Confirming clutch slip

[Artful]

I've had 13 vehicles in 15 years of driving and not one of them has been an auto. Half of them were total POSes so I'm well acquainted with clutch slip. Yet I'm not sure if my 695's clutch is slipping. The culprit is the APTC slipper clutch, first time I've ever owned one.

My understanding of a slipper always centered around decel. Slam into a low gear while deceling and the slipper does its best job to prevent you from eating shit when your rear wheel starts to try and slide.

I'm going out on a limb here and assuming that it should NOT slip under heavy acceleration (well, as heavy as a 695 can muster). Mine is slipping a bit when I really twist it. So going along the line of reasoning that my clutch is slipping but has been for two years, what should I be looking at for resolution?

I use AMSoil moto specific oil and the clutch is well bled. Pushrod o-rings were replaced recently as well even though they should have no impact on slippage.

So, sound like it's time to replace my plates? Bike is right around 25k so if they aren't cooked they most likely aren't far off.

[bikepilot]

Correct, it should not slip under accell.

I'd mic the plates to check their thickness before replacing them.  Often plates are fine and its only the springs that need replacing (and they are really cheap).

[Slide Panda]

My 620 with the same clutch didn't slip under WFO throttle.

Well 25k is a good run for any set of plates.... so slipping wouldn't be a shock at this point but it's been doing it for 2 years?

Does it happen all the time? Or does ambient/bike temp make a difference? Just pondering if you've got some water in the clutch fluid that's making for tiny steam bubbles in the heat. - But that's a bit of a while hare.

Hmm... I'm a bit at a loss

[Artful]

That's what threw me. It's done it to some degree for quite some time. Whenever I've had clutches slip in the past you get about a day of driving out of them and then you're parked. The slipping is only there at WTFO.

I guess it's time to pull the cover and see WOT's WOT.

[BK_856er]

My M695 starting showing some odd signs of slippage at WOT after ~20k miles.  I replaced the clutch pack and it solved the problem, but the old plates measured fine and looked OK.  More than other wet clutches, the APTC seems to be sensitive to the oil type.  On this bike I will only use Mobil-1 MX4T - several other oils I tried just don't cut it in the clutch department.  YMMV, but others have reported similar experiences.  Maybe try a switch and see if you can squeeze more miles out of the plates?  They are not cheap!  Also make sure your master cylinder is adjusted/functioning correctly and is not overfilled.

BK

(edit - I should add that I replaced all the springs + clutch plates at the same time, so I suppose my problem could have been the springs, but their length was fine, and the design of the APTC clutch assembly drives the plates together under acceleration)

[Speeddog]

I've had a customer's S2R800 APTC clutch be a problem child about slipping.

Started slipping, replaced with Barnett pack at about 35k miles.

Slipping under load was cured, but it dragged so bad that finding neutral at a stop was impossible.
Fiddled with it a good bit, couldn't get it to stop dragging.

Replaced it with a slightly used set of OEM plates.

Finding neutral was OK now, but still a bit of slipping.

Shimmed the springs 2mm, and all is good.

If you want to shim yours, I can dig out which shims I got.

[DarkStaR]

Mine will slip a little on fast WOT roll-ons, and WOT acceleration clutch pops.  I live with.

When It NEEDS to be relplaced, it'll get replaced with a non-aptc clutch.

[Artful]

Interesting, good to know I'm not the Lone Ranger on this one. I'd be interested in that shim info if you can dig it up SD, but may go the same route as DarkStar when it comes time to replace the whole shebang.

[bikepilot]

It may also be worth making sure the APTC mechanism is in good shape.  I know on the TLS which uses a similar mechanism (but puts 2x the hp though it) the ramps get worn over time and then the clutch starts to slip.  Replacing them or polishing up the bits in there fixes it.  Stiffer springs fix it too as then you don't need the counter-torque thingy to apply the extra pressure. 

In my experience generally aftermarket clutch plates are often of lesser quality than oem.

Wet clutches wear very, very little over time. I suspect that your plates are practically like-new.

[caperix]

Like others have said the APTC is very sensitive to oil brand, & as it gets older gets more sensitive.  Mobile 1 4t bike oil gives the best results though at around 25k on my 620 it would slip at WOT esspecialy after shifting.  My clutch discs looked to be in good shape & there was no visable problem with the APTC splines.  I installed a standard clutch out of a 800ss on my bike 10000 miles later still no issues even using the used plates.

[Speeddog]

Metric stainless shims, 12mm ID x 18mm OD x 1mm thick.

Part# 98089A389 at McMaster-Carr (mcmaster.com)

[Jarvicious]

Possible mild thread jack, but this may be informative to some.

So, the clutch wear can effect being able to find neutral at a stop?  I installed a 14t front sprocket over winter and haven't really noticed any clutch slip on hard accel (I'm assuming the clutch slipping would just cause the motor to run itself ragged without the byproduct of acceleration?) but finding neutral can sometimes be enough of a hassle to the point where I just keep the clutch in at stops.  I've been using Motorex 5 (or 10, don't remember) w50 for the last 12k miles and this is the stuff with the "gearbox additive" and all the reviews look good so I'm assuming it's decent oil.  What good would shimming the springs do and would it be worth it just to "try" if my tech has the clutch open for inspection or could it be detrimental if my clutch is actually operating normally?

[Howie]

Difficulty finding neutral is from "clutch drag" , the inability of the clutch to completely disengage.  Clutch slip is the inability of the clutch to transmit power.  Shimming the springs increases clamping power, helping the clutch to transmit power.

You need to find out why your clutch is dragging.  Start with bleeding the clutch.

[Twizted]

Have you got aftermarket levers installed? Mine slipped when I first installed some on mine until I adjusted the plunger.

[bikepilot]

Drag can be caused by warped plates, but not worn plates.  Its more often caused by something faulty in the actuator system (like air in the clutch line) or a notched clutch basket/hub. Some clutches will also drag a bit if they have oil they don't like (my montesa is really sensitive to oil type and will drag with anything other than its favorite, $50 a bottle Elf stuff).