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Bearing whine in fourth and fifth GS850G.

  • Thread starter Thread starter 81GS850
  • Start date Start date
8

81GS850

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Hey guys, getting this ole girl up and running again. It's an 81 GS850G with 65,000 miles on it.

I replaced all the fluids. 10w40 conventional motorcycle oil in the case and 75w90 valvoline in the rear end and bevel gear case.

I notice a bearing whine between 40-50mph. It's quiet 1-3, then 4th it gets louder and 5th is really loud. I'm suspecting the bevel gear case bearings. I know this isn't the bevel gear whine because I have that and know what that's supposed to sound like. Definitely a bearing. But I was wondering is there a bearing supporting 4-5 gear in the transmission that could cause this noise? Is this a common issue on higher mileage bikes?
 
Well, I found the issue... I had the dreaded driven gear nut break off. I'm having a heck of a time getting the housing out though! Any tips??
 
It's been said to first loosen the case bolts nearest the driven housing.
 
That finally got it out... I destroyed the bearing housing thought before I got it out.. Im going to get a used gear set and throw it in there.
 
Hi, I also have a bearing noise on my '79 850 between 40-50. Am I right that your problem was with the bevel gear/bearing assembly which is at the engine end of the drive shaft? If not could you give me a little more info so I can check this out on mine. I have just replaced the two bevel gear / bearing assemblies (between the gear box and shaft) with a second hand pair which felt very good, however the noise is still there.
Colin
 
Well, my driven bevel gear, that goes to the driveshaft, threads were broke off at the base and I think it allowed the bevel gear to walk around. It could very well be your problem. However I cant say definitive it is is or not. If you replace the gearset with another gearset it could be the pattern in the new gear set is already set and you didn't get it back exactly as it was. In this case there will always be gear whine. It's much like a differential in a car. If you use a used gearset and dont line it up and shim it like it was it will whine a little more.


A quick test, pull the drive gear on the side of the housing then try to maybe pry the driven gear towards the transmission output shaft. If you have a broken gear, this thing should move till it hits the shaft. However, it might not if the outer bearing hasn't came loose and is still press fitted to the shaft.
 
Thanks for the reply, I now know where you're talking about. As I mentioned I've changed the gears and since the noise is exactly the same with both sets I'll assume I haven't got an issue here. The trouble is with the noise coming in at 40+ it's a bit difficult to figure out exactly where it's coming from! No noise when the bike's run up on the stand even putting some loading on with the back brake. The gears / bearings were on sale on eBay at a price worth giving them a try so that's what I did. I also wanted to check the drive shaft etc. so was happy to pull things apart just for a check up.
To be honest, having established all seems fine with what I've checked, I'm just going to leave well alone now and keep riding. Your post just got me interested as the symptoms seem the same. When I get around to knocking up some rollers for the back wheel I'll hopefully be able to locate exactly where the noise is coming from, until then...... What the hell.
Colin
 
Well there is a setting backlash proceedure, make sure that is correct to minimize whine.
 
How common are these problems? With all the Gs that My brothers and I have had, we have never had any kind of drive shaft problem. I have replaced a hub spline once, but I had the wheel off for tires, inspected it, and it was worn so I changed it. I've Never seen a failure. I'm far from diligent on oil changes in the lubricants for the driveline, either.
 
81GS850 said:
That finally got it out... I destroyed the bearing housing thought before I got it out.. Im going to get a used gear set and throw it in there.
Click to expand...
No throwing allowed- these things were made as set and married for life. Fitup is critical- you'll likely have to play with shims to at least get it sorta close.
 
tom203 said:
No throwing allowed- these things were made as set and married for life. Fitup is critical- you'll likely have to play with shims to at least get it sorta close.
Click to expand...

Ive built a rear end before and understand the proceedure. I'll make sure to follow the manual to get it where it needs to be. But, this is a 60k bike so I'm not too concerned about whine.


850 combat, to answer ur question I've seen three including mine. Bikecliff has a writeup on his site about my exact problem. Then there's a thread titled one hundred and fifty seven feet Where the drive bearing locked up. I don't believe it's too common on low mile bikes but mines got 60k and it looks like it was hard miles.
 
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