2008 YZ250F Go-To changes/mods

Cmiller493
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Cmiller493
Edited Date/Time 9/29/2020 11:06am
Picked up a 2008 from a buddy of mine for super cheap and decided to do a bit of a build on it. Just wondered if there were specific things you guys remember people doing to that generation of Yamahas that made a worthwhile difference.

I know I won’t be able to get it to be competitive with the modern 250f’s but for the price I paid for it and the condition it is in I decided it was worth trying to build the best 08 that I could.

Any advice would be greatly appreciated.
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yz133rider
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yz133rider 9/13/2020 4:21am
9/13/2020 4:21am Edited Date/Time 9/13/2020 4:27am
Dr. D exhaust - 22.5mm triple clamps
Ti axles, Ti pegs and peg mounts,
The 09 swing arm and linkage was an improvement so could be worth tracking down. Saves some weight and improves handling.

Other than that i can’t think of much.
Oversized front brake rotor.

I’ve had 3 of that era yz250f and the clamps and exhaust make a huge difference.
Good set of tires, keep the axle adjust forward helps handling a lot.

It doesn’t have the top end pull the newer 250fs have but the low to mid is so usable and easy to ride. And that bikes hooked up everywhere it’s a great platform in my opinion. It’s the bike I’ve been the most comfortable on to this day.
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Cmiller493
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Cmiller493 9/13/2020 5:44am
9/13/2020 5:44am
It actually has a full GYTR exhaust. I have never seen the exhaust on another bike before but it has a resonance chamber so it looks pretty trick. It already has an oversized rotor as well. What is the reasoning for the ti axles? Here is the picture of the exhaust before I tore the bike down.

Cmiller493
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Cmiller493 9/13/2020 5:45am
9/13/2020 5:45am
I have had a few of the 10-13 generation bikes and I thought they felt super plush and forgiving but didn’t rev out at all. I assume the motor on this will feel very similar.
yz133rider
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yz133rider 9/13/2020 6:08am
9/13/2020 6:08am
Cmiller493 wrote:
It actually has a full GYTR exhaust. I have never seen the exhaust on another bike before but it has a resonance chamber so it looks...
It actually has a full GYTR exhaust. I have never seen the exhaust on another bike before but it has a resonance chamber so it looks pretty trick. It already has an oversized rotor as well. What is the reasoning for the ti axles? Here is the picture of the exhaust before I tore the bike down.

There dr d is one of the best exhausts for that bike if not the best. The ti axles just to save weight, you mentioned building the best bike possible giving ideas. The clamps is a very worthwhile mod if you do nothing else I’d put those on.

Ride engineering makes a set as does Luxon who post on here.
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Cmiller493
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Cmiller493 9/13/2020 6:55am
9/13/2020 6:55am
I will take a look in to buying both of those! Basically a really close friend of mine bought this new. Rode it for 3 years and then let it sit in his shop collecting dust. Maintained it very well but after letting it sit for the past 7 years I asked if he would sell it. After some long talks in the garage he finally decided to sell it to me for very cheap to see me do a build on it and bring it back to life. Bought the bike for 1200 and I am hoping I can have a really clean/tricked bike for a very decent price. My only concern is how I will enjoy riding it after coming off modern day 250f’s but my plan is to build a really nice 125 to have as my main bike and have this for when I want to get my 4 stroke itch.
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skypig
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skypig 9/13/2020 7:28pm
9/13/2020 7:28pm
yz133rider wrote:
Dr. D exhaust - 22.5mm triple clamps Ti axles, Ti pegs and peg mounts, The 09 swing arm and linkage was an improvement so could be...
Dr. D exhaust - 22.5mm triple clamps
Ti axles, Ti pegs and peg mounts,
The 09 swing arm and linkage was an improvement so could be worth tracking down. Saves some weight and improves handling.

Other than that i can’t think of much.
Oversized front brake rotor.

I’ve had 3 of that era yz250f and the clamps and exhaust make a huge difference.
Good set of tires, keep the axle adjust forward helps handling a lot.

It doesn’t have the top end pull the newer 250fs have but the low to mid is so usable and easy to ride. And that bikes hooked up everywhere it’s a great platform in my opinion. It’s the bike I’ve been the most comfortable on to this day.
What is the stock offset do you know?
What changes can be felt with the 22.5mm offsets?

Unfortunately, if I rode mine any slower I’d need training wheels!


yz133rider
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yz133rider 9/14/2020 3:31am
9/14/2020 3:31am
yz133rider wrote:
Dr. D exhaust - 22.5mm triple clamps Ti axles, Ti pegs and peg mounts, The 09 swing arm and linkage was an improvement so could be...
Dr. D exhaust - 22.5mm triple clamps
Ti axles, Ti pegs and peg mounts,
The 09 swing arm and linkage was an improvement so could be worth tracking down. Saves some weight and improves handling.

Other than that i can’t think of much.
Oversized front brake rotor.

I’ve had 3 of that era yz250f and the clamps and exhaust make a huge difference.
Good set of tires, keep the axle adjust forward helps handling a lot.

It doesn’t have the top end pull the newer 250fs have but the low to mid is so usable and easy to ride. And that bikes hooked up everywhere it’s a great platform in my opinion. It’s the bike I’ve been the most comfortable on to this day.
skypig wrote:
What is the stock offset do you know? What changes can be felt with the 22.5mm offsets? Unfortunately, if I rode mine any slower I’d need...
What is the stock offset do you know?
What changes can be felt with the 22.5mm offsets?

Unfortunately, if I rode mine any slower I’d need training wheels!


Stock is 25, going to 22.5 gives the front end a lot more grip. It’s very noticeable. It will turn much sharper and easier.
skypig
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skypig 9/14/2020 6:05am
9/14/2020 6:05am
yz133rider wrote:
Stock is 25, going to 22.5 gives the front end a lot more grip. It’s very noticeable. It will turn much sharper and easier.
Thanks very much.
Sounds good. Potentially at the expense of some high speed stability?

I wonder if the SFS type triples in 22.5 would be available for the old girl. My wrists would thank me.
Cmiller493
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Cmiller493 9/14/2020 6:10am
9/14/2020 6:10am
Definitely will be making that upgrade. As far as engine upgrades go, do these motors react well to mods? Wondered about a 269 cylinder works kit and cams or maybe some head work. What about carb mods? Besides o-ring mod and a Tokyo Mods light throttle spring are there any other changes I should make?
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SwapperMX 9/14/2020 7:48am
9/14/2020 7:48am
Cmiller493 wrote:
Definitely will be making that upgrade. As far as engine upgrades go, do these motors react well to mods? Wondered about a 269 cylinder works kit...
Definitely will be making that upgrade. As far as engine upgrades go, do these motors react well to mods? Wondered about a 269 cylinder works kit and cams or maybe some head work. What about carb mods? Besides o-ring mod and a Tokyo Mods light throttle spring are there any other changes I should make?
Yes. The first thing you should do before anything else is get that carb sorted. Forget anything else until you do. The Powerbowl 2 was the hot product with an adjustable fuel screw back then. See if you can find one. Otherwise the Boyesen Quick shot is the other option. If you wanted to chase horsepower, if you found a set of trick cams and an ignition, you're well on your way to getting some good ponies from that motor. That GYTR exhaust was from 06 from memory and fits 06-09 and damn those things were loud. They don't go close to passing current noise tests so make sure you have a back up plan if the tracks you ride at noise test.
Cmiller493
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Cmiller493 9/14/2020 8:02am
9/14/2020 8:02am
Good to know about the powerbowl! They can still be found on eBay pretty easily. As far as the gytr exhaust, if the Dr. D provides better performance I will probably get one of those and sell this gytr. Do ignitions make much of a difference on carbureted bikes as they do on fuel injected?
SwapperMX
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SwapperMX 9/14/2020 10:38am
9/14/2020 10:38am
Cmiller493 wrote:
Good to know about the powerbowl! They can still be found on eBay pretty easily. As far as the gytr exhaust, if the Dr. D provides...
Good to know about the powerbowl! They can still be found on eBay pretty easily. As far as the gytr exhaust, if the Dr. D provides better performance I will probably get one of those and sell this gytr. Do ignitions make much of a difference on carbureted bikes as they do on fuel injected?
Yeah absolutely they do. Especially if you want to extract some more horses out of that motor. Vortex ignitions were more prevalent then than they are now as the factory ignitions were single map and completely locked. Now all factory ignitions either have interchangeable couplers or tuning devices giving you a wide range of adjustability. Also back in that era those Dr D exhausts worked really well. Dubach was putting a lot of time and effort in to development and testing, especially on Yamaha's, so going that way would also be a good option. But in saying all this, I would suggest not going too crazy, just get that jetting sorted and get out and ride it. They were damn good bikes and super reliable.
Cmiller493
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Cmiller493 9/14/2020 11:40am
9/14/2020 11:40am
I actually completely agree with your last sentence. My worry is adding too much to this and making it less reliable. I just wouldn’t mind giving it a bit more juice so I don’t feel swayed to get a new 250f again. But yeah, these motors were bulletproof.
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Cmiller493
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Cmiller493 9/16/2020 11:32am
9/16/2020 11:32am
Is the wet sump kit a worthwhile upgrade? Does it affect reliability at all? Obviously nobody else uses that oil tank system but I didn’t know if it is fine for long-term use in these bikes switching to that system.
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Rider 5280 9/16/2020 11:50am
9/16/2020 11:50am
DrD exhaust = all I've run since 2003. Super good results, you can tell he really develops for effectiveness on the track (meaning they are forgiving of mistakes, too).

Since the YZ250F was Dubach's baby, his exhaust will be hard to beat on that bike especially.
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yz133rider 9/16/2020 2:01pm
9/16/2020 2:01pm
Cmiller493 wrote:
Is the wet sump kit a worthwhile upgrade? Does it affect reliability at all? Obviously nobody else uses that oil tank system but I didn’t know...
Is the wet sump kit a worthwhile upgrade? Does it affect reliability at all? Obviously nobody else uses that oil tank system but I didn’t know if it is fine for long-term use in these bikes switching to that system.
I haven’t known anyone who used one personally and I never used one. Doesn’t seem like something I would go for, as the bikes reliability is phenomenal and I wouldn’t want to ruin that.
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Cmiller493
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Cmiller493 9/16/2020 6:51pm
9/16/2020 6:51pm
That is exactly why I never did it with any of the 10-13 bikes that I have had.
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Skerby 9/29/2020 11:03am
9/29/2020 11:03am Edited Date/Time 9/29/2020 11:06am
DR D used to sell a radiator lowering kit for these bikes, people used to really like that mod.


These bikes were super reliable, but I remember my friend bought a new 09 and threw a rod through the case after like 30 hours, you really never know with mx bikes lol.

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