Surflex S1425 Clutch Kit...

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Miti
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Surflex S1425 Clutch Kit...

Post by Miti » Mon Jun 15, 2015 2:44 pm

Hi Folks;

I spent a few moments wondering exactly where to post this enquiry as the Surflex clutch noted in the title appears to fit so many Ducati models... 750GT/S/SS/GTS 860 GT/SS 900 SS/HRI/SD (and perhaps more).

It also fits the Hesketh V1000... Especially mine, which has a pre-producton engine... Parts of this may appear familiar to some:

Image

So, apologies if this thread appears in the wrong board (I'm sure admin will help me out if it is) as it's clearly not a Squarecase engine... ;)

My problem is that the clutch is slipping... Not horribly, but bad enough... :cry:

I've spent AGES getting this auld beast to run well and now that she is, the clutch starts to let go at around 4K rpm...

It was happening last year whilst we were in Holland for the Hesketh Owner's Club annual rally... This year she's had a chassis rebuild, new tyres, new chain and sprockets (rear changed from 48T to 46T, which is 'standard') an oil change (Millers ZSS 10W40, same as last year) and a new exhaust system (VERY fruity..!).

The new pipes really let the engine breathe properly and, combined with the new gearing, the bike is running really well... Apart from the clutch slip...

I pulled off the cover to check the various bits and pieces last year... But, the measurements of the Surflex parts doesn't match the spec I have in the original Hesketh manual (that is, if they are ALL Surflex parts..?) The Surflex site doesn't give min/max spring lengths and plate thicknesses, and I'm using old catalogue info to determine how many plates there should be in there...

I have a set of NOS Hesketh plates too - less of them in the stack, thicker friction plates...

So... Could anyone kindly advise what the min thickness should be for Surflex plates (steel and friction) and what, if anything, are the recognoseable differences between the various weights of springs available> Or even how to test the weight of these springs..?

I did search through the forum for "Clutch Slip" prior to posting... Found one thread referencing synthetic oil (the ZSS is semi-synth) which really help (I have seen probs with other bikes and modern oils with an abundance of friction modifiers).

Any help/advice gratefully accepted. -*!^-

Miti
Jeff Mitchell
Scotland
'82 Hesketh V1000 (Pre-production Engine)
'80 XS1100 'Midnight Special'
'81 XS1100 'Sport' (Trike Project)
'85 XS1100 'Sport (RedSport Project)

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Craig in France
Cagiva Gran Canyon
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Re: Surflex S1425 Clutch Kit...

Post by Craig in France » Tue Jun 16, 2015 12:16 am

Hi Jeff,

FWIW ...
Miti wrote:Could anyone kindly advise what the min thickness should be for Surflex plates (steel and friction) ...
The factory gave a specification for the clutch pack as an assembly: "not less than 37.5mm" (from a nominal of 40mm). There's no spec. for individual plates, altho' it may help as a guide that Laverda, who also used Surflex clutches, specified a minimum fiction plate thickness of 2.5mm.
Miti wrote:and what, if anything, are the recognoseable differences between the various weights of springs available> Or even how to test the weight of these springs..?
Again according to the factory manual(s), the standard spring length should be "not less than 28.9mm" (from a nominal of 30.4mm). However, it was/is a well-known 'fix' to install (at least) 3 of the stronger springs from the 450 single engine. According to the factory manual, the spec. for these 450 springs is:
"The initial length of each new spring is about 27.5mm and it takes a 21 kg weight to compress the spring down to 20mm".
Miti wrote:I did search through the forum for "Clutch Slip" prior to posting... Found one thread referencing synthetic oil ...
You shouldn't have any problem with synthetic oil - after all, Ducati specified the use of synthetic from 1976 onwards ;) . However, if you've previously used a mineral oil before switching to synthetic, you might get slip. Just wash the plates in paraffin, dry and re-fit.

HTH

Craig

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Miti
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Re: Surflex S1425 Clutch Kit...

Post by Miti » Tue Jun 16, 2015 1:54 am

Hi Craig;

Thanks for that, it's very useful info... The springs in my bike are MUCH longer than the spec quoted in the Hesketh manual... I know my bike has a pre-production engine, used to trial various mods before they were approved for production use (look how well that worked..) :~

Looks like the side cover is coming off again at the weekend (thank heavens for semi-setting flange sealants, eh..?)

The first time I took the clutch apart, I found that the plate stack didn't have the same number of plates as per the manual... I added an extra metal plate, which brought it up to the same number as the Surflex catalogue, but hasn't fixed the slippage problem... No noticeable difference actually... Are there any tips to do with altering the stack height for performance engines..? (I'm actually more concerned about the weight of the Hesketh having an adverse effect, not the power output...)

Many thanks

Miti
Jeff Mitchell
Scotland
'82 Hesketh V1000 (Pre-production Engine)
'80 XS1100 'Midnight Special'
'81 XS1100 'Sport' (Trike Project)
'85 XS1100 'Sport (RedSport Project)

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Craig in France
Cagiva Gran Canyon
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Re: Surflex S1425 Clutch Kit...

Post by Craig in France » Tue Jun 16, 2015 11:02 am

Miti wrote:The first time I took the clutch apart, I found that the plate stack didn't have the same number of plates as per the manual. I added an extra metal plate, which brought it up to the same number as the Surflex catalogue, but hasn't fixed the slippage problem.
I can't say for your bike, but essentially the Ducrappi clutch uses 8 friction plates and 8 plain plates. But there were variations ... :shock:. For example:

a) On the 1975-76 750/900SS models, all 8 friction and all 8 plain plates were the same.
b) On the 860 models (1977), the FIRST plain plate was a special - it's tangs are bent. This plate is fitted with the bent tangs pointing OUTWARDS.
c) By 1979, on the later 900 models (Darmah), things had changed again: it was now the LAST plain plate that was the special. This time the plate is inserted with the tangs pointing INWARDS.

Also:
In the 860 parts book, the first friction plate is also listed as a special, with its bent teeth being installed pointing OUT. In the later 900 parts book, this plate is also marked as a special; but I can't now remember if this is right, and the factory manual makes no mention of it.

What I suspect you see here is a gradual refinement by Surflex of their product. But what it all means for you, I really can't say ... :er:
Miti wrote:Are there any tips to do with altering the stack height for performance engines..?
Outside my realm of expertise, I'm afraid (and hey, let's be honest. These aren't really high performance engines, are they? Not then, not now ... ;)) . That said, I suspect your problem is down to tired/incorrect springs ...

P.s Do also check the flatness of the pressure plate. If this is bent, it can give rise to problems.

Ciao

Craig

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Miti
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Re: Surflex S1425 Clutch Kit...

Post by Miti » Tue Jun 16, 2015 2:14 pm

Thanks Craig, that helps a lot...

I have one plate with bent teeth... It will fit either at the bottom of the stack, if the teeth bend outward - if bent inward, the teeth "bottom out" in the clutch basket slots before the plate is actually at the bottom of the basket...

Or at the top of the stack, if the teeth are bent inward - if bent outward in this position, the teeth don't engage with the basket slots at all...

Now, if only I could remember which position I ended up putting it in... :roll: :roll:

Oil out and casing off tomorrow methinks...

Miti
Jeff Mitchell
Scotland
'82 Hesketh V1000 (Pre-production Engine)
'80 XS1100 'Midnight Special'
'81 XS1100 'Sport' (Trike Project)
'85 XS1100 'Sport (RedSport Project)

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Miti
Cucciolo - the Lil Pup
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Joined: Sun Jun 14, 2015 2:37 pm
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Re: Surflex S1425 Clutch Kit...

Post by Miti » Wed Jun 17, 2015 12:15 pm

OK... It's all in bits (again) :roll:

There are nine friction pales (all with the Surflex Logo) and they's all approx 3.4mm thick...

Eight flat friction plates - each 1.5mm thick

One "bent tooth" friction plate - also 1.5mm thick (it was at the top, facing inwards)

Stack height is 44.4mm

But the springs are obviously "alien". The shortest is 42.25mm, longest is 42.5mm...

The Hesketh manual shows nine friction and eight plain plates (I added the extra plain plate). The spec for the friction plates is std = 3.25mm with a min thickness = 2.75mm (ALL of mine exceed the std thicknes). Spring free length is given as 36mm, replace at 35mm...

Ah well... at least I know I can't swap my springs for the heavier Surflex items... Dunno how I'm going to test the spring weight..? I certainly don't have any handy 20Kg weights... SWonder if any body-builder pals could help..?

;)

Miti
Jeff Mitchell
Scotland
'82 Hesketh V1000 (Pre-production Engine)
'80 XS1100 'Midnight Special'
'81 XS1100 'Sport' (Trike Project)
'85 XS1100 'Sport (RedSport Project)

Vince
750 Sport [BEVEL]
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Joined: Tue Nov 09, 2004 12:28 am

Re: Surflex S1425 Clutch Kit...

Post by Vince » Wed Jun 17, 2015 10:03 pm

Having a weak spring in the bunch once was described to me can set the plates to flutter and slip. BTW there is a place in OZ called Mr Clutch that resurfaces friction plates with Kevlar,I have a set in my Laverda and they work REALLY well. I will go that way with my Pantah when the clutch wears out

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Re: Surflex S1425 Clutch Kit...

Post by BevHevSteve » Thu Jun 18, 2015 10:52 pm

1425 is the high performance alloy plate Kevlar friction material kit that comes with steel plates and standard springs. All my notes are at my shop so tomorrow I will look up the part #s on the included springs. That said, I stock 3 different spring kits by Surflex

https://store.bevelheaven.com/Engine-Re ... gs-Bevels/

It is also possible someone had synthetic oil in there and then went to Dino oil which also creates slippage issues....
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Miti
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Re: Surflex S1425 Clutch Kit...

Post by Miti » Sat Jun 20, 2015 4:13 am

BevHevSteve wrote:1425 is the high performance alloy plate Kevlar friction material kit that comes with steel plates and standard springs.... It is also possible someone had synthetic oil in there and then went to Dino oil which also creates slippage issues....
Thanks Steve... There is no doubt that the friction plates I have are steel - my bench magnet LOVES them... ;)

But I have no idea when they were purchased and fitted... I think the alloy kevlar plates are the latest development (also good to know they're available) but my old 'warhorse' probably has some of the first generation...

Image

I know, from discussions with V1000 owners who have had their bikes since in the very early days, many V1000's were plagued with problems caused by the clutch plates sticking together. This would cause serious difficulty in selecting first when the bike was cold and also cause nasty gearchanges until the oil warmed up properly... The problem was albeit completely cured by replacing the clutch friction plates. For reference; the original (problem) plates were black in colour, the replacement (cured) plates are red...

As noted previously, I've checked all the plates - fitted and NOS plates are within spec, with no signs of excess wear, warping or blueing, which is why I turned my attention to the springs...

After noting the differences between the fitted springs, the spec in the Hesketh manual and Craig's comments (previous) I turned my attention to the spring boxes... They're like a tin top hat: 25 mm wide rim, 16 mm OD on the "box" and 41 mm long... When cleaning these, I noted polished areas, both inside and out, that gave the boxes a very "well-worn" appearance... I also noticed that one of them had light showing through it ... Whoops..!! :shock:

So, before progressing further, I gave our HOC Tech Guru a call... He recollected the early clutch issues (his own bike had suffered pretty badly with the problem), but none concerning clutch slip...

He also offered to take a look-see for NOS Hesketh spring boxes and as if by magic, they appeared in the post today... ;D

GREAT..!! (ish) When I unwrapped the parcel, it was immediately apparent that the NOS Hesketh parts were different from the ones that came out of my bike...

Image

The NOS Hesketh items are on the right...

The rim is the same at 25 mm, the height is the same at 41 mm, the hole in the bottom is also the same at 9 mm... There the similarties end...

The NOS Hesketh parts are made from a much heavier gauge metal (about 1.5 times as thick) and the OD of the box is 16 mm on the old items and 20 mm on the NOS items...

So, where to now..? The NOS spring boxes don't fit into my pressure plate... :(

Do I try to find a 'Hesketh' pressure plate..? :?

Do I have the existing plate modified to fit the NOS boxes..? :?

Decisions, decisions... It'll all depend on availabilty of spares, of course...

BTW: The change in oil spec could also be an issue... I have no idea what was used prior to my ownership (the stuff I took out at the first oil change looked as though it had been in a few other engine prior to mine... :roll:

More, as things develop...

Miti
Jeff Mitchell
Scotland
'82 Hesketh V1000 (Pre-production Engine)
'80 XS1100 'Midnight Special'
'81 XS1100 'Sport' (Trike Project)
'85 XS1100 'Sport (RedSport Project)

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