New Clutch Hub Won't Slide On

[wirespokes]

Here I am working on another Guzzi clutch. The plates are within spec with good splines, but the flywheel and clutch hub were toast.

Putting the bike back together today I tried putting the hub on the transmission input shaft. Nope! Wouldn't go, no matter how many times I tried.

As it turned out, the last machining operation on the hub was something to do with beveling back the top of the splines. That left burrs on the teeth faces which prevented engagement.

The hub is hardened, so removing the burrs wasn't an easy thing - took about an hour with a small fine tooth triangular file.

Hopefully this one I got is a one-time thing, and none of you will run into the same problem. But if you do - you now have the answer.

[acogoff]

     I had to do the same thing about 5 years ago. Must have been from the same batch.

[Antietam Classic Cycle]

Here I am working on another Guzzi clutch. The plates are within spec with good splines, but the flywheel and clutch hub were toast.

Putting the bike back together today I tried putting the hub on the transmission input shaft. Nope! Wouldn't go, no matter how many times I tried.

As it turned out, the last machining operation on the hub was something to do with beveling back the top of the splines. That left burrs on the teeth faces which prevented engagement.

The hub is hardened, so removing the burrs wasn't an easy thing - took about an hour with a small fine tooth triangular file.

Hopefully this one I got is a one-time thing, and none of you will run into the same problem. But if you do - you now have the answer.

The latest batch of these hubs does fit tightly on the input shaft. What I do is press it on and off of a spare shaft a few times, until it can be installed and removed by hand.

I'll not complain about having to do this though - previous batches were too loose on the shaft, splines broached too deep, and would leak because the o-ring wouldn't seal.

[wirespokes]

Yeah, I'm not complaining about the fit - no quarrel there. But it wouldn't mate up, wouldn't even start to mate up. Getting rid of the burrs was what was needed.

A loose fit? No thank you! How did you seal them up? What a pain to go back in there for a leak and find it's the loose fitting hub. Was it undersize at the sealing surface?

Andrew at MG Cycle got back to me and said they check them ever since they got a bad batch four years ago. I don't think he wanted to admit that one possibly got past the inspection process, because mine would definitely have failed! It wasn't tight - it wouldn't even begin to go on.

So I got up early and got it all back together a little after noon. The gods did smile on me, though - you know how difficult it can be to mate up the driveshaft to the transmission? I've usually had to remove the final drive and it still can take an hour or two. This time I tried something different. I've got a bike jack, one of those small scissors lift tables, so I positioned it under the swingarm, final drive attached, and lifted it into position. Didn't take more than five minute to get things lined up well enough the splines slid together. I should have attached the boot while I was there, because doing it later when the bike was back on the ground was a challenge.

[Antietam Classic Cycle]

Yeah, I'm not complaining about the fit - no quarrel there. But it wouldn't mate up, wouldn't even start to mate up. Getting rid of the burrs was what was needed.

A loose fit? No thank you! How did you seal them up? What a pain to go back in there for a leak and find it's the loose fitting hub. Was it undersize at the sealing surface?

Andrew at MG Cycle got back to me and said they check them ever since they got a bad batch four years ago. I don't think he wanted to admit that one possibly got past the inspection process, because mine would definitely have failed! It wasn't tight - it wouldn't even begin to go on.

So I got up early and got it all back together a little after noon. The gods did smile on me, though - you know how difficult it can be to mate up the driveshaft to the transmission? I've usually had to remove the final drive and it still can take an hour or two. This time I tried something different. I've got a bike jack, one of those small scissors lift tables, so I positioned it under the swingarm, final drive attached, and lifted it into position. Didn't take more than five minute to get things lined up well enough the splines slid together. I should have attached the boot while I was there, because doing it later when the bike was back on the ground was a challenge.

The latest ones won't start, but you can feel when the splines are lined up. I used a press the first time, but just biffed it on and off the spare shaft with a dead-blow hammer last time. A few repetitions and it was good to go. I'm basically using the spare shaft as a broach.

I also polish the surface the seal runs on with a green Scotchbrite pad.

We (Mark Etheridge and I) use the same product to seal the "loose" ones - Permatex "The Right Stuff". I didn't have to go back in for any leaks - I could see it was going to be an issue during installation and preemptively applied sealer. I use a thin smear of it on all of them now. There were the correct i.d. where they sealed against the o-ring, but as I wrote, the splines were broached too deep and the splines extended into that seal surface.

[wirespokes]

Wish I'd known before assembling the thing. I'd have put some sealer on the splines.

There's a groove between the end of the splines and the last 1/2" of the unsplined end of the shaft. I wondered if that groove was for an oring.

In the five or six clutches I've worked on, none (that I know of) have leaked at the clutch hub. Maybe I've been lucky? Next time (and I'm pretty sure there will be, not that I'm anticipating anything) I'll be sure to seal those splines rather than lube them.

Thanks, Charlie!

[Antietam Classic Cycle]

Wish I'd known before assembling the thing. I'd have put some sealer on the splines.

There's a groove between the end of the splines and the last 1/2" of the unsplined end of the shaft. I wondered if that groove was for an oring.

In the five or six clutches I've worked on, none (that I know of) have leaked at the clutch hub. Maybe I've been lucky? Next time (and I'm pretty sure there will be, not that I'm anticipating anything) I'll be sure to seal those splines rather than lube them.

Thanks, Charlie!

I apply the sealer just as a precaution - hurts nothing, costs nearly nothing. I loathe having any leaks...

That groove inside the hub isn't for an o-ring, the o-rings are on the shaft - a thick one in the groove and a thin one against the bearing.

[wirespokes]

Yeah, I know that groove isn't for an o-ring, which would most likely get sliced up sliding over the splines.

Thanks for your help!  I'll be sure to use sealer next time.