2008 yz450f Front brake fault and fix.

2 replies to this topic
  • nukem996

Posted December 05, 2009 - 09:23 PM


Just thought i would share with you all a very peculiar problem that i had with my 08 yz450f. Noticed that if the front wheel was off the ground and i span it by hand that the brakes were dragging. The wheel would spin maybe two revolutions then stop. You could see that the brake disc was blue with all the heat that was generated and the bike handled differently. Finally after trying many things i swapped out my friends 09yz caliper, master cylinder and the brakes worked fine. So i knew this was the problem and put my caliper back on the problem reappeared.
I tried loosening the bleed screw to see if there was trapped brake pressure and this made no difference.
So i changed the caliper seal kit as per the Yamaha Manual and this solved the problem.
I've owned roughly 40 bikes and i've never seen this problem and very few people i talked to had heard of it either.
A great bike otherwise. the best i've owned yet. Once you replace the muffler..

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  • mikedabike

Posted December 05, 2009 - 09:33 PM


Happens occasionally. I had bought a new CBR 600 back in the day and it had the same issue. The caliper would drag just enough to keep putting heat in the brakes then you would go to brake and nothing because they would be overheated. Took it to the dealer and they could not duplicate because they would only test it for a short ride. I had the mechanic keep it and ride the bike home. After he rolled a red light on the way home because of overheated brakes they replaced the entire brake system. Said it was a bad caliper assembly form the factory.

  • Krannie McKranface

Posted December 05, 2009 - 11:10 PM


Not an uncommon problem on Nissin and other japanese caliper systems. Brake fluid is a poor lubricant once it oxidizes.

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