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I recently purchased a 2008 yz250f that is nearly bone stock. I have a few questions. I do not intend on buying a full system exhaust at the moment. Would it be wise to go for the silencer now and the header later. What difference would it make by just having the silencer? Also I need some tips on what exhaust brand to buy. I've always been an FMF guy but am willing to switch if it means better performance. I know that with the pipe I will have to jet it, but what other little things can I do to boost performance. Thanks Guys

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Skip the exhaust, you are paying for a name. If you want performance without breaking the bank then look into cams or a bore kit for the engine. Dont forget that suspension work will make a big difference as well.

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before you even touch the engine, get your suspension fully sorted. i have a 2010 yz250f and on that model the exhaust system is pretty good so its not really worth buying a new exhaust. on your model, the header is quite good but the exhaust isnt to flash. skip the header entirely and buy a slip on. dr.d and fmf are the best brands for your model. in my opinion the dr.d exhaust is better. doug dubach designs yamaha's on yamaha's budget but then go's all out and makes after market parts for them as his brand dr.d. hes done all the testing and knows what works best on the yamaha's. i strongly recomend him for most yamaha after market parts

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Skip the exhaust, you are paying for a name. If you want performance without breaking the bank then look into cams or a bore kit for the engine. Dont forget that suspension work will make a big difference as well.

I agree with doing suspension first, but I have been told that a hot cam and a big bore takes life (longevity) away from the engine. As far as a full exhaust goes, I don't think the H.P. improvements are worth $8 or $900 bucks, but you can pick up a complete system pretty cheap now and they definately make improvements with proper jetting or mapping with F/I and replacing the airfilter with a screenless No-Toil or Twin-Air.

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Big bores do not affect longevity at all, nor do cams. If you race in the 250 class and have a 290 kit, you are excluded. If they have a 300 class, you can run otherwise, you have to run with the big boys in the 450's. Does not make a lot of sense to me.

You do not remove the screen on Yamahas, nothing to be gained by doing that. A different air filter too, adds next to no hp (maybe .1) and just cleaning it after every ride makes more of a difference.

Ride your bike, practice. Save your money for track time and getting the suspension done.

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Big bores do not affect longevity at all, nor do cams. If you race in the 250 class and have a 290 kit, you are excluded. If they have a 300 class, you can run otherwise, you have to run with the big boys in the 450's. Does not make a lot of sense to me.

You do not remove the screen on Yamahas, nothing to be gained by doing that. A different air filter too, adds next to no hp (maybe .1) and just cleaning it after every ride makes more of a difference.

Ride your bike, practice. Save your money for track time and getting the suspension done.

Why would taking out the screen on a yamaha not make a difference. More air flow = more power. My mechanic would argue these facts. I know that it all made a difference on my bike. Maybe you are correct about the other thing with longevity, but that is what I've been told. What you stated would easily add the biggest gains in H.P. but I was told it shortens life. And yes, in my area doing a big bore on the 250 means you have run in the open class or you risk being protested. I agree that suspension is the most important thing to do first for anyone. I do things to my bike because it's like a hobby not because I need more H.P. or speed. I'm 43 yrs. old and my wife buys cloths and furniture and I buy MX gear and parts and bling.I'm not argueing with you because you may be correct about what you have stated. I'm just passing on what I've learned from those who know more then me.

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yosh slip on,most likely no jetting change, i heard the yzs benifit from cams. slip on $300 hot cams $400 and there bolt on cant beat that.

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The large screen size on a YZ flows more than the bike needs, so removal adds nothing.

AFAIK, the only bikes that the screen affects power is on the Hondas.

And more air flow does not always equal more power. An engine is a pump. The exhaust,head, cames, bore, stroke, carb type and bore, air boot, air filter and air box all affect power. Which ever item is doing the restricting, until it is de-restricted, you can enlarge everything else and it will not make more power. Often, when opening a air box more than a certain size (typically 6 or 7 square inches on a 250) does not add to power. It does cause a drop in vacuum signal which in turn requires larger (not technically richer) jetting to compensate for the weaker vacuum. People assume needing larger jets means more fuel which means more power. To see this for yourself, take two identical bikes, ride a set easy course, confirm the fuel consumption is the same. On one bike, remove the entire top of the airbox, jet to suit. On the other bike, open the airbox the typical recommended amount for it and jet to suit. Both bikes should produce identical power and again, on the test course, have identical fuel consumption.

Perhaps after an engine is ported, has cams and a good pipe, the scren might be a choke point.

The bottom ends on almost all bikes are very robust and far from being overtaxed. Often, doubling an engines power is still manageable with a stock clutch and trans. So the extra 20% gained from a big bore is a cake walk. A bigger effect on longevity is maintenance and rider abuse. Then it does not matter the engine size.

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The large screen size on a YZ flows more than the bike needs, so removal adds nothing.

AFAIK, the only bikes that the screen affects power is on the Hondas.

And more air flow does not always equal more power. An engine is a pump. The exhaust,head, cames, bore, stroke, carb type and bore, air boot, air filter and air box all affect power. Which ever item is doing the restricting, until it is de-restricted, you can enlarge everything else and it will not make more power. Often, when opening a air box more than a certain size (typically 6 or 7 square inches on a 250) does not add to power. It does cause a drop in vacuum signal which in turn requires larger (not technically richer) jetting to compensate for the weaker vacuum. People assume needing larger jets means more fuel which means more power. To see this for yourself, take two identical bikes, ride a set easy course, confirm the fuel consumption is the same. On one bike, remove the entire top of the airbox, jet to suit. On the other bike, open the airbox the typical recommended amount for it and jet to suit. Both bikes should produce identical power and again, on the test course, have identical fuel consumption.

Perhaps after an engine is ported, has cams and a good pipe, the scren might be a choke point.

The bottom ends on almost all bikes are very robust and far from being overtaxed. Often, doubling an engines power is still manageable with a stock clutch and trans. So the extra 20% gained from a big bore is a cake walk. A bigger effect on longevity is maintenance and rider abuse. Then it does not matter the engine size.

I will take you for your word. I am not a mechanic so I can't argue what you have stated. I will show my mechanic who has been in the business for 30 plus years and builds high performance engines for shops, local pro's and as far as California. He guides me on everything I do and I know he knows what he is talking about. You get a lot of opinions on this sight and I'm not sure they are all good. I will report back with what he says on this. His business is JMD Pro-Porting out of NJ.

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Trust me, he's right. The 01-11 YZ250F uses the same air filter as the 03-09 YZ450F.

To the original poster: The stock exhaust on the 2008 yz250f is very had to beat, Yamaha did it right. Your going to have to look for performance else where for best bang for the buck. Cams...but not hotcam's (Williamsmotowerx, web camshafts, TUF racing etc) if you really feel you want more power.

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Your friend may know of me though I will not release my last name online. I am an ex-Yamaha factory tech, based out of NJ way back when.

Intense is right on about the pipe. These bikes right from the factory are pretty state of the art. Certainly better bone stock than even many A class riders are. The only thing they ever have to have done is set the suspension up for the riders weight, riding style and ability then have the jetting fine adjusted.

In many cases, a guy who puts a pipe on one of these actually goes slower because the power delivery is not longer smooth.

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No one from NJ knows anything.

You lose 30 IQ points crossing the border.

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Hey, I resemble that remark. I lived in Essex county. I have friends in the cement business.

Now Bergen county, mid and south Jersey, that is completely different.

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Hey, I resemble that remark. I lived in Essex county. I have friends in the cement business.

Now Bergen county, mid and south Jersey, that is completely different.

Hey, I'm from south Jersey. Not to far south, Little Egg Harbor. Anyway William 1, I will no longer challenge your expertise knowing your background. I have the full FMF powerbomb and 4.1, No-Toil screenless filter and the Dyno Jet P.C./ V. I bought the bike with all of these goodies with 3 hrs. on bike. I most likely would not have done it because of cost. The bike runs like a champ but I have nothing to compare it to. I had the suspension done and I put RG3 triple clamps on it and a few other things. Are all the mods that were done to it a waste of time? 08 RMZ 450. Thanks. I'm sure you no my friend Joel of JMD. He is your age, former pro and really knows his stuff.

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Always feel free to challenge me. I do make mistakes. A lot.

Unless you are a near pro rider, the only mod on the bike worthwhile is the suspension. Doing jetting/setting up the FI is not considered a mod.

Every kid gets a new dirt bike and is convinced he needs a pipe. All his clueless friends are telling him how choked up the bike is and how much faster it will be. So the kid gets a pipe. Never mind that most of the riding will be on the street, helmet-less in front of his friends. Yeah, I know, I sound jaded. The reality is the bikes are so much better than 99.99% of the owners that most things actually make the bike slower. Most pipes do not really make more power, they merely shift it around. Where the stock pipe is designed for smooth, linear power delivery, a lot of the aftermarket pipes steal power from the lower end of rpm only to return it up high. So with the new pipe, you feel a 'hit' and conclude you are $600 poorer and feel the power hit so there fore it is faster. Then you go to the track and the pro on the clapped out '82 XR200 spanks you. What tha.....?????

The key to speed is smoothness. You want a fluid power delivery. Abrupt power delivery will cause wheelspin. Great for burn outs, not great when you want to pass someone.

However, most guys own a dirtbike for fun, plain and simple. Most (me included here) do not or no longer race. We trail ride, we tinker, we spend more time talking during a ride than actually riding. So putting money into do stuff to the bike does not have to make sense or be practical. What is important is that people realize this and do not kid themselves or try to fool others.

I run a WR250F. Way more bike than I need. I ride like a grandpa. But I dig the technology (I'd be happy to have a Duc 996, even if I never could ride it) and like a real performing engine, even if I only actually run it hard for 15 minutes during a four hour ride.

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Always feel free to challenge me. I do make mistakes. A lot.

Unless you are a near pro rider, the only mod on the bike worthwhile is the suspension. Doing jetting/setting up the FI is not considered a mod.

Every kid gets a new dirt bike and is convinced he needs a pipe. All his clueless friends are telling him how choked up the bike is and how much faster it will be. So the kid gets a pipe. Never mind that most of the riding will be on the street, helmet-less in front of his friends. Yeah, I know, I sound jaded. The reality is the bikes are so much better than 99.99% of the owners that most things actually make the bike slower. Most pipes do not really make more power, they merely shift it around. Where the stock pipe is designed for smooth, linear power delivery, a lot of the aftermarket pipes steal power from the lower end of rpm only to return it up high. So with the new pipe, you feel a 'hit' and conclude you are $600 poorer and feel the power hit so there fore it is faster. Then you go to the track and the pro on the clapped out '82 XR200 spanks you. What tha.....?????

The key to speed is smoothness. You want a fluid power delivery. Abrupt power delivery will cause wheelspin. Great for burn outs, not great when you want to pass someone.

However, most guys own a dirtbike for fun, plain and simple. Most (me included here) do not or no longer race. We trail ride, we tinker, we spend more time talking during a ride than actually riding. So putting money into do stuff to the bike does not have to make sense or be practical. What is important is that people realize this and do not kid themselves or try to fool others.

I run a WR250F. Way more bike than I need. I ride like a grandpa. But I dig the technology (I'd be happy to have a Duc 996, even if I never could ride it) and like a real performing engine, even if I only actually run it hard for 15 minutes during a four hour ride.

I hear ya. It's fun doing things to the bike if you can afford it. I still race in the 40 plus Vet class and I'm a fast C slow B rider. I recently had a MX crash which resulted in major reconstructive bone surgery to my left leg. I'm now off my bike for the season and my wife is mad at me for wanting to still race and ride.Maybe when I recover I will trade the bike in for a WR 250 and ride like an old man to. With 5 1/2 years to go untill I can retire, I'm really taking a chance. Oh well.

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I'm sitting in Essex County now. I never ride my streetbikes.

Clueless drivers on cellphones, cops every 10 yards and really bad roads.

I'm too fat and old to ride MX. Most of the tracks are designed to seperate you from your bike.

But there is still a ton of offroad riding around. So my WR250 gets lots of use.

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I'm sitting in Essex County now. I never ride my streetbikes.

Clueless drivers on cellphones, cops every 10 yards and really bad roads.

I'm too fat and old to ride MX. Most of the tracks are designed to seperate you from your bike.

But there is still a ton of offroad riding around. So my WR250 gets lots of use.

When I was at the Jimmy Weinert Mx Training Facility last month, I met and hung out with the legend Jamming Jimmy Weinert, and he is still tearing up the track on a CRF450R at 60 yrs. old. Never to old. He was an inspiration.

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You aren't Jimmy Weinert.

Most MX riders eventually get tired of being hurt all the time and either quit riding all together or find a safer way to still ride.

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