G: Gearbox (Twin) Cracked G4 final drive shaft

TouringGodet

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The bike lost the ability to shift into fourth gear. I opened up the gearbox, and the double gear G11 won't slide off the G4 final drive shaft. I see 5 cracks.

G4Crack.JPG
 

oexing

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Due to oil starvation the brass bush seized on G 3 gearshaft. Seizure expanded the bush and cracked the thinwalled G 4 drive shaft. How does the G 3 look , brass remains on it ? Or shaft/bush fit extremely sloppy ? Please add more photos .

Vic
 

oexing

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Hmmm, looks good to me. How is the fit of shaft in bush, very sloppy ? Any other defects in the gearbox ?

Vic
 

greg brillus

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Has the gearbox been together for some time or apart recently........i wonder if the input shaft was pressing on the end of the output shaft...........it is showing signs of this. The input shaft should have at least a half a mm of end float with the G 2 cover fully tightened home.
 

TouringGodet

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The drive sprocket was done back in the 1980's as well. The G3 is quite loose in the bushing.
 

greg brillus

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Haven't seen one split like that before..........I know it might sound extreme, but I wonder if the mating gear which would be the G 8 or a G 8/1 is in fact the wrong gear and has been causing bad or incorrect meshing, thus overloading the tips of the teeth.......Fit the layshaft and this mating gear back into the box to see if this might be the case.
 

Alyson

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Haven't seen one split like that before..........I know it might sound extreme, but I wonder if the mating gear which would be the G 8 or a G 8/1 is in fact the wrong gear and has been causing bad or incorrect meshing, thus overloading the tips of the teeth.......Fit the layshaft and this mating gear back into the box to see if this might be the case.
since the '80s ? I'd think if it was the wrong gear trouble would have started some time ago. I don't see any bluing in the shaft/bushing so must have had the oil level correct, and I don't want to start talking about the dip stick :O
 
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