piston/cylinder scored

[B-Nasty]

I put a big bore kit on my spree. First tank of gas mixed the right amount of oil in. I did the engine break in then went easy on it for about 20 miles. After this I started going full throttle in short sequences. yesterday I was cruising around and keeping it about 20% under full throttle and it died. I could tell the kick starter had more resistence then normal. I suspected at this time the oil injection had failed and i blew my top end. I pushed it home and pulled the top end off. the piston and jug have some scoring. everything was in right so I tested the oil injector. I hooked up a drill to the shaft and it pumps oil out fine.
Any ideas what caused this? The rings look fine so I am thinking I will try to salvage it and pre mix my fuel from now on. What ratio should I premix at?

[swimmingfree]

you shood done at least 200 miles before you went to wot .. did you do heat cycle ?????
swimmingfree ...

[B-Nasty]

yes I did heat cycle then followed these break in instructions. http://www.mototuneusa.com/break_in_secrets.htm Ive broken in many of 2 stroke dirt bike top ends this way. I never went wot for more then a couple seconds...and I only did that a few times. I also let the scooter idle warm up for 5 min before I ride it.

[Mystic]

did you change the main jet?

[swimmingfree]

on and off from wot is not good when you get off the gas heat spick and if you did notr up jet it make it wors ....
swimmingfree

[B-Nasty]

yes i changed the jet...

[bakaracer]

I put a big bore kit on my spree. First tank of gas mixed the right amount of oil in. I did the engine break in then went easy on it for about 20 miles. After this I started going full throttle in short sequences. yesterday I was cruising around and keeping it about 20% under full throttle and it died. I could tell the kick starter had more resistence then normal. I suspected at this time the oil injection had failed and i blew my top end. I pushed it home and pulled the top end off. the piston and jug have some scoring. everything was in right so I tested the oil injector. I hooked up a drill to the shaft and it pumps oil out fine.
Any ideas what caused this? The rings look fine so I am thinking I will try to salvage it and pre mix my fuel from now on. What ratio should I premix at?

What was the right amount of oil you mixed in the tank? What jet did you put in? Did you cut the stock head to the diameter of the new bore and had a squish band cut into it?

[indetrucks]

I don't know how you are NOT supposed to ride a spree WOT for 200 miles. How on earth do you even put 5 miles on these things in a month? 200 miles on city streets without ever going WOT is crazy.... you'd be limited to getting honked at and pushed onto the sidewalk

This applies to all my 2 stroke dirt bikes that I put new top ends in.
Once that baby is warmed up, I give her a few rev's, go up and down the block at medium pace. Then WOT and ride it like I stole it.

I mix it at 32/1 though and pretty sure these little scoots are oil injected at a 50/1 ratio (which is NUTS to me)

My Honda NSR50's owners manual said to mix those at 50/1 and they are race machines. 50/1 is not enough oil for a little bike that will be ridden at WOT for most of it's life.

Not sure about all this 200 mile stuff? Unless it's a longevity thing?
But shoot, at less than $100 for a piston, cylinder, rings and gasket... I'm ok with a new top end every year or so... even on a scooter. What's it take, 45 minutes?