Are circa 1970's Bonneville T140 V left and right gearchange engines interchangeable?
Answers:
Hello Greeves,
I'm not 100% absolute certain on this .
I worked in a Triumph shop for many years and owned many.
But,I got away from them in '75 as an occupation.
The L/H shift configuration was done exatly as you stated.
There was no major re-engineering.
To convert an Old R/H shift to L/H config could actually be done by any competent mechanic/engine machine shop.
To Convert "New" L/H Shift back to Old R/H,,You'd need
*Primary Cover..(or plug the shift shaft hole)
*Old Style R/h Shift Shaft
*Old style R/H Outer Gearbox Cover & gasket
*Inner GearBox Gasket
*?I dont know if the Shift Levers/Foot Levers are interchangeable or not.
Most likely they ARE,except pinch bolt would be "upside down".
Worst-Case,,,add a R/H shift lever
+ Plug the Shift shaft Thru-Hole in l/h engine case,,some gearbox oil,,a
With the exception of having to "creatively" plug the shaft's Thru Hole in R/HCrankcase.
It's all a Direct Interchange of Parts,,Replace the "New" with "Old"
The entire rest of the Engine/Gearbox unit is all the same,,far as I know.
All the Unit 650/750 Twins are basically interchangeable from '63 Forward.
Many,Many of the parts from them are even interchangeable back to the Pre-'63 Non-Units.
The Position of the Shift Shaft/Foor lever on Either Configuration ,,,in it's relation to Chassis ,Footpegs,and whatever else,,
It's such that there's No Interference or other considerations.
Some motorcycles have engines mounted in a way that a Shifter Swap such as this,,,would bump into something on Other side.
If Each respesctive "set of parts" were maintained as a sort of "Kit",,,
The Bike could be converted back & forth at will.
Which could be "valuable" to Resale.
The only actual "Modification" done is plugging the Engine Case hole,,,which could be done in a number of quite effective but "NON-permanent " ways.
I would NOT permanently Expoxy a Plug in-place,for example.
I'm not 100% certain that ALL the "Old"R/H shift shafts are the same.
Up till the last 5speeds that I messed with in mid '70's,,they were all the same.
I cannot imagine any change,,and doubt there was any change for '76 L/H conversion( other than to accomodate the Thru Shaft,of course)
The whole set-up could even be modified with some Minor machine work to have a shift lever on BOTH sides.
A Hybrid,,and user-selectable by simply re-positioning the Foot Lever to side-of-choice.
The Modification would be to "merely" Mod the R/H shift Shaft's Inner End to receive the L/H Shaft.
I never Tried it or investigated such a conversion..
But I do know that the Basic requirement is Simply a SLOT milled across shaft's end to accept the crossover shaft's spade-drive connection.
A Glorified "Flat Blade Screwdriver-meets-Screw Slot" type of configuration.
The only hitch would be a Possible LENGTH difference,,requireing one piece or the other to be extended.
Maybe,,maybe not??
I only mention that as a Possibility,,,if such a mod were desireable to anyone for any reason,,
It would quite feasible and rather simple.
An average "home mechanic" could do the entire Retrofit job.
It's straightforward and simple.
One potential Glitch---reaching the HOLE to plug it,,which should not be a prob,,,It SHOULD be easy even with the gearbox works all in place.
Or,,pluggable from Primary Side.
One "TricK",,,is that Those Gearboxes demand the Shift Quadrant be set in a Certain Position while the Shift lever is maintained in a certain position ,,as the Inner Cover is slipped on and the 2 Gear Shift mechanisms Mesh.
Their Engagement requires a certain Mesh.
To Recap:
** Any Unit-Construction engine will swap Directly into Any Unit-Construction Frame
--Only significant differences are Crankcase Breather hose,and ----Cyl Head/Rocker Box Engine Mounting aka "Head Steady".
A Gazillion Triumphs have NO such mount installed.
_There's a rare few differences in Alternator Wiring,,all are easily adaptable---(the One exception is the '67's "ET Magneto" requiring ET Ign Coils---a SCARCE setup)
***L/H to R/H Shifter Conversion is simply a Parts Retrofit.
Only necessary "Modification" is plugging the Hole in Engine Case on Primary Side
Such a Conversion would be Readily Reversible back to Absolute,100% Original
***Old R/H to L/H COULD be done by Installing L/H Parts.
A "Permanent Modification" Necessary would be drilling the Thru Hole in l/h crankcase.
This Conversion would be readily Reversible to Original.
But the Added Hole would remain---however,,it's located in a place where it would be "externally INVISIBLE" on an assembled Motorcycle.
*** A "Quick-Change" Hybrid could be Fabricated with appropriate parts selection & combination,,,,and some simple, Moderate Machine Shop work to Connect the 2 shift Shafts
This setup too ,would be Readily Reversible back to Original Config by simply replacing the Type-specific parts.
The one "permanent MOD" would be the "HOLE" necessarily Added to a Pre-'76/R/H shift Engine Case
I can't imagine any good reason for doing such a thing,,but it IS
Do-able relatively easy & inexpensively without any horrible permanent disfiguration of the bike
Hope any of that helps
The "Conversion" was a bit more involved than that but near enough, finding suitable bungs to keep the oil in and finding the gearbox end cover should be the main problems, however unless you reverse the gearleaver you still end up with a 1 down 4 up gearchange and stupid ratios, well O.K for english street racing ( High Street, Market street, Manchester road etc) not Laguna Seca, with a high 1st, close 2nd 3rd and 4th and big Gap from 4th to 5th .
If its going half decent under hard acceleration you can't get your foot from the road and under the lever to change from 1st to 2nd in time, It needs to be down for down then no finesse is needed,
So if you can find one a complete T120 R or earlier 4 speed gear cluster might be the answer, The pre 74 650 is as fast, if not faster, smoother and more economical than the 750 and the end of the line TR650 a joke
yes, but you need to do extensive adaptations to mounting areas
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