77 GS750 Sprocket whine & chain adjustment

[93Bandit]

Howdy all,

I was finally able to get my 750 road worthy and took it for a proper 75 miles shakedown test ride over the weekend. Overall it ran pretty well but it still needs work. This being my first chain drive bike, I have a few questions.

Firstly, how much drive sprocket whine is normal? It's pretty loud from ~25mph up to 60+ (after 60 the wind noise starts to cover the whine sound, but it's still there). Doesn't matter what gear I'm in and is only present under load (cruising and accelerating). The sound goes away when I let off the throttle to coast. I have no idea how many miles are on the chain and sprockets. When I bought the bike the chain was pretty stiff and lots of surface rust. As I've been working on the engine, I periodically coat the chain in 90wt gear oil and spin the rear wheel by hand to try to revive it. Rear wheel spins a lot easier now. The rear sprocket doesn't look too worn, but I haven't taken the cover off to check the front sprocket yet.

Secondly, do you check chain tension/sag with the bike on the rear wheel or with the bike on the center stand? I read the service manual but it does not specify (unless I missed that part), however it looks like the bike is on the center stand in the images.

I do intend on replacing the chain and sprockets at some point but there are other areas of the bike that are in need of greater attention.

[rphillips]

Do 1/2" with bike on wheels & someone sitting on bike with their weight on the seat, measure middle ways between front & rear sprocket. Wouldn't adjust it on the center stand as it will tighten up a lot when dropping it down on it's wheels Also, with an older chain you will find lose & tight spots as you roll the bike, don't let the tight spots be too tight... Remember just my opinion.

[Gorminrider]

rphillips said what I would have per old chain tightspots and taking slack up against a weighted resting bike. But you can do it yourself just get on ,reach down and wiggle it yourself when you get the feel for the slack....you have to loosen chain before tightening-ie: give the wheel a kick forward with axle loosened, then tighten the axle a bit to make the adjuster-bolts work against the end of the swingarm... There are marks as you know-these generally work for me but the general consensus seems to be not to trust em-I'd investigate if they AREN'T accurate ...which goes to alignment etc..until you're satisfied it's ok anyways

but PER THE WHINING, I haven't ever had it from a chain but even so, do sight down the chain for straight between sprockets and look close at the chain as it goes onto the sprockets...Take the front sprocket cover off if you want to get serious) if it IS from the chain, it'd have to be the chain winding badly onto a sprocket? Ideally the chain would wind on easily and not be "polishing" one side of gear teeth. If you see weirdness, you might have an extra washer or wrong spacer on the axle...

[Rich82GS750TZ]

https://www.thegsresources.com/_forum/forum/technical-forums/-4-cylinder-engine-drivetrain-clutch/90411-chain-missing-an-o-ring

Bandito, I've linked the chain thread I created. My guess is if you took your your chain off you'll probably find it's roughly in the same condition as mine in this video that's in post # 22 of the thread.

Think about a 530 conversion. It wasn't the easiest thing I've ever done, But the help I got here gave me the courage I needed.

[93Bandit]

Thanks for the help guys.

I will do all these checks for tightness and straightness. As for the whining, I've ready threads where sprocket whine is discussed it some act like it's normal to a degree, but I suspect the whine I'm hearing is excessive. I'm swamped at work again so it'll probably be a while until I get the time to dig into this unfortunately. Seems like work is feast or famine.

Rich, I do intend on a 530 conversion eventually, thanks for the link to your thread. I just have more urgent issues to address first on the bike. Just gotta keep chipping away at it.

[Gorminrider]

Gearboxes can whine too. But I'm hoping it's not that because it's not really common on these bikes especially chain drives so it's probably not harmless.... example sound: old English cars particularly in reverse(Morris minors and the like) come to mind.

[rphillips]

My "99" Bandit has a strange gearbox whine, "only" in 4th, & "only" between appx.1500 & appx..2000 rpm. very prominent when there, absolutely nothing when not there. Was concerned when I first bought the bike, but has never been nor cause any problems. I still hear it but just don't even pay any attention to it anymore.

[Gorminrider]

huh. Interesting.^^ ... I really should listen closely- maybe I have some too- but if it's there, it's not as remarkable as you guys describe. Whine was really bad on the shaft-drive 650 though ,until I fixed it...

[rphillips]

On mine you don't need to listen closely, It almost sounds like a straight cut gear instead of helical. Very noticeable. Like said, I've had it a few yrs. now & a few K miles & no better no worse doesn't seem to affect anything. Only bike I've ever heard it on.

[93Bandit]

On mine you don't need to listen closely, It almost sounds like a straight cut gear instead of helical. Very noticeable. Like said, I've had it a few yrs. now & a few K miles & no better no worse doesn't seem to affect anything. Only bike I've ever heard it on.

That's a good description of the sound. Sounds exactly like a straight cut gearset.

[Rijko]

On mine you don't need to listen closely, It almost sounds like a straight cut gear instead of helical. Very noticeable. Like said, I've had it a few yrs. now & a few K miles & no better no worse doesn't seem to affect anything. Only bike I've ever heard it on.

Pretty common on the B12 I hear ... caused by riding low rpm in high gear.