WR400 Rev Limiter may be the culprit...

I just finished testing my bike w/ a GPS. It begins to cut out at 90 mph in 5th and 72 mph in 4th. I didn't time the lower gears. 5th gear's ratio is .84, 4th's is 1.05. That means 5th is 25% higher than 4th and if you multiply 72 by 1.25 you get 90. This means the bike appears to be cutting out at exactly the same rpm in any gear. I tried 160, 165, 168 and 180 main jets with the same results for all jets. This leads me to believe that the "REV LIMITER" built into the WR400 is cutting the bike at a given rpm rather than fuel flow. It appears that the 180 jet give me better power. I get up to the rpm limit more quickly so I kept in the 180.

Please let me know if you agree. Thanks, Ron

was that a top speed of 90 with stock gearing(sprockets)? i didn't think it was that fast!it sure doesn't feel like 90 on my bike-2ooo Wr4oo-stock gearing. just wonderin.

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DRZ400E: Where's the power on this thing?

This is a 2000 WR400 with stock gearing. You are right. It doesn't seem like 90 MPH but it is! It tops at 72 in forth...sure gets there fast! By my calculations a 27" tire with a 15 tooth front sprocket and a 50 tooth rear with a 5th gear ratio of .84, or a 4th gear ratio of 1.05 (both stock) will require 10,000 RPMs to hit these speeds. I'm trying to find out if the bike stops there becuase of a REV limiter or because I'm jetting it wrong.

i woulda never guessed 90!! WOW!! well i think your math is right-it is hitting the limiter. what are you lookin for-more rpm's or more top speed? don't you think 10,000 is enough? i'm sure it could handle it but it would definetly come at a cost :).

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DRZ400E: Where's the power on this thing?

Thanks Bonez. I agree, 10K is enough. I simply want to confirm that 10,000 rpms is the limit. If not, I need to find out why the bike cuts out at that point.

You can click on the "search" button up top there... and type in "rev limiter" when you get there.

It will show you other peoples posts in the past with info about the rev limiter.

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