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Best Mods for XR250?

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If you had to pick a handful of performance mods to do to a stock XR250, what would they be?  I'm talking specifically engine performance (I like the suspension just fine the way it is).

The reason that I ask is because my XR250 is bone stock and it is lacking in the power department. I love the power of my XR400, but it is just too heavy for the type of riding that I do.

How can I get XR400 power out of my XR250 without breaking the bank and without sacrificing XR dependability?

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If you had to pick a handful of performance mods to do to a stock XR250, what would they be?  I'm talking specifically engine performance (I like the suspension just fine the way it is).
The reason that I ask is because my XR250 is bone stock and it is lacking in the power department. I love the power of my XR400, but it is just too heavy for the type of riding that I do.
How can I get XR400 power out of my XR250 without breaking the bank and without sacrificing XR dependability?
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Well personally, I would make it street legal. I would put real bark busters on it (full guard acerbis etc). After market silencer, jetting (possibly Gordon's mods). Maybe a hot cam (don't have experience with that).

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You can get a 320 kit for them - but will cost you.

Aftermarket camshaft will boost HP.

Also, removing restrictions in the intake and exhaust systems can increase air flow and potentially boost power output further.

There are aftermarket exhausts for the XR250R such as the FMF Powercore 4 slip on performance muffler. 

High octane fuel.

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Stock valves are too soft. Don't touch the cam unless you are going to replace the valves, rockers, and cam all at once. Once you start revving the post 96' XR250R you will have to adjust the valves every 15-20 hours until you replace them.

Now, I raced a 2001 XR250R last year for half a season. I did not touch the motor, it was low hours. I installed a TM34 carb with a home-made adapter, XR400R air boot, Opened up the intake, left the stock header on it but ran the XR's Only Oval Exhaust (the classic looking pipe with the downturned tip) and jetted it properly. The results were a screaming XR250R with no bog, good low end torque, and pin the throttle and row the gears woods racer. I had the forks modified by Bruce Triplett (Terrain Tamer). The stock motor with the mods I did was too much for the stock suspension.

Even with a modified suspension there is not enough travel for more power than I made. A big bore kit is pointless unless you are flat tracking or something. It will get you seriously hurt in the real world if you really max out the power with only 10 inches of travel and tiny valve chambers in those 41mm forks.

I weigh around 225 with my gear on.

Edited by Firestone
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I almost hate to go to messing with the XR250 because of its untouched condition, but it just leaves something to be desired in the power department. I think I would rather sell my XR400 and then just purchase another bike to modify and ride hard, that way I could leave this 250 in its pristine condition.

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Gordon mods are very, very inexpensive and have yielded nice results. I did not do the pipe modification because I'm in love with the lack of noise. Where I live a little extra power is nice. The xr gets killed on big hills.

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7 hours ago, Wonderspoon said:

 I'm in love with the lack of noise. 

I feel the exact same way. I hate to gut the factory pipe or put something else on it simply due to the increase in noise.

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On ‎7‎/‎4‎/‎2017 at 8:26 AM, Firestone said:

The stock motor with the mods I did was too much for the stock suspension.

It will get you seriously hurt in the real world if you really max out the power with only 10 inches of travel and tiny valve chambers in those 41mm forks.

I agree. When I push the bike hard for any extended period of time I can feel the suspension go away. I guess the oil gets hot and then it seems to get bouncy by just riding on the springs. I also have black marks under the fender where the tire has made contact.

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I feel the exact same way. I hate to gut the factory pipe or put something else on it simply due to the increase in noise.


The muffler mod is reversible in a pragmatic sense because the holes can be plugged with screws. I don't need the temptation. I'd rather find power elsewhere.

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You'll never make much power with the stock muffler.

If you want power and no noise the XR250R is not for you. It is the loudest 250 thumper class bike I have ever heard when it makes power. 

The XR600R makes a lot of relatively quiet power.

Edited by Firestone

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You'll never make much power with the stock muffler.
If you want power and no noise the XR250R is not for you. It is the loudest 250 thumper class bike I have ever heard when it makes power. 
The XR600R makes a lot of relatively quiet power.


I was thinking about this the other day. IMO the way to effectively ride a stock-ish XR is to find the zone the bike wants and sit there. Even a Spode like me can push the motor and suspension into a dangerous place if you get too froggy.

But if you dial it back to a spirited trail pace, you can sit there all day and have the most fun you can have on two wheels.
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1 hour ago, Firestone said:

You'll never make much power with the stock muffler.

If you want power and no noise the XR250R is not for you. It is the loudest 250 thumper class bike I have ever heard when it makes power. 

The XR600R makes a lot of relatively quiet power.

I am finding out this the hard way.  I recently got an '81 xr250, and I'm disappointed in how loud it is with the stock muffler.  I've had several thumpers in the past, and they all seemed much quieter.  I'm happy with the power, but 3/4 throttle and higher, it really gets loud.  Now, when I drive the mile down to the mail box, I have to keep it slow so I don't piss off the neighbors.  I've read some threads where folks have added extensions to the tail pipe to quiet things down, and one of these days I'll see if something like that helps.  If I learn anything useful, I'll post it here.

tom

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I took a buch of weight off flywheel when i had a 250. did it on a lathe,didnt seem to bother low end,and that surprised me,but revved a lot quicker.

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7 hours ago, Firestone said:

On that 81 you might try running a Q series FMF or equivalent. 

Thanks for the tip, but for my $400 bike, I'm looking for something a little more economical.  My idea is to make or buy something that could be inserted for quiet ride to the mail box, and un-corked when I want to rip.

tom

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Thanks for the tip, but for my $400 bike, I'm looking for something a little more economical.  My idea is to make or buy something that could be inserted for quiet ride to the mail box, and un-corked when I want to rip.



tom

I know some guys have had luck with vw beetle downturned pipes. Not sure how your 81 exhaust is and if it will work. I always wondered if the relatively low exhaust heat from an old school thumper might work with a db snorkel but those went the way of the dodo.

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On ‎7‎/‎4‎/‎2017 at 8:26 AM, Firestone said:

Even with a modified suspension there is not enough travel for more power than I made.

Firestone, I found a mid 2000's CRF250 for parts and I am thinking of picking it up for the forks and shock. Thoughts?

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It's a good front end you will need to revalve a bit as the low speed is too hard. You will also need to put a shortening spacer inside the fork to limit the travel and shorten the springs. The rear shock is a complete mystery to me, I imagine the linkage may be incompatible with the shock mounting saddle but that is a guess. 

If you don't race it will be a great setup but you probably won't ever ride hard enough to need that much front end. I would most likely spend my money on Bruce's Suspension mods in that case. 

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On 7/5/2017 at 6:05 AM, Off-Road Adventures said:

I almost hate to go to messing with the XR250 because of its untouched condition, but it just leaves something to be desired in the power department. I think I would rather sell my XR400 and then just purchase another bike to modify and ride hard, that way I could leave this 250 in its pristine condition.

Bingo!

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I am actually thinking about using the forks on my XR400 because I haven't ever figured out why they are so violent.

I can get the complete rolling chassis for $500. 

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