Clunk when pulling away

[stewgnu]

Hi All,

I've noticed a bit of a clunk when moving off.  (And also occasionally when changing up a gear whilst feeding clutch out slowly).

I popped the bike on a stand and there does seem to be a lot of play in the driveline- the wheel will turn a good inch or so fore and back before the prop turns.

Any help/pointers on this would be great.

 

Stew.

[docc]

The wheel motion / play is normal. What is not normal is if the noise/feel has changed suddenly.

 

Check for slop in the U-joints of the drive shaft, inspect the wheel bearings (especially the rear), that all of the engine/chassis mounting bolts are present and accounted for, look at the two bushings of the "torque reaction rod" above the rear drive.

[emry]

I was thinking torque rod, my bushing were dust after 8k miles.

[The Monkey]

If the little needle bearing in the nose of the bevel box is shot that could also produce such a clunk. grab your bevel and look for excessive movement. Likewise the needle bearing associated with the drive line itself (inside the bevel) grab your driveshaft and see if it swims about at the aft end.

[stewgnu]

Cheers fellas, I did notice a small amount of play in the wheel bearing, didn't think it was too bad but i'll check the other bits too.

 

Ta,

Stew

[guzzimeister]

Hi

 

one other pointer. On mine the prop shaft coupling to the bevel box was loose on the shaft despite tightening the pinch bolts as hard as I dared. I cured this by disconnecting the shaft from the bevel box, smearing Quicksteel (metal loaded epoxy) over the shaft and reassembling. The bevel box pivot bearing is the most likely culprit, it's an unsealed very cheap roller bearing which rusts to nothing in 2 years if not regularly greased. This allows the box to wobble on the wheel spindle producing the clunk as play is taken up under load.

 

Cheers

 

Guzz

[stewgnu]

Knackered bevel box needle bearing definitely part of the problem, loads of play, seems crushed.  I suspect by me.

Been reading the old threads on removal as it does seem to be a git to extract...

[stewgnu]

Okey dokey.

New bearings now fitted in bevel box (...terrible things I have seen...i am now emotionally scarred... ).

This has most definitely taken up a measure of clunkage (new word born right there) in the system.  But not all of it.

 

So... next is the torque rod bushins as there's play in the arm.

I've had a search thru old posts, so sincere apologies if this is old ground, but was there any consensus on getting replacements?

There was mention of a Fiat matching part??  Did anyone get a part number?

 

Stew

[Zooter]

Much of this is beyond what I have gathered so far, but seems like a basic maintenance item neglected. Pointers gratefully received.

[stewgnu]

Yep.  I think it's on the 'Rear wheel checklist' and I, for one, will be greasing that badger up like a piggy every time it comes off.  (Plus rotating the inner race).

 

Still getting a measure of clunkathon though....

[stewgnu]

The wheel motion / play is normal. What is not normal is if the noise/feel has changed suddenly.

 

Check for slop in the U-joints of the drive shaft, inspect the wheel bearings (especially the rear), that all of the engine/chassis mounting bolts are present and accounted for, look at the two bushings of the "torque reaction rod" above the rear drive.

 

Docc, what am I looking for with regards to checking for 'slop' at the ujs?

[docc]

I'm likely not the expert on that, but we'll get some help here, momentarily.

 

For certain, check that the pinch bolts both fore and aft are not loose allowing slop at the collars which should pinch down tight to the output/input shafts. If the drive shaft has ever been taken off, it's a bugger to get the collar lined up perfectly that the pinch bolts don't crossthread.

 

With the wheel off, it's easy to remove the entire rear drive by separating the shaft. ( mind the alignment mark or make one!) The U-joints should have no play in any direction and rotate in both directions without any grinding or popping.

 

Good luck getting grease into both the back and front. Don't put more than a film of grease on the splines or it won't want to go back together (forms a pneumatic trap).

[stewgnu]

Heh, yes I had the box off to replace the bearings and there's still the factory yellow blob on mine for prop alignment.

Thankfully the u/j's seem pretty solid as far as I can tell.

I'd read a few threads on this area so was somewhat prepared for some of the foibles (I ended up leaving one of the prop splines kinda dry-ish to aid refit and she popped on with a small fart).

 

All those posts on greasing the front u/j!  Guzzisti must be recognisable by worn tooth enamel...  I managed to bend a gun tip in my garage door that'll juuust poke thru the swinging arm and latch on.

[stewgnu]

Update:

New wheel bearings fitted, cush stripped, cleaned, + drilled, new oil in backbox, installed rossopuro reaction rod (thanks Harry) fitted with new rose joints.

 

Clunk is gone!  C'est magnifique!

Admittedly the exact source of the problem still remains unidentified as I did everything all in one go, but I'd guess wheel bearings as per docc's original advice.

 

Added bonus in fitment of crossover-less headers (thanks Harry!) : Access to alt cover improved plus bike looks wayyy better, sounds even more rrrockin and, is it my imagination (?) but she seems to pull more strongly too!

 

Damn these bikes are fine.

[sp838]

Jealous of your rossopuro reaction rod. I looked everywhere, including contacting them directly, and couldn't find one. I went with the Ghezzi Brian rod, which is nice, but not as cool as the RP billet one.