its frustrating as all i require is the drive gear
as pictured from an ebay listing
imgur.com/a/AFUuQdJ
looks like it could just tap onto the rear of the basket providing internal diameter dims are correct

ok so after replacing the pri driven pinion gear back of clutch basket it sheared once more 
i now believe this "may" be due to a fault with the kick start mech not clearing away from the driven gear properly on kick starting resulting in kick back and  damage 
anyone here ever had a similar issue perhaps?
i now dont think its a timing related issue as i timed it bob on with both dial indicator and points checker
would the kick gear engaging with the pri driven gear result in this issue?
have managed to find a clutch basket replacement but would be better placed refitting if i knew the exact nature of why the kick gear is fouling the pri driven really?
cheers again
D

I guess its not the time to ask stupid questions but i'll can take the flack.
Is there a chance your timing it way wrong & its running backwards [which they could technically do] & if that was the case it's do big damage if you touched the kick start as it would engage & do a good impression of trying to part the motor in the kick gear department.
Regarding the kick shaft assembly after you kick & it fires then kick gear on the kick shaft is fired out of the way.
But if it kicks back [or actually starts backwards] it pulls the gear into mesh harder until the shaft stop meets the case stop with nowhere to go so something has to give.
I feel for ya. It'd be a right P--off let alone twice.
One question, does it push start & run.
Talking timing, in theory to run backwards it needs to be 1.8mm after tdc rather than 1.8mm before, but it wouldn't need it be that far wrong to run in reality just near tdc.
But i guess with it kicking back super hard but not starting at all it sound more like say 4mm btdc rather than 1.8.
I'm lost & just rambling on. Hope ya get some joy soon.

Just to add Tension clip #9 has to be in the groove on the gear & it's ear has to be in the case groove but in saying 'that' the only problem 'that' would cause is that the gear wouldn't want to engage unless you lean't the bike way over to the right side, but it still wouldn't cause your issue because if it started & ran like that it would just keep the gear at bay & may sound noisy rubbing the intermediate gear but while motor is turning forwards nothing bad can happen.
www.partzilla.com/catalog/yamaha/motorcycle/1976/dt175c/starter
 

thanks again 
have just examined the kick assy and the clip (Clip
90468-26048-00 ) had come loose so possibly that was a factor?, just trying the kick and all engages fine and works as should (without clutch basket on) 
strangely it bumped first time (was scared of the kick doing more damage) however there was an issue relating to clutch reassembly so tore it down again reset the clutch and tried to bump it and thats when the pri driven gear gave out but just before that it was knocking the kickstart ( kickstart was moving a bit) could be the clip being lose or preventing the idle gear from returning  guess 
in addition the bike ran great for all of 20m last time the pri driven gear gave out no sign of possible timing issues, it just sort of broke on a random kick start 
could be timing still i guess however it ran fine first time i bumped it and nothing had changed timing wise meantime so it might appear the timing issue is intermittent but i was very careful to time it 1.8mm BTDC using dial and points checker (there's a tang on the coil housing that lines up with a line on the stator that indicated 1.8mm BTDC and verified with the dial guage
as i say to rule out possible timing stupidity on my part i will get the mech to time it for me and go from there and check the piston/rings  isnt causing a possible intermittent seize 


 

I have a question...  did you replace the basket or just the kick gear under the basket?

good question
just the pinion gear and kick gear not the whole basket replaced
this time managed to find the basket, last time couldn't locate one for trying
parts list show it as whole item basket and pinion gear but the one i did find was a perfect fit for my basket
 

The internal diameter was the same? 
 

Hi yes was a snug fit and exact same dims as the one that broke prior 
 

To be sure the kick gear is going back out of the way, with plug out, if you pushed the kick lever fully down then let it right up then revolve the motor backwards on the mag flywheel "clockwise" & the kick gear should 'not' pickup. Should be back out of the way. That's no help though if it kicks back while kicking as is engaged & holds engaged until shaft returns to the stop where damage results. Just saying that to be sure under normal running that gear is out of the way.

Another random thought. If it has a mechanical advance in the flywheel are you timing it held fully open, otherwise, if not, then you'd end up towards 3.5mm advanced when running which it sure wouldn't like. I'm not sure you could get timing that far out as points would need a very wide gap. Maybe I've said that before. Maybe I'm talking rubbish. Joys of getting old, keep telling same stories lol.