Piston problems!

[*Quad*King*1986]

so i was kinda just cruising around the other day, i wasnt riding hard or beating on it and all of a sudden it just sorta bogged out. but since i wasnt supposed to be riding in the area i was at i pusshed it into the woods real quick for a closer inspection. i tried to start it and it kicked over after about 5-6 kicks but then i heard metal clinging-clanging around, i killed the engine and looked at my motor and noticed my exhaust was loose so i hand tightened the olts a best as i could and started it up again (i thought the metal noise was my head pipe vibrating around on top of my head and making tht noise. so it started up and ran like sh*t. i killed the engine and pushed it home! once i figured out it wasnt a carb/jetting problem i looked at my VF3 reeds i just installed last week, of course they were not the problem either... so then i looked into my intake port to find out my piston broke apart. i took the motor apart today and thankfully my sleeve is fine, i checked the bottom of my case and couldnt find any damage or cacks at all. looks like all i need is a new piston & rings. looks like its time to install my +3 crank and fix a few tiny things while the motor is off why would my piston break apart like that though? ive never had this happen to me.... here are some pics i took below

 

[nboldman]

Time to split the cases!

 

[Awk08]

my guess is incorrect cylinder to piston clearence, causing it to slap the bottom of the cylinder on the way up, busting the skirt

it's gonna need a new bore to match the new piston,
not just slap a new piston rings in so it does the exact same thing again

how many hours on this motor ?
what was the compression ?
who bored it for that piston ?

 

[Blaaster]

Sorry to be the bearer of bad news, but your gonna have to split the cases!

 

[*Quad*King*1986]

ya i know i gotta split em, but at least i'll have the +3 after all is said & done (im trying to be positive over here guys!!! lol)

 

[*Quad*King*1986]

i honestly dont know awk. i bought my top end off someone on ebay and i didnt get a full break down on those things. and i was gonna buy a compression & leakdown tester last week but never got around to it, it might of saved my top end had i bought it. i'll learn from this mistake though and will not let this happen again. but then again who knows?!?!?

 

[Blaaster]

ya i know i gotta split em, but at least i'll have the +3 after all is said & done (im trying to be positive over here guys!!! lol)

Positive thing is that you get to use the +3.I:I

Another positive is that you are on a steep learning curve.I:I

 

[*Quad*King*1986]

Positive thing is that you get to use the +3.I:I

exactly! cause its setup for it now... but ive been running stock stroke. i have the money to buy it now but i wanna do it right and get new seals etc...

 

[blasterdemon7]

It always feels good to get stroked.I:I

 

[Larry's Shee]

Can you tell if it's a forged or cast piston?

As to 3mil, what do you mean that it's already set up for it.

Positive thing is that your case or jug isn't missing pieces.

So this was a used piston and jug you bought?

 

[nboldman]

It always feels good to get stroked.I:I

Lol, have some green! I:I

 

[*Quad*King*1986]

Can you tell if it's a forged or cast piston?

As to 3mil, what do you mean that it's already set up for it.

Positive thing is that your case or jug isn't missing pieces.

So this was a used piston and jug you bought?

Yes I bought a used top end with head work, it was ported and setup for +3 stroker & port matched... Except I run stock stroke. So I've been waiting to get it for a while now. Looks like now is the perfect time huh? The topend had low hours on it but not exactly sure how many.

 

[*Quad*King*1986]

And In not sure if it is forged or cast? I was wondering the something. I will take a better look at it tomorrow and try to figure it out.

 

[*Quad*King*1986]

my guess is incorrect cylinder to piston clearence, causing it to slap the bottom of the cylinder on the way up, busting the skirt

it's gonna need a new bore to match the new piston,
not just slap a new piston rings in so it does the exact same thing again?

Sorry if this is a dumb question lol but would adding the correct crankshaft (+3) that it's setup for solve this problem? I'm just confused. This sleeve is great no scratches, cuts, dings, burrs, etc.Why exactly is it that I need to bore it out if I put the correct piston size in it? You've never steered me in the wrong direction before so I trust you, but I just wanna know why? KNOWLEDGE IS POWER...and then there's Yamaha Blaster! Haha

 

[Blaaster]

The reason why your piston exploded is possibly that the jug was worn, causing the piston to flog around and destroy itself!

Have you had the new jug measured?.

If so, if it is within specs and has a good amount of crosshatching in it, there should be no problems fittind a new piston and rings.

I personally would have the bore honed so that the new rings have a chance to bed properly!

 

[*Quad*King*1986]

The reason why your piston exploded is possibly that the jug was worn, causing the piston to flog around and destroy itself!

Have you had the new jug measured?.

If so, if it is within specs and has a good amount of crosshatching in it, there should be no problems fittind a new piston and rings.

I personally would have the bore honed so that the new rings have a chance to bed properly!

No I didn't have it measured since the guy who referred me to eBay is well known on this website and pretty much told me he knew they guy from this forum & other forums too... He said the guy I got it from knows his stuff and that he is very trust worthy. Also when I received it in the mail it was put together and ready to put & ride. It was put together to spec so I didn't wanna take it apart since at that time I didn't have a torque wrench or a good understanding of 2 stroke motors. Since then I've learned a lot from this forum and doing my own research and talking to other members.

 

[Blaaster]

So this guy, told you about this guy. You are way to trusting my friend.

Before you fit a new piston it is a good idea to see if the bore is out of specs.

Fitting a new piston (even a forged one) in a sloppy bore is asking for trouble.

 

[*Quad*King*1986]

sorta.... it was more like "hey check this auction out on ebay" and after talking about it and i started an entire thread on that top end i decided to grab it before someone else did since it was a really good deal. but ya i def was taking both of thier words on it.