ET: Engine (Twin) Rapide Gearbox - Very 'tight' gearchange

greg brillus

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Some gearboxes are a bit sensitive to too much pressure on the detent plunger spring, you can check easily by undoing the plunger cap G 37 a turn or so and see if this is better. The issue with the 5 speed box also is that the gears are harder to engage because the "Dogs" are much larger and fewer of them to a standard 4 speed box, so the shafts have to be rotated much more to engage and shift through the gears. Sometimes with regards to the detent spring I close it up fully in the vice and this shortens it by about a mm or so. Another trick is to change the tip shape of the plunger to a slightly more ball shape rather than such a point, this allows it to move easier as the contact area is a bit less. On some boxes with changes to the 5 speed the camplate spindle pushes down on the camplate making it hard to turn, try cracking it free a half turn and try...............It can be just the bottom of the spindle, or the tinny lip a half inch up from there that just might need a whisker removed if this is the cause. I use 80W/90 gear oil in all the bikes I do, except the racer which I used 40 weight Castor oil. Cheers..................Greg.
 

vibrac

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All good stuff especially on 5 speed but Peter did not say he had 5 speed box see post 1
 

Phil Arundel

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Thank you for all the replies.
In my case the gear change is ok for 1st, neutral and 2nd gear. Selecting 3rd &4th is very difficult, as if something is binding. On closer inspection I found that the offside selector fork surface is binding on the camplate- I intend to remove some of the material from the selector fork surface to give a little more clearance.
Anyone else found this to be the case?
 

Marcus Bowden

VOC Hon. Overseas Representative
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2007 doing the Irish Rally prior to the Annual in IOM my detent spring broke, start off in first then kick it into 4thand ride with foot on indicator, spent an evening fixing it with good selection of broken ESA (engine shock absorber) springs as it all had to come off anyway. When home to fit a correct new spring drilled two of the chain wheel holes larger to access with a socket, haven't done all the children's twins yet but next time they get stripped will do. It saves having to remove ESA, every thing new it is very stiff , I cut a couple of coils off if I recall.


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Phil Arundel

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Where did you source the new parts?
Hi Peter, the parts came with the bike. I bought the Rapide as a reconstruction job.
The gear cluster is new. I found that the selector arm was fouling the quadrant plate so made an adjustment. I can now get 2,3 & 4th gear but not neutral & first. Very frustrating.
 

Bill Thomas

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Morning Phil, Is the camplate pivot pin tight in the roof of the gearbox.
Or has the boss been repaired, The hole only has to be a Nat's out , To mess things up.
Cheers Bill.
 

greg brillus

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Geez Bill, You took the words from my mouth..........That's what I was thinking too. Had one just like that late last year, the spindle boss had been extensively repaired and the fork pins and slots in the cam plate were larger than standard.............Had to remove small amounts of metal here and there to fix it.
 

Bill Thomas

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Phil, We are talking about when you move the indicator ?, And not just the outer selection part.
Cheers Bill.
 

Phil Arundel

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Yes, moving the indicator. Bill, I will check your suggestion Re the cam plate pivot pin. All parts are new so I will follow your suggestions.
By the way I can now easily get 2,3&4th gears but there is some resistance which prevents selecting neutral & 1st.
Back to the garage for me .
 
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