How much is too much?

[10 inch Terror]

Hi all,
I have just cut down an old side casing so that i can use it to check for kickshaft clearance and also to measure clutch plate separation accurately. Obviously the kickstart needs to clear the top plate but how much separation on the plates is too much? I've heard different things from different people. It varies from 1mm to 2mm depending on who i speak to. Any advice very welcome cheers Pete.

[YAMLAM]

124 views and not one reply ! someone must know ?

[RICSPEED]

all i can suggest is to check with a clutch known to be good then use these mesurements when checking other clutches

[Adam_Winstone]

I've read that you can have too much clearance but I think that this is WRONG! The reason for saying this is that the clutch doesn't know how much clearance it has during separation, all it needs to do is grip solid under spring pressure and release fully under separation. Providing there is enough room for full separation once the assembly has come up to running temp' then more is not an issue. Indeed, I commonly run the 5-6 plate deep baskets with 5 or 4 plates, often with thin steels and stepped top plate, which gives WAY MORE separation than is needed but the clutches work perfectly.

Remember that clutches only need to do 2 things, grip under spring pressure and release under separation. Provided the clutch provides these 2 elements then it doesn't matter if you have more pressure (one extreme) or more separation (the other other extreme).

Adam

PS - NB: My comment has nowt to do with Ricspeed's reply... typing at the same time

[drunkmunkey6969]

I know what you are saying Adam, but dont you think that the springs can be left to do 'too much work'? So suppose loose play was massive at about 4mm for example and the springs were only just under tension, you could then maybe take up 2mm by using thicker steels etc....thus compressing the springs slightly (2mm) which allows the springs to exert more force onto the pressure plate.......?

[Adam_Winstone]

Yes, spring pressure/pre-load can be varied and enough spring load is crucial as too little spring pressure will not hold the clutch. However, too much pre-compression of the springs could also result in limiting further compression/travel distance and result in the springs becoming coil-bound, stopping the clutch from working and wasting any of the additional depth that you've paid for when buying a deep rear sprocket.

Providing the clutch fully holds and fully releases then all is well and 'a miss is as good as a mile'.

Also, think about it another way. If you take a standard 4-plate assembly (corks, steels, top plate, inner bell, pressure plate, circlip, the lot) out of a standard rear sprocket and fit it to a deeper 5-plate sprocket then the pre-load of the springs will still be exactly the same as it was in the 4-plate basket, as the springs pushing down on their inner bell seat and up against their pressure plate seat (governed by circlip limitation and combined plate thickness) dictate the pre-load/spring length. So, in this case, nothing has changed in terms of pre-load or the clutch's ability to stop slip, however, the space (depth of travel) for plate separation has increased by the increase in sprocket depth (unless the springs go coil bound). As a result, the plates are far less likely to bind when hot/swollen and the chances of having a satisfactory clutch operation is improved. Whilst the additional depth will not be required by the 4-plate assembly, the clutch's function is not affected by having this room available.

I know what you are saying but if you're using valuable basket space, by adding thicker plates, to increase pre-load on the springs then you are also further compressing the springs and potentially limiting any further compression. If this is the case then I'd question whether they are the right springs to start with? The 2 biggest problems with most 5 or 6-plate assemblies is that people keep cramming in steels and corks until there is no longer enough room in the basket for plate separation or that the increased travel required is not provided by springs that go coil bound too early (how many times do those that have binding/drag issues find that their bottom cork is nowhere near the bottom of the basket when the clutch compressor is fully in?!). I realise that this is a somewhat different issue to the pre-load point that you are raising but it is an overlapping issue that trips up many that spend good money on expensive clutches, only to run into problems because of using the wrong springs.

I do agree that increasing pre-load can be a very good thing though, providing further compression is not hindered.

Adam

[drunkmunkey6969]

Also, think about it another way. If you take a standard 4-plate assembly (corks, steels, top plate, inner bell, pressure plate, circlip, the lot) out of a standard rear sprocket and fit it to a deeper 5-plate sprocket then the pre-load of the springs will still be exactly the same as it was in the 4-plate basket, as the springs pushing down on their inner bell seat and up against their pressure plate seat (governed by circlip limitation and combined plate thickness) dictate the pre-load/spring length. So, in this case, nothing has changed in terms of pre-load or the clutch's ability to stop slip, however, the space (depth of travel) for plate separation has increased by the increase in sprocket depth (unless the springs go coil bound). As a result, the plates are far less likely to bind when hot/swollen and the chances of having a satisfactory clutch operation is improved. Whilst the additional depth will not be required by the 4-plate assembly, the clutch's function is not affected by having this room available.

Fair point, well made, and all true.....providing this slack setup is working ok to begin with, the basket depth will not alter the performance. And most 4 plate setups do work, no matter how badly set up, as they are predominantly used on low power motors (except where someone knows how to set one up properly and doesn't wish to upgrade to a 5/6 plate etc). But if you take suggested 'loose play' setup you describe above and put it in a high power motor, you may find it slips.....until the loose play is decreased and spring load increased with thicker steels.

Concur? Disagree?

[Adam_Winstone]

Yep, your method of improving spring pressure through increasing pre-load may resolve a specific motor's slip but a change of spring could also resolve this, with no change to the free space available. Indeed, this improved pre-load could be achieved by fitting longer springs, thicker or stronger springs but each of these could also result in a spring that became coil-bound in a shorter distance, which is why so many 'uprated' springs work well in 4-plates but may be very bad for 5-plate use. In many of these 5/6-plate assemblies the best springs are reasonably long (to give good pre-load) and are made of tough/strong wire so that they can not be too thick (avoiding coil-bound issues), have fewer well spaced coils (again to avoid coil bound issue), and compress much shorter (equalling further travel into deep sprockets) that other 'uprated' springs that work well in 4-plates (sorry to use the 5/6-plate example to try to illustrate the point).

On the flip side of my 5/6-plate example is the example that does support your issue and is something that I totally agree with... that being that if you use good springs, with suitable pre-load, then most motors don't need more than a strong 4-plate, providing you don't mind a stiff clutch lever action. I still run a 4-plate 10 spring clutch in one of my motors and that does not slip but also does not need much travel to allow full separation of the standard 4-plate assembly. More space than necessary can be a waste of potential but again it comes down to specific motor and rider requirements.

It is really about suitability of clutch to motor in question. The frustration for many is that the wrong combination of parts gives nothing but headaches, and with many thinking that more plates = better clutch (not understanding relationship of cork to steel area PLUS spring specification PLUS space for separation) so space for separation and spring specification get overlooked

Additional pre-load will be beneficial for some clutches, whilst excess space will not affect others, meaning that neither one of us is wrong. It is just about having the right clutch for the right motor.

Adam

[10 inch Terror]

Thanks for the replies Fellas. I've got 1.5mm between the top plate and 1st clutch plate with the lever pulled fully in. All seems ok to me. Thanks again Pete.