Gearing down a CRF250X

[sbmar]

I'd like to know if someone can steer me in the right direction to limit my learning curve a touch.. I'd like to lower the gear ratio on my 2006 CRF250x to where my very low speed performance in first gear acts more like a tractor. Top speed is of no real interest as all I do is very tight trail riding at very low speeds and I like like to be able to go slower without using the clutch as much..

Does anyone know where I can find a larger rear sprocket ( say 6 teeth or so) ? I was able to find a one tooth smaller front sprocket, but would prefer using a larger rear one.. I can deal with the chain guide mods as needed for the additional clearance. I've peeked around but I have not been successful yet.

Thanks in advance..

Tony

[redrider58]

well, what orig. gearing do you have you your bike. 13/49 or 14/53?

well if you have the 14/53 gearing, you did the right thing dropping a tooth in front. and i think the highest tooth sprock for the rear is a 54 made by vortex or sunline. so i would recommed going down another tooth in the front. plus it is cheaper then getting a new rear sprocket. but i have heard about when the smaller the counter shaft sprocket is....it is harder on the chain because it is a tighter turn around.

personally, i think the 14/53 setup it pretty good. i wouldn't mind droping to a 51 or 50 tooth just to have a little more speed. and i ride a lot of super tight single track. just my 2 cents.

-Michael

[highmarker]

One can do all the calculations of sprocket sizes and ratios' etc, but when it comes right down to it there are physical limitations to what works out. For example the chain guide was pretty much designed for a 51 or smaller rear, even the stock 53 wraps the chain pretty tight through it, so you don't want to go bigger on back. So your best start is to simply put a 13t on the front, it'll work with the stock chain length.

If that's TOO low then start making the rear smaller. At some point you'll have to take 2 links out, which will require a new rivet m link. Some folk don't want to mess with the chain so wait for new chain and sprocket time to make any big changes.

There's also the factor of where the axle ends up, being a lock to lock tight woods rider I wanna keep the wheelbase short, so favor a chain and sprocket combo that's short.

If your desire to keep the stock 14 is chain life, I wouldn't worry about it, the elements will kill it before the increase in bending radius. Plus the 13 gives a little more clearance for trail junk to get past it, I had trouble getting sticks and junk jammed in between the 14 and the case saver. Also ditch the sprocket guard if you ride in junk.

So after all my rant, pick up a cheap primary drive 13, throw it on there and give it a try.

[keithpincock]

+1 on the 13 tooth front. It is cheap to try and easy to change back if you don't like it.

[sbmar]

Guys,

I appreciate all the input and will share what I have learned and done..

Renthal makes a 12T ( I had a 14-53) and it fits with zero issues.. No rubbing, etc, & a piece of cake install.. Cheap too (under $30), so if anyone else likes to ride slow like this old guy, this is a no-brainer.. It looks like you can run from 12T to 15T (or maybe 16T) with no issues as to adjusting the chain.. Overall gear ratios are now 60.6:1 in 1st vs 51.8 stock, and 12.9:1 in 5th vs 11.3 stock.. Biggest change you could feel was in 1st, 2nd & 3nd (tight and close) which I wanted.. Top end / easy cruise speed for me is just fine..

I also had my front forks lowered by 2" and slid up the front tubes in the triple clamp about 3/4" inch and dropped the rear shock adjustment about 3/4".. I Installed a Kouba CRF3 Link and now I am a happy 100% flat-footed 69.5" old time trail/trials rider that likes to tractor around with no interest anymore in jumps, etc.. I installed a MX51 front (90/100-21 and a Maxxis Desert IT rear (120/100-18) so I have as much cleat on the ground as practical with both using ultra heavy duty Bridgestone tubes and a double rim lock on the rear should something stupid happen and I need to come home on a flat................................Love it!!

Again, thanks for all..

Tony

[vincent52100]

Hi, I'd like to know how you dropped the front fork 2". I just got an '04 CRF250X and , with some arthritis in my legs, its a chore getting on and off. What all did you end up doing to the rear suspension? Thanks a lot.

[sbmar]

Vincent,

I removed the fork tubes and sent them to AS Racing located in Canyon Country, Calif.

I found them thru this site:

http://www.crfsonly.com/catalog/extra_info_pages.php?pages_id=10 ,

that I think is really good as to info and buying parts.. Excellent service and very fair $$..

Tony

[vincent52100]

Thanks for the info! Will give them a try.

[Roger M]

One can do all the calculations of sprocket sizes and ratios' etc, but when it comes right down to it there are physical limitations to what works out. For example the chain guide was pretty much designed for a 51 or smaller rear, even the stock 53 wraps the chain pretty tight through it, so you don't want to go bigger on back. So your best start is to simply put a 13t on the front, it'll work with the stock chain length.

If that's TOO low then start making the rear smaller. At some point you'll have to take 2 links out, which will require a new rivet m link. Some folk don't want to mess with the chain so wait for new chain and sprocket time to make any big changes.

There's also the factor of where the axle ends up, being a lock to lock tight woods rider I wanna keep the wheelbase short, so favor a chain and sprocket combo that's short.

If your desire to keep the stock 14 is chain life, I wouldn't worry about it, the elements will kill it before the increase in bending radius. Plus the 13 gives a little more clearance for trail junk to get past it, I had trouble getting sticks and junk jammed in between the 14 and the case saver. Also ditch the sprocket guard if you ride in junk.

So after all my rant, pick up a cheap primary drive 13, throw it on there and give it a try.

You can use a larger rear sprocket than stock without issues with the chain guide if you add 1 link to the chain--this moves the axle back enough to provide clearance. I am currently using a 54 rear, which is available from Honda. Note that a 14 tooth front sprocket is the largest that will go on and clear the swingarm.

[mossman77]

I'm so confused...I'm running the stock 14/53 gearing with a 110/100 rear tire, so that's equivalent to going up a tooth or two on the rear sprocket isn't it? If so, I'd want to come down a tooth or two to effectively get back to the stock gearing correct? Basically, 1st gear isn't high enough for the type of riding I do and 2nd is too high most times such that I am constantly feathering the clutch. What do I need to change?

[mlatour]

Running a larger overall diameter rear tire (110/100) will have the effect of going down a tooth on the rear, not up.

On top of the diameter change, there is also the added physical weight of the tire (inertia/mass) that will somewhat affect acceleration.

 

No matter what final drive ratio you pick, the gap between the 1st and 2nd gear ratios will remain the same.

Maybe there's a way to swap in some CRF250R gearbox components (close ratio versus the X's wide ratios)

 

I run 13/53 with a 100/100, same as you 1st gear is a real tractor and do most of my riding in 2nd (slow technical trails)

which requires always keeping a finger on the clutch lever but in many situations that low 1st gear is still very handy.

At tire replacement time I'm upsizing to a 110, hopefully not loosing too much grunt in the process.

Edited September 17, 2016 by mlatour

[mossman77]

Just realized I have a brand new 13T sprocket sitting in my closet. Might as well put it on and see what it feels like.

[mlatour]

If you don't mind loosing some top speed, you won't regret trying 13/53.

 

The first time I rode my 250X it still had the 14/53,

new to off-roading I expected 1st gear to be much 'slower' for creeping along tight trails,

promptly switched to a 13 before the second trailride.

 

Although it doesn't change the gap between 1st and 2nd,

you'll likely find 2nd gear more usable now and requiring less clutch work.

[Tr0y]

Ok I have got to ask. I have the baby X running 14/48 and can hoist the front wheel over anything I have come across riding in the woods of the upper midwest, in and out of muddy gullies and there is nothing I haven't been able to climb yet. 13/49 or 14/53 will the bike go 50 on the top end with that ? 

[mlatour]

I've got a cheap China speedometer on my 250X, driven by the stock odometer cable

(a speedo is required here to conform to some trail networks that share public roads to connect trails).

It seems somewhat accurate if I compare distances ridden versus the network maps / mileage.

 

With a 100/100 tire and 13/53 gears it still goes over 55MPH quite easily, I'm sure 60+ if WFO.

(I've never held the engine wide open all the way, it's a used bike so not 100% confident of it's past maintenance history)

 

3x 1" holes in the airbox and a #135 main jet are the only engine 'mods', stock exhaust.

Edited September 18, 2016 by mlatour

[Chuck.]

My X is geared 14/51 plus a 4.00R18 tire that is larger than a knobby (about 1/2 CS tooth) and it tractors right down to slow speeds.  Bottom end throttle response is a lot like a XR250R and I ride it that way and only use 1st for tight switchbacks and some very tight ST. Most trail riding is 2nd & 3rd. Can even do 3rd gear starts, 2nd gear is easy. Smooth throttle response is more important than gearing for smooth low speeds, especially in first gear. As a comparison I have a much modified 01 XR200R; Powroll 218 engine (more torque than a stock dry sump XR250), USD forks, disc brakes. With its lighter weight and shorter wheel base the XR is much easier to ride on tight technical trails. But the X seems to pull harder out of the corners and is less likely to lift the front wheel exiting switchbacks (both in 2nd), probably because of the longer wheelbase.  The X also seems to have a much broader powerband, and certainly much more top end horsepower.

 

Smooth tractable bottom end power is the sum of several small things:

Add a flywheel, this make the X a trail bike. I have the heaviest Stealhy.

Tune the carb.  I use JD and followed a TT thread to adjust the AP.

Use stock exhaust. I've used Yosh and R, and prefer X.

Disconnect the TPS, this reduces extra spark lead at part throttle and softens part throttle bottom end. No change in WOT spark lead.

Set idle speed at 1800-1900rpm.

Remove as much throttle cable play as possible wo cable binding,  this smooths "off closed" throttle response. If you have cable binding check the routing because they tend to move into the wrong place when the tank is removed. 

 

Two more things if you want a smooth easy clutch:

Use ATF in the tranny. I use Valvoline synthetic Dextron VI ATF, provides very smooth clutch operation. Avail at local auto part stores.

Change clutch leverage for less lever pull and a wider range of engagement, helps for slow speed technical. I added an extension to the engine clutch arm and a low friction Motion Pro SlideLight cable.

Edited September 18, 2016 by Chuck.

[mossman77]

Add a flywheel, this make the X a trail bike. I have the heaviest Stealhy.

 

 

A flywheel will reduce engine braking correct?  I am constantly feathering my clutch to reduce engine braking, which quickly fatigues my forearm.  In fact that is typically the reason I call it quits for the day.

 

And I see Steahly makes a complete replacement flywheel for the 250X.  Are these better than the weighted plates? 

 

And how do the Race Tech flywheels compare to Steahly?

Edited September 19, 2016 by mossman77

[Chuck.]

Another thread said TT makes the CRF250 flywheels for Stealhy.

IMO complete FW is the way to go. Best money spent on my X.

 

A flywheel will not reduce engine braking, but turning up the idle speed will.  I do that on my XRs to reduce braking and stalling.

I have the idle turned up only a bit on my X for the same reason.  I tend to run a gear higher in my x which also helps reduce engine braking.

 

Spec idle speed on my XR is 1100rpm and I set it at 1700, I set the X at 1800rpm.

[mossman77]

I ride in 2nd most of the time and have to feather the clutch a lot to keep the motor from lugging. If the new flywheel can mitigate that, I'll be happy. I'll also increase the idle some to help with engine braking. Now I just need confirmation that the 6141 is actually the lighting version and not the 6141L.

Edited September 20, 2016 by mossman77

[Chuck.]

Steahly has 4 flywheels listed for the CRF250R/X models, the only difference I can see is weight over stock;

Does TrailTech offer different weights?

Edited September 20, 2016 by Chuck.