250-500cc urgent help needed please, WR300 seized

I run mine at 45 mph on the roads for short periods (a mile or two) all the time, no concerns. 68 mph is a LOT of revs, though. Combine the speed with a cold motor and possibly lean jetting, and boom!

Hey, if you buy a new bike, how much do you want for your WR that's all blowed up?

Leo might buy it. Engine is in the shop already and I spent all day today going through every bolt and cleaning all up to original shine

Isn't this a known way of seizing a 2t engine? REV it out hard and blip the throttle while the engine is still at high RPMs?

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I'd just drink beer if I was you and at home ... Good luck with your chosen path.

Sure, but a KDX will run a 50 mph nearly forever, even if you forget to put premix in it and drain all the oil out of the gearbox. Those things have got to be one of the toughest bikes ever made. I had one and I miss it sometimes!

The Carb experts need to correct me here... When you have the bike running down the road at a good clip of speed and your roll off the throttle and coast, the carb drops back down to the pilot jet (off the main jet). If the bike is at all lean it will be SUPER LEAN when you do a quick deceleration. This is when most bikes seize up. So, I'm not sure the whole engine temp was your problem. IMO, the bike was too lean and your fuel mix should be closer to 40:1.

Here's a great video from Jeff Slavens about lean jetting. At the 4:30 mark he talks about 'cutting the throttle' after a fast run and how a lean condition will blow a motor very easily.


View: http://youtu.be/zVzqqpgviyI

Yeah, the throttle lift problem can happen in lots of scenarios on a 2-stroke. For example, on long descents if you have the throttle closed under engine braking. It's not so much being lean that's the problem, but since the top end lubircation comes in with the fuel, being lean also means being light on oil. In theory it could also happen slowing down from a high speed with the throttle closed. I try to blip my throttle in these scenarios, but a short decel or a smaller hill shouldn't be an issue.

Based on where on the piston it's worn ("4 corners"), I think that indicates a thermal mismatch. The high revs and possible lean condition only make that situation worse.

For what it's worth, according to gearing commander (http://www.gearingcommander.com/), on stock gearing 60 mph in 5th is like 7500 rpm. That's a whole lot of revs on a cool engine at light, constant throttle.

At 60 mph the engine is definitely revving pretty hard. On top of that it doesn't take much throttle to keep it there. Less throttle less oil, and at 50:1 you've all but eliminated the safety net.. Don't be silly mix it at 40:1 or more. I consider the 50:1 advertising a marketing gimmick.. Would like to see a pic of the bottom side of the piston crown. If it's black or has a dark spot, it got to hot. When this happens you have even less oil getting to the top end because it gets burned to the underside of the piston crown. This is where that safety net would be usefull.!!

Didn't know about Slavens method for motor warm up. Makes sense that you get less spooge that way. Got to be careful tho.

For what its worth, Jeff Slavens has a ton of 'How To' videos on YouTube. He speaks mostly to KTM but on a 2-Stroke the same concept carries over as is the case of the 'carb jetting'. Just FYI

will having a rekluse auto clutch help to prevent the throttle lift problems as it free rolls a bit when i roll off

apparently not. my bike has rekluse.

Rekluse should not freewheel at all above the lockup speed.

my understanding is that it only engages when power is applied, when power is not feeding the clutch, it's freewheeling.

there is small amount of clutch drag, but thats about it.

I do not think my engine locked up though when it seized.

Like Kyle says it should lock up on decel.

The Rekluse is a centrifugal clutch, meaning it engages based on engine speed. It shouldn't care if power is applied or not, just speed.

donno.. maybe it's just 2 stroke effect.

all i know is that when engine quit, i pulled the clutch in and coasted to stop. but my rear wheel did not try to lock up.