08 YZ450F Exhaust fix

so before looking into it i did the same thing i cut my factory 426 muffler down about 4 inches repacked its and put my pmb end cap back on, all i have to say is my power core 4 is in the mail as we speak:bonk:

Respectfully submitted:

A shorter overall exhaust system length raises the harmonic range of the exhaust system to a higher point in the rev range, making it more of a top end pipe.

Harmonic range or Harmonic frequency?

The '08 muffler has no such internal end point,

Seriously?

Good Thread.

Harmonic range or Harmonic frequency?

Pressure waves travel through an exhaust system within a narrow range of speeds near sonic regardless of other influences. The length of the pipe determines the engine speed at which the pressure waves reflected back to the exhaust port will arrive there at the desired moment. Higher RPM means less time between engine cycle events, which means the pipe will need to be made shorter (other things being equal) to allow the reflected pressure waves to return sooner.

Seriously?

Yes. In order for the inversion of pressure to take place, a sudden increase in pipe cross section, or the actual end of the unobstructed pipe must exist. The '08 pipe places baffling in the exhaust path, but has no internal chamber that the pipe opens into to serve as an end point.

OMG , this sounds like rocket science. My stock '07 450 muffler just looks like a straight thru muffler surrounded by packing. Now the WR's exhaust goes thru the twisties to get to the other end.

My stock '07 450 muffler just looks like a straight thru muffler surrounded by packing. Now the WR's exhaust goes thru the twisties to get to the other end.
True. So?
OMG , this sounds like rocket science. My stock '07 450 muffler just looks like a straight thru muffler surrounded by packing. Now the WR's exhaust goes thru the twisties to get to the other end.

There is a lot more to exhaust tuning than it looks. All aftermarket pipes look like straight through perforated pipes with packing around them, but they all perform differently, and in most cases better than the stock perforated pipe with packing around it.

I guess you guys are right. But, if the OEM is smart enough to build these bikes, you'd think they would be smart enough to build a pipe for it.

And I also wonder why the Pipe companies (Dr.D, FMF, Pro Circuit etc) don't make their own bikes.

Don't get me wrong, I have given alot of money to all 3 of these companies for their pipes and I usually talk myself into thinking the bike runs a little better but for the price, I really can't tell that much differnce, but they look cool. And the Pro Circuit I got for my old '04 CRF250 was so loud, it was kinda embarassing.

I like Dr D the best but they all seem over priced to me.

I guess you guys are right. But, if the OEM is smart enough to build these bikes, you'd think they would be smart enough to build a pipe for it.

And I also wonder why the Pipe companies (Dr.D, FMF, Pro Circuit etc) don't make their own bikes.

Don't get me wrong, I have given alot of money to all 3 of these companies for their pipes and I usually talk myself into thinking the bike runs a little better but for the price, I really can't tell that much differnce, but they look cool. And the Pro Circuit I got for my old '04 CRF250 was so loud, it was kinda embarassing.

I like Dr D the best but they all seem over priced to me.

The manufacturers are trying to produce the best equipment they can for the widest range of riders for the least amount of money possible. If they focused on an exhaust pipe as much as aftermarket companies do, the bikes would be very fast, but would end up costing a lot of money. Whenever someone educated in a topic looks at any part, he will find a way to improve it, but the cost to do so is sometimes very high.

The 06 is the least restrictive, 07 is straight through muffler with smaller end cap, and 08 is shorter with much restriction to create back pressure and reduce sound while at the same time reducing size. Also The 07/08 have a larger mid pipe diameter than the 06. The 08 is a great idea from Yamaha, however much of the low end grunt has been lost from 06/07 and the 08 muffler weighs more than stock 07 muffler, which is larger.

But who knows sometimes slower is faster. Sometimes in bike tests the bike that feels the most mellow, is the easiest to ride, and can lead to faster lap times.

All I know is for me the 08 in stock form is sluggish on bottom, 4 stroke exhausts are way expensive, so I figured I would try a cheap alternative before I dump some loot on an exhaust. I had A DR-D on my 06 YZ450 and was quite happy with that, price was nice as well.

I am trying to adapt an 06 muffler to my 08 while retaining the larger diameter 08 header. Does anyone know of a gasket that will accomplish this? ... it will have to be very thin, maybe like 1/32. The 08 gasket doesn't fit the 06 muffler. I was considering just using RTV hi-temp silicone, but that will get messy.

Thanks.

Thats gonna be tough to make that seal properly, very tough. I would suggest checking ebay for a stock 07 muffler. The 07 bolts up perfect to the 08 Header. Then put your 06 end cap on the 07, and you will be much happier with your 08.

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