Ducati Monster Forum

Moto Board => Tech => Topic started by: stopintime on September 25, 2013, 01:57:18 PM

Title: Clutch master/slave calculation
Post by: stopintime on September 25, 2013, 01:57:18 PM
I'm trying to figure out if my parts will work on a dry clutch engine and how the pull will be.

The combo in question: Dry clutch - coffin master - Yoyodyne slave

AFAIK the coffin master bore is 13mm and it's pivot to plunger distance is ~21mm
...this compared to a radial at 15mm bore to 18mm pivot (?)

From a coffin to a radial, the effect of a larger bore is reduced by the 'shorter pivot ratio'
33% larger piston against ~17% shorter pivot.
This means I move about 16% more fluid with a radial...
Usually not what people want for a street bike.

So, we buy larger bore slave cylinders - mine is a 29mm (?) Yoyodyne against stock at 26mm (?)

If not mistaken, I have 16% less piston movement at the master AND 25% less at the slave.
Is that going to be too little movement to fully release a dry clutch?

Title: Re: Clutch master/slave calculation
Post by: Speeddog on September 25, 2013, 03:26:18 PM
You may be on the edge.

The standard goldline masters, such as on S4, S4R are 12mm.
But the pivot distance is ~25mm.

The coffin clutch masters I have around here are 12mm.
Look up from the bottom on the front lower side of the reservoir, there's a part number like  XXXX12 for a 12mm.
Title: Re: Clutch master/slave calculation
Post by: stopintime on September 26, 2013, 01:08:01 PM
I've tried to see what it says, but I can't  :P
Yoyodyne says something about a 13mm being standard
http://www.yoyodyneti.com/ProductInfo.aspx?productid=10.4670.14 (http://www.yoyodyneti.com/ProductInfo.aspx?productid=10.4670.14)

I guess I have to check it out if I get around to this engine swap.
If it doesn't release, I can put on my stock slave and maybe later do the master instead.

[Dolph]
Title: Re: Clutch master/slave calculation
Post by: Speeddog on September 26, 2013, 01:48:00 PM
I use a flashlight, mirror, and 10x magnifier to read the number on the coffin masters

Title: Re: Clutch master/slave calculation
Post by: ducpainter on September 26, 2013, 02:01:15 PM
Quote from: Speeddog on September 26, 2013, 01:48:00 PM
I use a flashlight, mirror, and 10x magnifier to read the number on the coffin masters


I do that to see my computer monitor.  ;D