Moderator: chasthor

Gear selector shaft PITA

Stoo63
Junior Fizzy Nut
Stoo63
Junior Fizzy Nut
Joined: 11:17 PM - Feb 27, 2016

8:38 PM - Mar 08, 2018 #1

Hi guys, possibly going over old ground here but please bear with me.
So. I'm rebuilding my 76 pedal engine. Standard 394 4-speed box. However the "hooks" on the gear selector don't want to consistently engage with the drum. Sometimes they " clunk" into place nicely, other times they rest between the pins on the drum.
When turning the drum by hand it moves pretty smoothly. (Most of the time) A little rotation of the shafts helps.
However when you add the gear selector to the mix, the "hooks" are inconsistent.
Tried new pattern selector shaft (piece of junk) - no improvement.
Turned the selector fork shaft round per Chas's earlier post so circlip faces opposite side from manual.
Tried operating it without the positive stop lever - slight improvement -sometimes.
Tried different springs to draw the " hooks" into the pins on selector drum - nope.
Its been shoogled, shaken, cajoled and cursed
Selector forks and drum don't seem to have any great deal of wear - low mileage engine.
Any tricks to get four nice chunky clunks time after time would be greatly appreciated.
Cheers
Stewart
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chasthor
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chasthor
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Joined: 7:40 PM - Jun 29, 2005

6:27 AM - Mar 09, 2018 #2

Are you attempting this with only one engine casing Stuart? I only ask, as with that configuration, the assembly does try to splay apart.

I don't think its possible to fit the right selector fork in the left position and vice versa, so I don't think that this is your problem. Do you have sufficient lubrication on all the running surfaces? There is a lot of metal to metal contact with this assembly and really does not like to run dry.
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mech73
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mech73
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Joined: 8:43 PM - May 19, 2007

10:16 AM - Mar 09, 2018 #3

In addition to what Chas has suggested. The gears need to be rotating (slowly by hand is fine) and also the sprocket and clutch centre nuts need to be fitted and at least nipped up as otherwise the two gear shafts don't necessarily sit in place correctly relative to each other and the drum/forks.
Lincolnshire exile in North Hampshire

Brighton 08/09/10/11/12
East Coast 10/12
IOW 08/09/10/11
Northern 12
Uttoxeter 08/09/10
Spa Francorchamps 11
New Forest 09/10/11/12
Billing 07/08/09/10
Eagle 08/09/10/11
Ace Cafe 09/10/11


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Stoo63
Junior Fizzy Nut
Stoo63
Junior Fizzy Nut
Joined: 11:17 PM - Feb 27, 2016

8:01 PM - Mar 09, 2018 #4

Thsnks guys. Will add a little more lube. I have only tried it with the nuts tightened, mech. Tried various torques go see if it was sticking coz too tight/loose. Had it apart a half a dozen times now ( one of them to change the selector fork shaft so circlip is opposite way from diagram as per Chas's tip) It seems that the selector wants a stronger spring to draw it down onto the drum. Even tried swapping over the two springs (selector/positive stop lever) as stop lever seems too be slightly stronger spring. The eccentric adjuster doesnt seem to be interfering either. Perseverance is a virtue, they say......
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chasthor
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chasthor
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Joined: 7:40 PM - Jun 29, 2005

7:23 AM - Mar 10, 2018 #5

Can you post any pics?
We may be able to see something.
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Stoo63
Junior Fizzy Nut
Stoo63
Junior Fizzy Nut
Joined: 11:17 PM - Feb 27, 2016

12:04 PM - Mar 11, 2018 #6

Will try to get somd pics up soom Chas.
Just git caught up with a gileda coguar needing recommissioning. ?
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mech73
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mech73
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Joined: 8:43 PM - May 19, 2007

9:28 PM - Mar 11, 2018 #7

So what is exactly happening or not happening?

Is the drum stopping in the wrong place so that the barbs on the change arm are missing the pins? If I remember correctly in each gear position, the flat part of the change arm (between the barbs) should be resting against two of the pins, with an even gap between barb and pin for both barbs.

or are the barbs riding up over the pins? if so is it in both directions or just one? The spring should only be required to pull the arm down to the correct initial position. It's the undercut in the shape of the barb that holds it on to the pin as you operate the gear shaft to rotate the drum. Is there any wear on the barb where it contacts the pins or wear on the pins themselves.
Lincolnshire exile in North Hampshire

Brighton 08/09/10/11/12
East Coast 10/12
IOW 08/09/10/11
Northern 12
Uttoxeter 08/09/10
Spa Francorchamps 11
New Forest 09/10/11/12
Billing 07/08/09/10
Eagle 08/09/10/11
Ace Cafe 09/10/11


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chasthor
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chasthor
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Joined: 7:40 PM - Jun 29, 2005

3:21 PM - Apr 01, 2018 #8

So where are we with this?
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