GS650 gearbox or final drive?

[Anonymous]

I'll ask again because this wasn't on the old forum for long before it was replaced by the (excellent, well done folks) new one.

My GS650 Katana (shaft drive) developed a horrible noise recently. There's a rough whining noise that increases in pitch with speed - much worse in 3rd, 4th and 5th and getting higher in pitch all the time. It disappears completely when the throttle is closed or when I pulled in the clutch. The motor runs perfectly and all gears are present so I'm assuming it's the output shaft or the final drive shaft.

Other than basic disassembly, all of this is Suzuki dealer stuff according to the manual but has anyone any experience of this? Any opinions would be appreciated.

 

[Anonymous]

Probably the clutch itself

Probably the clutch itself

NOTICE: My knowledge is currently limited to automobiles. I understand that most things will apply to motorcycles but somethings will be different!


When you pull in the clutch, the only thing that happens is the gear box disconnects from the engine. The drive shaft still spins and to the best of my knowledge, so does the gear box.

While going down the highway, if you hit the throttle while in 4th or 5th does it feel like the transmission slips a little? Is the clutch a little mushy when shifting?

My guess with my limited knowledge is that your problem is in the clutch itself. If it was in a manual transmission car, I would guess that the sound you are hearing is caused the the clutch plates slipping against each other. I don't know of motorcycles use similiar clutch plates. I have not bought a repair manual for my GS650GL yet. Maybe some other members on the site can tell us how to check the clutch.

 

[Anonymous]

Mmm, I hadn't thought of the clutch. I started the motor again at the weekend and listened to the noise - it seems to be in the engine cases all right.

The noise appeared suddenly after a gearchange as I accelerated in 3rd. The clutch seemed to shift okay as I limped home. I didn't notice any slip but I wasn't accelerating hard in case I broke something else (you know, left hand poised over the clutch like I was back on a 2-stroke again!).

Anyway, I'll consult the Clymer manual and see what it says about checking out the clutch. First time I've ever wished for a 'simple' clutch problem to fix!

Thanks for the advice.

 

[mcconnell]

GS650 gearbox or final drive?

With the change over from the old forum to the new, I don't know if you got my earlier responses to this.

Your descriptions still sound like a broken secondary drive. With the bearing preload gone, the gears are not aligned and make a loud whine when under load, and no noise when not under load, ie, accelerating and decelerating. A quick test: Unclamp and pull back the rubber boot where the drive exits the engine/transmission case until you can see the drive shaft coupling. Poke it with a screw driver and see if it moves side-to-side or forward-backward. There should be no movement.

By the way, my experience with two worn out clutches on my '83GS1100GD show no noise with a slipping clutch, except for the engine revving with little or no bike acceleration.

 

[Anonymous]

I hadn't seen your earlier reply so thanks for that info. I'll take a look at the drive shaft coupling.

 

[Anonymous]

You're right about the secondary driven gear - the universal coupling can be moved side to side and up and down. Looking at the exploded view in the manual, there are two bearings in this assembly and I presume at least one has broken up.

I'm out of my depth now, so here's a stupid question in the hope that somebody knows the answer - the Clymer manual says this assembly can be extracted without stripping the whole engine. If so, and I have it professionally rebuilt, will it go back in again and still have the correct engagement and gear backlash? The manual doesn't say but it's full of dire warnings of expensive gearbox damage if it's not done right.

On the other hand, if repair means splitting the crankcases, this'll be a longer-term project and I'll start saving now for a rebuild.

 

[mcconnell]

GS650 gearbox or final drive?

At least on the GS1100G, the part can be replaced with the engine in the frame; just loosen all the engine mounts to get that additional 1/16 inch of clearance you need.
And loosen the engine case bolts around the secondary drive unit so it can be GENTLY pried out of the case. This is after you have removed the rear wheel and swing arm.

As far as the shims to set the backlash, maybe I was just lucky, but I tranferred the shims from my bike to the new parts, bolted back together, and everything is quiet. The presumption on my part is quiet is good.

The replacement parts cost me $100 at the salvage yard, though I got other quotes up to $175 for just the parts (both the driven and drive gear sets. They are a matched set)

 

[Anonymous]

That's exactly what I wanted to hear!

I'll take the unit out first and see what I'm dealing with but at least I know it's possible - hopefully on the 650 too. And it never hurts if I seem to know what I'm talking about when I go looking for parts! Thanks for your help.