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Trusty WR450 died and left me stranded!


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I was riding rough gnarly trails all day. I popped over another fallen log and my '07 WR450 (all stock except the GYTR unplug and jetting kit) did a cough and die. I hit the button and the engine just spun over real easy and fast. After several attempts, I swung out the kick starter and gave a couple of stabs. Uh oh, way too easy. Plenty of spark and fuel, but seems like no compression. Get out the rope get dragged 25 miles back to the truck by a KTM and listen to jokes the whole way home.

What happened to my WR? It was running perfect up until that point.

Thanks.

Edited by cardoc
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Check your hot start lever and plunger to make sure it's not stuck.

Surely that would make it harder to kick, not easier.. The more air you introduce during startup, the harder the bike is to kick.. Try kicking it at WOT and you'll see what I mean..

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Thanks for the info and ideas. I have ridden Yamaha four strokes for years and they have proven to be rock solid reliable. That's why this was weird. I finally took it apart and here is what happened. First of all - IT WASN'T THE BIKES FAULT! Several months ago I was riding in Baja and by fluke, a branch got jammed between my shock body and the frame. It damaged the plastic air boot/air box. I have since, cleaned it all up and have been riding it with no issues. Well, it turns out, a small broken piece of plastic from the broken air box, after all this time, found it's way through the carb and down into the seat of one of the intake valves and held the valve open - no compression. Removed the small piece of plastic, new head gasket, checked everything else, put it all together and good as new! My fault or a fluke branch - whatever you want to call it. Thanks again for the input.

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Wow, very interesting.

I had just bought a new 09 WR450F because I had heard how reliable they were and just after that, yours was one of the first posts I saw on thumpertalk! I thought ... AHHHH ­čśĆ

Amazing to hear you could get it going again with no real damage.

Whew.

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  • 2 weeks later...

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