250-500cc Seized wr 300 - 4 hrs after rebuild - lectron

Hey guys finally got my 2004 wr 250 back together with a factory 300 kit and a lectron.

Now today on its 3rd ride I was riding to my local riding spot on a dirt road, bike had been warmed up, about 15 minutes in I went from 3rd, to fourth and then to 5th, a few seconds after getting into fifth the back wheel locked up for a few seconds then freed up. I just came to a stop and towed it home.

Pulled it right apart and has seized to the right side of exhaust port, piston and rings are toast.

Cylinder is currently being cleaned up to remove built up aluminium. There is one small mark in the nicosil, however the bike shop has said that it's probably ok.

Now the lectron is a 38mm purchased second hand here in Australia, originally purchased in the states to suit a wr300.

Now all I altered was the idle not even half a turn, apart from that the bike seemed to run beautifully.
What I'm concerned with is maybe the power jet was set incorrectly?
How is it adjusted and what part of the carb is it? Is it part of the choke?
Sorry for these stupid questions just a bit confused about tuning the carb.

Anyway does this sound like carb caused the issue?

Fingers crossed the cylinder is safe to use as I've just finished spending a fortune on this engine I really don't wanna have to recoat a 4 hour old cylinder.

Let's see some pics of the damage, but I doubt that carb can cause this and so quick.

Sad to hear that, I think it can be for sure a jetting issue, maybe not directly related to the lectron but to some air-intake, the carburator boot is known to have a weak seal...
Another option could be cooling failure, false piston ond/or ring clearances... Not enough premix...

Regards.

I re-jetted for a dune trip and replaced the carb into the boot. Didn't pay close attention to the clamp and tightened it. It did not seat completely and rubbed a big hole on right side of intake. Made bike run real lean/hot but didn't seize motor even after 3 hours dune riding. Bought new carb boot and now pay careful attention to hose clamp tightening.

Sucks, but at least you know what happened and this thread will probably help someone else.

Hey guys thanks for your replies. The cylinder apparently is ok to re use, the local shop I had check it out didn't want to give any 100% guarntees, however there head mechanic had said if it was his bike he would definetly give it a shot. Theres a small mark right at the edge of the booster port, however they don't think it will cause any dramas or spread.

After seeing the piston they believe its cooling related, they seem to think an air lock in the cooling system? I did top up the coolant the day before the ride, all I did was lean the bike over to get some of the air bubbles out. They however think I should have ran the bike without the radiator cap to let the air out that way, because I didn't they believe an airlock occurred in the cooling part of the cylinder causing heat to build up at that point.

Motor was assembled by a competent motorbike mechanic, ive had him do my old wr250 and had no dramas, I highly doubt its caused by something hes done. I put engine back in frame.

Engine had an A size piston, do I order another A size now? im going to get a wossner kit and put it all back together this week and see if this cylinder is gonna play nice. I will check the ring gap on reassembly.

The carb boot has a few small cracks on the outside, but these don't go through. The bike didn't have the high idle or any other symptoms of an air leak.

Bike was running 32:1

Ill pull the carb apart and check the rod for you. Ive got some photos of the piston, and the plug. The plug photos were taken the day before it seized.