An FYI on front hubs/differences

[DanTheMan]

I just found out this little tidbit yesterday while I was putting my new front tire on my bike. I'd installed the new tire on my spare front rim off the '81 GS850G parts bike I have in the garage.
The hubs have a very slight difference in o.d. where the speedo drive sits. The one from my '80 GL has the speedo drive lip outside the hub, the one from the '81 G has the speedo drive inside the hub. The speedo drive from my '80 won't work on the '81 and vice versa. Nearly wrecked my speedo cable with this discovery. I had it all together, and went to spin the wheel, and it wouldn't spin, the speedo drive was trying to rotate with it. At least I caught it before any real damage was done. I had the wheel real clean, and the inside lip of the speedo drive as well. I put the one from the '81 on, and all seems to be well. I'll know for sure when I can take it for a ride when the snow leaves again (1/2" on the ground now).

 

[GS750]

Was the drive unit meshed into the hub correctly??

I have also found this problem a few times and I have previously noted slight differences in the width of the teeth on the ] piece that meshes into the wheel.

If they dont fit they are an easy changeover.

 

[DanTheMan]

Was the drive unit meshed into the hub correctly??

I have also found this problem a few times and I have previously noted slight differences in the width of the teeth on the ] piece that meshes into the wheel.

If they dont fit they are an easy changeover.

Actually, it was. It was so close, but there's a difference in circumference on the od of the two hubs. I haven't measured it with a micrometer, but it's only enough to jam up the speedometer drive that fits over the hub flange rather than inside. I had wire brushed the flange clean of all dirt and grease as well.

The teeth appeared to be the same width. It just bugged me because I had to pull the wheel again.

 

[salty_monk]

Nothing careful use of a dremel couldn't sort out it seems....

 

[DanTheMan]

Actually, I just discovered the difference. I'm close to non-observant sometimes. I was replacing the wheel bearings in my "new" front wheel (found a wobble at 70 mph, one wheel bearing had some slop in it) so I looked more closely at both wheels, the one off my '80 GL has just the aluminum hub flange the speedo gear fits over, the one off the '81 G has an extra sheet metal flange over and around the actual hub the speedo gear fits inside of. So, on a fische, the part numbers will be different. In actuality, the gear from an '80 will work on the '81 by removing the sheet metal flange, but if you use the '81 gear on an '80 there will be a lot more crud that gets in around your wheel bearing as there will be no dirt/water shielding.

 

[BassCliff]

Hi Dan,

Do you remember that Johnny Cash song, the one about the guy working at the auto plant? He would sneak a part home every day in his lunch pail. Eventually, after 20 years or so, he had himself a Cadillac.

"The transmission was a '53
And the motor turned out to be a '73
And when we tried to put in the bolts all the holes were gone."

"I got it one piece at a time
And it didn't cost me a dime
You'll know it's me when I come through your town
I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is around."

I don't know why, but your post made me think of this song.


Thank you for your indulgence,

BassCliff

 

[DanTheMan]

I remember that song, never did see a picture of the end product though, just had one in my head.

I really don't know what made you think of that either......^o

 

[GS750]

yeah I knew that song too, Kind of reminds me of my bike lmfao!

 

[Chuck78]

I know it's two years later, but has anyone noticed any width differences on the speedo drives? I put 81 GS650GT forks on my bike to get dual discs, and the forks are the same width at the triples, but 4mm narrower where the axle bolts in. The speedo drive needs to be narrower to use the spoked wheel that I just built or the original 77 GS750 wheel in these.

I do remember seeing some different parts listings for 77 vs78-79, so I think maybe my 77 fork is possibly the anomaly, especially because I have seen GS650E models with spoke wheels but this GS650GT shafty had mag wheels, I assume they both use the same fork legs???? HELP!!!!