yz400f low lw end power high upper end power

[fordman06gt]

I just purchased a 98 yz400f, it seems to lack low end torque and power, once its in the rrs its fine. I rode a 04 wr450 and the wr450 has much much more power on the low end. Is the power difference from the yz 400 that much less than a wr450. The yz400 doesn't seem to have much stuff. the engine is 6 months old built by a yamaha dealer so the compression and condition is near new. I am not sure if I should sell the yz 400 and go to a 450.

What is the stock sprocket size? I know it has a 450 pipe on it, other then that I don't know if any other mods are done, but I don't know, this is my 1st 4 stroke, my last bike was a 2000 cr500.

[Birdy426]

You might try changing the exhaust cam timing to WR spec and see if that is more to your liking...

[Alternative]

Stock sprockets are 14/50 I think. You may want to try re-jetting the carb, might be a bit lean on the bottom end, does it splutter at all? Do a search on here and you'll find all the info. you need to jet it properly.

[SXP]

I just purchased a 98 yz400f, it seems to lack low end torque and power, once its in the rrs its fine. I rode a 04 wr450 and the wr450 has much much more power on the low end. Is the power difference from the yz 400 that much less than a wr450. The yz400 doesn't seem to have much stuff. the engine is 6 months old built by a yamaha dealer so the compression and condition is near new. I am not sure if I should sell the yz 400 and go to a 450.

What is the stock sprocket size? I know it has a 450 pipe on it, other then that I don't know if any other mods are done, but I don't know, this is my 1st 4 stroke, my last bike was a 2000 cr500.

I notice the same thing between my 400s and 450. The 450 has a longer stroke which gives you more low end grunt.

[fordman06gt]

Do you know what way you move the exhaust cam for wr timing? I would think counterclockwise????? is that correct?

[ender_swift]

Just gear it down a bit. But it would depend on what type on riding the previous owner did, and what you plan on doing.