The mysterious piston eating 250 YZ

Hello guys,

Back in November I found an interesting deal on a 250 YZ 07'. I went at seller's house to see the bike at good price, dude welcomed me dressed half gangsta half farmer, smoking weed... Probably a French cousin of the "Pro Works Bikes" seller from Craiglist...

Surprisingly, the bike was pretty clean but after a quick test ride, I noticed that rod/piston/cylinder were toasted from the weird sound the bike was doing. For sure, the bike was tired but still pretty fast. It has Doma silencer and suspension revolved.

We started to negociate price, a couple of minutes and a few joints later, the guy finally agreed to sell me the bike the price I wanted, which was pretty low considering hours of work and fresh parts the bike needed.





Here starts the story...

After a couple of ride in order to get used to the bike, I decided to restore it for 13' season.
While stripping down exhaust for reinflating it, I had a quick look inside exhaust transfer just to check piston and cylinder.

Ouch, as you can see, the poor boy was so old that it began to biodegrade....



I knew it was time to strip down engine for replacement of piston, rod, bearings, nikasil, etc...













I found a good deal on Ebay for a Wiseco crank kit, brand new cylinder with piston and gaskets so these old parts will soon join the Dead Parts room which is unfortunately way bigger than trophy room...

In the end, this bike will cost probably the same cost as a used 2007 250 YZ at normal price but good point is that I ll be sure of engine's health.

I heard bad things about Wiseco cranks, I have already purchased it, hope it won't blew the new motor.

However, I am still surprised that bike ran still pretty well since piston was nearly atomized and cylinder cracked.... Is it something usual on 250 zingers ?

I'll post updates about the bike, I eventually decided to take advantage of the situation to begin a rebuild project. I already put new wheel, swingarm and linkage bearings, fresh grips and ordered a Pro Circuit silencer. I am also questioning about realizing carbon fiber ignition cover.

Thanks for you time and reading my poor English, I know this project is not very creative but I wanted to share with the story with you and grab some good tips for my bike :-)