Yz426f dyno graph test result (dynojet)

Yz 426 f

- Iridium spark plug

- Hotcam exhaust cam

- open Rino exhaust

- valves in spec

Graphs shows some different runs.

Has 50hp on the wheel, but needs tuning!

I just drilled and tapped a hole for the BK carb mod.

I think I need a smaller stationary jet. What is your guys take on it? And what do you think about the 50whp. What is stock and is this decent?



A stone-stock YZ426F (2002) produced right around 46-47 RWHP in most tests.  Obviously, inertia dynos are inherently imprecise measuring instruments, but after throwing out the ridiculous claims at either end and averaging all of them out, that was about it. 


50 HP is a 7% gain, which is very respectable.  For comparison, the '03-'05 YZ450 models had about 47-48, the '06 an even 50, and the '08-'09 were close to 52 HP.  50 is pretty serious power for 26 cubic inches. 

Thanks Greyracer! I appreciate your reply's! You seem to know alot about these bikes!

Thanks again for helping me with my timing video's not so long ago (you recall?). This is the same YZ on the graph

I have my WR carb set up like a YZ carb, and I found that the BK mod did almost nothing for me.  My issue was always bogging at low RPM when I would crack the throttle hard, I also suffered from flame-outs on the trail.  I had the same issues before and after the BK mod.  I had my AP squirt start timed such that it just missed the slide, and then played around with the duration from 0.25 sec up to over 1.0 sec with very little change in performance.  I removed the BK mod and went with the O-ring mod, and have never been happier.  The O-ring mod solved both the bogging and flame-outs.  I've read opinions here that the O-ring mod is really only a band-aid fix, with the real problem being an improperly jetted carb or poorly adjusted accelerator pump.  My experience was far better with the O-ring mod.  Try them both to see which works best for you.  Both are super cheap and quick to do.

Does anyone know how much hp the 2014 yz450 has? Just out of curiosity

Thanks for your input! I will look into it. Do you have any insight on the jetting advice?

Does anyone know how much hp the 2014 yz450 has? Just out of curiosity


MXA claims they got just over 58 on their dyno (58.17), but it seems in line with some other articles.  Each dyno will read differently and air conditions are also variables, so take it for what it's worth.  They did note that this was after they changed the mapping, because they felt it was lean from the factory.  Mapping doesn't usually add horsepower, but will move the powerband around based on what map is used.



Thats strange. Is that whp? That means their 426 makes more HP stock than mine with some mods. And how can they adjust mapping, the 426 has no injection?

Oh my mistake! Thought you was talking about the 426 haha

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