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Strange gearbox issue

Submitted by tony_wood on Sun, 01/05/2022
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Heavy Twins

Hi. I have finally finished rebuilding my 1960 Dommie 99 - it only took 4 years! So now I have the joy of running in the engine and gearbox after substantial rebuilds with various new parts installed. However, as usual, not all is ‘harmonious’. I’ve got a problem with selecting first gear. When sitting on the bike the pedal moves up to what feels like full extension but the first gear doesn’t engage. I can get it to engage by flexing my foot upwards really hard, but that’s not too comfortable. The easiest and most reliable way I’ve found is to use the back of my heal hooked under the front of the gear lever to pull the lever up. It’s the same whether the bike is at rest or moving, although going from second to first when moving is a bit easier. All other gears select smoothly up and down the box with no problem. I’ve tried moving the footrest and the gear lever on their respective splines to various positions but can’t get a satisfactory position that allows an easy first gear selection.

Has anyone else had this sort of problem? Any advice gratefully selected.

Thanks

Regards

Tony

Submitted by robert_tuck on Sun, 01/05/2022

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I have had this problem ,in my case it was caused by new and larger boots . I have an orriginal long gear lever and have noticed that most replacements are shorter  and these would be impossible for me. In the end I found a slightly lowered footrest with gears lever re-positioned made it just workable .I take size 10  . I will post what is the length of my gear lever. It may be you have a short one.

Thanks Bob. My new gear lever is the same length as the original one - both are 5.75 inches from the pedal centre to the splined hole centre. I’ve worked out that I just can’t get the final bit of upward flexing of my foot that I need if I just use my toes to operate the lever. I’ve found that if I slide my foot forward on the foot peg I can use the area of my foot above my instep to lift the gear lever just enough to engage first gear. However, that’s a bit of a faff because I have to remember to move my foot forwards over the foot peg before changing down every time I want to go from second to first. It’s not a boot size problem for me as my boots are only size eight.

Regards

Tony

Submitted by tony_wood on Sun, 01/05/2022

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Hi David. I think the indexing is ok because I can easily get first gear if I pull up on the gear lever by hand or use my heel to hook up the gear lever. Maybe it’s just that my feet are smaller than the average Dommie rider?

Regards

Tony

Submitted by ian_soady on Sun, 01/05/2022

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... the opposite problem with a unit Triumph 500 I rebuilt some years ago - couldn't get my size 12s under the gear lever whatever I did. Didn't like it anyway so part-chopped it for a 1931 Sunbeam with hand change!

Submitted by robert_tuck on Sun, 01/05/2022

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5.75"   is the same as my orriginal lever  , If you have an extra long  primary chain it would shorten the distance between  footrest and  gear lever. a bit an make it harder.     Had to think twice about that !!. Certainly old age has made my ankles less flexible .  A really clean lifting clutch  also  helps easy gear engagement . I was like you resorting to using the back of my heel at lights.

Submitted by mikael_ridderstad on Sun, 01/05/2022

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When you assembled the gearbox, did you file the slot in the inner cover as Mick Hemmings said in his video? It could be that the quadrant hits the bottom of the slot when engaging first.

Submitted by tony_wood on Sun, 01/05/2022

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Hi Mikael. Luckily I purchased Mick Hemmings’ gearbox rebuild video shortly before working on my gearbox so I took the appropriate action with a file to slightly enlarge that inner cover slot. The problem remains a bit of a mystery but at least I can now ride my bike even though first gear is ‘challenging’

Regards

Tony

Submitted by tony_wood on Sun, 01/05/2022

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Bob. That’s an interesting point about a longer primary chain making the gear change lever distance shorter. That makes sense. However, I actually had to remove a link from my primary chain and then add a half link in its place as the stock chain was too slack. I’m not sure if that is a contributing cause to the problem but it could be playing a part in it. The clutch operates really nicely (new complete clutch bought from RGM). Interesting that you too occasionally have to resort to the ‘heel change’ technique to get first gear!

Regards

Tony

 


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