leak jet

Just reading your forum since a friend of mine just picked up a '03 WR450F and is having a bog problem. On my '03 WR250F I resolved the bog primarily by blocking the leak jet completely by soldering it closed. This forced the max squirt from the accelerator pump. I had tried jets down to 50 I believe before I blocked it without success. I also have a P-38 installed but I am not really sure that has played much of a role. The leak jet mod did. I think we'll try this on my friends bike. You might want to experiment with that as well. Hope that helped....

You are on the right track. Tuning the WR450 and jetting will make the bike rip! :)

if you go to the first page of this thread you will find a link to the tech bulletin yamaha put out about leak jets and pump diaphragms. it lists the stock numbers and all the options available through yamaha. the '03 wr450 used a 70 leak jet. the '04 uses a 60. smaller jet, more juice. the '04 is still pretty choked up stock. it makes you wonder if a 50 wouldn't be the ticket for one that's been opened up and can breath. my 60 should be at the shop in a couple of days. i'll post on any improvement.

I'd agree with those about the acc pump air jet adjustment if higher needle position didn't work.

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