Hi all this is abit of a strange one , went out today did hill climbs ect and went one the road to clear off the mud on the tyres when getting up to speed the clutch slips as I can here as the rpm picks up past mid to top it starts slipping , now my question is why did I not pick up on it when going up hills under load where I would of expected to feel it slip . Or is this an adjustment issue as i put new levers on it , apico ones off ebay , the levers are loos so they aren't adjusted with put slack between the engagement screw and the piston . 

Because there is more torque on the clutch in the higher gears

 

Low'ish  gear and high revs , you can't check a clutch.

High gears, under strain, lower revs induces the slip, as feetup says, more torque. On the road, you were probably high gears, increase the revs, torque produced, clutch slips.  It's nothing to do with levers, it is the clutch!

sorry!

No I understand just , the previous owner had ATF i think as the oil is red so I have ordered some 75weight light gear oil and try that but I think checking the plates will be the best way to know what is required,  but part of me knows the plates are probably worn 

. Thanks 

As strange as it seems having the clutch slip a bit on the road in top gear is pretty much not an issue as it is not a road bike. Having a progressive engagement in a section is much more important. Having said that if it really bothers you changing the oil to ATF may help as ATF has friction enhancers. The other thing to try is to take fine emery cloth and dress the steel plates to break up the surface polish that happens to the steels after years of use. 

I would propose that a clutch slips at higher RPM due to horsepower not torque.  

Torque will flatten out at a certain RPM and horsepower will increase at higher RPM's.

Think of it this way:  The torque of the engine vie crank length bore etc is the internal torque made by the engine design. The back wheel is also a form of resistive torque due to its diameter / radius and made by the wheels contact with the ground turning it.  The engine driven back wheel torque at the rear sprocket is met with torque from the wheels outside diameter as it contacts the ground and both forms of torque meeting at the clutch pack. It is the horse power (rate of work) vie engine  RPM that changes that relationship.

If you disconnect the chain of the bike and roll the bike forward the back wheels radius will create torque around the rear axle, that is outside back wheel torque made purely by pushing the bike forward vie friction of rubber on dirt.

The rate of the torque being generated around the rear axle is the horsepower. The faster the bike is pushed forward as in being driven by an engine creates two opposing torque values with the fighting for supremacy happening at the clutch pack.   

Torque may be the symptom but it is the horsepower (speed) that is the instigator of the problem   

When you turn the throttle you are creating horsepower (rate of work / speed) potential and to a defined point (not infinite) more CYCLES of torque 

 

 

 

Edited July 9, 20206 yr by billyt

I see what you're saying Billyt, but in a low gear at high revs, ie horsepower, no slippage!   Therefore not sure your right.

Still think it's torque!  When you check a car clutch, high gears on a gradient at lowish revs, and plug in more revs to get the slip. It has nothing to do with high revs producing the horsepower, it's all about the torque generated. Think about auto clutches, they are just torque converters. The clutch uses the torque!

 

1 hour ago, jonboy883 said:

I see what you're saying Billyt, but in a low gear at high revs, ie horsepower, no slippage!   Therefore not sure your right.

Still think it's torque!  When you check a car clutch, high gears on a gradient at lowish revs, and plug in more revs to get the slip. It has nothing to do with high revs producing the horsepower, it's all about the torque generated. Think about auto clutches, they are just torque converters. The clutch uses the torque!

 

@faussy one for you ?  (more resistant to movement in high gears)

5 hours ago, b40rt said:

@faussy one for you ?  (more resistant to movement in high gears)

i vaguely remember arguing something in the past, but cant even remember what side i was arguing. Wouldnt want to start contradicting myself ?

I think you’re in violent agreement. The torque (force applied) is the same but horsepower is work done which has that load component to it because the wheel is moving further for the same force. So the horsepower is also the same as it can result in multiple transfers of energy. Acceleration of the bike + wheel spin (throwing dirt backwards uses energy) + mechanical losses (clutch slippage being one component). I think that the only missing piece between you is where the horsepower is expressed, rear wheel vs crank. It’s a common mistake to apply static analysis to a dynamic system and that is what Billy is saying. Torque can be static but horsepower requires motion.

6 hours ago, faussy said:

i vaguely remember arguing something in the past, but cant even remember what side i was arguing. Wouldnt want to start contradicting myself ?

Touché ?