understanding pipes

The two I have look exactly the same on the outside.  I am going to measure just to see how much different they are.  
__________
"Every time I start thinking the world is all bad, then I start seeing some people out there having fun on motorcycles. It makes me take another look." -Steve McQueen

daggit:
Yeah the length of the header and the size of the chamber work with the bleed of the stinger .
So a fat pipe would give you power at a later stage and higher rpm for busting out of corners.

Because mine look the same I was thinking that the thick metal took up space inside making it a smaller chamber?  
__________
"Every time I start thinking the world is all bad, then I start seeing some people out there having fun on motorcycles. It makes me take another look." -Steve McQueen

Daggit, from what you've written it sounds like you may have read this but for anyone interested this is about as good an explanation as you will find http://www.motorcycle.com/how-to/how-twostroke-expansion-chambers-work-and-why-you-should-care-3423.html

I've run a gnarly in woods and on tight tracks.  It did well in the low and mid but tended to loose some bit of topend on RM-250's. It may act a bit different on the CR

In my experience the gauge of pipe material will play a small roll in throttle response.  If you compare an FMF fatty with the Factory Fatty (slightly thinner gauge) the Factory Fatty has slightly better throttle response other than that there is little or no difference that I can tell.

As far as gearing:
The larger rear or smaller front will tighten up gear spacing.  This will allow you to run a gear higher at times depending on your needs and conditions, but also shortens each gears usable range.  Some bike respond well to adding a tooth because of gearbox gear spacing.
Reducing teeth will do the opposite it will widen out the gear spread, this can be advantageous when smoother power delivery is needed or wide open conditions.

I think if I was looking for a rideable top speed set up for a 250 I would look at either the FMF SST or PC Platinum/Works and maybe try dropping one or two teeth from stock (check out Rocky Mountain ATV they have there house brand rear sprockets on sale for 20.00 your could get a couple different sizes without breaking the bank.  http://www.rockymountainatv.com/vehicleSelectProd.do?prevVehicleType=2&prevMake=4&prevModel=102&keyword=&vehicleTypeId=2&make=4&model=102&applyFilter=Change+Vehicle&year=2001&navTitle=Drive&navType=type&webCatId=9&webTypeId=124&prodFamilyId=24558&stockId=&listingId=&uri=%2FproductDetail.do#vehicleSelect  
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Colorado

2006 RM-250

I've read this article before as well..really helps with understanding the physics.

Dagg, does changing the silencer do much for the power increases throughout the rpm's ie. different packing, more/less or pifferent brand?  
Patrick
1989 Cr250r.

Sorry, Goose, but it's time to buzz a tower.

Mount Hope, Kansass

Smalltown.

Blown out packing in the silencer can cost you some power, I like to use FMF packing
I have tried the home depot high temp and other fixes but real packing IMO outperforms them.

As far as length of silencer a shorter silencer will tend to give you better low end power and throttle response.  
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Colorado

2006 RM-250

Thanks Mark, I appreciate it.  
Patrick
1989 Cr250r.

Sorry, Goose, but it's time to buzz a tower.

Mount Hope, Kansass

so, would it be better racing a harescramble with my stock silencer and a pro circuit platinum header than using a shorty R304 and the platinum header?  

I run the r304 and did a back to back with the stock pipe and the r304. I also hav ethe PC works platinum. You may be able to tell a little difference between the two but not much. I dropped teeth in the rear for my open desert runs.  
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____________________
MIKE
Phoenix, az
(07 yz250)
(99 yz125)


Every bush has its day (sanders, 2009)
Lack of enthusiasm is for the weak and timid. (alex, a.k.a. yz250 forever)

"I know much about nothing at all"(Maple, 2009)

what one did you find works better for lower end power?  

my rm125 has a 50 tooth on the back (1 bigger than stock) and i run the stock pipe and shorty silencer. my bottom end is pretty impressive for a 125 i didn't stall it once this past weekend  
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if its got wheels or a skirt your gonna have problems... best t-shirt ever

03 rm125

2stroke eff tee dubba u

Thanks Mark.
I am loving the gnarly but I just wanted to understand it better.

On the first ride in the desert the bottom end spun the tire out from under me.  It was great. I went from a fatty with a 51 to a gnarly 50,

It is amazing how you can move the power around.  
I have always run stock everything, I was a family desert cruiser.  lol

But with racing it is opening up a new world to me.  

I am going to Ocitillo Wells to test the gnarly with a 48 for the hair scrambles.
I am switching the chain and both sprockets, so I keep the sets together.  
__________
"Every time I start thinking the world is all bad, then I start seeing some people out there having fun on motorcycles. It makes me take another look." -Steve McQueen

smalltown_guy:
I've read this article before as well..really helps with understanding the physics.

Dagg, does changing the silencer do much for the power increases throughout the rpm's ie. different packing, more/less or pifferent brand?

From what I have read , you need the proper amout of resistance or bleed after the expansion chamber.  that is why there is no universal silencer.  Each bike need one that is right and packed properly for that bike.  
__________
"Every time I start thinking the world is all bad, then I start seeing some people out there having fun on motorcycles. It makes me take another look." -Steve McQueen

Dag or mark: when you say you change the rear sprocket(dropping or adding teeth) do you just switch the rear sprockets, or do you also put on a new chain and front sprocket? or do you keep a complete set for each rear sprocket? (like a chain and and front sprocket for a 50T rear and another chain and front sprocket for the 51T rear?)  
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2006 YZ250

- FMF Gold Series Fatty
- Yamaha Racing Graphics Kit
- Twin Air Filter
- Vforce 2 Reed Valves
- Clarke long range tank
- Cycra Handguards
- Longhorn Triple Clamps
- Pro Grip-Grips
- Pro Taper Handlebar
- Renthal o-ring chain and sprockets

I have a very nice set on my bike now (50).  so I will keep it together.
I have a separate chain and front sprocket for the 48 and another chain for the 51.
They are different lengths and they are worn differently.
I don't want to ruin my new chain on an old sprocket.  
__________
"Every time I start thinking the world is all bad, then I start seeing some people out there having fun on motorcycles. It makes me take another look." -Steve McQueen

Oh ok i thought it might be like that..thanks  
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2006 YZ250

- FMF Gold Series Fatty
- Yamaha Racing Graphics Kit
- Twin Air Filter
- Vforce 2 Reed Valves
- Clarke long range tank
- Cycra Handguards
- Longhorn Triple Clamps
- Pro Grip-Grips
- Pro Taper Handlebar
- Renthal o-ring chain and sprockets