TR6 Throw Out Bearing Fork Problem

[Got_All_4]

I guess this is asking a question and a discussion. Just got back on my frame and getting ready to install the tranny and while assembling the fork for the throw out bearing the pin would not screw in. I was planning on reusing the parts I took out. So I went and purchased a new fork and pin but once installed the bearing carrier binds up and only goes 2/3 of way back. I tried another carrier and it only went 1/2 way back. To get it fully back I have to pound it back. Now I decided to reinstall the old fork for a test and the new pin screws right in and everything works perfectly and smooth. Did a lot of inspection and measuring between the two forks and can't find any major differences/problems. What I did find was the two pins were 11k closer then the old one. So I carefully ground off 5k on each side and beveled the pins. The casting between the forks was high so I ground those down. Nothing I've done made a difference. The one thing I can't change is the pin height. Seems to be 21k higher then the old one and that measurement is from the bottom of the shaft to the top of the pin.

I purchased the new fork from my local Triumph parts store and he mostly sells Moss stuff. If you look closely at the last pic the fork has a part number on it and starts with TRF. Is that The Roadster Factory? I know they have a lot of the LBC parts remanufactured to their specks and I like how more robust the new fork is. Since I bought a new one I would like to use it and there is a small issue on the old fork too. Now is there anyone out there that has had the same problem or thinks they can offer a solution. I started this on Tuesday and it is now Saturday so it's getting very frustrating.

 

[charleyf]

First the TRF is most likely from The Roadster Factory.
Second one problem that I found recently ( While putting a TR6 tranny on a TR3) was that the location where the fork fit on the cross shaft was slightly different than original. When I removed the capture bolt at the end of the cross shaft, I was able to get the fork to move freely. To get it to work I used a smaller bolt ( from 5/16" to 1/4" and used a nut on it) at the end of the cross shaft. That gave the cross shaft room to move to allow the fork to fit against the carrier properly.
Are you also having problems getting the pin to screw into the fork as much as you want? If so you need to determine which of the three parts is the problem. Is it the new fork, the cross shaft or the pin. I suspect the problem is the diameter of the lower portion of the pin. If you need to remove some material from one part and are concerned about weakening the pin. I would say you might consider adding a second bolt and nut( grade 5 -1/4") through the fork and cross shaft. This has been a recommendation from other owners. I did use it on my most recent restoration. It adds a back up for the screw in pin.
Charley

 

[sp53]

I would try what Charly suggest with the 1/4 bolt to see if that makes a difference with a little wiggle room. seems to me there is a lot of moving parts that need to mesh together on a 2 foot rod. if I remember correct the shaft has a little notch for the bolt. perhaps the shaft itself is bent a fuss or bedded in a certain way that the new parts are working against you. Or the brass bearings on the end inside the bellhousing have too much play or not enough and the combination of mixed parts is causing the problem. do you have a different shaft?

steve

 

[charleyf]

I would try what Charly suggest with the 1/4 bolt to see if that makes a difference with a little wiggle room. seems to me there is a lot of moving parts that need to mesh together on a 2 foot rod. if I remember correct the shaft has a little notch for the bolt. perhaps the shaft itself is bent a fuss or bedded in a certain way that the new parts are working against you. Or the brass bearings on the end inside the bellhousing have too much play or not enough and the combination of mixed parts is causing the problem. do you have a different shaft?

steve

After studying the whole system I came to the conclusion that the bolt at the far end of the cross shaft has little use. The cross shaft is centered by the fit on the bearing carrier. In a deeper analysis. It may well be that the new fork is off by about 1/32" or less and giving that bit of room for cross shaft movement is enough to make up the difference. And allow the bearing carrier to adjust to the proper position on the front cover it rides on.
Charley

 

[Got_All_4]

I posted a message 2 days ago and don't know where it went. So here I go again. Good thing I have a machine shop. First I took the bearing off the carrier. Then slid it on the shaft and ungauged the fork. Closely look at everywhere anything was suppose to touch and not. Carefully filed off around the fork pins. That helped a little. Filed some more and help a little more. I noticed that when the pin in the bearing carrier was on the bottom there was less resistance. So I took out the pin and ran the carrier in my metal lathe. Took off a couple of thousands on both sides where the pin rides. Then took a few off on the back flange. Installed it on the shaft and slid perfectly fine and had complete rotation as I worked the fork back and forth. I reinstalled the pin and the throw-out bearing and everything is working fine with no slop. I didn't mention that I installed the pin in a different location so the carrier wouldn't ride in the worn dimple.
What sucks is I called Moss technical department for help I think on the 9th and they still haven't gotten back to me.

As far as the extra 1/4" bolt I've been doing that for years with great success. The fork and the shaft were used and was planning to reuse both. But a chunk of casting came off the boss where the threads are.

 

[charleyf]

It sounds like your expertise got you through the problem.
Charley

 

[Got_All_4]

You know I've got to wonder since there are so many problems with the tapered fork bolt that many overtighten them and there is so much stress on the bolt they are bound to fail with the added work of moving the fork against the pressure plate. In machining many tools and tooling are held in place buy a taper. A Morris Taper and all it takes is a light tape to hold them in place.

 

[CJD]

Alas...more poorly manufactured parts.