Piston Smashing !!!!!

[masonryman13]

Ok, got 1 of the 84r's back together-- bored .80 over, reeds, blah,blah,blah-- after about 6 hrs. of riding(on & off) this is the result. $120.00 piston down the drain, cylinder work-- screwed, and I haven't found what caused this. I am beginning to wonder if this head, I purchased used, wasn't shaved or something. I guess that's why a smash test is reccomended. What's your guess about the top of this piston looking like Woody Woodpecker had fun?????

[chavo80]

what the condition of the spark plug>is it the recomended ngk for your motor>lets see pics of the dome of the head you are running>thats odd

[masonryman13]

here is the dome/head. spark plug is a br8es. its still in-tact. ????

[kxrider]

what type of gasket do u use?? cause if its tha thin metal one ur piston might be sitting a little to tall but other than that u might have pulled sum trash in

[250Rsteve]

If it was the plug it would only be in the center of the piston. That is from detonation, and its also bad on the rod bearings. I would make sure to check them before you put it back together.

[rjatv]

Yah thats not your spark plug that did that, something got inside and did that. And by the way if your really paying $120.00 for your pistons your paying to much, i can save you some money here http://rjatv.com/index.asp?PageActio...&Category=1752

[Daddio]

I can't tell for sure but it looks to me like most of the damage is on the exhaust side of the engine. Am I right? If so I would guess detonation. What octane is your fuel?

[masonryman13]

Fuel octane is as high as i can get at the pumps...92. mix is 32:1. I am going to guess that some trash got in from the bottom end. When i started this rbld. the bottom had been sitting for @ 8 mnths. I got it from a friend so i am not sure where all it had been moved/sitting. I thought I cleaned out the bottom well enough, but EVIDENTALLY NOT..!!!!!
And by the way if your really paying $120.00 for your pistons your paying to much,--Thanx, I will check out your site.....

[250Rsteve]

well if it came from the bottom end it had to get around the rings. Is there any cylinder wall scaring? If not I still say its detonation. I have been around forced induction cars that go lean and beat the pistons just like that. Its always more to the outside because of the heat buildup there. Also try using less oil in your mix as the more oil you use the more it leans it out.

[masonryman13]

Yes to the cylinder wall scar. Whatever happened in there also caused the ring guides to press together on one side. rings are still in-tact, so it wasnt a piece of that. there are a couple of pieces of actual metal(a magnet sticks to them) in the top of the (aluminum) piston. i guess i will split the cases(god knows i dont want to)--i've never done this......gotta make sure the crank bearings are still good...