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Hi Guys,

I am acquiring parts for a RM125/ XL185 build,

Just wondering as a starting point what gearing are are you running for a tight MX track.

Big bore, Cam, Head work, Exhaust and a 28mm Flat slide.

Regards Mark

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So its a 5 speed gearbox ? I found the 5 speed gearbox to be too gappy and put a 6 speed engine back into bike.

I ran a 12 t front for mx, with a 50/51 rear, for the 6 speed stock capacity 200

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  1st thru 5th are the same ratios atc 200x and xr 200r. The 2 wheeler's 6th is tacked on top. The 5 speed from the 3 wheeler fits in the same space as the 2 wheeler's 6 speed. The 3 wheeler's gears are wider and stronger to handle the higher loads imposed on the trans by the big fat  3 wheeler tires. I never use 6th on an mx track on my xr so I'm not sure using the 5 speed is a real issue for mx. I've had my xr for 25 years and have had to replace 2nd and 3rd gears. They seem to be the weakest if you're hammering your xr on an mx track.

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Unfortunately to comply my EVO bike must also have a "twin shock" motor, that is the reason for selecting the XL185, the early XR200 are so rare over here in OZ.

12/50 sounds like a good start, tracks here in OZ are generally tighter compared with USA.

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   The best I can remember the only visible external difference between the early and later motors is the foot peg mounting lugs cast into the engine cases on the earlier motors (2 and 3 wheelers). They're gone on the later models.

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