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Old 05-08-2013, 07:00 AM   #4681
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Oddometer: 613
Thumb CRF-250L Gearing Thoughts

We pretty much universally agree that the stock gearing is TALL. It's geared perfectly for doing 65-70 with good fuel economy in 6th. But, who does long periods of 65-70 on a bike like this?

From my riding, here's how I feel about the rev band at cruising speed (5th/6th gear):

4-5000: can lug under load, but usually cruises ok.
5-7000: smooth, good power. This it the meat of the torque curve. This is where I like to ride.
7-8000: Still reasonable to ride for a long time, but a bit buzzy. If there's a higher gear available, I'll upshift instead of cruising at these revs.
8000+: acceleration, passing, etc. only. It's pretty harsh and buzzy up there. Plus, power drops off hard after 9k.

Here's what stock gearing looks like in 5th and 6th:

Code:
	5	6
RPM	1.115	0.963
3000	25.5	29.5
3500	29.8	34.5
4000	34.0	39.4
4500	38.3	44.3
5000	42.5	49.2
5500	46.8	54.1
6000	51.0	59.1
6500	55.3	64.0
7000	59.5	68.9
7500	63.8	73.8
8000	68.0	78.7
8500	72.3	83.7
9000	76.5	88.6
9500	80.8	93.5
10000	85.0	98.4
10500	89.3	103.4
As you can see, 5th is pretty good for most riding. Going 13/42 or 13/43 lets you keep the stock chain, and puts 6th gear down to where the stock 5th was. If you do lots of 60+ riding, one of those combos should be great. Cruising at 70+ takes a hit, but 70mph flat feels just fine to me.

13x42, 13% reduction from stock: (13x43 is 16%)
Code:
	5	6
RPM	1.115	0.963
3000	22.6	26.1
3500	26.3	30.5
4000	30.1	34.8
4500	33.8	39.2
5000	37.6	43.5
5500	41.4	47.9
6000	45.1	52.2
6500	48.9	56.6
7000	52.6	60.9
7500	56.4	65.3
8000	60.1	69.6
8500	63.9	74.0
9000	67.7	78.3
9500	71.4	82.7
10000	75.2	87.1
10500	78.9	91.4
Many people here don't use the bike for commuting (like I do), and if they can buzz to the trails and back, that's plenty. For them, getting a new chain and a 48t makes a lot of sense. By adding two links, you can run 14x48 and put the axle at the stock location. This leaves 60mph as a very comfy cruising speed, but makes 70mph 8500rpm, which I consider unbearable. The sweet spot is 50-55mph in 6th, which for many people is just perfect - they never go over 55mph for any significant length of time anyway.

14x48, 20% reduction from stock:

Code:
	5	6
RPM	1.115	0.963
3000	21.3	24.6
3500	24.8	28.7
4000	28.3	32.8
4500	31.9	36.9
5000	35.4	41.0
5500	39.0	45.1
6000	42.5	49.2
6500	46.0	53.3
7000	49.6	57.4
7500	53.1	61.5
8000	56.7	65.6
8500	60.2	69.7
9000	63.8	73.8
9500	67.3	77.9
10000	70.8	82.0
10500	74.4	86.1
Finally, the most aggressive off-road option, 13x48. This also needs two links. What's nice is that once you have the 48t rear (and have removed the chain guide to make it fit), you'll be able to swap between 13t, 14t, and 15t front sprockets without swapping chains. 15x48 is essentially the same gearing as 13x42, so you can switch from 13x48 rock-crawler gearing to 15x48 and cruise the highway at 70mph with just 4 bolts and a chain tension adjustment.

Here's 13x48, 29% lower than stock. This pretty much maxes out at 55mph, with 40-50 the sweet cruising speed.

Code:
	5	6
RPM	1.115	0.963
3000	19.7	22.9
3500	23.0	26.7
4000	26.3	30.5
4500	29.6	34.3
5000	32.9	38.1
5500	36.2	41.9
6000	39.5	45.7
6500	42.8	49.5
7000	46.0	53.3
7500	49.3	57.1
8000	52.6	60.9
8500	55.9	64.7
9000	59.2	68.6
9500	62.5	72.4
10000	65.8	76.2
10500	69.1	80.0
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Old 05-08-2013, 07:02 AM   #4682
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Flatland or Emperor Bash plate

Quote:
Originally Posted by Vspec View Post
Emperor Racing is about 39$ more but seems a better product.

For those who own either what is the consensus?
I have Flatland. I agree RH hose connection protection could be better, also it could be longer underneath, and fit to the two front bolts could be better. At least access to the oil drain plug is better than stock, especially after going to the magnetic drain plug with the M14 hex instead of the 12.
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Old 05-08-2013, 07:08 AM   #4683
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CRF-250L Gearing Thoughts

Auto-X Fil:

Nice buncha math. If you're a car guy or a drag racer, it's worth it to add to those charts the "equivalent" car axle ratio...like 15/45 = 3.00 (45/15=3)
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Old 05-08-2013, 07:24 AM   #4684
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Quote:
Originally Posted by Ed@Ford View Post
Auto-X Fil:

Nice buncha math. If you're a car guy or a drag racer, it's worth it to add to those charts the "equivalent" car axle ratio...like 15/45 = 3.00 (45/15=3)
I have all that and way more in my spreadsheet. I even have hp and tq curves and iteratively solved for the best shift points in each gear to maximize acceleration.

FYI, this engine dies so hard up top, and the gearing is so tight, that this bike makes a perfect example of something that should be shifted well below redline.

The best shift points for the stock gearing are:

2 - 9850
3 - 9400
4 - 8950
5 - 8900
6 - 8850

The real take-away for those with a tach is that there's no reason to spend any time above 9k rpm.
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Old 05-08-2013, 07:35 AM   #4685
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Quote:
Originally Posted by Auto-X Fil View Post
I have all that and way more in my spreadsheet. I even have hp and tq curves and iteratively solved for the best shift points in each gear to maximize acceleration.

The real take-away for those with a tach is that there's no reason to spend any time above 9k rpm.
Fil: My seat of the pants kinda told me short shifting is what this engine likes...and even 9K is frikkin' buzzy enough....thanks
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Old 05-08-2013, 07:48 AM   #4686
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@Auto-X Fil

Good post thanks for the info.

I am currently running 13/42 and I am able to use my stock chain, I think it could stand to have another tooth or two in the back, but I am completely satisfied with the low end that I am getting at the moment, at least for the type of riding that I do.

I haven't heard much talk on a 15T front, does it fit OK?

Sent from my rooted XT912 running AOKP Aviator
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Old 05-08-2013, 08:20 AM   #4687
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Quote:
Originally Posted by MBRedline View Post
@Auto-X Fil

Good post thanks for the info.

I am currently running 13/42 and I am able to use my stock chain, I think it could stand to have another tooth or two in the back, but I am completely satisfied with the low end that I am getting at the moment, at least for the type of riding that I do.

I haven't heard much talk on a 15T front, does it fit OK?

Sent from my rooted XT912 running AOKP Aviator
I'm running 13/40, and that seems to be fine for what I do. Ramz did a 43 rear, but said it was difficult to fit. Remembering someone who did a bigger sprocket in the back but had to put the chain guide on upside down. That was quite some time ago. http://www.rickramsey.net/CRF250Lmods.htm#gearing
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C14 - CRF250L, always cleaned while it's raining

CRF250L Service Manual http://www.hondampe.com.au/docs/owni...F250L13_OM.pdf

SAPB screwed with this post 05-08-2013 at 08:31 AM
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Old 05-08-2013, 08:22 AM   #4688
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Tire mileage

I know there is a lot of factors involved in tire mileage but has anyone got 4000 miles out of the rear? I'm trying to decide if I should change my rear tire before taking off on a 2000 mile trip or just wear out the one that's on it that's approaching 2000 miles already. I'll probably ending up changing it for peace of mind but would still like to know. Thanks
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Old 05-08-2013, 08:27 AM   #4689
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Quote:
Originally Posted by Oldtimer View Post
I know there is a lot of factors involved in tire mileage but has anyone got 4000 miles out of the rear? I'm trying to decide if I should change my rear tire before taking off on a 2000 mile trip or just wear out the one that's on it that's approaching 2000 miles already. I'll probably ending up changing it for peace of mind but would still like to know. Thanks
My mileage just clicked over 2,100, and there's more miles left on it, and I hate to take off a good tire. Any place on the way for your trip where you could get a tire while during the trip? If not, probably just swap it now. Someone else can chime if they got 4K kind of miles on an original.
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C14 - CRF250L, always cleaned while it's raining

CRF250L Service Manual http://www.hondampe.com.au/docs/owni...F250L13_OM.pdf
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Old 05-08-2013, 08:35 AM   #4690
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Quote:
Originally Posted by SAPB View Post
I'm running 13/40, and that seems to be fine for what I do. Ramz did a 43 rear, but said it was difficult to fit. Remembering someone who did a bigger sprocket in the back but had to put the chain guide on upside down. That was quite some time ago. http://www.rickramsey.net/CRF250Lmods.htm#gearing
I didn't have to do any fab work or remove the chain guard to get a 13/42 on but it was tight. I would say 14/42 or 13/43 would require guard to be removed or at least fabricated a bit.

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Old 05-08-2013, 08:51 AM   #4691
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Quote:
Originally Posted by MBRedline View Post
I haven't heard much talk on a 15T front, does it fit OK?
Here's one random guy who says he did:

http://www.thumpertalk.com/topic/997...#entry10500135

And some detail on where to get them - search for CBR250R sprockets:

http://www.thumpertalk.com/topic/995...ront-sprocket/

Really, the only reason to go 15t on this bike is if you're getting a big rear, like the 45t or 48t, and want to be able to swap from street to off-road gearing. I think this is why we haven't heard too much about it, although for certain people, it makes sense.

I commute on my bike, and am leaving it 14/40. My buddy does mostly off-road, and is going 13/48. Having the 15t around means that if we want to road trip it, he can have his bike ready to go in less than 10 minutes.

Quote:
Originally Posted by SAPB View Post
I'm running 13/40, and that seems to be fine for what I do. Ramz did a 43 rear, but said it was difficult to fit. Remembering someone who did a bigger sprocket in the back but had to put the chain guide on upside down. That was quite some time ago. http://www.rickramsey.net/CRF250Lmods.htm#gearing
13/42 drops right in. 13/43 requires flipping the chain guard front-to-back, in order to provide enough clearance. Either will work with the stock chain length.
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Old 05-08-2013, 10:17 AM   #4692
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13x42, 13% reduction from stock: (13x43 is 16%)

13/40 must be minus 7.9%, that's what I had to plug into the speedo DRD.
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C14 - CRF250L, always cleaned while it's raining

CRF250L Service Manual http://www.hondampe.com.au/docs/owni...F250L13_OM.pdf
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Old 05-08-2013, 10:28 AM   #4693
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Quote:
Originally Posted by SAPB View Post
13x42, 13% reduction from stock: (13x43 is 16%)

13/40 must be minus 7.9%, that's what I had to plug into the speedo DRD.
Using the sprocket formula on 12OclockLabs site I came up with -11.6% for 13/42 but I think it is still reading a couple mph high at 55mph, I plan to re-adjust soon. 13% sounds like that would be about right. I have heard that the speedo is not dead accurate from the factory so that could be part of the problem.

Sent from my rooted XT912 running AOKP Aviator
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Old 05-08-2013, 10:32 AM   #4694
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Quote:
Originally Posted by MBRedline View Post
Using the sprocket formula on 12OclockLabs site I came up with -11.6% for 13/42 but I think it is still reading a couple mph high at 55mph, I plan to re-adjust soon. 13% sounds like that would be about right. I have heard that the speedo is not dead accurate from the factory so that could be part of the problem.

Sent from my rooted XT912 running AOKP Aviator
Didn't ride with the Garmin with the 14t. The speedo reacts quicker, the Garmin lags (electronically apparently), kinda like looking down at your feet as you walk with a digital camera. But maintaining a steady speed, it's smack on now.
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C14 - CRF250L, always cleaned while it's raining

CRF250L Service Manual http://www.hondampe.com.au/docs/owni...F250L13_OM.pdf
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Old 05-08-2013, 10:44 AM   #4695
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If it stops raining by the time I get off work I may input 13 and go test it out, if I remember right at 60mph 1% would be like 0.6mph difference so that should put me in there pretty close if I'm around 1-1.5mph off at 60mph.

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