My 2008 Yz 450f Review


340 replies to this topic
  • djtroy

Posted August 04, 2007 - 06:53 AM

#41

It would be more likely that the additional back pressure is doing that. It seems you have based your assumption that there is less restriction in the new exhaust on a larger header diameter and a shorter silencer of the same internal design as the '07. The '08 muffler is not at all the same.

http://www.motocross...F3E7ECC2A3CD20C

Besides, it doesn't work like that. The ongoing myth that back pressure created by any sort of exhaust restriction is of some benefit to a 4-stroke continues to amuse me.



The 07 had great low end power and the 08 exhaust system is redesigned so I was thinking this had to be the reason for the lack of low end power on the 08. Thanks for the explanation.

  • grayracer513

Posted August 04, 2007 - 07:27 AM

#42

The 07 had great low end power and the 08 exhaust system is redesigned so I was thinking this had to be the reason for the lack of low end power on the 08. Thanks for the explanation.

It may have something to do with it, but they also changed the cams in '06, again in '07, and again for '08. There's also the question of the advance curve, which is the only significant change made among the 3 distinctively different '03-'05 models.

The exhaust might well be a factor, though. I know that low end power was improved a little on my own '06 by adding a Dr.D system, and I've seen reports that exhaust mods have improved the '07. One guy stated that all he did was to put the end cap from an '06 on his '07, and that that gave the low end a boost. Exhaust systems are "tuned" by selecting their diameters and lengths (in the most simplistic sense), and by the positioning of "steps" in the pipe, to control the timing of pressure waves within the pipe so that they arrive at the exhaust pot at a particular moment. These waves move at the same speed regardless of engine speed, so the pipe only "works" within one narrow RPM range. Below that range, the best thing to do for increased power is to reduce any restriction to its lowest possible level.

I clearly recall that when the '06 came out, most people complained that it had weak low end. The same complaint was made about the '07 at its introduction. It's kind of funny, don't you think, that each of these 3 bikes has been criticized for being weak off the bottom, but when the next successive year comes out, they all of a sudden have great low end power?

  • djtroy

Posted August 05, 2007 - 08:10 AM

#43

It may have something to do with it, but they also changed the cams in '06, again in '07, and again for '08. There's also the question of the advance curve, which is the only significant change made among the 3 distinctively different '03-'05 models.

The exhaust might well be a factor, though. I know that low end power was improved a little on my own '06 by adding a Dr.D system, and I've seen reports that exhaust mods have improved the '07. One guy stated that all he did was to put the end cap from an '06 on his '07, and that that gave the low end a boost. Exhaust systems are "tuned" by selecting their diameters and lengths (in the most simplistic sense), and by the positioning of "steps" in the pipe, to control the timing of pressure waves within the pipe so that they arrive at the exhaust pot at a particular moment. These waves move at the same speed regardless of engine speed, so the pipe only "works" within one narrow RPM range. Below that range, the best thing to do for increased power is to reduce any restriction to its lowest possible level.

I clearly recall that when the '06 came out, most people complained that it had weak low end. The same complaint was made about the '07 at its introduction. It's kind of funny, don't you think, that each of these 3 bikes has been criticized for being weak off the bottom, but when the next successive year comes out, they all of a sudden have great low end power?



I heard the 07 was supposed to be smoother but I didnt hear what was said about the 06 when it came out. All I kow is my 06 and 07 lift the front tire in second when you roll on the throttle. The 08 doesn't
Take it for what its worth.:ride:

  • Whyzee429

Posted August 05, 2007 - 06:02 PM

#44

the 07 was weak from the factory? maybe it's just an illusion caused by the smooth power delivery. I cant imagine needing more power from my 450 lol

  • polarbear

Posted August 06, 2007 - 11:13 AM

#45

Sounds like your are unhappy with your 08. This makes me nervouse cause my buddy ordered one and all he's ever ridden are hondas and he finally decided to try a yammie and now I'm worried! Thanks a lot for the extra stress...LOL!

  • djtroy

Posted August 06, 2007 - 12:54 PM

#46

Sounds like your are unhappy with your 08. This makes me nervouse cause my buddy ordered one and all he's ever ridden are hondas and he finally decided to try a yammie and now I'm worried! Thanks a lot for the extra stress...LOL!



Are you guys dating each other? Did you pay him to buy it? :naughty:

  • WB450

Posted August 06, 2007 - 01:10 PM

#47

Are you guys dating each other? Did you pay him to buy it? :naughty:




I think he's worried about looking like a ahole in his buddies eyes, maybe he can pick it up cheap down the road.:applause:

  • DPW

Posted August 06, 2007 - 03:41 PM

#48

All I kow is my 06 and 07 lift the front tire in second when you roll on the throttle.


hmm...I wonder how the '10 YZ350F will lift the front wheel in second if a 450 can't?

  • grayracer513

Posted August 06, 2007 - 04:43 PM

#49

hmm...I wonder how the '10 YZ350F will lift the front wheel in second if a 450 can't?

Perhaps we can take NASCAR history as a guide. In the scope of my memory, the NASCAR displacement limit was 430 CI. The 427 Fords and Chevys and the 426 Mopars were generating 600+ hp and going 200mph. NASCAR decided that the cars were too fast, so they dropped the limit to 405. Soon, the smaller engines were generating 600+ hp and going 200 mph. One thing led to another, and after a while, the cars were limited to 5 liters (305 CID) and had restrictor plates in the manifold. They were, however, generating 6-700 hp and going over 200 mph.

I doubt that any one will think that a 350 in the state of tune a YZ250F ends up in for pro racing is slow, or that it will have any trouble lifting the front wheel. But I don't think it will do what the AMA wants done, what the hell ever that might be.

  • djtroy

Posted August 07, 2007 - 08:11 AM

#50

I think he's worried about looking like a ahole in his buddies eyes, maybe he can pick it up cheap down the road.:applause:




Ya I was kidding

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  • Camrose Cycle

Posted August 07, 2007 - 09:33 AM

#51

I still don't feel as though this bike is lacking major bottem end power. Ya, i do work for a dealership but by no means would favor the yammie because of that reason. MAybe it is that im at a differnet elevation than the others, but this bike has no problem lifting the front end when snapping the throttle. I still think that most people are just being tricked into thinking its slow off the bottom because of the pipe being so mellow sounding. Again, im not saying im correct, that is just my own opinion.

  • honda597

Posted August 09, 2007 - 02:51 AM

#52

I still don't feel as though this bike is lacking major bottem end power. Ya, i do work for a dealership but by no means would favor the yammie because of that reason. MAybe it is that im at a differnet elevation than the others, but this bike has no problem lifting the front end when snapping the throttle. I still think that most people are just being tricked into thinking its slow off the bottom because of the pipe being so mellow sounding. Again, im not saying im correct, that is just my own opinion.


I would have to agree that the bike does not lack in the bottom end of the the delivery. The 08 is not only stronger off the bottom it also has more in the midrange,which was demonstrated at my friends supercross track today, where he has tricky step on step off section followed by an 80ft tripple.
On the 07 i struggle to clear the tripple,on the 08 i actualy over jumped it to my suprise. This bike is even more deciving than the last.:thumbsup:

  • Wolfgangs650r

Posted August 09, 2007 - 08:03 AM

#53

Read my 600$ mod this was for a 2007 450

  • MXKyle

Posted August 10, 2007 - 06:03 AM

#54

I got a chance to put in a few hot laps on a buddies '08 yesterday. If this is Yamaha's plan for future power delivery then I've bought my last Yamaha. This is from a guy that has ridden nothing else for the past twelve years. I simply hated the motor.

Swapping bikes on the track made it seem even worse after doing laps on my '06. The owner's previous bike was also an '06. We spent the rest of the day talking about which aftermarket pipe he should buy. He was really disappointed.

--KT--

  • DPW

Posted August 10, 2007 - 06:05 AM

#55

I got a chance to put in a few hot laps on a buddies '08 yesterday. If this is Yamaha's plan for future power delivery then I've bought my last Yamaha. This is from a guy that has ridden nothing else for the past twelve years. I simply hated the motor.

Swapping bikes on the track made it seem even worse after doing laps on my '06. The owner's previous bike was also an '06. We spent the rest of the day talking about which aftermarket pipe he should buy. He was really disappointed.

--KT--


What was the power delivery like? Smoother...too smooth?

Just curious what is your skill level?

  • adamdf

Posted August 10, 2007 - 06:44 AM

#56

I got a chance to put in a few hot laps on a buddies '08 yesterday. If this is Yamaha's plan for future power delivery then I've bought my last Yamaha. This is from a guy that has ridden nothing else for the past twelve years. I simply hated the motor.

Swapping bikes on the track made it seem even worse after doing laps on my '06. The owner's previous bike was also an '06. We spent the rest of the day talking about which aftermarket pipe he should buy. He was really disappointed.

--KT--


Care to comment on the handling and cornering of the 08 vs 06?

  • MXKyle

Posted August 10, 2007 - 09:57 AM

#57

What was the power delivery like? Smoother...too smooth?

Just curious what is your skill level?


Way too smooth. As in still waiting on it. Like riding a WR but the power was there and the bike is really fast down the straights. The problem is that you have to stab the clutch to get it to snap out of the turns.

My skill level? Or lack of it? That's the same question I wonder every time I see a ride report. I also wonder what type of riding and what kind of dirt.

I held an AMA pro liscense for four years and qualified for the main in pro supercross. Yes, that was a while back but I still ride every week and I'm in better shape now that I was then.

Check out this clip of the track we were riding at. Mostly sand and you can see we actually want some wheelspin. These are all 450's. The fast one is a yellow '06 YZ and the other is a RM. You can see my blue fender once in a while.

Posted Image

--KT--

  • MXKyle

Posted August 10, 2007 - 10:23 AM

#58

Care to comment on the handling and cornering of the 08 vs 06?


I spent a lot of time getting my '06 to where I liked it. I'm happy to say that I don't have any issues with the handling and never feel like I'm at a disadvantage in the turns. I recognize that some of that is that I have conformed my riding style to suit the bike but that's ok if it works. The '08 felt almost the same right out of the box. It would probably be even better if it were set up exclusively for me. None of the pushing that I had to dial out of my '06 if that's what you mean but not all that much better than what I'm used to right now either.

If I didn't have over 140 hours on my '06 I wouldn't want to get rid of it. I'm still shy of holding onto a 4-stroke very long. I was hoping to upgrade but now I may look for a left over '06 (I think I know where one is) and save a ton of money.

--KT--

  • attackmoto46

Posted August 10, 2007 - 10:23 AM

#59

What track is that in FL ?

  • MXKyle

Posted August 10, 2007 - 10:48 AM

#60

What track is that in FL ?

Bithlo





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