Clutch Fork Update/Reinforcement

[Rasta Monsta]

Anyone reinforced their clutch fork? I am seeing failures on them, and as they are NLA, I am wondering how we can keep them in service longer.

[idontknow]

Any pictures? There's a few forks and associated linkage in the transmission so I'm not too sure which you are talking about.

[Grandad#3]

Do you have a picture of one that is broken and are they all breaking at the same place? I bought a good used one just to have on hand in case of breakage.

Cheers,
Larry

[Rasta Monsta]

Here is a pic. Cracking/bending area circled:

[Schumi]

There are some heat treats that it could go through that may be able to increase the strength, and at least increase the surface hardness, that may extend the life. I may look into this.

[Cocacolakidd]

I have heard of a few fellows that built up that area with a hard rod procedure. Basically welding with a type of chrome alloy (called Hard Rod) arc weld rod - thus super strengthening the weak area on each side...Some even go to lengths to run passes all the way down the fingers including the tips and then machining the fork tips back to tolerances and micro polishing the result. Thus leaving a much harder surface for wear resistance besides strengthening the unit as a whole.

[bebbetufs]

Would it not be possible for a good welder to make a new fork out of sheet metal or aluminium? It would have to be machined for the bearings off course.

[Rasta Monsta]

That is a cast part that needs to tolerate substantial loads. . .I doubt lighter material would work.

[drcbike]

While I have a 944 turbo I have experienced three o' these beasties breaking over the past 6 years or so. I have a much heavier duty clutch to keep up with the upgraded engine but they still break in the same place.

I like the notion of welding the reduction points and will look into it...

[Rasta Monsta]

Welcome, drc!

If you don't have anyone in mind, maybe we should run a fork by Lonnie Gilberston's place and get his opinion? Still got a busted one to show him?

[Rasta Monsta]

Originally Posted by Cocacolakidd

I have heard of a few fellows that built up that area with a hard rod procedure.

More info on this would be greatly appreciated. . .could you reach out to these fellows, or get them to stop by here? Between myself and my buddies here in Portland, we are about to have three of these units in hand and ready to reinforce. . .

[Rasta Monsta]

No more? Really? C'mon racers, I know this is a common failure. . .

[Arizona_928]

hey, that's my bent fork.

[Rasta Monsta]

Indeed it is, and we thank you for your contribution!

[porschetub]

These forks could be heat treated @ the curved section but need to be done by a someone who knows what the are doing,crankshaft repair people would know.
If the clutch master cylinder is over travelling this will bend the fork.
As an engineer I don't believe you could fabricate something much stronger without spending huge $$$$ ,but repair of the fork ends is not difficult any hardfacing type welding rod could be used to build up these wear area's but correct preheating must be carried out,cheers

[mikepellegrini]

There's this current thread over on the 951 forum: blaszak clutch fork photos

I tried to buy an Optibelt tool from him but got the run around - he's not very customer service oriented - but many people speak well of his machine work.

Blaszaks' site: index

I couldn't find a link on his site for the clutch forks, but I think I remember seeing one on the thread, somewhere.

[wild man]

Originally Posted by drcbike

I have a much heavier duty clutch to keep up with the upgraded engine

What pressure plate, exactly, are you running?

[wild man]

Two weeks and no response?

OK then, does anyone know if chances of breakage/bendage would be higher if using a centerforce PP, vs. stock?

In regards to reinforcing it via welding, I take it that the procedure is to run a hardrod bead on either side of both fingers, and maybe along the backside, in the breakage prone areas?

I'm no master welder by any means, but I do know that cast iron needs to be preheated so it will not crack. But the only "hard" type of rods that I know about are nickel rods ( I've never used one though). Are these the ones that you are supposed to use? I will be replacing my clutch with the $1205 CF plate/disc kit (with 930 disc) before years end, and don't want to have to take everything apart again if the fork fails.

[Rasta Monsta]

I just spoke to my machinist about this yesterday. He suggested adding material to the throwout bearing so it rests on the entire fork "finger" instead of just half of it. He also suggested adding stops to the bearing so it doesn't spin in the fork.

Before proceeding, though, he wants to do a metallurgic analysis of the bearing material to see what it is made of and determine the best way to weld it.

FWIW, he was not enthused about welding on the fork. He was concerned that the heat involved might actually weaken the part.

[wild man]

Interesting. I'm no expert by any means, but I was not aware that the strength of cast iron could be manipulated via thermal processes (heat).

Let us know what you come up with, regarding that.