston will be in every nook and cranny - oilways, pump, oiltank etc and will need a full stripdown, If you have a sump filter it will save worst passing through pump, but finer particles may well have reached tank.

Due to lead times I would start with barrels if not scored source some more pistons, otherwise rebore time!. While you are waiting you can strip bottom end, clean it out and I would check crank journals while apart, split it and remove gunge from centre. Owners club have shells etc.

just so you don't feel alone I will try to attach picture of piston that melted last year and caused me to do all of above.

Having had a good look at your first pics, your pistons may after all be later ones as early ones would show a clean machined edge under oilring. so just bad luck

I have had similar failures with my Dominator. All with Hepolite pistons. Most likely down to youthful thrashing the bike mercilessly. Were the previous owners old codgers or go-faster riders? But not all failures are down to abuse. One failed 200 miles into careful running in. Some pistons just seem prone to cracks. Not something that you see much of these days. Are present-day pistons better made? Discussion point.

I think you are just unlucky. I would certainly recommend splitting the crankcases to get all the debris out.

Adrian

Good to hear that you're back on the road.

Do you usually have parts left over?

Andy

If there not left over it could mean they dropped in when you weren't looking. These old bits that a life of there own you now ð

One of my evil-minded friends was in the habit of dropping the odd nut, bolt or whatever underneath any bike that was in the process of a rebuild just to cause the hapless rebuilder consternation. The cad.