New cush rubbers?

[wirespokes]

The 87 LM (owned it a year now) recently got a new clutch, not because it was worn out, but due to a notchy shallow trans input spline. I've heard the spline could have worn due to problems with the cush drive, so dismantled the rear wheel and found no corrosion with everything working as it should. The rubbers looked good so left them.

It's interesting how little wear it takes to hang up the clutch plates - I'd guess the notches weren't more than a couple thousandths deep.

I've heard of drilling holes in the rubbers to soften them. is that really necessary? The clutch feels fine now, and it's a huge improvement over the way it was before. I never could get the feel of when it would engage, it was different every time. I finally replaced the clutch when it wouldn't release at start up. 

Are the new rubbers any softer than the originals? Mine only have 35K and look perfect. I've heard the new ones are pretty much the same as the originals.

Now that it's working as it should, I don't want to find out next summer the splines are notchy again. What do you recommend?

[Tom]

Since you've already inspected them, I'd say leave them in and run the bike.  Next time you change out the rear tire, inspect them again and maybe drill them if needed.  The main thing is that you inspected them and have an idea as to their condition.  The "given" with that is also to do a whole drive-line inspection and maintenance.  U-joints, trans. output shaft...yada yada..lube.  etc.

[pehayes]

Just a clarification.  You won't 'drill' them, you will 'bore' them.  A drill bit would just grab and tear.  It wont cut the rubber.  Take a short piece (2" or 3") of thin wall steel tubing and file a sharp edge at one end.  Lathe or drill press helps here.  Use that tube the same as you would a drill bit.  The sharpened tube slices a neat rubber core through the rubber wedge leaving a hole.  IIRC, you can do three holes in each rubber wedge.  A  3/8" hole cloer to the tip point of the wedge and two side-by-side 1/4" holes nearer to the top of the wedge.  No magic precision here.

You would never personally feel the variance in drive line action due to this wedge modification.  The purpose is to ease or soften the individual engine pulse impacts along the u-joint and drive line splines.  It is a very tiny effect but improves component life over a long stretch of time.

Patrick Hayes
Fremont CA

[Tom]

Thanks for reminding me.  I actually started out that way with a drill bit, switched over to the gasket cutter tool when I saw that it was tearing.

[Matteo]

Nobody wants rubbers with a hole in them 

[guzziownr]

I used a regular bit and a drill press.  Made a little jig to hold it in place.  No tearing noted.

[acogoff]

     Just try freezing them first.

[Orange Guzzi]

You just had to start an argument over drilling, not drilling, taking every other one out, grease them or buy new ones.

[wirespokes]

Thanks guys.

Yeah, I have read about removing every other one, drilling holes and not drilling holes. Some even say to replace old ones since age hardens them.

This bike was 30 years old with 24K on the clock when I got it, and had something like four or five owners. The PO warned me (just like the rider's manual states) to ride it like a race bike. Whatever that means? Maybe they took that to mean - drag racing and compression braking, among other things? So who knows how it was treated before. I'm easy on clutches so hopefully everything will be just fine now.

Mark at Guzzi Classics has the impression shallow splines work as well as the deep ones, so perhaps it was some hard riding along with poor tuning that wore them. When I got it, the idle was around 1500 and the carbs were out of synch.

Ok, I'll wait until the tire wears out in eight or ten K and see how the rubbers look. By the way, how DO they look when they're going bad? I've got a durometer - anyone have a reading on good ones?

Matteo - yeah, holey rubbers aint no fun! Just this morning my sock got wet cause of one!

[Dinsdale]

My other bike is a DR650 - far cry from a Gutz.  However, the cush rubbers in them typically last around 15,000 to 20,000Km.  You can tell by annoying increase in backlash.  One thing which will extend their life is to give them a soak in oil, or better still, ATF.  New (or newly soaked in ATF) cush rubbers make quite a pleasant difference to your ride.

[wirespokes]

I'd never heard of soaking rubber in ATF to soften it. Do the DR rubbers look like they're made of the same stuff as the Guzzi?

[guzziownr]

Some oils contain ingredients that swell and soften the rubber seals to prevent leaks.  That's why a bike that has been sitting for a long time will leak as the seals dry out.  ATF has the same stuff, just more of it.

[wirespokes]

Good point! I wasn't thinking of that. Thanks.