GS850GZ final drive failure

[Anonymous]

My GS850GZ final drive has failed without warning. I've only had the bike since December and there's been no indication of any problems like noises or noticable drive slack.

Everything was fine as I drifted out of home on my way to work the other morning. I always take it easy to warm the bike before the first major road where you can't hang around. About 100 meters down the street and hang a left, changing back to 2nd for the corner, into 3rd and back into second for a right at a roundabout. As I straightened out of the roundabout I thought I'd missed a gear (it was 6:30am) because the bike lost drive. Flicking the left foot changed gears but still no drive. Right then it was obvious trouble was afoot in the final drive from the slight clicking in that area. My mechanic reports that the rear(boss and shaft) have stripped. One second hand replacement being fitted.

My experience says GS final failures aren't common. Anyone care to comment?

(Had to push the bike half a block to a friend's place. That was not fun! At least it didn't break in the tollway tunnel or too far from home).

[SqDancerLynn1]

Not sure what you are refering to. there is a gear that bolts to the wheel that drives the differential??? Failure is usually caused by a lack of lubrication, requires a genorous application of thick chassis grease, normally done whenever the wheel is removed

[Anonymous]

They're not only uncommon, yours is the first failure of this kind I've read about (in normal street riding). Maybe the prior owner didn't keep up on gear oil levels at the mid and rear of the system?

[Anonymous]

Not sure what you are refering to. there is a gear that bolts to the wheel that drives the differential??? Failure is usually caused by a lack of lubrication, requires a genorous application of thick chassis grease, normally done whenever the wheel is removed

There's a boss bolted to the wheel with an inside spine. This mates with the output shaft of the final drive. It's well maintained now, but I guess that's no indication of past maintenance. I'll get a look at it next week when I collect the bike.

The shaft drive gears are in good condition.

My shop has never seen this failure before. My family and friends have owned 4 GS' over the years and it's a new one on me except for an 1100 owned by my brother which failed at 120,000km due to a manufacturing flaw in one of the front bevel gears.

Stuff happens 'suppose.

[Anonymous]

If I'm reading this correctly, the failure is attributed by the owner to the rear end unit. I've owned 5 GS shafties since 1986: four consecutive 850's and now an 1100GK, for a total of almost 200,000 miles. Not one failure on any of these rear ends. I've never even heard of failure by anyone else.

What does fail, and what I suspect has happened, is that the "driven gear", the unit that has six prongs that is installed on the rear wheel, stripped the teeth. This happened to me in 1987 on my first GS850GZ, a 1982 model. Reason: lack of lubrication. These teeth should be liberally coated with thick black moly grease every time the rear wheel is off. Not one failure of this kind since 1987. To be sure, I remove and inspect this driven gear for worn teeth every time the wheel is off. I also have two rear wheels, each with its own driven gear, which I alternate.

One more item: the 1982 and 83 GS850G driven gear is made of softer metal than the early 850's. I use early 850 (79 and 80) driven gears on my GK. They all interchange perfectly.

Nick

[Anonymous]

If I'm reading this correctly, the failure is attributed by the owner to the rear end unit. I've owned 5 GS shafties since 1986: four consecutive 850's and now an 1100GK, for a total of almost 200,000 miles. Not one failure on any of these rear ends. I've never even heard of failure by anyone else.

What does fail, and what I suspect has happened, is that the "driven gear", the unit that has six prongs that is installed on the rear wheel, stripped the teeth. This happened to me in 1987 on my first GS850GZ, a 1982 model. Reason: lack of lubrication. These teeth should be liberally coated with thick black moly grease every time the rear wheel is off. Not one failure of this kind since 1987. To be sure, I remove and inspect this driven gear for worn teeth every time the wheel is off. I also have two rear wheels, each with its own driven gear, which I alternate.

One more item: the 1982 and 83 GS850G driven gear is made of softer metal than the early 850's. I use early 850 (79 and 80) driven gears on my GK. They all interchange perfectly.

Nick

Picked up the repaired bike this afternoon and had a look at the old unit. The driven gear was the main cause (stripped) and the output shaft was worn, so replaced the shaft unit and driven boss to be sure. Reckon there's less drive slack now - but that could be imagination.

It's great to have the wheels back.