What's Da Diff between the 04 and 05 YZF 450 engines?

10 replies to this topic
  • Dmacsimum

Posted December 09, 2004 - 08:32 PM


I'm wanting to actually know what did Yamaha do to the 05 engine to tame it down some over the 04 YZF 450 engine IE: Cam, Fly wheel etc? I sure would like to see the engine output graph of both engines to see how they changfed the power bands...

  • Harry Paratestes

Posted December 09, 2004 - 09:33 PM


The compression ratio is lower, intake ports are smaller, airboot is different and I think they changed the cam timing slightly. Pretty much the opposite of what tuners do to increase power and "hit".

  • Idaho_Wolverine

Posted December 10, 2004 - 03:21 PM


I dont understand all this "add to the flywheel" and "tame it down" crap. If it is too much for you, buy a dang 250!!!

I have jetted and put a full yoshi on my 2003 YZ450F (you know, the one with the lighter flywheel) and I love it!!

I just dont get it.... :cry:

  • grayracer513

Posted December 10, 2004 - 04:13 PM


It really is something of a mistake to say that the engine has been tamed at all. Tweaked is more accurate. It still makes a fat bunch of power. The difference is that the whole power curve has been moved up the RPM scale a little so that it isn't quite as brutally explosive off idle, but still pulls like crazy midrange and up.

Yamaha mentions a revised carb, and in fact, everything with an FCR on got a revised carb this year. The biggest change there is that you will no longer have to tweak the fuel screw every time a bug sneezes.

The compression is lower, but I don't think you'll noticed the drop from 12.5 to 12.3 as much as the improved air flow and power output that the redesigned combustion chamber, which is what changed the compression, provides.

Yamaha says they remapped the ignition. They don't mention cam timing, but knowing that Doug Dubach has been messing with altering the exhaust cam timing, and the nature of his relationship with Yamaha, I'd be really surprised if a degree wheel did not show that this was also done on the '05.

You remember all the people who told you that the '03 or '04 was too much bike for mortal men, and that it "hit like a two-stroke", right? They were wrong, weren't they? Don't sell the '05 short until you ride it.


  • Dmacsimum

Posted December 10, 2004 - 11:06 PM


Thanks all for the replies. I could not understand why Yamaha would want to "Tune down", the 450 for 05 when they have had made such an animal in 04! I believe Dirtbike Magazine goes on to say such in their article for the test of the 05 YZ450FS dirtbike. I was hoping they had just smoothed out the power band some and not had taken away any horsepower.

Slow down on the Roid Rage Juice dude, I mentioned nothing of being scared, or the possibility of the 450 being to much of a bike for me. While I'm no pro, I have road a CR500 bored over 30 before many times. Even with a heavier flywheel on the old CR500 it was still faster than your little 450. :cry:
Anyway, I was only wanting to know what has Yamaha done to their 05 from the 04 engine for I have read in a dirtbike mag there was a big difference in power between the two.

I get it :cry:


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  • Idaho_Wolverine

Posted December 11, 2004 - 06:47 PM


Sorry about the rant man...

I know you did not say you were skeerd of the power, just all the stuff I have been reading of late just confuses me. I have read alot of articles in the past about how the 03 is too abrupt, and too snappy. And the 04 was a little better (Yamaha added more flywheel). And now I have read that the 05 power delivery is too soft, and that the 05 Honda 450 has more "Snap"!

What do these damn magazines expect!

You tell Yamaha for 2 years in a row that there bike is "too aggressive" and is "too snappy" so they try and fix it now all of a sudden they are soft!

Again, nothing against you. I just snapped man, sorry.

And like you said, its not as nasty as a bored out 500 2 stroke!

  • elsinoredaze

Posted December 11, 2004 - 08:37 PM


It really is something of a mistake to say that the engine has been tamed at all. Tweaked is more accurate. It still makes a fat bunch of power. The difference is that the whole power curve has been moved up the RPM scale a little so that it isn't quite as brutally explosive off idle, but still pulls like crazy midrange and up.


I'm probably one that yamaha was targeting with the 05 setup.I was all set to buy the CRF 450 because it was "supposed " to be tamer than the stock yamaha 450.After reading on this website the advantages of the 5 valve system I decided test ride the yzf... felt great!!!I didn't get all the fuss about the "hit" of the yzf.Little did I know at the time that both Honda and Yamaha had changed their 05 450 engine to make it more like the other.

Like you say the power is there... just not in the same place.This engine reminds me of my first car with a multivalve engine... it just pulls and pulls and pulls...when it signs off change gears and it just keeps on pulling.

One thing I don't like is the long throttle ... getting on it while standing feels awkward because of how far I have to open my wrist... looking into a shorter throttle.

  • Dmacsimum

Posted December 11, 2004 - 10:01 PM


Opology very appreciated! I just couldn't figure out where you were coming from with what you wrote at first. Now that you have explained yourself though, I too can feel what your talking about. I myself welcome more power. I have always tried to pump up anything I touch in order to get the most from it what ever it is.

I also find it funny people cry out for the biggest baddest most powerfullest beast of a bike, then when Yamaha makes such a creature (IE: the 04 YZ450FS) people complain it too fast, to powerful etc.. At first I just wondered if it was a ploy for the after market companies to fight back because with such a hot bike, no hop up parts are really needed for this beast of an engine..... Hummmmmm... that could be one reason also...

Thanks to all!!!!!!

"Full throttle it, and ride hard!"
Dmacsimum (D Macs i Mum)

  • Satch0922

Posted December 12, 2004 - 07:44 AM


Yamaha made a pure race bike in 03 and 04 but 75% of the riders that buy these bikes aren't racers. That is all there is. Yamaha would rather sell boat loads of bikes (like Honda did with the CRF) and let the racers hop them up if they want or need to. Hopefully ths strategy won't backfire on them.

I have ridden the 03, 04 and 05. They are all different in power delivery. My favorite is the 04 powerband. JUST RIGHT! :cry:

  • starttman

Posted December 12, 2004 - 08:50 AM


i got the 03..it has the heavier aftermarket,flywheel on it. I am not a racer. i like the way the throttle delivers the goods without ripping out my arms.the 450 reminded me of the time I was 15 and rode my dads old 73 kx450..i had it in 2nd gear and snapped the throttle. the bike had so much torque it threw me straight off the back in a wheely I cannot describe.after that ride my dad had to place an order for a new preston petty rear fender.you young bucks don't know about that stuff....

when your 38 and just wanna do a few laps on a motocross track and not die...you will understand what all the hoopla was about.

some times you wanna maserati...sometimes a camero...i'll opt for the camero

my .02

  • Satch0922

Posted December 14, 2004 - 09:39 AM


some times you wanna maserati...sometimes a camero...i'll opt for the camero

my .02

LMAO !!!

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