OZ ATV :: The Australian ATV Forum

[crx450r]

ok
my first gear is very tall and i'm finding it hard in the sand with stalling alot
i have to rev it quite high to get it moving
i'm currently running a 14 38 set up
it currently does 100 kph in third gear full throttle
what gearing should i change to???
i don't want to go out and buy 6 different sprokets to make it feel comfortable
any advice would be greatly appreciated
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TRX 400 ex 2005/crf450r 2004 Hybrid
13:1 moose racing piston
ported and polished head

[dangerman4]

gearing was allways gona be a chalendge with your choice of engine,
whats its max speed in 4th? and are u happy with its max speed?

what size are your rear tyres?

maybe throw a rekluse clutch in there if they make them for the crf

[bobnoxious]

Hey mate,

I used to race buggys and lifted the following information from a builders forum
hope it helps , you may have to get out the calculator though

The following is an example of a CBR1000 Honda motor installed in a buggy.

In the following we are assuming the motor tops out at 10,000 RPM, this is conservative considering the design of most modern motorcycle engines that are designed to rev very high.

10,000 RPM divided by the primary reduction of 1.786:1 = 5599.10 RPM.

(Primary reduction is the gear drive between the crankshaft & gearbox).

5th gear, (and there are actually 6 gears) is 1.174:1 ratio.

5599.10 RPM divided by 1.174:1 = 4769.16 RPM.

Your final chain drive is 17-60 teeth, that’s a 3.529:1 ratio.

4769.16 RPM divided by 3.529:1 = 1351.41 RPM.

This is the speed of your rear axle.

The 25x12.5x9" Bearclaw tyre has an actual circumference of 2050mm, (2.05m) at 8 psi.

1351.41 RPM x 2.05m = 2770.39 metres per minute.

X by 60 gives metres per hour = 166223.4.

Divide by 1000 gives KPH = 166.223 KPH.

Now that’s in 5th gear & it’s not an overdrive gear either.

That’s not allowing for the fact that you can still shift up to 6th gear, & also not allowing for tyre growth which will also increase your speed.

If for some reason you could not achieve 10,000 RPM, (and you WILL achieve it)
Because of wind resistance or its getting scary, lets say you only got to 8,000 RPM.

You will still be doing 132 kph, (in 5th gear).

could also use this method to srot out some of the bullshitters on the site ref topspeed - just a thought

Bob

[crx450r]

cheers bob i'll have a look into it
and its funny you say that dangerman
i'm selling my old ktm to fund a new rekluse clutch for the crf
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TRX 400 ex 2005/crf450r 2004 Hybrid
13:1 moose racing piston
ported and polished head

[bullet]

Buy the sound of it you could go to something like 13-40 quite easily. If you go less than 13 on the front you may find that the chain top and bottom gets pulled too hard over the swing arm and causes excessive wear.
For that reason you probably won't find a 12T that fits any way.
1 tooth down on the front is worth approx 3 teeth bigger on the rear.
So try the 13T on the front first and see how you go.
I don't think it will be a wasted investment, and after fitting that you will be able to decide more easily what to do with the rear.
Eg. If you want to gear down that much more again you will need to get a 41T for the rear.
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Can-Am X Team
Bullet #Y12. MrsB #Y18.

[bigjon]

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Don't close your eyes during the crash, you'll miss the best part