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  #1  
Old 02-10-13, 15:22
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GSXR 1000K8 Clutch Travel

Chris and I have been having a few problems with clutch drag on our GSXR 1000 K8. Having stripped and rebuilt the hydraulics we don't think the issue is at that end. I have now stripped the clutch itself and am about to replace it. Before I stripped it, I measured the travel of the inner basket when the clutch pedal is fully depressed - 1.4mm. Does anyone know what the range should be and if this is within spec?

Thanks.

C (Puzzled of Worcestershire)
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Old 02-10-13, 17:09
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From what I remember getting the correct mastercylinder is critical. The yam engine I ran needed a larger cylinder than expected to generate any 'feel' in the pedal and operation was fine with either .625 or .75 but the Hayabusa I ran was so stiff on .75 you couldn't push the pedal yet .625 didn't displace enough fluid. I think 0.70 was a compromise that I could just about operate comfortably.
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Old 02-10-13, 17:18
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Yup - already done that Nick. Gone up from 0.5" to 14mm dia m/c. Also replaced seals on slave. Now just want to cross check basket movement.
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Old 02-10-13, 17:31
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Clive, the movement on the 'bussa is much more than that, I'd say 5mm, but I'll measure and check.
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Old 02-10-13, 21:07
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Clive,
I'd tend to agree with Rob - my WP has about 4mm travel on the basket cover so it looks like you're not getting enough separation? Hopefully someone else with a K8 can chime in....

By the way, the car looks very nice in the flesh - a fantastic job by all involved.

Oh, and glad you bettered your PB over the weekend.

Steve
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Old 03-10-13, 00:51
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Been doing some digging. The manual lists the Suzuki clutch master cylinder diameter as 12.72mm and the slave as 35.73mm. The ratio of the piston movements will vary as the square of their radii. With 1.4mm slave movement this implies a master cylinder movement of around 9mm. I'm not too familiar with bike clutch levers but this feels the right sort of level for a hand lever unless there is some other mechanism at play which alters the mechanical advantage. My master cylinder is now larger than original at 14mm diameter which would reduce the travel required to deliver 1.4mm of slave movement. I'll measure the pedal linkage tomorrow (I can't rebuild the clutch as I had planned since the Suzuki dealer sent the parts to the wrong address so it'll give me something to do!). In the mean time, any thoughts welcome. Be really interested in your measurements Rob as I can't believe they will be significantly different to the GSXR 1000.
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Old 03-10-13, 09:22
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Clive, I've just checked my car as best I can and I use around 2-3 mm travel, the clutch peddle has a stop and only uses around 2/3 of its travel. Just put a bigger master cylinder on it and stop quoting the square of the radii !
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Old 03-10-13, 09:29
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you can never be too techincal...for Team Wraith...we've already gone up in m/c size....
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Old 03-10-13, 09:50
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try a bigger one then? or does the clutch disengage at the top of its travel, then you push the peddle further and the dragging just doesn't go away? Or is the bite point right at the bottom of the travel? If the latter you need a larger M/C, if the former there is something wrong with the clutch. Simples, come on guys
I'm sure you should be able to 'feel' where the problem is, let me have a look?
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Old 03-10-13, 10:17
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Quote:
Originally Posted by Rob Stevens View Post
try a bigger one then? or does the clutch disengage at the top of its travel, then you push the peddle further and the dragging just doesn't go away? Or is the bite point right at the bottom of the travel? If the latter you need a larger M/C, if the former there is something wrong with the clutch. Simples, come on guys
I'm sure you should be able to 'feel' where the problem is, let me have a look?
... I love my radii...

The bite point feels like it is in a normal place - towards the top-side of the mid point I'd say. Our issue is that we get drag of varying degrees when the clutch is fully depressed leading at times to needing to be held back by the wing on the start line. It also makes it impossible to get back into neutral without turning the engine off. We get no clutch slip under load once we are up and running.

We have blead (sp?) the thing a million times both ways, replaced the slave cylinder seals and fitted a larger master cylinder. No difference. I then put a 4.7mm dia ball bearing in between the slave and the actuation push rod to test release vs slip in case I wasn't getting enough travel for some reason. Little / no difference. I then added more packing until I got to the point where with the pedal fully released in gear there was massive clutch slip. However, it still struggled to go into neutral with the clutch depressed and still "rocked" forward on its wheels when revved. This suggests to me that it can't be clutch travel or hydraulics but this is what I keep being told it "must be". If I put any more packing in I think I'd push the clutch out through the garage wall ;-). Just to be sure I stripped the clutch and polished all the plates and cages to ensure they weren't snagging on anything. Cut my fingers to bits but made s0d all difference.

I've also been told by a Suzuki tech that the oil is critical. I originally used Silkolene Pro 4 Plus 5-40 fully synthetic but the tech chap told me this will have contaminated the plates and we should use Comp 4 10-40 semi synthetic only. Apparently we will need a new clutch incl steels to cure. However, others, including the chap that built the engine, don't share this view and say the fully synthetic should be fine. I've bought 6l of Comp 4 and dropped all the 5-40 out just to be on the safe side once I change the clutch plates.

With our wet sump we also fill higher than the factory spec. It could also be that filling to a higher level is submersing the plates deeper in oil and causing more viscous drag. No way of testing until the whole thing is back in one piece with a new clutch although a quick test with a lower oil level on the old clutch didn't seem to make much difference. Odd that no other K8 pilots have hit this issue though if this is the problem.

It feels a bit like the economy - everyone has a clearly defined and firmly held view of what it is - and each one is different! In reality it is probably a combination of all of the above.

I am awaiting delivery of a set of clutch plates so want to make absolutely sure that everything else is OK whilst it is in bits. Hence looking at travel whilst the cover is off (I've sent you a spread sheet - and no I'm not kidding ;-)).

Answers on a postcard please?

Chunter, chunter...
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