250-500cc Shattered piston on my '11 wr300

I don't understand why you guys go so many hours on a piston.... Super cheap to throw and piston kit in and be good to go.... keep it under a 100 for aftermarket

I think he meant under 100 hrs not dollars.

No excuses here. I check compression every couple of months so thought I was ok until I decided to pull the reeds off to inspect the intake side. Lesson learned is that compression can be fine past 100 to 200 hours, but the piston will still be wearing on the intake side. Still waiting for my relined cylinder and wossner piston kit from Millennium Technologies. Should be here next week. Also ponied up for some porting and head work from them just to see what it will do. I also replaced the main crank bearings and seals (thanks Rancher1!) and flushed the bottom end a dozen times w/kerosene. Lots of tiny piston fragments showed up in the first few flushings so kept at it until no more were detected, then did a few more for good measure.

Only upside to waiting 3-4 weeks for a relined cylinder is it gives you/me lots of time to inspect everything else. So far I've replaced the linkage and swingarm bearings; installed new seals, wipers, and inner and outer bushings on the forks (Yamaha yz/wr factory kit for 48 mm kyabas) along w/new oil; serviced the shock w/new oil, adjusted the carb and installed a new float valve in hopes of better mileage (the original float valve was worn around the seat ever so slightly upon very close inspection); new f&r sbs brake pads, new fmf gnarly and TC2, new plastic, new seat, new tires, new grips. I think that's the thick of it... New graphics and foot pegs soon.

LoL @ Brian Scott....I see l'm not the only one who gets bored during an engine rebuild

PowerSeal is a little north of Philadelphia. I used them and will be bring the kids 144 jug there next week.

I meant 100 hours or every season even play riding... Better to spend $200 then go 3 years and waste a crank, cylinder and piston....

Compression is not a great measure.... You can have great compression yet a piston that's wore out and ready to break the skirt off and grenade your motor...

Personally on OEM stuff I throw rings in at 50 hrs and while kit at 100

Been play riding for a couple years on my 12 wr300. I started to pick up ths pace and do some riding at race pace. Noticed the bike was easier to kick and losing bottom end grunt. Top end felt fine but figured it was time to do the piston and rings. I started up the WR to warm up trans fluid to change and started to get that surge/running out of gas thing. Shut er down and broke her down and sho 'nuff had the "death smile" on the piston from the intake port.
Got a vertex piston kit off ebay for 119 and a full athena gasket kit for 50. I figured might as well get some extras.

Put it back together and fired it up and yep it was time. Feels solid and tight. I did 2 heat cycles and doing woods ride tomorrow.
Feels tighter now but I can really tell it's muffler packing time...

Did all that work and right when I was ready to clean up, my kickstand cam breaks... Jeez....