SBK Clutch issues...

[He Man]

I took my friends 749S out for a spin today and after replacing the clutch pack with a STM pack, i noticed that the previous owner had a very odd arrangement of clutch plates. either way the stack height measure roughly 39.5mm

the STM pack was roughly 36/7mm. It also came with 9 friction plates and 9 steel plates. So starting with a steel plate, there would be a friction plate on top last, so i threw in the thinnest steel plate in the pack which was a bit less than 1mm. The bike has a horrible 1st gear launch. it groans like mad and catches instantly and sky rockets foward. i cannot slip the clutch much, its either 8-9 seconds t oget the bike going or 1/2 second launch. What could be the issue here? Whats teh stock stack height? Whats the stack height range for a slipper clutch?

Some other details about the bike. When i opened her up. i did notice that the posts are not connected to the central hub. It looks to be a Motowheels unit since the posts seem to be removable. The central hub seems to not hug the base that holds the posts, it can spin about 1mm in each direction. I didnt take it apart, but the central nut was torqued down. Also, it uses a stock ducati pressure plate that was PC'ed red ( it has all the markings of my monsters stock plate). Aren't slipper cutches suppose to have a different number of teeth? Theres no slit on the posts...

Another problem that might be related, when down shifting, the bike drops into the lower gear but it acts like its in neutral. i can come to a complete stop and the bike will be idling as if it were in neutral, but i know its in gear because i felt it click in. this happens mostly in 1st gear. It has no issues going up, and it has no issues from higher gears going down. Neutral is easy to find. Bike has no problem getting to highway speeds and gunning it. Though since it is not my bike, i dont know how gunning it feels on it. it feels really gentle. where my monster it feels like all hell is breaking loose. i assume its just the position.

Any insights would be helpful. The only recent mods were CRG levers and STM Clutch pack.

[Speeddog]

It would help to know *which* MotoWheels unit you're talking about.

AFAIK, slippers won't work properly with a non-slipper pressure plate.
I don't know if 749S came with a slipper or not, perhaps an OEM Ducati slipper pressure plate will work with the MW unit.

Did the clutch work properly before you swapped the plates?

What was odd about the arrangement of plates?

[He Man]

I didnt swap the plate (sorry if thats what i wrote) i swapped the clutch pack. I looked for pics of various Slipper kits just now,and it looks a lot like the STM slippers. the clutch drum is a two piece design and looks just like this.




Prior to replacing the clutch pack, neutral was hard to find, and you could let the clutch out in 1st gear ( and i'm 100% sure its in 1st gear) and have the bike standing still. You would not be able to feel the springs through the clutch as your normally would.


The plate had more than 3 instances where two metal plates were used next to each other. It started off with 2 (which AFAIK is normal) then a friction then a metal, then a friction, then 2 metals etc. over all, if my memory is correct, there were more metal plates then frictions.

STM packs came with 9 and 9, maybe im suppose to have a curved plate in there? no idea how im suppose to tell which one of the orignal plates is curved, and the teeth look so worn, i would of thought its a stock one, which means the curve one probably isnt curved anymore.

[Speeddog]

How worn are the slots on the basket?
If they've got deep grooves, the clutch can behave as you described.

[He Man]

there arent any real grooves in it. thing looks pretty fresh. I think the previous owner didnt put more than 3,000 miles on the new basket.

any idea about the idling 1st gear?

[BK_856er]

So you have a slipper clutch?  Those are not stock on a 749s.  You can tell the curved plates by pressing the edge on a flat surface.

Here is some good info to read:

http://www.ducati-upnorth.com/tech/clutch2.php

And below is a Surflex clutch pack in my MW slipper.

BK

[BK_856er]

Also FYI, here is the plate order for a MW slipper from their instructions (friction goes FIRST):

"Now you can begin installing the clutch plates. It’s important that you follow the right pattern when installing the plates. The clutch pack that you receive may have additional plates. There should be at least two plates that are dished. They will appear slightly thinner then the others. Here is the proper order to installing the clutch plates on a Motowheels Slipper clutch."


1.   Friction plate
2.   Steel dished (1.5mm)
3.   Friction plate
4.   Steel (2.0mm)
5.   Friction plate
6.   Steel (2.0mm)
7.   Friction plate
8.   Steel (2.0mm)
9.   Friction plate
10.   Steel (2.0mm)
11.   Friction plate
12.   Steel (2.0mm)
13.   Friction plate
14.   Steel dished (1.5mm)
15.   Friction plate
16.   Steel (2.0mm)

BK

[He Man]

Friction goes first?? I didn't know that. Ill repack it with the friction plate first and give it a try. HOwever the STM clutch pack i got did not have any curved plates. the 9 steel plates were in one plastic wraping seperate from the frictions.

I will try to find some from the other pack and swap one in. Also do yoiu know where i can find the stack height range for an STM slipper? what about your motowheels slipper?

[hypurone]

My Yoyo slipper has a stack height of 36.5 for my RS and def put a friction in first and a steel in last. It will drag heavily if a friction is next to the pressure plate... You can double up steels together so you can achieve a desired stack height. As also prev mentioned there are diff thickness steels. And Yoyo offers an optional steel pack of three diff thicknesses for getting/keeping the stack height within range, so mebbe STM does too...

[He Man]

at some point isnt using 2 steel plates every few friction plates too much? I figure that was what caused all the previous stalling, hard to find neutral because the original pack had a significant amount of material left.

I threw in a metal plate after hte last friction plate, a friction plate on the pressure plate just doenst make any sense. 
 
STM Doesnt offer various stack heights, they are all uniform, though the old kit had plenty of metal plates, i just counted them, it had 14 metal plates of various sizes, so ill try to restack it.

[BK_856er]

You can mix and match old + new steel plates to get the overall stack height that you need.  The curved plates will be mixed in with the others as new and it might be difficult to distinguish - they might be thinner, they might have a tiny dimple, or you can press the edge on a flat surface to identify them.  Get the order and height right and see if that fixes your problems.  After that you might want to open it up and clean/grease the balls.  Slippers need attention now and then.  Still not sure what slipper you are running.

BK

[He Man]

I'm not sure waht slipper im running either.

I opened it today and played with the stack height. I mannaged to remove 2mm off and the groaning stopped. however the bike is very shaky during take off (normal street take off from light). i was following the bike by foot and the clutch will catch/slip/catch/slip while feeding the clutch from stand still, thus casuing the shakyness.  i tried to adjust the stack by adding the 2mm back, and it groans, so i take away 1mm, and it grabs and slips again.

One of the clutch psots are slightly bent, that may have something to do with it. I took the old pressure plate off (stock plate) and swapped my speedy moto plate on, and the bike worked fiine, but it slipped a little. So i tried putting my S2R1000 stock pressure plate on, and it began to slip/grab again.

I looked thru all the old steel plates, none of them are curved, they are all flat as the earth.

i havent ridden the bike throughly yet since there is a lot of traffic, so im not sure if the 1st gear issue is still there.

[BK_856er]

Sounds like progress!

The non-flatness of the dished plates is very subtle and not easily seen.  You need to test for it.  The dished plates are not critical, so you may not have them, but they can smooth out the action by acting like springs to oppose the force of the pressure plate (that's how I think of them at least).

Be sure your plates are clean and dry.

It's pretty easy to pull the hub and clean/inspect, just be sure to use the correct tools and torque the big nut properly.  Is the bent post hanging up the hub?  If so, four spings might be a temporary option.

BK

[hypurone]

I would also look at the steels and see if any of them have what are known as "hot spots". They look like a highly polished area, often with bluing in color from the heat. If so, swap those out for good ones and retest. Same with the frictions tho you won't have hot spots per se but more of a "burned" spot that gets hardened.

[He Man]

All the metal plates are brand new and look fine. I have all the tools to take apart the slipper, ill do that this weekend and rebuild the thing and inspect it. The post is bent about 3degrees off center. Can you remove the posts from the STM slippers? ( i think its an STM atleast)

i remember looking at teh curve disk for the barnett packs, you could defintely see that there is some sort of deflection, it was explained to me the exact same way you stated, just helps seperate the pack.

I have all 6 springs in the bike, but since one of them is bent the force is being applied a bit awakrd, ill try removing that spring and the one directly in front of it and see if it helps the launch. My guess is that it will, but because theres less force on the clutch pack, im losing power thoough slipping.