Author Topic: Plunger gearbox attachment  (Read 537 times)

Online Greybeard

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Plunger gearbox attachment
« on: 06.04. 2016 14:12 »
I find removing and replacing the gearbox is a bit of a faff on these semi-unit construction machines. Firstly you have to undo the engine and either remove it from the machine, or turn it to the left enough to get at the gearbox to crankcase attachment. I assume my machine is standard in that the top of the gearbox is held onto the crankcase with a couple of  3/8"? shallow-head Whitworth screws while the bottom edge is secured by nuts on a couple of 3/8" Whit studs. My 3/8" drive socket with universal joint doesn't have enough room to get onto the top screws. The only way I could loosen and tighten the top screws was by using a spanner end-on with a bar in the other end to turn the spanner; not conducive to keeping the screw head looking nice! 
To allow the gearbox to come away complete the bottom studs have to be removed. This requires locking both nuts on one stud so it can be turned. Same process in reverse when refitting the studs. At least you can use a spanner for these.
Any ideas on how to make this job easier?

Offline muskrat

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Re: Plunger gearbox attachment
« Reply #1 on: 07.04. 2016 07:08 »
Yep, take the whole lump out *work*
I tried to do it that way once when I first got mine. After 2 days struggle I gave up.
I think one or two here replaced the studs with bolts.
Cheers
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Online Greybeard

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Re: Plunger gearbox attachment
« Reply #2 on: 07.04. 2016 10:32 »
Yep, take the whole lump out *work*
I tried to do it that way once when I first got mine. After 2 days struggle I gave up.
I think one or two here replaced the studs with bolts.
Cheers
With the engine diagonal across the frame it's easy enough to get the box out.  Couldn't be arsed to lower the hoist which would have been necessary to get myself over the frame top tube to lift the lump out!
I thought about getting some screws for the bottom edge but then I realised that the unmachined shank on the studs gives better alignment.

Do you know, if the gearbox has its internals removed is it possible to pull the box straight off the studs?

Offline muskrat

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Re: Plunger gearbox attachment
« Reply #3 on: 07.04. 2016 15:00 »
I think it would be but I've never tried.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline duTch

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Re: Plunger gearbox attachment
« Reply #4 on: 08.04. 2016 09:22 »

 
Quote
Do you know, if the gearbox has its internals removed is it possible to pull the box straight off the studs?

 I can't see why not, but easier to undo the studs.  I lost the studs years ago, and use four screw in bolts. I would suggest longer studs with permanent locknuts for removal of the stud, but is the same end result as replacing them with bolts anyway- or better.
 I have bolts with about 3/8 or so of unthreaded shanks that are fairly snug in the flange holes, for better location(as I realised you already said).
 
Quote
Any ideas on how to make this job easier?

 If I can find those pics of the sprocket cover mod....
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Offline Tone

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Re: Plunger gearbox attachment
« Reply #5 on: 08.04. 2016 16:42 »
Mine is fitted the same with bolts, I did manage to get to the bottom ones with a 3/8" knuckle, but I did take the engine right out.

Online morris

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Re: Plunger gearbox attachment
« Reply #6 on: 08.04. 2016 20:21 »
Do you know, if the gearbox has its internals removed is it possible to pull the box straight off the studs?

That's a definite yes.

Mine came with 4 bolts, but I replaced all 4 with studs because I don't like screwing bolts in and out of the engine. Afraid of stripping threads... *problem*
I then slid the empty box on (with the sprocket on) and mounted the internals. The advantage then is also that you don't stress the primary oil seal with the risk of damaging it. A bit of work, but then again it's not something you need to do every other week or so.
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