Author Topic: 350 Shift Fork Casting Differences  (Read 733 times)

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Offline moonpup

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350 Shift Fork Casting Differences
« on: April 22, 2018, 05:37:52 PM »
Just noticed a casting difference on a couple shift forks and considering that there is only one part number for all 3 used on the 350's, was wondering if anyone here knew of any changes made during production on these or what else might explain this?

Where the fork guide pin goes thru, the fork pictured on the right has a rounded outside casting, while the one on the left has a blunt surface on that same area.

Also, the third pic shows another fork I found where a previous owner has apparently taken a fork with the rounded casting and ground it blunt like the one on the left in the other pics.

?????
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Offline slawsonb

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Re: 350 Shift Fork Casting Differences
« Reply #1 on: April 23, 2018, 12:16:02 PM »
I'm not aware of any clearance issues, but that would explain the flat...
...bert

Offline BRT-GTR

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Re: 350 Shift Fork Casting Differences
« Reply #2 on: April 23, 2018, 05:31:10 PM »
             In the gearbox I have on the bench, all 3 shift forks have a small flat forged to the outside of the pin boss. However the center (forward facing) fork for the 3/4 gear selector has also had the flat gound deeper to provide additional clearance from the crankcase.

           Bridgestone Service Bulletin, dated Sept,11,67  refers to the shift fork hole for the guide pin being enlarged to improve gear changing.   Although not mentioned in the text, the drawing clearly shows the flat on the pin boss.
         These mods were intoduced on the factory line from serial no. 00250, June 19, 67.
       
   If I remember correctly, I believe Ziggy posted that he had bought a new fork that did not have a flat and he had to file/grind        one to clear the crancase.                                                                    Brian.
« Last Edit: April 23, 2018, 06:21:22 PM by BRT-GTR »
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Offline moonpup

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Re: 350 Shift Fork Casting Differences
« Reply #3 on: April 23, 2018, 06:28:59 PM »

.....snip..... However the center (forward facing) fork for the 3/4 gear selector has also had the flat gound deeper to provide additional clearance from the crankcase.


Just a thought, but having that one out of place on the drum might explain the shifting difficulties some members have had recently.

Oh.... and thanks for clearing this up for me!  banana
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Offline BRT-GTR

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Re: 350 Shift Fork Casting Differences
« Reply #4 on: April 23, 2018, 07:02:55 PM »
       Mike,     Yes could happen.

     It is always good practice to replace interchangeable parts where they were originally installed and have bedded in.
  So for the record, if you didn't mark the shift forks before pulling the drum out, here's how to identify where they go. May not work for earlier engines.

     Left side, 5/6 gear,     Has a small groove ground both sides of the longer fork tip.   Fit  rear facing

        Center, 3/4 gear     Flat on the guide pin boss has been ground deeper.              Fit forward facing

   Right side, 1/2 gear     No idea how you select this one ;D :D ;D but if lucky (or not) you may find a small indent half way     
                                    down the longer side web where the 2nd gear pinion has been hitting it.    Fit rear facing


   
« Last Edit: April 24, 2018, 05:26:24 PM by BRT-GTR »
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Offline davis

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Re: 350 Shift Fork Casting Differences
« Reply #5 on: April 23, 2018, 08:39:47 PM »
Checked a dozen shift forks and could not find Brian's "small groove gound both sides of the longer fork tip" so may be not understanding what he means properly. 5 were roughly ground and none with a flat cast feature. Really disconcerting is one was ground across one side of the whole finger below the pads! A conversation with Steve Reed comes to mind when he said each transmission was probably hand fit. It looks like the casting was designed for a different hole location but the hole needed to be drilled closer in, thus leaving the casting hanging out more. Does it make sense to just grind all the shift forks?

Offline BRT-GTR

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Re: 350 Shift Fork Casting Differences
« Reply #6 on: April 24, 2018, 08:57:39 AM »
       Bob,
               After Serial No. 01001, BS introduced a  small groove ground into the longer tip of the 5th/6th shift fork to improve the oil supply and reduce scoring. I think you can see it on Moonpup's top picture, r/h fork unless it's an effect of the light.

             Only the forward facing centre fork needs to have the guide pin boss ground back, to avoid catching the crankcase.

        Two shift forks on the engine I'm currently rebuilding (numbered in the 6000s) also have extensive crude grinding between the pads to take the metal back.  I would guess the forging/stamping dies used to make the forks were becoming worn or damaged and were not forming the forks properly.

        The more we learn about these machines, the more baffling they become !!.  Later machines do not show the same build standard/quality as earlier machines. Were BS losing interest or were the workers becoming complacent about the quality of their work ??   What do others think ?                                                                 Brian.
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Offline moonpup

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Re: 350 Shift Fork Casting Differences
« Reply #7 on: April 24, 2018, 09:30:39 AM »
Here are a couple pic's that show the groove in the top pad and the grinding between the pads.
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Offline davis

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Re: 350 Shift Fork Casting Differences
« Reply #8 on: April 24, 2018, 09:55:26 AM »
More of the same. Left grooved, center area grind, right common area of contact with gear.

Thanks for the info guys. I can now grade my shift forks into groups with their individual locations. While frustrating, it is interesting. Wish a complete guru guide for this interesting machine could be compiled.

I would say when the future looked bleak for production less money was available to repair, and upgrade tooling.

Offline OldSwartout

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Re: 350 Shift Fork Casting Differences
« Reply #9 on: April 24, 2018, 07:19:43 PM »
I don't know how much this may have affected the shift fork issue, but from the beginning of the machine age until the late 80's, early 90's, there was a lot of variation from the engineering drawings done by the manufacturing people to make things actually work.  There may have been some of that here, maybe the grind on the center fork was never an official process, just something done at the manufacturing or even on the assembly line to make it work.

I was an engineer for a very large corporation. During the time when we were upgrading standards to modern tolerance standards and international quality standards such as ISO 9000, etc., we had to review thousands of drawings, internal procedures, etc. and verify and upgrade them.  We found hundreds of process variations from the drawings that the manufacturing personnel had made, some in the process documents and many undocumented that were done on the shop floor to make things work and were passed on from person to person.
Karl Swartout
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Offline BRT-GTR

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Re: 350 Shift Fork Casting Differences
« Reply #10 on: April 25, 2018, 11:41:31 AM »
       Pic 1,    This is how the fork groove was designed and is a good match with Moonpup's picture above.

       Pic 2     Here's mine, someone was a bit over enthusiastic grinding this one. An example of the variation from design that      can creep in over time or as different people take over the job as Karl says above.
                   Sorry to put a spanner in the works but it is not only the centre fork that can exhibit grinding between the pads. My left fork also has it.
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Offline BRT-GTR

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Re: 350 Shift Fork Casting Differences
« Reply #11 on: April 25, 2018, 11:51:59 AM »
         Pic 3     Notice all 3 forks have a small flat forged into the guide pin boss as part of their manufacture but the centre fork only has been further ground back to provide greater clearance from the case wall. This is the grinding I referred to above as a guide to identify the centre fork.  Does this appear on your centre forks ?.
 
         Pic 4      Close up.
« Last Edit: April 25, 2018, 01:19:19 PM by BRT-GTR »
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Offline moonpup

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Re: 350 Shift Fork Casting Differences
« Reply #12 on: April 25, 2018, 12:00:01 PM »
Brian, your center fork looks like the one in my original pic #3 that I thought was the handy work from a previous owner. Looks like a factory job now.... :o
« Last Edit: April 25, 2018, 12:02:12 PM by moonpup »
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Offline Steve Swan

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Re: 350 Shift Fork Casting Differences
« Reply #13 on: April 25, 2018, 04:04:31 PM »
I am really enjoying reading threads such as this discussion on shifter forks.  I've been reading a number of various threads in the forum, really great stuff,  you Bridgestone folks are very thoughtful in your approach in your care-taking of these bikes.  I have not participated nor introduced myself on the forum (yet), however i will soon.  I bought Ric Hapke's '68 GTR and await its delivery to me via Haulbikes.  Once i have the bike in my possession, i will introduce myself, i am looking forward to preserving it as an unmolested survivor rider.  I really appreciate the time and effort you folks put into your bikes and forum contributions.  Thank you!  Steve Swan, Fort Collins, Colorado.

Offline BRT-GTR

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Re: 350 Shift Fork Casting Differences
« Reply #14 on: April 27, 2018, 06:59:18 AM »
        Pup,
                My engine had not been split before so was reasonably sure the supplementary grinding of the flat on the center fork was factory done. Still not sure if it was done on all machines - anyone else find this ?

    Steve,      Welcome to the site and BS ownership. Plenty of help available here - just ask. Manuals available above, under downloads. Enjoy your GTR but be careful, BS machines are addictive.   Good to know someone appreciates our ramblings  ;D.
                    Brian.
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Offline Steve Swan

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Re: 350 Shift Fork Casting Differences
« Reply #15 on: April 28, 2018, 03:17:18 AM »
        Pup,
                My engine had not been split before so was reasonably sure the supplementary grinding of the flat on the center fork was factory done. Still not sure if it was done on all machines - anyone else find this ?

    Steve,      Welcome to the site and BS ownership. Plenty of help available here - just ask. Manuals available above, under downloads. Enjoy your GTR but be careful, BS machines are addictive.   Good to know someone appreciates our ramblings  ;D.
                    Brian.

Thanks Brian !

 


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