Clutch Slave Stroke

[Dzaster]

I recently swapped out clutch for whitebunny setup and have used the d21 bearing collar from Nissan dealer. I seem to be having little trouble dialing in the  pedal freeplay and clutch engagement/disengagement.

My setup is 510 wagon with KA and I believe a 80's truck 5sp, short tail.

 

Slave I measured to be 3/4" bore and master is stamped with 5/8"--both pretty standard combo from what I've been reading.

 

I found a thread where Datzenmike said the clutch slave stroke should be around 1.18". I've measured the stroke of my clutch slave to be around .75". This is with slave piston bottomed out to its body with rod and external tension spring holding it in place. I have pedal adjusted with master rod almost all the way extended out of its housing to try and get the most possible stroke with pedal. Also confirmed that slave begins to extend almost instantly as pedal is pressed. I pulled the slave's boot off so I can inspect where the piston is when pedal is fully depressed. There is a least a .25" before it reaches the bevel towards the mouth of its bore.

 

With it setup like this I get grinding in reverse and most other gears feel extra notchy going in as if when pedal fully depressed clutch isn't totally disengaged. I have been able to adjust everything to where I can get it in all gears with no grinding, but it seems at that point the fork is pressing the release bearing against the pressure plate fingers some. Don't want to run it like this as it may lead to clutch slip.

 

So should my slave have a ~1.18" of stroke with a press of clutch pedal? 

 

If so, I'm wondering if perhaps a larger bore Wilwood slave would lead to more displacement of the slave with a single pedal stroke? Wilwood seems to have .70" and .75". 

 

I have bled the system everytime I adjusted because I crack the bleeder on slave just to be sure its returned piston fully. Slave I just have someone pump and holdwhile I crack bleeder valve. The Master I bleed by pressing clutch, holding and cracking the line-in fitting at the master's body. Am I doing this wrong?

 

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Edit: I had a thought to test whether the slave was maxing due to not enough displacement from master or whether the slave was stopping due to fork/pressure plate. I was able to adjust the nut on the slave rod further in to simulate a shorter rod and, in deed, the slaves piston did extend further out.

 

So at this point, maybe the issue is mechanical rather than the hydraulic system.

 

 

 

 

[datzenmike]

Clutch slave adjustment....
Loosen the lock nut on the slave push rod and back the adjustment nut off.(looser) Now turn adjustment nut in until there is 2-2.5mm or about 0.08" to 0.09" of play between it and the clutch arm. This will give the required clearance between the release bearing and the clutch diaphragm fingers inside.

 

Clutch pedal adjustment

The pedal in the up position should be 8" above the floor. The rubber bump stop can be adjusted to get this.

Pedal free play.... push down with finger on pedal pad. It should move 2-3mm before the slack is taken up and there is resistance from the master cylinder. To adjust, loosen lock nut on master push rod. Remove clevis pin and turn push rod in or out to get proper clearance. Replace clevis pin and clip.

[DanielC]

A larger bore slave cylinder will mean less stroke.  Think of it this way.  The master cylinder had a set bore, and a length of stroke.  That will move X cc's of fluid.  If the slave cylinder has a larger bore, that slave will not have as long of a stroke.  But it will move easier, but possibly not far enough.  On the other hand, if the slave cylinder is smaller, it will move farther, but the force to move the master cylinder will be greater.

[metalmonkey47]

A larger bore slave cylinder will mean less stroke.  Think of it this way.  The master cylinder had a set bore, and a length of stroke.  That will move X cc's of fluid.  If the slave cylinder has a larger bore, that slave will not have as long of a stroke.  But it will move easier, but possibly not far enough.  On the other hand, if the slave cylinder is smaller, it will move farther, but the force to move the master cylinder will be greater.

 

Holy shit Daniel I think you just helped me figure out my clutch adjustment issue on my 620... Didn't even think that the clutch master I just replaced before the motor went in might be wrong bore...

 

 

 

+1 Ratsun

[datzenmike]

Most are 3/4"... is there even a 13/16", 7/8" or larger???? The clutch arms and pivot point is set, so the pressuer plates must be designed to work in this range. If they are taller the release collars are shorter to compensate. Altering the slave push rod stroke itn't the answer.

[Dzaster]

If the overall stroke between a 3/4" and 5/8" Master Cylinders are same and the only differences are bore sizes, at the same amount of pedal stroke wouldn't the 3/4" displace more fluid to the slave?

 

 

@datsenmike, I did originally put a 13/16" nismo slave cyl. but that one yielded worse engagement than the slave(3/4") that was originally on my transmission. I believe this is due to it being that much larger a bore, the NISMO was getting even less stroke. Also, pedal was just too soft since I'm using stock D21 clutch/PP.

 

 

Here's the slave. I swapped out the rod to the adjustable one that I had from original slave.

 

 

I did get it all adjusted great finally with the original 3/4" slave. Pretty much just as you explained it datzenmike. 

 

Thanks guys.

[ggzilla]

Yes. The larger slave requires the larger master

 

NISMO: To reduce the pedal load when using a sports clutch, improve half-clutch operating characteristics and provide proper clutch connection positioning, the size of the operating has been increased from 3/4 inch to 13/16 inch. This reduces pedal pressure by as much as 14% compared to a standard part.

 

NOTE: clutch discs equipped with cushion plates should not be used with the big operating cylinder. It is only for the sports clutch.

[Dzaster]

A larger bore slave cylinder will mean less stroke. 

 

My bad, I see it now. He said SLAVE, not MASTER like I originally thought. 

 

I'm not using the NISMO. Already sold it.