Lockup clutch slipping at low revs

[luke2152]

I realise this is similar topic to another current thread.  Bandit 12 with TD04@1 bar as per my build thread.  FBM lockup.

When I'm giving it some and the revs are up the lockup does its thing and no clutch slip.  When I'm being lazy and just roll the throttle open in top gear, as I hit full boost before the revs are up it slips.  It didn't do it before and strangely enough it started when I switched from full synthetic to mineral (must be coincidence?).

So to that end (other than putting new fibres in) should I put heavier bolts in the flyout arms to make it engage sooner or heavier spring to clamp it better before the lockout does its thing.  Or just stop being lazy.

[Gixer1460]

I'd vote heavier arm weights - generally easier on the fingers at sub warp speed. Mixing the oils on pre semi soaked plates won't help but the slip should eventually subside as semi gets diluted with mineral!

[MeanBean49]

Might be a good idea to put some fresh OEM clutch fibres in if youve had fully synth in it.

But yeah bit more weight on the arms will help at lower revs. I have to have quite a lot of weight on mine to stop it slipping at low revs because of the torque it makes.

Trade off is it makes clutch a bit heavier, and can make fast launches difficult, mine starts to creep forward if i give it a few revs with the clutch in.

[Duckndive]

30 minutes ago, MeanBean49 said:

Trade off is it makes clutch a bit heavier, and can make fast launches difficult, mine starts to creep forward if i give it a few revs with the clutch in.

that's clutch drag

nothing to do with the lock-up "as it does nothing until the wheel turns"

[wombat258]

If you are not drag racing, and only need the lockup to cope with the extra torque of the turbo, you need more spring pressure, and not more weight. Think about it . . . if you had the same spring pressure as a set of Barnetts on the pressure plate when the engine is not spinning, the clutch lever would be stiff, and would ALMOST be able to handle the turbo. You need only a bit more pressure, and this is supplied by the weights when the clutch output shaft is spinning. Low spring and high weights = flat out launches in drag racing. High spring and low weights = broad operation of engine for circuit or street, without the stiff clutch feel at the lights. For diaphragm cluch use HD springs and extra seating washers to increase the spring pressure to standard installed height. For coil springs add washers to get springs to standard installed height.

[MeanBean49]

2 hours ago, Duckndive said:

that's clutch drag

nothing to do with the lock-up "as it does nothing until the wheel turns"

Yeah, sorry mong moment, i use a ducati brembo master and it makes lever mega light but doesnt disengage clutch quite as much as stock, only wants to creep above about 5k, but only does it with lockup fitted. Really wierd thinking about it now.

[MeanBean49]

24 minutes ago, wombat258 said:

If you are not drag racing, and only need the lockup to cope with the extra torque of the turbo, you need more spring pressure, and not more weight. Think about it . . . if you had the same spring pressure as a set of Barnetts on the pressure plate when the engine is not spinning, the clutch lever would be stiff, and would ALMOST be able to handle the turbo. You need only a bit more pressure, and this is supplied by the weights when the clutch output shaft is spinning. Low spring and high weights = flat out launches in drag racing. High spring and low weights = broad operation of engine for circuit or street, without the stiff clutch feel at the lights. For diaphragm cluch use HD springs and extra seating washers to increase the spring pressure to standard installed height. For coil springs add washers to get springs to standard installed height.

Not what ive found. High rpm i dont need much weight on lockup to stop slip, low/mid rpm with no weight on lockup no hd spring would stop slip, only way I could cure it was add weight to the lockup so its putting more pressure on the pack at lower rpm, slip stopped. Heavier springs make lever stiff at standstill, weight on the lockup wont affect lever stiffness at all when not moving. Mine makes 200ft lbs at 6k though so a little bit more than a TD04 setup to deal with

[wombat258]

My experience...

290 hp turboed 1100WC doing circuit race work in a car with 10" slicks and wings. Used the same clutch pack for 3 years racing with NO slip, even when pulling from 4500 rpm out of corners. Used both diaphragm and coil spring MTC lockups. The clutch pedal is not overly heavy.

Used lower spring/higher weight setup for 1300 hillclimb in car for hillclimbs because needed to launch harder, but had to keep rpm's above 6000 to avoid slip.

User even less spring/low weights in the old Z1R with 1270(?) kit in a laydown dragbike to do hard launches. 8.9's at 149mph on 6" car tyre slick.

[luke2152]

I seem to remember someone telling me  you could assemble bandit clutch with 2 stock diaphragm springs?  Is it true.  I think I have a spare one somewhere.  And I'll put a bit more on the lock up arms.

Seems strange that I did 1500mile on synth with no slip and within 100mile of putting mineral in it started slipping.  Would expect the opposite.

[wombat258]

Depends on the brand of mineral oil and what friction modifiers they use. If it is a car oil it should not be used in a bike engine. Car oils do not have to cope with wet clutches, and their friction modifiers ruin clutch frictions immediately.

[MeanBean49]

6 hours ago, wombat258 said:

Depends on the brand of mineral oil and what friction modifiers they use. If it is a car oil it should not be used in a bike engine. Car oils do not have to cope with wet clutches, and their friction modifiers ruin clutch frictions immediately.

Adding more springs/stiffer springs has to make the lever heavier all the time, a lockup will only make the lever heavier the higher the rpm.

Its not really anything to do with peak power, its where peak torque is. If peak torque is low down the arms of the lockup wont put enough force on to stop slip, not somthing you would notice on the strip, but very noticeable when on the road doing roll ons or on trackdays.

[Duckndive]

7 hours ago, MeanBean49 said:

Adding more springs/stiffer springs has to make the lever heavier all the time, a lockup will only make the lever heavier the higher the rpm.

Its not really anything to do with peak power, its where peak torque is. If peak torque is low down the arms of the lockup wont put enough force on to stop slip, not somthing you would notice on the strip, but very noticeable when on the road doing roll ons or on trackdays.

That's exactly the way I had the clutch on my air cooled draw thru....

I used 3 stock springs and a nut and bolt on all 6 stands ....lever was as light as a feather and you only noticed a slight slip on the road between 3 -5K.....before the arms locked up...

On the Oil Boiler I ran 2 stock springs and 2 inner valve springs again a nut and bolt on all 4 stands no slipply slippy

On Oil I run Supermarket £10 for 4 Lts 10-40 Mineral Oil ......

Edited September 25, 2018 by Duckndive

[MeanBean49]

18 minutes ago, Duckndive said:

That's exactly the way I had the clutch on my air cooled draw thru....

I used 3 stock springs and a nut and bolt on all 6 stands ....lever was as light as a feather and you only noticed a slight slip on the road between 3 -5K.....before the arms locked up...

On the Oil Boiler I ran 2 stock springs and 2 inner valve springs again a nut and bolt on all 4 stands no slipply slippy

On Oil I run Supermarket £10 for 4 Lts 10-40 Mineral Oil ......

Its all a bit of a balancing act isnt it? 

Depends on your own setup, how you use the bike and how you want it to feel.

I dicked about with allsorts of different combos until I got it how I wanted, its not perfect but is the best setup for trackdays for me

[Duckndive]

23 minutes ago, MeanBean49 said:

Its all a bit of a balancing act isnt it? 

Depends on your own setup, how you use the bike and how you want it to feel.

I dicked about with allsorts of different combos until I got it how I wanted, its not perfect but is the best setup for trackdays for me

Yes absolutely as there are so many variables...on the road a simple change in riding style can make a huge difference 

on the strip if you launch the bike at the same rpm and tyre pressure it’s quite easy to find a base line set up.....then the fun starts when you tweak it for that bit more ....but once you have a base line set up lunch rpm and tyre pressure are the key 

[Duckndive]

The oil boiler clutch also suffers from plates drying out after a few hard launch s on the strip..and it then gets very grabby    I always take a couple of spare stacks for quick reloads 

Edited September 25, 2018 by Duckndive

[wombat258]

5 hours ago, Duckndive said:

The oil boiler clutch also suffers from plates drying out after a few hard launch s on the strip..and it then gets very grabby    I always take a couple of spare stacks for quick reloads 

Drill extra holes into the inner basket to provide more cooling oil to the pack.

[Duckndive]

18 minutes ago, wombat258 said:

Drill extra holes into the inner basket to provide more cooling oil to the pack.

It’s all ready been done and anyway the plates wear and you have to keep the stack height right ....

I don’t have the problem now as I use a slider 

[jonny1bump]

You can use heavy duty diagram spring and one normal spring and handle  bar pressure will not be too harsh. The bandit clutch is small and weaker then gsxr. You can swap out and use gsxr as an upgrade.

As said base pressure is getting you going off mark and as wheel speed increases then centrifugal force on arms increase as spins faster. Take it's simple lock up though out type and does not use hold off springs.

But again as your actually moving the weights on arms will be helping a little. When you gun it your pulling high torque so as suggest new clean fibres and little more  base. If it was mine I would swap out bandit clutch straight away, also gsxr basket allows oil to drain out sufficiently, so that will not be a concern.

On the pro stock bike you can tune the hold off springs to alter the way clutch actually comes on. The amount of data and discussion myself and Ray had with clutch is immense.

Now Clive clutch with slider that's different beast altogether.

Hope this helps.

 

 

Edited September 29, 2018 by jonny1bump