Sheared off GT750 Tach Drive Shaft

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Mgmark
On the main road
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Joined: Tue Jun 12, 2012 3:15 am
Country: USA
Suzuki 2-Strokes: ‘75 GT750, '19 Triumph T100
Location: Chattanooga, TN

Sheared off GT750 Tach Drive Shaft

Post by Mgmark »

This is also posted in the "Customs" section as part of my bike build.

The tach drive wasn't spinning in the motor when I got it started for the first time, and here is what I found whan I pulled it.
The tach drive shaft is well and truly seized in the housing and is sheared off, and the water pump drive gear is rather badly split. The pump cross shaft down in the cases seems to spin easily so hopefully all is well inside the bottom end itself.
So how to remove the lower section of the drive? Split the cases?

Mark
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tz375
Moto GP
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Re: Sheared off GT750 Tach Drive Shaft

Post by tz375 »

The cross shaft only comes out with a crankcase split. It is retained by a half round dowel pin on the bearing. That shaft should rotate with slight resistance because it is turning the water pump. If there is no resistance, that would indicate a water pump without any stiction which is unusual.

I stripped one B model motor on which the top bush for the water pump was missing so the water pump and cross shaft gears were worn beyond belief. It's the only motor I found that on, but the bottom half of the crankcases was a 73 as was the crankshaft but with later type pistons, so it's not surprising it was having a bad life.

Old motors have interesting stories to tell. :roll:
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