Clutch Woes - Seeking a solution

[AC-460]

You need to fix your pedal ratio
in this photo it doesn't even look like that clevis is even going to reach the hole....also because the ratio is wrong the pedal isn't going to travel very far before it bottoms out in the master cylinder. You can go to a smaller master but it still wont let the pedal move far enough before it bottoms out in the master

I will revisit the measurements, though I'm sure that's been done before, but you are right, in that doing this eliminates one issue.

Though as can be seen in the photo below from early in my first build stages, the pivot ratio and hence leverage into the clutch master is well in my favour. I don't believe this was altered during the current rebuild but I will check for completeness.



As a top pivot clutch pedal system what's the suggested ratio between distance above and below the clutch master connection point onto the clutch pedal?

So how big is your slave Paul???

Slo[/quote]

[stephen low]

As said this was an early picture and there is now a rose joint bolt at the end of the clutch push rod and attached at that pedal attachment hole.

I'll measure the 3/4 master to see what the maximum stroke is for this rod. Would it be safe to assume the 3/4 and 5/8 masters have the same stroke but just different bore sizes? Don't think they are from the same manufacturer though.

If I was forced into this option it will be a messy correction at the front of the painted footbox , that's all.

[AC-460]

don't worry if its not pushing exactly straight it will still work fine ....it worries me that the ratio on you brakes is going to be wrong aswell

[stephen low]

The brakes worked ok and I haven't changed them at all so this shouldn't be an issue.

However putting the clevis-rose attachment point higher up the clutch pedal will reduce the length of push achieved on the push rod though wont it?

There will be less pedal travel higher up so doesn't this also affect throw distance as a function of less hydraulic fluid movement?

Slo

[iva bigan]

Slowly
I dare you to just drill another hole and put us out of our misery,and if we're wrong I can live with that.

Iva Bigan

[stephen low]

Another short update -

Having finally bleed the system to be sure of proper operation I did measurements as to the fork movement at clutch pedal rest, full depression and just at point of release.

I needed this knowledge to determine whether I could increase my slave sizing to increase hydraulic force at the expense of reduced fork movement.

The photos below show the results - excuse the quality but the camera was struggling to take clear photos.

Slave set up and measuring reference.



Movement markings and travel distances

The 100mm mark represents clutch pedal at rest, the mark at 74mm represents full pedal depression and at 82mm the release point when the wheels would rotate.



Translated at the thrust bearing this means I am at correct or slightly over depressing at full travel. So I don't believe I have sufficient travel to change the slave as an option.

I am going to double check these travel distances on the bellhousing and fork too now that this is all apart, as I ended up dropping the gearbox out on Saturday.

I will get the Mcleod clutch fingers tested to see how much stiffer these are compared to a standard AU clutch option I could use as one choice.

I also have an opportunity to use a McLeod internal hydraulic system but reading the McLeod tech advice they suggest a 3/4 master and a pedal ratio of 6:1 anyway.

Finally I am also going to review how I can properly raise the master neatly to improve the pedal pressure in my favour. But I'll also measure how this affects plunger stroke so I have all the rights facts to hand.

I was never going to just make a hole higher up the pedal and re-attach as the misalignment in the master would ultimately be detrimental for sure.

So not yet fixed but clearly it will be.

Thanks for all the advice guys it has been a learning curve for sure.

Steve

[BITTEN]

We had a very similar issue.
As strange as it sounds the solution was simple - a smaller not bigger master cylinder bore size but dont guess.
Measuring the pedal ratio is the key then call a brake and clutch person who knows what they are talking about and they will tell you what bore size you need.
Our clutch went from literally a rock to a pleasure.
Good luck

[stephen low]

Thanks Rotax

And yes I first went from a 3/4 to 5/8ths master and improved the feel immensely.

Conversely I was hoping to go larger in the slave which gives the same effect but I clearly don't have the travel available to do this.

Heading out now to such a source though.

Cheers

[stephen low]

So a final post to indicate the fix I achieved.

Discovered the McLeod pressure plate was rated at something like 1700kg clamp pressure compared to 1100 kg for a standard AU variant.

So I've simply swapped over the pressure plate and now have a moderate pressure clutch pedal which I am more than happy to drive and use now.

I had thought of one way to nicely raise the master if I wanted to do this but wanted the core equipment to be my starting fix.

Thanks all for the suggestions and now I can move forward onto other jobs and keep this begga moving forward towards its own motive action.

Cheers

Steve