250-500cc 3rd seizure on a 12 wr300

I think I have had enough, time to throw in the towel on this bike.
I have a 2012 WR 300. Bought the bike new in the spring of '12. After @ 10- 15 hours the moter seized. PJs cycles warrantied the Bike and did the work even though i did not buy the bike from them. They said they did a leak down on the bike and the intake manifold was the problem. I believed them as this seemed to be common. I kept a close eye on the intake after that. It seized again after 49 hours after the work. Intake was fine, and yes i had re-jetted to altitude. I sent the cylinder off for replating and a piston and put it together myself; wondering if i was way off on jetting I put a Lectron Carb when I reinstalled the cylinder and piston. Yep, it went again at 92 hours.
I ride for the most part tight technical trails loads of rock and ledges mostly slow speed stuff. Common is that it seizes in 5th gear and above half throttle (witch the bike does not see often) i think if i rode at the high speeds it would seize way more often.
Now I have to tear it down again and start over. I am going to take it to a friends shop and do a full leak down as I suspect there is still a leak. Maybe Crank seal? if it does this would mean the dealer that did the warranty work would have lied about a leak down.
Anyhow any insight would be greatly appreciated.

not attacking but what brand of oil and ratio? gas with ethanol?

Either your gas/oil ratio is bad, the work wasnt done right, or something was missed during the rebuild(s). I believe its an issue with your oil because how would the engine seize after so many hours? Somethin aint addin up here.

Motul 510 oil, 44:1. 91 octane, only ethanol available around here.

Try more oil next time even though manual says 50:1. You can get pure gas here http://pure-gas.org/index.jsp?stateprov=NM

what color is the spark plug

Obviously your jetting is NOT correct. Quite often half throttle for extended periods is the leanest point of the jetting.

Raise the needle 1 clip or go up 2 sizes on the main next time.

Amsoil Interceptor at 40:1.

He has the Lectron. I thought it was supposedly next to impossible to seize with the Lectron. I suspect a crank seal or something unusual. I used Lucas from the auto parts store at 50:1 for about a year with no ill effect.

I've seen this exact issue before on a 125 caused from a leaky crankcase seal. Check under the magneto for oil seepage from the crank seal.

On a side note on your fuel oil mixture. Average riders run about 32:1. If you are a light throttle twister, fire roads rider, then 40 to 60:1. Aggressive riders (high rpm for long distances) set up their carburetors to run at 24:1. More oil will prevent bottom end failures and give longer life to high-revving engines. This may seem way out of the ball park from what you are normally used to hearing, but dyno testing a properly jetted bike makes the most power when it is run at 24:1.

Also, reading into your original post a bit further. For average riders, the typical lifespan of a piston and ring set is about 40-45 hours. Stretching it to 92 hours, without even a re-ring is really pushing it. Aggressive riders tend to have a much shorter lifespan on components.

Thanks for all the replies, I have owned several 2 strokes over the years and have had good luck at 44:1 and my spark plug looks good, even with the old Mukuni. I put the Lectron on for a number of reasons as well as the jetting. The piston and rings in the bike 92 hours where replaced at 49 hours, total time on them where 43 hours. I will let you all know how it goes with the Leak Down test, hopefully we will know more tomorrow night.

So we put pressure in the motor today, Big leak from the Left side at the power valve cover. We opened it up and the air was coming out of the bushing that the Booster valve rides in. When I had the motor rebuilt under warranty they had no bushing in stock but said we could re-use the old ones, I told them to go ahead. When the motor seized the second time i did not replace them as well. So a series of misjudgment on my part and trusting the dealer who did the work. I will rebuild and have new bushings on order.
I plan on pressure testing the motor again after i get it back together. Any one heard of this malfunction before?

I will do another pressure test after the motor is back together. Thanks for the input, I agree the exhaust side is not the prime suspect but is was blowing a ton of air. The scoring on the cylinder wall did match up with the suspect booster valve but the major damage was 90 degree opposite side from the booster.

I'm dealing with the same issues it seems like.
http://www.cafehusky.com/threads/cr125-and-144-scored-piston-and-cylinder-pics-and-vid.39246/

I'm kinda stumped??