Lambretta cassette clutches – Part 2: CP Smooth Master | REVIEW

So, you are looking for a decent Lambretta performance clutch and fancy one you can fit without a compressor tool?

I just removed an AF road after 8 years of abuse to fit a new Casa Performance Smooth Master. Here’s a close look at a those options:

AF RAYSPEED 6-PLATE ‘ROAD’ CLUTCH: From £235

AF’s 6-plate Road clutch is great VFM even if it isn’t perfectly concentric.

Look ma, no clutch compressor required!

What is it?

The 6-plate ‘Road’ is a cheaper, Indian-made 6-plate clutch which follows the design of the AF Rayspeed Surflex ‘Race’ clutch. Rayspeed had the Road version produced to fill in stock levels when they were struggling with supplies from Surflex.

Production costs have been reduced by machining components from castings rather than from billet. The clutch uses motorcycle style plates with a non-cork-based friction material and 12 ‘ears’ (tines) on each plate. A dedicated crownwheel is included with the kit in either 46T or 47T. An alternative crownwheel costs £80.

After 8 years of abuse it only needs new plates and a replacement bronze bush.

Fitting:

Assembly of the clutch could not be easier thanks to the ‘cassette’ design which allows the complete clutch to be removed and replaced as a single unit without need of a clutch compressor. The cassette arrives fully assembled and ready to bolt in.

A dedicated tool is included in the kit allowing you to hold the clutch while the centre nut is tightened. With no central tab washer the nut is now retained by a combination of Belleville washer and a dab of Loctite. The clutch centre actuator contains a bearing and is a simple push fit into position.

The one problem we found on assembly was that the crownwheel was not machined perfectly concentric. This resulted in a slight variation in chain tension as you rotate the clutch. This situation is less than ideal but relatively common even in standard clutches, poorly made crownwheel bushes or duff front sprockets. On the AF clutch the variation was not excessive and we simply adjusted the chain guides so that the chain never became too tight.

My AF Road Clutch has crossed many mountain ranges, including this one in Serbia.

In Use

The main objective of upgrading from the standard four friction plates is to obtain a clutch that can handle a greater power output without requiring a clutch lever action which would trouble Hercules. In that respect the AF Road is a reasonable compromise. It is stiffer than standard but still light enough at the lever that my wife can use it around town. Having said that; when I first met her she was an alligator wrestler in the circus.

The one down-side of the motorcycle style plates is that the clutch bites more suddenly than with traditional cork plates. It is not completely on or off, but the biting point is narrower than usual and requires some acclimatisation.

The AF clutch was first fitted to my Avanti TT225 test engine in possibly the most arduous configuration for testing a clutch: a torquey motor producing 20 ft/lbs and 4.4:1 final drive gearing (TV200 15×46). With that set-up the clutch would briefly slip in the higher gears when you set off and the engine was cold, but unlike a cork clutch which would quickly burn out if it started slipping, the AF Road seemed to grip harder once warm and would then behave normally. When used with the 5-speed Cyclone box and 19×46 sprockets the clutch spins faster so it has to transmit less torque. In that layout the AF clutch behaves impeccably.

PROS:
• The most obvious advantage is in cost. The Race version is built to tighter tolerances but costs £400 whereas the Road version retails for £225.
• Component parts are available separately (e.g. friction plates £22 a set)
• Weighs less than standard: only 1.6kg for complete clutch and crownwheel.

CONS:
• Only fits engines with GP-type side casings
• Machining not perfectly concentric or even tidy
• Narrower biting point
• Will slip when faced with really powerful engines.

Finishing of the AF Road clutch is best described as ‘rustic’

VERDICT:

It recently dawned on me that I’ve been using the AF Road clutch for eight years without ever once undoing the screws that hold the plates together. It was in my engine when I toured 15 European countries visiting Serbia and Ukraine. In all that time it’s never given me a moment’s grief and I’ve never needed to carry a clutch compressor. The clutch comes out as a single unit and goes back together the same way.

Upon stripping the engine recently I found that the ears on some of the aluminium clutch plates were mushroomed over and burred. One of the ears had even broken off and was lying in the oil, but this is after 8 years of abuse with various engine configurations up to 25hp. The rest of the clutch appears fine and certainly the steel Crownwheel looks good for reuse because the softer aluminium of the clutch plates have not sawed into it.

If you are building a very high-end engine producing over 25hp then this is probably not the clutch to go for. Certainly the original Surflex version is better made and will cope with more power before slipping. However for the majority of us, running more mildly tuned engines, then this is a very good value clutch system that is reliable and simple to fit.

It may not be the prettiest clutch on the planet, and a little ‘fettling’ to tidy it up any machining burrs before fitting is probably wise, but I certainly can’t criticise its performance or value for money. With a new set of clutch plates I’d expect it to do another eight years. Great value for money that!

You can find the clutch here, but AF Rayspeed haven’t really caught up with the web shop revolution yet so you’ll have to use Google to find somewhere to purchase one directly.

CASA PERFORMANCE 6-PLATE ‘SMOOTH MASTER’ CLUTCH – £610

CP’s confusing range of clutches are colour coded. The Power Master cush-drive clutch is green while the Smoot Master is gold anodised.

What is it?

The Smooth Master is Casa Performance’s new 6-plate cush-drive clutch that even fits into standard engine casings and side casings. It is a slightly simplified and slimmer version of the 7-plate Power Master clutch that is fitted to the SST and SSR 265 engines.

What does it do?

The 10-spring Smooth Master performs a few tricks that most other cutch systems don’t.
• Adjustable spring tension. By fitting either 5 or 10 springs you can vary the tension at the clutch lever. According to the Casa Performance boys, 5-springs should be fine for my TS1 and easy to pull at the lever even with a standard side casing. With the full 10-springs they reckon the Smooth Master should be able to handle 40hp but obviously the lever action will be much tougher. This is where the rack-and-pinion CasaCover, or the Chiselspeed clutch cover conversion, come in to reduce hand strain.
• The Smooth Master has a central pressure plate incorporating a thrust bearing, but the centres are swappable (two supplied) so it works with LI/SX/TV side casings unlike the AF one which only fits with GP side casings. The flat GP centre has a threaded hole to help extract it from the retaining O-ring.
• The other trick is that it incorporates four round rubber donuts in the Crownwheel which absorb harsh gear or clutch impacts, extending the life of the gearbox, chain and clutch.

The basket and sprocket are separate parts.

Doesn’t my Lambretta already have a cush drive?

If you already have a standard-type engine then yes it does, on the front sprocket. You could argue that you don’t need two systems doing the same job, however:

• There are engines that don’t have a front cush-drive, such as the BSG 305 and also Tino Sacchi’s Targa Twin. I didn’t think the gearchange felt that clunky on the Targa Twins that I tried recently at TD Customs in Germany. On the other hand prolific Brummie Lambretta customiser Gary Dickenson criticised the harshness of the clunk when he engages gear on his Targa 250. The Smooth Master clutch, with its inbuilt cush-drive, is a made-to-measure solution for the Targa Twins.
• A second cush-drive doesn’t do any harm in a Lambretta. Indeed it was the original solution the Innocenti fitted to the early LI models with their cush-drive Crownwheel. These sprung crownwheels seem to have been abandoned in favour of solid ones only because they were unreliable (prone to falling apart like Vespa ones) and more expensive to machine. A second cush-drive (that doesn’t fall apart!) should actually be a good thing for gearbox and chain life.

Construction

The Smooth Master has six friction plates which are Lambretta layout (six steel ears per plate, unlike AF’s 12 thicker aluminium ears per plate). The top and bottom plain plates are thick aluminium, the rest are steel.

The clutch centre can hold up to 10 springs. Assembly is by 10 Torx-head screws without need for a clutch compressor. Again the full cutch can be removed from the crownwheel as a unit once you remove the special slim clutch nut and washer from the centre.

Like the AF clutch a special holding tool is required to torque the centre nut, but no tab washer is needed.

Heat Treatment

One of the poshest features is something that you won’t see at all. Other clutch systems that are machined and then heat-treated tend to distort during the hardening process. This leads to eccentricity and variable chain tension exactly as found on the AF Road.

The previous Casa Performance solution was to have hardened parts ‘rectified’ after hardening which means re-machined after heat treatment to rectify any distortion and make things run perfectly concentric again.

More recently they have managed to skip the rectification stage by using another heat treatment solution which takes place in a vacuum and does not introduce significant distortion. What they spend in the considerable additional cost of the heat treatment they save in the parts not needing to be re-machined afterwards.

In Use

To me, with only 5-springs fitted the lever pull felt slightly tougher than the well-worn AF clutch but still perfectly manageable. It’s heavier than a standard clutch but you don’t need to be Charles Atlas.

So far I’ve not done many miles with the Smooth Master but I like the way it functions. There seems to be zero clutch drag so I can easily slip it into 1st and back to neutral at the traffic lights. So far the clutch hasn’t slipped either, but I still need to ride in top gear with a passenger which will really test whether 5 springs are sufficient or if I need to fit more.

As for the cush-drive element, yes the gearchange definitely feels smoother and less clunky. It’s a really noticeable improvement but it wasn’t so bad before that I considered it to be a problem. Think of it as a life without ice cream – if you never knew ice cream existed you could manage quite merrily without it. Once you know what ice cream tastes like though, it’s not a treat you’d like to live without.

However, if I had an expensive motor without a cush-drive on the front sprocket, then it might be a different story.

You can buy the Smooth Master here.

PROS:
• Will definitely improve the life of the transmission and protect the teeth of vulnerable Lambretta gearboxes.
• Adjustable spring pressure according to number of springs. In the future they plan to supply 2 different spring tensions so you can mix and match for four different set-ups from one clutch.
• The Crownwheel can be disassembled and alternate tooth number chain-rings can be fitted.
• Carefully machined and heat treated for concentricity
• The Crownwheel runs on a proper needle roller bearing and not a plain bush

CONS:
• Expensive – it’s far more than double the cost of an AF Road clutch
• Lambretta-style steel friction plates have fewer, slimmer ears than the AF clutch and therefore are more likely to mark the clutch bell.
• At a shade under 2kg the Smooth Master is heavier than a 1.6kg AF Road clutch but still lighter than an Innocenti 4-plate.

OTHER OPTIONS

There are so many good Lambretta clutches available on the market now that I’m constantly amazed that anyone thinks there’s a need for another.

Some other good alternatives that I’ve tested include:

LTH ‘Leidolsheim’ 7-plate. A motorcycle-plate solution the works great and is pretty much fit-and-forget. 480 Euros in steel or 566 Euros for the Ultralight version with an aluminium basket (shown above).

Readspeed ‘Red Devil’ 6-plate. This is an affordable evolution of the Lambretta design with a good quality centre spider, plates and Crownwheel. The Red Devil works well and costs £299.

Casa Performance ‘Power Master Standard’ 7-plate (Purple). This is a version CP’s highest performing clutch only without the Cush-drive basket in order to fit standard engines and side-casings. Priced at £470.

Text, images and videos: Sticky