Clutch Slip Under Acceleration

I have a problem in that under heavy acceleration from about 6000rpm, my clutch often slips.

I know clutch slip is normally worn friction plates so i'm replacing mine. However, although the old ones are worn they are still in tolerance according to the manual.

My question is:- can clutch slip be due to the friction plates if they are still in spec or must it be something else in this case?

The push rod is straight and not in anyway bent or covered in crud so i know its not that. Also the metal plates are not blue or warped out of tolerance. I'm also going to replace the seals in both the master and slave cylinders as a matter of course. The bike has done 40000 miles.

Thanks for your help.
Simon

 

What year bike and how many miles? For example my 1st I replaced both. The frictions were with in spec but after 50k+ miles they became hardened and slightly glazed. Looked good but was bad. The steels I think have a tolerance of about .005" warp. Mine were around .010-.012". You need a super flat surface to measure on. I've ALWAYS replace both. For what little money is involved it's not worth taking everything apart again. Or ruining one good part because it's mate is bad.

 

From your earlier post I see you have lots of time on bikes so you likely know your way around. This doesn't address your question directly but I thought I might ask if you have considered the spec on the oil you are using?

 

They are in spec, but i might just as well replace them. The bike is 98 with 40000+ miles on it.

The oil is a good quality 10/40 semi and made for bikes, although i have used fully synth at times in the past.

Attached is a pic of the clutch drum with marks where the plates rub. Does anyone think that this could cause the clutch to slip?

Cheers
Simon

 

The springs should also be checked - on a 5th gen the free height should be no less than 42.6 mm (1.68in) - standard height is 45.6mm (1.80in). With slippage problems, if any were suspect, I would toss in a new set while it's apart.

 

Oh yea I forgot but on mine there is a conical large washer thingy, forget the real name, that also applies pressure. There is a spec for it's height. I didn't bother to measure I just replaced that too. You may want to take a look at yours.

 

Seems unlikely unless the grooves are so severe that they impede the motion of the plates. If you have a machinist's straight edge or similar, place it over the surface and shine a light from behind - see if any comes through. If you can get the basket off, you can use a fine file to carefully clean up the surfaces, removing as little material as possible. Normally that might make the engagement uneven, but it would have to be pretty bad to prevent the plates from gripping each other sufficiently. Before I did all that I'd probably just replace the entire set up - frictions, steels and springs and then see how it works before tearing any more apart.
​

 

What oil is in the engine atm? Brand name etc

 

The oil may be the proper type, but if it says "friction modifiers" added it will cause your clutch to slip.
If the clutch keeps slipping the metal plats will get hot,warp,and turn blue and have no temper . Better take care of it pronto.
The attached photo of the clutch basket marks has nothing to do with it, and are normal.

With clutches you need to replace ALL of the metal parts if they
are warped or out of spec or turned blue. Lay them on a glass plate and use a thickness gauge and try to slip it under the edge of the metal disk.IF it goes under you have a problem. Remember with clutch friction discs and metal plates, it is all about tolerance stack up. Each part may only be off .001 or less, BUT when you add up all the plates then you can have .007 or more out of spec measurements.

See what I mean?

 

That clutch basket has nothing to do with this, and is a normal looking clutch basket.

 

It is called a pressure plate.
BTW... You can have a normal pressure plate, good friction discs,good metal plates and good springs and the clutch still slips because the friction discs are ( ) years old and are hard and dried up from sitting. Half of the disk had been submerged in oil and the other half dries up from not being in the oil.
The cork swells up from being soaked in oil so what happens is the oil soaked part is one thickness and the dried up part is thinner and so you only have 50% friction. But usually you cannot tell because people try to ride the bike and the old clutch plates get covered with oil from engine rotation, and it is harder to tell.

That is WHY that when you get new friction discs it says to soak them in engine oil for 4 hours before installing.
Otherwise the cork has not swelled up and when you add up all of the thicknesses of the friction discs the total thickness would be off.

See what I mean?

 

They were warped "only" .005 thousandths. To me that is unusable.
But the question is.... had they turned brown or blue?
That would immediately disqualify them even if they were not warped.
A good metal clutch plate is completely flat. Lay each one on a sheet of glass.
Or an a milling machine table. Or a formica table top.

 

Thanks for all the replies. Good to know its not the basket

I'm going to replace the friction plates, metal plates, pressure spring and springs while i have it apart. I hadn't thought of tolerance build up I must admit (i should of as i'm an engineer!)

Cheers
Simon

 

No it's called SPRING, CLUTCH 22441-MB2-003 IS P/N14

Honda | Suzuki | Yamaha | Can-Am | Ski-Doo | Sea-Doo | Motorcycle | ATV | Scooter | Parts | Accessories

I also applies pressure to the pack in this clutch set up.

 

Grey Wolf is right, but it still acts to put pressure on the clutch plates.

 

Quick update - i replaced all the plates (friction and metal) and springs and the spring and spring seat and its all good now. When i measured all the individual items they were all within spec, so it just goes to show that things aren't always clear cut like the manuals suggest.

Cheers
Simon

 

Just done replacing my clutch, my does not have any play when you release the lever......Took them all off and the friction plate and metal plate. They are look new no sign of worn. Replace with Barret clutch...it is better but does not feel like when it's new. Oh well :sad: