What causes clutch drag?

[CraigMcleod]

Why does my clutch drag, is it normal?
So when cold there is some clutch drag but then goes off. When hot the rear wheel will move slightly then stop, but then stat to speed up until spinning away freely. Hit the rear brake and it stops for a while and then starts again. Why is this? Everything is standard and fresh engine oil.

 

[Bumblebee]

Oil viscosity will cause this...it's perfectly normal, happens on every bike I've ever owned.

I find it happens less on this bike than some of the others...

 

[Mythos]

What @Bumblebee said. Both of my bikes with wet clutches roll a little stiff when they're cold. The clutch plates stick together somewhat from the film of oil between them. Fresh oil sticks to parts better and will probably cause the plates to stick together more than old oil does. If your rear wheel spins more freely after you have spun it a bit, that is probably because the oil seal between the clutch plates id breaking. Run the motor, the oil becomes hotter and it sticks to parts less. Apply the brake, the piston presses the pads together. The piston does not retract on its own when you release the brake, the brake disk turning is what presses the piston back into the caliper. The pads then skim the rotor until you hit the brake again. This explains how applying the rear brake might cause the rear wheel to spin less freely immediately after you apply the rear brake. Front brakes do the same. You might hear them squeal when you roll the bike after it has say a long time. That's just the pressure in the brake system squeezing the pads a little tight against the disks. It goes away when you ride.

What you have described all sounds normal as long as the drag isn't severe and it goes away when you operate the bike.

 

[Mythos]

When it's cold, you may also notice the bike creeps forward in first gear with the clutch lever pulled all the way to the grip. Same thing, the clutch plates are sticking from the oil seal between them.

 

[CraigMcleod]

What @Bumblebee said. Both of my bikes with wet clutches roll a little stiff when they're cold. The clutch plates stick together somewhat from the film of oil between them. Fresh oil sticks to parts better and will probably cause the plates to stick together more than old oil does. If your rear wheel spins more freely after you have spun it a bit, that is probably because the oil seal between the clutch plates id breaking. Run the motor, the oil becomes hotter and it sticks to parts less. Apply the brake, the piston presses the pads together. The piston does not retract on its own when you release the brake, the brake disk turning is what presses the piston back into the caliper. The pads then skim the rotor until you hit the brake again. This explains how applying the rear brake might cause the rear wheel to spin less freely immediately after you apply the rear brake. Front brakes do the same. You might hear them squeal when you roll the bike after it has say a long time. That's just the pressure in the brake system squeezing the pads a little tight against the disks. It goes away when you ride.

What you have described all sounds normal as long as the drag isn't severe and it goes away when you operate the bike.

Yes this all makes sense. The engine hasn’t been ridden for sometime (4-5 years). It’s on an Abba stand so have been able to spin the rear wheel up and change gears. It probably needs a proper good blast rear brake pads are new but again not seen any miles yet.

 

[CraigMcleod]

When it's cold, you may also notice the bike creeps forward in first gear with the clutch lever pulled all the way to the grip. Same thing, the clutch plates are sticking from the oil seal between them.

So this is why they sometimes bang into gear from neutral to first at the traffic lights

 

[WuzzaCBXRider]

So this is why they sometimes bang into gear from neutral to first at the traffic lights

Holding in the clutch for a bit before shifting into gear solves that issue. Gives the drum more time. And if the oil is clean there shouldn’t be any ‘creep’ with the clutch pulled in. If so the fiber plates may be too worn or soaked with sticky old oil from non use.

 

[Mythos]

So this is why they sometimes bang into gear from neutral to first at the traffic lights

If the motor is cold and idling a bit faster, that will make it bang into gear harder. I don't find my Hayabusa objectionable in this regard but the other bike I rode for 13 years clunked into 1st gear pretty hard. I sometimes rolled the bike forward and that helped soften the clunk. I noticed holding the clutch lever in while the bike warmed up helped as well. If it were possible to lower the idle speed on the busa, setting it to 1000 rpm would help. ...but we don't have a manual idle speed control on the busa.

 

[CraigMcleod]

Holding in the clutch for a bit before shifting into gear solves that issue. Gives the drum more time. And if the oil is clean there shouldn’t be any ‘creep’ with the clutch pulled in. If so the fiber plates may be too worn or soaked with sticky old oil from non use.

I’m still building this bike, maybe need to get it put for a blast and see how it settles down

If the motor is cold and idling a bit faster, that will make it bang into gear harder. I don't find my Hayabusa objectionable in this regard but the other bike I rode for 13 years clunked into 1st gear pretty hard. I sometimes rolled the bike forward and that helped soften the clunk. I noticed holding the clutch lever in while the bike warmed up helped as well. If it were possible to lower the idle speed on the busa, setting it to 1000 rpm would help. ...but we don't have a manual idle speed control on the busa.

Ive noticed they do idle high, wonder why? My gen one often clunks too, other times it just clicks in when stationary. I’m still building my gen 2, I’ve spent sometime focussing on build details and carbon etc. Not actually ridden it yet

 

[Hayabusa Wannabe]

I figured out on my cars from when the gearbox is frozen during the winter, I will double clutch a bike, ergo release the clutch in neutral and then clutch again and shift. This smooths out the shift even more, particularly for that difficult shift to first gear and shifting while stationary. I do not truly understand the bike gearbox but assume that a smoother shift means that this activity is fine and not harmful to the components. Finally time to ask the techs here I guess haha?

 

[Kiwi Rider]

....... Finally time to ask the techs here I guess ....

Huh? Oh, sorry, I wasn’t listening.... what were you asking?

 

[Hayabusa Wannabe]

Huh? Oh, sorry, I wasn’t listening.... what were you asking?

Double clutching: Is this okay to do on a bike?

 

[Kiwi Rider]

Double clutching: Is this okay to do on a bike?

I guess... but unnecessary, just ram it through, dog gearboxes are tough lol

 

[Bumblebee]

Double clutching: Is this okay to do on a bike?

Double clutching? Been a long, long time since I've done that...was on an old army truck when I was a young rookie.

Never double clutched a bike nor felt a need to, bikes have a synchro-mesh transmission but I suppose double clutching wouldn't hurt them one little bit.

 

[Spudley]

When was the last time you changed all your hydraulic fluid, brakes and clutch ?.

 

[CraigMcleod]

When was the last time you changed all your hydraulic fluid, brakes and clutch ?.

It’s had new fluids throughout, all parts are either new, reconditioned or ‘very’ low mileage….
Thread 'Frame up Build with mods and carbon fibre.'
Frame up Build with mods and carbon fibre. | Busa Mods

 

[Bumblebee]

I wouldn't be concerned about this little clutch drag...

One handy feature of my Bazzaz system is I can adjust the idle...

 

[Spudley]

Stack height at clutch is correct ?.

 

[Mythos]

I figured out on my cars from when the gearbox is frozen during the winter, I will double clutch a bike, ergo release the clutch in neutral and then clutch again and shift. This smooths out the shift even more, particularly for that difficult shift to first gear and shifting while stationary. I do not truly understand the bike gearbox but assume that a smoother shift means that this activity is fine and not harmful to the components. Finally time to ask the techs here I guess haha?

I was taught to do this on the old dump trucks I used to drive in order to shift faster. It was either double clutch or pause at Neutral between each gear. If you ask me, the double clutching achieved the same effect as pausing, it just added a little extra time between gears and doubled the wear on the moving clutch parts. Of course, we're talking about a stick shift with an H pattern vs a 1 down, 5up motorcycle shift pattern. With the bike, you never cross Neutral except between 1st and 2nd gear. It wouldn't even be possible to double clutch between other gears. Matter of fact, I have to try to get the bike transmission to go to N between 1st and 2nd gear. It usually wants to click right past N. If it works when the bike is stationary, might as well do it but that would be the only time I would see double clutching as being useful.
The gearbox is still a mystery to me too but I have a feeling just holding the clutch lever a second will do the same thing. Maybe it lets the clutch hub and transmission slow down if it was sticking a bit from the oil seal we've been talking about.

The quickshifter I used on my other bike shifted smooth and that was only 90 mls without using the clutch or releasing the throttle. Then again, it sometimes would miss a shift and that wasn't very smooth or very fast. Interesting wheelie when it popped back down to the previous gear though.

I wouldn't be concerned about this little clutch drag...

One handy feature of my Bazzaz system is I can adjust the idle...

Yep, the clutch dragging a little bit is normal. Both my bikes did it. A lot more when cold.

I didn't know a Bazzzaz could adjust idle!! Man, it's high time I read up on what else I can do with that thing other than manage fueling.

Stack height at clutch is correct ?.

Possible if the clutch plates were just changed but assuming the clutch height was correct when installed, susiquent wear would result in slipping, not dragging.

 

[Mythos]

Ive noticed they do idle high, wonder why?

Of course they idle fast when cold. I suspect the ECU makes it do that to counteract the stickiness of cold oil. I just googled and 1000 rpm idle is about the norm for motorcycles. My busa idles just below 1100 rpm or closer to 1000 when it warms up. I think it goes to 1200 for a while when cold. It's been a while since I've ridden it. An inline 4 cylinder might sound like it's idling faster than a twin but I suppose that would just be that we have twice as many engine pulses compared to a twin cylinder.