A mixed Box and an Over-tyred kid

This is my last grumble about the cost of this stuff. I promise. Today I discovered some interesting stuff about my gearbox. I am typing down what I currently understand (or think I do) before I forget.
Ok, here goes. Please comment or email me with corrections.. derek at astralyte dot com dot au

IN the late 60's the company Quaiff built 5 speed gearboxes for triumph. Truimph bought the rights in early 70's and proceeded to make a very crappy version. Gears too narrow, hardening shite, etc. These are called a-series 5 speed boxes
. In June 1971 some T120's were released from the factory with 5-speeds. the engines and frames were stamped T120RV. Some say they don't exist. Some say there were 2-300 made to allow them to use them in 'stock' races. I have one of these bikes.
These boxes were blowing apart withing sight of the showroom and made redundant after 2 years and replaced with the b-series. Due to the general shiteness of the a-series very few remain as they have long since been replaced with b-series boxes.
There are many interchangeable parts, as the mainshaft is pretty much the same. The layshaft is different and can only accommodate a top-drive (5th) gear changeover. There are different levels of updates available, but none are my concern... YET
You can probably guess by now the great news I got today. Being a bit of a murphy's law magnet, I couldn't have guessed the crazy combo.
Mainshaft seems normal. Absence of serial numbers on most of the gears means They are (I can't remember now) probably quaiff or custom made????
The Third Main Gear with no remaining case hardening has 18 teeth. This is odd as the matching laygear still has the correct number of teeth. It is also suss that the mismatched numbers are on the same gear that is worn beyond the case-hardening. Perhaps mismatching has worn it, OR it is a custom gear that was NOT hardened as well as the genuine ones.
The third Layshaft gear is marked only with a small X instead of a serial number. This could mean it is a custom gear, or maybe has had the teeth re-profiled to fit the 18 tooth main 3rd.
The layshaft, driving Dog, 2nd, 4th and fifth are all A-series gears, which is diabolical news. To set this right (really and completely) will cost up to a thousand dollars.
In the meantime I have sourced a genuine B-series Main 3rd to replace my worn out custom one. I will assemble it and assess whether the profiles still match. On the bench my lay-3rd rolls ok with the other gears, so there is some hope.
I have also ordered a B-series lay-5th (high drive) to replace the chipped one. This is a straight change over. (famous last words I know).

Tomorrow I count ALL the gears as I have just realised that it may have a custom close ration conversion. Doubt it tho'.




Buying parts can be upsetting at the best of times, but when you have a kid with you the opportunity to pick the brains of the triumph guru goes out the window. Here's one solution....