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200X motor build with XR parts

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Hey-

well my old 85 200x motor is in need of repair. i have been reading up everywhere about what parts work from the XR to the ATC.

what i have in mind:

10.5 to 1, 66mm 1983 XR200R piston kit. (1 and a half mm overbore, old compression was 9.6 to 1)

1983 XR200R cam sent off webcam to be modded

1983 XR200R carb and intake mainfold.

Large diameter supertrapp exhaust system, custom fit.

new oil pump assembly and have the crank checked by honda, new cam sprocket and bearings.

still in question. i have many many XR200R parts, i want to know more about the differences in trannys. i heard the whole 6 spd from the XR will fit in. i have a full tranny from that 83 with one broken gear, 40 dollars for a new one, but i also have a 1990 XR200R tranny still in the motor, should be fine.

what can i do? anyone know?

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Sounds like a plan to me, couple of potential problems:

One poster tried to use a 81-83 XR200 right case on his newer engine and had clearance problems with the gear set.

The XR200Rs are 10:1 CR and have a 66mm bore, 66.5 is the big bore kit.

The 81-83 XR200R manifold angles the carb to the right to clear the shock, 86 and newer XR200R manifolds do the same, XR185/XR200 (twin shock) manifolds angle the carb to the center. On some the model number will be molded onto the manifold; 81-83 = KA2, Xr185/200 = 446, 86 and on = KT0.

Early carbs are PD28A, later are PD97A but they seem the same and use the same slide and needle.

I suggest calling PowRoll for more details on the best mods for your intended use, they can also tell you how to check the rod and valve guides. PowRoll also sells a HD timing chain that is better than OEM. Their Torque Cam makes for a very nice running motor.

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Part numbers for the '85 200X and the '83 XR left crankcase match up, but not the right. No numbers match between the 200X and the '90 XR.

Try the '83 tranny in the 200X. Fully assembled (with a gasket) there can be no binding whatsoever. The countershaft should spin easily by hand.

Normmal wear and tear aside, I guess its still a crapshoot whether the tranny will shift once all is said and done, but it would be good to know if there is interchangeability between these two motors...

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Chuck, powroll says the stock XR bore was 65.5mm and stock 200x was 65mm. i want to get the higher compression piston for the 81-83 XR200R, for a little bit more power. Nice to know what each manifold does, i have a XR185 and a XR200R so if one doesnt work the other may help. On 3WW i read that you can use the XR tranny with the stock 200x side case, unless the xr tranny isnt setup for forward kick... have to look into that.

i was going to go the cheaper route and go to webcam for my cam, 270 for PowRoll and 125 for WebCam. but i have heard great things about that powroll cam!

People have also talked about just using different gears on the countershaft. I believe gears from the XR185/200 TLR200 and the 200x can be swapped around. by doing so you can sort of change the "gap" between gears from what i was reading. might be a good idea.. just have to keep researching for what others have done before. but most of this tranny swap idea is on the far far side of my concern for this rebuild, i mean if its not broken why fix it right?

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