low end grunt

What is the best mod I can do to help improve the bottom end power, the bike is stock, with no mods. any info would be great!

thanks

47t rear sprocket for lower gearing.

Here is a good like for you.


https://wr250rforum.forumotion.com/t5-chains-and-sprockets?highlight=gearing

There is no low end grunt. Get used to the bike and learn how to use this baby. Once you are used to it you will like it more and more. If not take a 450 when you want grunt. Thats my idea. I rode all and ride the seams out of the pants with any bike grunty or not.
The feeling of power comes in at aprox 6000rpm. Gearing will not help to get you the feeling.
I will only change gearing when riding technical mounain stuff needing 1st gear at sections..

It's  a short stroke,  big bore 250, with decent size ports.  By design, it's a motor that makes power higher up.   The only thing that will help low end,  is more displacement.  Lowering  the gearing will allow it to get into the power quicker,  and plonk around at low speeds better.  Airflow mods will increase top end and midrange to some extent,  but the only way to get low end is to change the nature of the engine.   Advance the cams a little. Add stroke,  things that make it shift power lower.  With fixed cam timing,  you only have a certain Rpm range an engine will work well in.  A 250cc engine will never grunt well,  and if it does,  it won't rev out well.  

For a 250 dual sport, it's a lot more biased to sport without being a race bike.   300cc really wakes it up by all accounts.

Traveller wrote:

It's  a short stroke,  big bore 250, with decent size ports.  By design, it's a motor that makes power higher up.   The only thing that will help low end,  is more displacement.  Lowering  the gearing will allow it to get into the power quicker,  and plonk around at low speeds better.  Airflow mods will increase top end and midrange to some extent,  but the only way to get low end is to change the nature of the engine.   Advance the cams a little. Add stroke,  things that make it shift power lower.  With fixed cam timing,  you only have a certain Rpm range an engine will work well in.  A 250cc engine will never grunt well,  and if it does,  it won't rev out well.  

For a 250 dual sport, it's a lot more biased to sport without being a race bike.   300cc really wakes it up by all accounts.

While all the above is true, my bike is the hardest-to-stall 250 I can remember riding. I spend a good percentage of my working days plonking around and over all sorts of crap, and this bike cops it all without a whimper in the soldier-on department. I've had a TTR250 for years, and it can be quite unforgiving at times in the low-end, though a mighty solid little workmate all round.

guys all of your replies are a bit arrogant. read the question more carefully before you reply. He is asking what can be done. Not what cant be done.
You can do the following<
12 54 sprockets.
big bore kit
air box
rekluse or other slipper
megabomb
chain tension perfect
air down tire
suspension rebound high front low shock

while most of these mods do not increase the engine torque they increase the feel and traction
to say nothing can be done is self defeating, a hell of a lot can be done.

learn to say yes

what happen to that Australian guy, he knew a lot.

Reread my reply. It's not arrogant, it's honest. I build high performance engines, and the nature of this 250 is to be biased to the upper RPM. Short stroke, big bore, large ports. It's has quite a bit of low end for what it is. You can't change the basic nature of the motor, it's designed to make power higher. It's just basic engine design. The things that make it work better in the low end, are gearing it down and reducing restriction in the exhaust. Intake restriction doesn't come into effect until further up the RPM scale. At low RPM the cfm requirements are quite low.

Every normally aspirated engine has a designed peak torque RPM. From that RPM point, you have approx. a 1500 RPM window (above and below, 3000 total) where it's still highly efficient and makes power. On modern fuel injected engines, it's closer to a 4000 RPM window. Get below or above that, and it's outside of the sweet spot. Variable cam timing, exhaust power valves, variable runner intakes, all those are crutches to make the torque peak variable and widen the usable power band. Exhaust power valves change the pulses at lower RPM to overcome the overlap of a cam that's designed to make power higher. Variable runner intakes use a longer runner down low to increase cylinder fill, then swap to a shorter one at higher RPM to make power up higher. Variable cam timing advances the cams for power lower and changes the overlap, retards them up higher. Done properly you can really increase the usable RPM range. BUT, bore and stroke ratio and total displacement dictate the basic nature of the engine. This is a small displacement engine that's trying to make decent power while still having a wide operating range. For what it is, it's a great little motor. What it isn't, is a torque monster down low.

Gear it to get into the power range faster, ride it harder, reduce restrictions, ride it.

Gearing is everything on these bikes. I like to keep mine quiet, so the airbox and pipe are stock. When I was running stock sized tires, I found that 13/47 gearing was excellent for true dual sport riding. I now have a 110/100 back tire and ride mostly off-pavement, so I switched to a 13/50 setup. It gets into the power band so quickly it's like a whole different bike. I couldn't be happier with the results. If I ever wear the engine out, I will likely install one of the available big bore kits, which will definitely improve low end grunt.

Lee

Traveller wrote:

Reread my reply.   It's not arrogant, it's honest.   I build high performance engines, and the nature of this 250 is to be biased to the upper RPM.   Short stroke, big bore, large ports.   It's has quite a bit of low end for what it is.   You can't change the basic nature of the motor, it's designed to make power higher.   It's just basic engine design.  The things that make it work better in the low end, are gearing it down and reducing restriction in the exhaust.   Intake restriction doesn't come into effect until further up the RPM scale.   At low RPM the cfm requirements are quite low.

Every normally aspirated engine has a designed peak torque RPM.   From that RPM point, you have approx. a 1500 RPM window (above and below, 3000 total) where it's still highly efficient and makes power.   On modern fuel injected engines, it's closer to a 4000 RPM window.  Get below or above that, and it's outside of the sweet spot.   Variable cam timing, exhaust power valves, variable runner intakes, all those are crutches to make the torque peak variable and widen the usable power band.    Exhaust power valves change the pulses at lower RPM to overcome the overlap of a cam that's designed to make power higher.   Variable runner intakes use a longer runner down low to increase cylinder fill, then swap to a shorter one at higher RPM to make power up higher.   Variable cam timing advances the cams for power lower and changes the overlap, retards them up higher.  Done properly you can really increase the usable RPM range.   BUT, bore and stroke ratio and total displacement dictate the basic nature of the engine.   This is a small displacement engine that's trying to make decent power while still having a wide operating range.   For what it is, it's a great little motor.   What it isn't, is a torque monster down low.  

Gear it to get into the power range faster, ride it harder, reduce restrictions, ride it.  

Great stuff. Thanks for taking the time to break a complex subject into a bunch of easier-to-digest bites for weekend riders like me. This forum needs a "like" button.

ADVFTW wrote:

What is the best mod I can do to help improve the bottom end power, the bike is stock, with no mods. any info would be great!

All of these responses have merit, IMO.  Traveller's info helps you understand what you're up against and to set the right expectation, and some of the others give you some tweeks to make the headway that can be made.  For me, I took some advice from WWGuy a while back and started by changing out my gearing and messed with the suspension some.  I went 13/48.  This made a dramatic change for about $100 and the bike is still quiet.

After that you are talking about: revalves, full exhaust, programmer, airbox mod, exup and ais delete, big bore kits with porting and stroker cams, etc (a few $grand$).  You'll get some improvement and lose some MPG's.

My personal advice:  start with tires (D606's / MT21's), sprockets, suspension adjustment for a few hundred bucks.  Ride for a while, then move into the other mods slowly after your are sure, and if you feel it's needed.  Look at wwguy's riding thread... he rides into places that would make most sphincters pucker right up on a mostly stock bike.