Honda CRF250X - Gearing January 25, 2006 version  Introduction   My Modifications   BigBore/TopEnd   Maintenance   Jetting   Gearing   Comparo   Pictures

Gearing is here understood to mean the relatively unchangeable internal crankshaft gear, clutch outer gear, transmission gears, and the normally changeable front and rear drive sprockets. The rear tire also plays a part in gearing; as you change the tire size, and thus the circumference, the overall gearing of the bike is changed.

This table shows MPH in each gear at the indicated RPM for a stock 250X with stock gearing and stock rear tire.

RPM	1st	2nd	3rd	4th	5th
1000	2.3	3.2	4.2	5.4	6.8
2000	4.7	6.4	8.4	10.7	13.7
3000	7.0	9.6	12.5	16.1	20.5
4000	9.4	12.7	16.7	21.4	27.4
5000	11.7	15.9	20.9	26.8	34.2
6000	14.0	19.1	25.1	32.1	41.1
7000	16.4	22.3	29.3	37.5	47.9
8000	18.7	25.5	33.5	42.8	54.7
9000	21.0	28.7	37.6	48.2	61.6
10000	23.4	31.9	41.8	53.5	68.4

Stock Gearing / Stock Tire

This table shows the MPH range in each gear at the indicated RPM range for a 250X with a 13-tooth front sprocket and a non-stock rear tire. This is my 250X.

RPM	1st	2nd	3rd	4th	5th
1000-1999	2.2 - 4.5	3.0 - 6.1	4.0 - 8.0	5.1 - 10.2	6.5 - 13.0
2000-2999	4.5 - 6.7	6.1 - 9.1	8.0 - 11.9	10.2 - 15.3	13.0 - 19.5
3000-3999	6.7 - 8.9	9.1 - 12.1	11.9 - 15.9	15.3 - 20.4	19.5 - 26.1
4000-4999	8.9 - 11.1	12.1 - 15.2	15.9 - 19.9	20.4 - 25.5	26.1 - 32.6
5000-5999	11.1 - 13.4	15.2 - 18.2	19.9 - 23.9	25.5 - 30.6	32.6 - 39.1
6000-6999	13.4 - 15.6	18.2 - 21.2	23.9 - 27.9	30.6 - 35.7	39.1 - 45.6
7000-7999	15.6 - 17.8	21.2 - 24.3	27.9 - 31.8	35.7 - 40.8	45.6 - 52.1
8000-8999	17.8 - 20.0	24.3 - 27.3	31.8 - 35.8	40.8 - 45.8	52.1 - 58.6
9000-9999	20.0 - 22.3	27.3 - 30.3	35.8 - 39.8	45.8 - 50.9	58.6 - 65.1
10000-10999	22.3 - 24.5	30.3 - 33.4	39.8 - 43.8	50.9 - 56.0	65.1 - 71.6

Rick's 250X

The engine is running at about 60% of what I consider top speed. I reckon that this speed is not harmful in any way to the engine and I suspect the valves are not being pounded too terribly hard at this speed. This engine speed is in what I call the 'green zone'.

I make an effort to hear and feel the engine at this speed, and when I'm in other gears, I try to stay at or below this same engine speed. Of course, I sometimes twist the throttle and wring out the engine a bit, but never for sustained periods of time. I think staying in the green zone contributes to my engine's health and well being.

I think the green zone could also extend very easily to the 7000 RPM row, with no significant impact on the engine. This expanded green zone would give me a ground speed of between 18 and 24 MPH in 2nd gear. 2nd gear is my workhorse gear (the yellow column). I often use 2nd gear for tight trails, and 18 to 24 MPH is pretty fast, at least for me it is. Rolling off to 10 MPH for tighter sections keeps the engine at just over 3000 RPM, which is not so slow that the engine/carb begin to falter. The response is still plenty crisp, so I don't have to go to 1st gear very often.

When the trail opens up a bit, I like to get into 3rd gear (the orange column), and the bike really begins to fly. The throttle response is great without the necessity of having to go beyond the expanded green zone. I think 31 MPH on a fast trail is plenty fast enough, thank you.

One last thought. Although my 13-tooth front sprocket takes away some top end speed, I find it adds just a bit on the bottom end to allow me to chug up steep hills at 10,000' elevation, or higher. The 14-tooth sprocket just didn't allow me to go slow enough for the really slimy, steep hills that we have here in Central Colorado during the monsoon season in July and August. My 270 big-bore kit added some power, but I consider that I was just getting back to sea-level performance with that mod. Perhaps the 302 kit will allow me to go back to the 14-tooth sprocket...

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