I pulled my 250r motor apart and...

[irish_triker]

The head and piston were all chewed up. They looked like the moon with a bunch of little craters in them. My motor was locked up still, so I figured something managed to get into my motor and somehow drop down into the crank after finishing off my head and piston.
I stopped by my friends house a couple days ago and he showed me his head off his blown up yz490 and his head looked like mine, except not as bad.
So my question is, did something manage to get into both our motors? Or did we do something wrong that caused our heads to look like this? I run 32:1 oil mixture and 91 octane pump fuel. The motor was mostly stock. I'll try uploading pics, but idk if it will work from my phone.

Thx for any help.

[Auto_Demon]

first get better pics

[dcreel]

Could be detonation as well (running lean)Once detonation (pinging) starts it removes metal material from the piston and inside the cylinder head and the sharp areas get hot which will fire the intake charge prematurely which makes the problem worse, and makes the damage happen faster.

[KASEY]

YOU definately had something go thru the motor,,, maybe a wrist pin needles or crank bearing,,, tear it all the way down. with all that junk in the topend your going to have to split the cases,,,,,,

[Silverado]

yeah those pics are bad and I am novice, but end I can see that is not machined metal, something has gone bad....very very bad

[irish_triker]

I was thinking it might be lean, but I check the plug often and it looked like it was running perfect. I even did a plug chop on it and it showed good signs. It was running rich when I bought it from the previous owner. Could it have made my motor weak so when I did get it running good, this happened?

[ATCrider42]

How do valves look? Ha, just kidding........

[dcreel]

How do your valves look?

[irish_triker]

The valves look good, but my cam is toast! Lol

[Dirtcrasher]

The last 250R I tore down had lost the one pin that locates the piston rings. Never spun the ring or caught a port or did any damage. Guess I caught it just in time!!

[dcreel]

How do valves look? Ha, just kidding........

[bcredneck]

thats exatclly what happend to my bosses 81 yz 125 the damage was probley caused by the crank berrings
did anything get bettwen the pistion and the port

[Toledo_Tommy]

Sorry to hear that , nothing i can really add except these guy are 100% correct . You need to split the case to find what exactly went wrong , Good luck.

[squirrel1182]

that piston looks brand new compared to the one that came out of my yz. lol. have fun splitting the cases. Thats why my yz's drug out back the shed. lol

[irish_triker]

Well I don't really wanna tear cases apart because I'm just getting a whole new engine. I was just wondering if this looked like a lean condition because I don't want to fry a new motor.. lol I was also wondering what size carb I should get. I'm going with a 310 kit.