Mk11 gearbox options

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Mk11 gearbox options

Postby StewartPorter » Fri Mar 08, 2019 9:55 pm

Hi all, my collection of bits for my ''58 Sq4 resto didnt contain any gearbox casings. There is, fortunately, a full-length gb7 mainshaft. The majority of gthe he other bits seem to be from various BAP boxes.
I've read that gb cases are the same and that i should be able to fit the specific gb7 gubbins in. However im dubious. Ive got the offer of a G1-2 shell and casings and gear cluster. Is there any way I can make this fit a '58 plunger? If not are there any alternatives to a full-spec GB7 box.?
Cheers
Stewart
'59 D1Bantam, '60 5Ta Speed Twin, '76 Yamaha FS1-E, '58 Sq4 (Lazarus project)

Simon.Gardiner
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Re: Mk11 gearbox options

Postby Simon.Gardiner » Fri Mar 08, 2019 10:26 pm

Stewart:
I'm no Square 4 expert but as a lot of Ariel stuff is interchangeable I'll hazard an answer for you. GB gearbox cases are the same for Square 4s and all other 4-stroke Ariels except the HT!
(OK, I cheated - check the info on Drags site here https://www.draganfly.co.uk/index.php/a ... egory/709- and in the 52-58 GB gearbox parts section listing which includes the cases and gives designations for the few items that are or are not Square 4 usable, including the cases.)

HTH

SG
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)

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Re: Mk11 gearbox options

Postby roger.fellows » Fri Mar 08, 2019 10:43 pm

The cases I've looked at recently have been G - 1 - 5 as far as I remember. Maybe the 2 and 5 stand for 1952 and 1955, but that's a guess. I recall Paul Jameson saying that a GB 6 case will take the Sq4 mainshaft as a straight swap, memory not always reliable. Does the G-1-2 say GB7?

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Re: Mk11 gearbox options

Postby Simon.Gardiner » Fri Mar 08, 2019 11:55 pm

Ahhhhh - G-1-2 stamped on a Matchless/AJS(or HT) Burman box in a dark corner of my garage.....
So, cases no good (primary chain adjusted by slots for the top mounting stud in the engine plates) but the gear cluster is useful (except for the mainshaft and - for a Square 4 - the final drive sleeve/gear).

SG
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)

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Re: Mk11 gearbox options

Postby roger.fellows » Sat Mar 09, 2019 11:50 am

If I understand you correctly the adjustment method is the same, Simon - a drawbolt from rear engine plate to peg on gearbox??

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Re: Mk11 gearbox options

Postby Simon.Gardiner » Sat Mar 09, 2019 8:51 pm

roger.fellows wrote:If I understand you correctly the adjustment method is the same, Simon - a drawbolt from rear engine plate to peg on gearbox??


Roger - not quite, there's no peg on the gearbox, the drawbolt uses a collar between the nut (on the top bolt) and the engine plate (as I seem to remember, it's a while ago that I had the Matchless).
Another point is that the grearbox doesn't have a speedo drive (it was off the back wheel), so the layshaft isn't any good if you want a gearbox-driven speedo.
(Might be able to trade such a box for someone doing an HT though - although they don't seem to be very rare, I see Drags have several used ones!)

SG
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)

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Re: Mk11 gearbox options

Postby roger.fellows » Sat Mar 09, 2019 9:10 pm

Ahaa, look for G-1-5 then Stewart

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Re: Mk11 gearbox options

Postby StewartPorter » Sat Mar 09, 2019 11:01 pm

:roll: rThanks guys. After a few days trawling the internet, it's easy to see why there's not a " definitive" burman guide anywhere : what a convoluted puzzle!! B52/GB BA/CP AMC/ARIEL Aaaaaargh!
However, I now have some further numbers to conjure with : GB28C55 stamped on the outer casing ( which, characteristically, is , of course, the middle casing ) This would seem to be a March 1955 box from a Matchless G80S or similar. None the wiser, however, whether this might mean that it's more compatible with a Sq4......
Will keep an eye out for a g1-5 shell although i can't find any noticeable difference between the two shells.
Then, of course, there's apparently an issue with offset lugs......
It'll all become crystal clear soon, I'm sure :roll: :lol:
Cheers
Stewart
'59 D1Bantam, '60 5Ta Speed Twin, '76 Yamaha FS1-E, '58 Sq4 (Lazarus project)

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Re: Mk11 gearbox options

Postby Simon.Gardiner » Sun Mar 10, 2019 3:21 pm

Stewart:
BA boxes (big Squares didn't use CP) ended during the '52 model year, and that series is where you'll have to deal with offset lugs. Mk11 had GB boxes so unless you're going to try and build a BA from your various bits don't fret about lug offsets!
I think the Ariel GB box was the only one with the wide hole in the top mounting that allowed the gearbox to be pivoted on the lower mounting, all others had a 'normal' (round!) hole top and bottom, and the top of the gearbox moved via slots in the cycle parts. (I stand to be corrected on that but it's certainly true for the AMC/Ariel HT variant).
My spare G-1-2 case was also from a G80S, it's just bare cases 'cos all the innards except the shafts (ie gears and selector mechanism) have been used in Ariel GB boxes. If you can get that Matchless box at a good price (and it's not clapped/broken) I'd suggest getting it as a source of most of the internals (or handy spare internals) for a GB7.
Bit concerned that you can't spot any differences between G-1-2 and G-1-5 shells - assuming the numbers do differentiate AMC and Ariel types. Check the top lugs and the clutch cable location (as well as the shape of the kickstart cover and the big filler plug in the back of the AMC version....) if you can't see any differences maybe the numbers are meaningless after all!
Oh - I think you've missed Panther off the list of confusing Burman variants :twisted:

Enjoy! :D

SG
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)

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Re: Mk11 gearbox options

Postby StewartPorter » Sun Mar 10, 2019 5:40 pm

Hi Simon, was getting my numbers confused. Obviously G-1-5 very different and ive managed to get one. Also just went ahead and got the g-1-2 for guts. Once all the bits arrive I'll update on progress.
(Ive also got a 1cp m/4 shell kicking around!!) - looks like I may be going into the Burman business :lol: :lol:
'59 D1Bantam, '60 5Ta Speed Twin, '76 Yamaha FS1-E, '58 Sq4 (Lazarus project)


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