Scura clutch swap

[Guest Mattress]

I'm confused. Or ignorant. You guys are talking about failing "clutches"; but previous pictures and above post about hairline fractures made me believe it is a "flywheel" failure.

 

Am I losing something in terminology or my understanding of the assembly? Do you use the word clutch to refer to the flywheel/clutch together?

 

If the flywheel is cast aluminum then I think it should be suspect. Aluminum has no true fatigue limit (stress below which no fatigue will occur) like steel; however you can design so that the component sees a stress that would result in no fatigue over component lifetime.

 

Above statement does not regard material defects. For aluminum castings, fatigue is very defect sensitive.

 

Point is I've taken away from these Scura discussions that it is not likely anything about one plate clutch, other than that if may be overstressing the aluminum flywheel, or the aluminum flywheels are dodgy.

 

Don't know why I care, I don't have a scura. I'd feel better riding with a wrought aluminium flywheel though.

[Ballacraine]

What's the vote on which is the best way to get at it? Crab the frame, or engine off the front?

 

Engine off the front is the way to go.

 

Nige.

 

I'm confused. Or ignorant. You guys are talking about failing "clutches"; but previous pictures and above post about hairline fractures made me believe it is a "flywheel" failure.

 

Am I losing something in terminology or my understanding of the assembly? Do you use the word clutch to refer to the flywheel/clutch together?

 

If the flywheel is cast aluminum then I think it should be suspect. Aluminum has no true fatigue limit (stress below which no fatigue will occur) like steel; however you can design so that the component sees a stress that would result in no fatigue over component lifetime.

 

Above statement does not regard material defects. For aluminum castings, fatigue is very defect sensitive.

 

Point is I've taken away from these Scura discussions that it is not likely anything about one plate clutch, other than that if may be overstressing the aluminum flywheel, or the aluminum flywheels are dodgy.

 

Don't know why I care, I don't have a scura. I'd feel better riding with a wrought aluminium flywheel though.

 

Sometimes the reference to 'Clutch' is an abbreviation for 'Clutch Assembly'....I think that may cause some confusion.

 

The flywheel is aluminium and the single plate clutch basket is bolted to it.

 

It is the flywheel that is the Achilles Heel.

 

Nige.

[Guest Mattress]

Engine off the front is the way to go.

 

Nige.

Sometimes the reference to 'Clutch' is an abbreviation for 'Clutch Assembly'....I think that may cause some confusion.

 

The flywheel is aluminium and the single plate clutch basket is bolted to it.

 

It is the flywheel that is the Achilles Heel.

 

Nige.

 

 

Thanks Nige. That clarifies it for me. And for what it is worth, I agree with you about the Flywheel. I have no data to support my belief, just intuition and my background as a metallurgist.

 

Aluminium is quite a bit less stiff than iron/steel too. I wonder if the clutch or clutch plates could be causing it to flex? Or maybe it was just a marginal design.

[mark.gilmore]

I think you are overreacting a bit. Theres been a few cases with pictures splashed all over this website and people go beserk. Considering the number of single plate machines made, Im not sure the faliure rate is any worse than the old 2 plate clutch. I know a guy who had one of those shatter on him too. I know, I know, you dudes who have had the failures think Im whistling in the cemetery. My Scura has over 10k miles on it and its works flawlessly. Its the best feeling cycle clutch I have, including the latest japanese hardware. At most, I think Id pull it and check the bolts for torque and inspect for any possible cracks in the flywheel but I prefer to keep my stock clutch.

 

This is what I thought.I had no reason to believe I had an issue.All I did was check, and look what I found.

 

 

 

http://www.v11lemans.com/forums/index.php?...st&p=103125

 

I must say I'm inclined to agree with KB on this one. Yes, my clutch might be a good 'un, but it might not, so I guess I'm going to have to pull it apart and at least look at it, for my own peace of mind. I'll keep the forum posted on what I find. What's the vote on which is the best way to get at it? Crab the frame, or engine off the front?

 

Engine off the front

[Ballacraine]

Thanks Nige. That clarifies it for me. And for what it is worth, I agree with you about the Flywheel. I have no data to support my belief, just intuition and my background as a metallurgist.

 

Aluminium is quite a bit less stiff than iron/steel too. I wonder if the clutch or clutch plates could be causing it to flex? Or maybe it was just a marginal design.

 

Very poor design IMO.

It would probably be fine in a race bike that gets torn down regularly, but it really is not suited to a road bike application. Too fragile.

 

I think there are a variety of contributory factors, most of which have been put forward on a lot of threads on this subject.

I don't want to try to re-iterate all of them here as I am bound to miss a few out

 

The ones that spring to my mind just now are:

 

The bolts may not have been correctly torqued at the initial assembly stage.

( Incorrectly calibrated torque wrenches or Luigi coming back after dinner with vino! )

 

The cross sectional area around the boss is not generous.

 

Aluminium may not be the best material to make a flywheel out of anyway? (Discuss! )

 

The alloy may be subject to creepage, allowing the bolts to work loose.

 

Contributory factor?

 

Tickover set too low, leading to hunting.

This not only adds to the single dry plate clatter, it may help shake those bolts loose?

Once the bolts are loosened off some, the rattle gets worse leading to fracture as the alloy flywheel crashes against the bolts??

 

Mine had a low tickover when I bought it.......I adjusted it.

When I dismantled to replace the clutch the bolts were not as tight as I was expecting and penetrant crack detection of the flywheel after strip down showed the start of cracks around the bolt holes. This was at less than 7,000miles.

 

Nige.

 

 

 

 

 

The one you mention could well be one too.

[mark.gilmore]

Very poor design IMO.

It would probably be fine in a race bike that gets torn down regularly, but it really is not suited to a road bike application. Too fragile.

 

I think there are a variety of contributory factors, most of which have been put forward on a lot of threads on this subject.

I don't want to try to re-iterate all of them here as I am bound to miss a few out

 

The ones that spring to my mind just now are:

 

The bolts may not have been correctly torqued at the initial assembly stage.

( Incorrectly calibrated torque wrenches or Luigi coming back after dinner with vino! )

 

The cross sectional area around the boss is not generous.

 

Aluminium may not be the best material to make a flywheel out of anyway? (Discuss! )

 

The alloy may be subject to creepage, allowing the bolts to work loose.

 

Contributory factor?

 

Tickover set too low, leading to hunting.

This not only adds to the single dry plate clatter, it may help shake those bolts loose?

Once the bolts are loosened off some, the rattle gets worse leading to fracture as the alloy flywheel crashes against the bolts??

 

Mine had a low tickover when I bought it.......I adjusted it.

When I dismantled to replace the clutch the bolts were not as tight as I was expecting and penetrant crack detection of the flywheel after strip down showed the start of cracks around the bolt holes. This was at less than 7,000miles.

 

Nige.

 

The one you mention could well be one too.

http://www.v11lemans.com/forums/index.php?...t&id=5940My bolts were all tight

 

 

 

 

http://www.v11lemans.com/forums/index.php?...&id=5947and this is why it made a clack-clack noise.

[mznyc]

Mark that is one ugly picture :!:

Has anyone had or know someone who's had a failure on an US spec bike.There's some debate that the US clutches are not affected.All I know is that clacking at idle is not confidence inspiring!

I'm planning on tearing it down at the end of the season to have a looksee.Cross my fingas till,.......

[mark.gilmore]

Mark that is one ugly picture :!:

Has anyone had or know someone who's had a failure on an US spec bike.There's some debate that the US clutches are not affected.All I know is that clacking at idle is not confidence inspiring!

I'm planning on tearing it down at the end of the season to have a looksee.Cross my fingas till,.......

 

splendid idea.

[Skeeve]

Very poor design IMO.

It would probably be fine in a race bike that gets torn down regularly, but it really is not suited to a road bike application. Too fragile.

 

I think there are a variety of contributory factors, most of which have been put forward on a lot of threads on this subject...

 

Aluminium may not be the best material to make a flywheel out of anyway? (Discuss! )

 

Just curious: how much weight is saved by the aluminum flywheel [assuming use of the RAM original, which has some basis for being "a proper design"] vs. a steel unit that has been properly lightened to the max safe level for longevity? IE: if we're talking a couple ounces of rotational inertia, a steel "race" single-plate clutch assembly clearly would be preferable to the aluminum RAM (or otherwise), no matter if it's a little more expensive: it's just always going to outlast the Al unit! If we're talking "oi, there's 1/4 kilo gone missing!" then I can see where someone who's always dicing it out w/ other sport bikes on fast rides might want the faster revving.

 

Of course, all this assumes that the location of the relative masses are mostly identitical; a steel clutch that's lighter than the aluminum version but has all it's mass concentrated at the periphery is still going to rev slower than an Al one w/ most of the weight near the rotational center. But you all know that, I'm just being redundant...

 

[Ballacraine]

TBH There is little difference, I can't remember the exact figures, although I did weigh them.

 

For a race bike there may be some benefit...For a road bike not.

 

I must admit I like the action of the original single plate Scura clutch and was loath to consider changing it.

I felt it was a time bomb waiting, so I made the effort to change it and was glad I did.

 

Road going, seat of pants comparison before and after?

 

Before:

 

Original was very sharp on drive uptake.....Not a problem, but worth knowing about before the first launch! Loved the revvy (for a large V twin shaftie) nature it gave the engine.

The clatter in neutral was disconcerting, even knowing that it was transmission backlash due to hunting at tickover rather than clutch chatter as such, and the shock loading would not have helped the cause of the alloy flywheel.

 

After installing 10 Spring V10 Clutch assembly:

 

Tickover smoother (slightly heavier flywheel helps)

Take up not quite as sharp.

Almost as rev happy as original unit. Which surprised me some.

 

Verdict.

 

Much prefer the V10 unit now installed.

 

Nige.

[pete roper]

To the best of my knowledge the original, *aftermarket* RAM units are pretty much unburstable. The problem with the Scura units was that some plank at Guzzi insisted they be re-engineered for the V11 Scura.

 

On the weight issue? I've ridden lots of bikes with RAM clutches. I've also ridden heaps with the late model twinplater with the very light steel flywheel and ring gear. IMHO the difference in the engine's ability to spin up and down is undetectable between the two. Perhaps if you're ridding 99% the whole time you *might* pick it. Personally I think that the main effect is psychological. The single plater does on the whole have a lighter feel and smoother take up but there are of course downsides.

 

Having a single plate, although it is slightly larger in surface area than an individual plate from the twin plater, it is still smaller and will wear quicker than the twin plater.

 

Removing more material from the wheel of the late lodel twin plate flywheel would be difficult. It's pretty much been shaved as far as it can be. What would be possible is milling some slots in the ring gear between the mounting bolts if you really wanted to. To be honest though I think that it would achieve very, very little.

 

As I've said before. I have no problem with the twin plater, but for those that wish to stick with a single plate unit? Buy a RAM. They work, they are proven and they probably aren't any more expensive than the twin plater. Damn sight cheaper than cutting the gearbox off the back of the block anyway!

 

Pete

[stogieBill]

I believe I'm going to stick with the single plate RAM replacement flywheel and clutch. However, I have been unable to find a source in the US. Does anybody know of a source for the after market RAM flywheel and clutch plate.

 

TIA

[max scura]

Saturday Agostini in Mandello changed my original clutch with another RAM kit (aftermarket,very similar to the original one....).After 30000 km it was perfect,also the flywheel....my Scura is the number 688,maybe Guzzi mounted a good kit on my bike....

[Greg Field]

The Cali single-platers can be cut to be lighter than a RAM, and being steel, you never have to worry about them cracking. I have one in my Eldo, and will put one in the Billy Bob when it's time for a clutch. I greatly prefer the action and feel of the single-platers. Early single-plates had very harsh engagement. With the latest plates, engagement is at least as gentle as on two-platers.

 

Oh, there's a loceal (Seattle) guy looking to sell a used RAM if anyone wants one. He's a drag-racer, and it has eight runs on it. He found he got better times with the heavier flywheel.

[Guest Mattress]

http://www.v11lemans.com/forums/index.php?...t&id=5940My bolts were all tight

 

 

From the picture it looks to be a casting, possible sand cast. They could have had a batch of bad castings. Might explain why some seem to have no problems.

 

Only way to know is to do a failure analysis, which is where a metallurgist would look at the fracture surfaces (or if part is whole, open up the crack and look - destructive test) under a scope for some casting defects. Still, if no defects present you can usually determine if it was material overload or fatigue.