Author Topic: Yamaha 250 gearbox swaps.  (Read 7370 times)

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Offline rocketfrog

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Re: Yamaha 250 gearbox swaps.
« Reply #15 on: August 16, 2013, 11:14:22 am »
Political correctness is a doctrine,fostered by journalists and politicians, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."

Offline rocketfrog

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Re: Yamaha 250 gearbox swaps.
« Reply #16 on: August 16, 2013, 11:15:13 am »
Political correctness is a doctrine,fostered by journalists and politicians, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."

Offline rocketfrog

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Re: Yamaha 250 gearbox swaps.
« Reply #17 on: August 16, 2013, 11:16:06 am »
Political correctness is a doctrine,fostered by journalists and politicians, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."

Offline crossedup2

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Re: Yamaha 250 gearbox swaps.
« Reply #18 on: August 16, 2013, 12:10:26 pm »
This stuff is gold! Thanks for the effort with the photos Rocketfrog.

IT 250H rebuild is to happen soon. I'll keep my eyes open for this stuff.

Peter B
Anything Yamaha. AT1, CT1 (X3), RT1, DT3 (x3), YZ125X,  YZ250E, YZ400D, IT175E, IT250H, XR500RC . Always looking for Pre 78 Yamaha stuff....

Simo63

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Re: Yamaha 250 gearbox swaps.
« Reply #19 on: August 16, 2013, 12:37:53 pm »
Great work Jason. This need to go into the bible or something similar.

Offline rocketfrog

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Re: Yamaha 250 gearbox swaps.
« Reply #20 on: August 16, 2013, 03:00:19 pm »
If anyone has attempted to source gearbox parts for an IT250K they would know the rarity of the 3rd/4th pinion gears and the matching gear wheels.

IT250H/J gear sets seem to be more abundant, although the ratios might be different you could retrofit the older g/box in toto to get that K engine built.

The final drive (sprocket combination) gearing is obviously altered simply enough, although there are limitations as to what can be achieved as the results tend to favour one end of the spectrum at the cost of the other.

Whether the power characteristics of the longer stroke engine match the old gear ratios is not known. I would be keen to hear if this experiment has been tested practically, perhaps Nathan could keep us posted if he decides to go this way.
Political correctness is a doctrine,fostered by journalists and politicians, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."

Simo63

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Re: Yamaha 250 gearbox swaps.
« Reply #21 on: August 16, 2013, 03:05:57 pm »
If anyone has attempted to source gearbox parts for an IT250K they would know the rarity of the 3rd/4th pinion gears and the matching gear wheels.


Really?  I think I have a gear set for the IT250K at home ... will have to drag it out and check it against your posts here Jason.

Offline rocketfrog

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Re: Yamaha 250 gearbox swaps.
« Reply #22 on: August 16, 2013, 07:55:23 pm »
I would be keen to get some measurements on the input shaft if you have it handy. Just a curiosity more than anything. The IT crowd would snap it up in a heartbeat if you have no need for it.
Political correctness is a doctrine,fostered by journalists and politicians, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."