Should be a good fit, as in a clearance hole, not sloppy. I recommend sleeving the hole with steel for a better fit. Alternately, I have used grade eight hardware there and tightened it with all my strength. It's a pretty common issue with pre-units. Bill
Bikes 1974 Commando 1985 Honda Nighthawk 650 1957 Thunderbird/T110 "Flying Tiger" Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
Thanks HT, I couldn't imagine it was engineered that way, but it's been like that in my ownership for 30+ years! Just always a bloody awkward job when adjusting the primary, especially with only one-sided adjuster! This time round I am doing what you suggested, having the hole sleeved, and also got an adjuster for the other side. Just find it strange, the hole isn't ovalled at the ends and seems oversize all through, as though it was meant to have a larger stud than the 7/16". If you're curious, the bike is on Britycle's customer bike site-Dave's triton thru the decades. Cheers Dave
Ta for the compliment Al, though it doesn't look that great at the mo with bits all over house and workshop! Got any pics of yours?
No linking of brakes, merely a home made cable operated rear. I didn't like the way braking force altered over bumps, and having to bend the rod round obstacles. The idea originally came from a mate's A10, I think it was, and I just copied the idea using an old honda cb125 rear cable and some fittings I made in my old school metalworkshop in the early 80's. Also has a needle roller swingarm setup made at similar time.
Do you have anything to add on my original enquiry, I'm still curious!
Since the gearbox mount' s hole is round, I'd probably turn a bolt to fit in the lathe then drill out the engine plates and gearbox adjuster to suit.
If I didn't have a lathe I'd probably see if I could get a good fit with something metric (maybe M12?) and drill the plates and adjuster. A little naughty I know but if it were a nice fit I could live with it.
Thanks Rohart, initially I was thinking about focussing on the bottom mount, on mine the stud has some slop in the g/box hole and also in the engine plate holes. However, I think my application is somewhat different to yours, where mine is T120 engine and gearbox in a featherbed frame, with adapting mounting plates. So the bottom pivot is less of an absolute guarantee of parallelness of crank and g/box shafts, compared with your manufacturer's plates and mounting holes. Plus, I run a duplex chain, with a unit thrust washer type clutch, making the situatiion a little more demanding in respect of shaft parallelism and sprocket alignment. I guess that's why Triumph were happy with only a right side g/box adjuster on all but the last pre-units, with simplex chain and a clutch drum that wobbled about quite a bit.
I've left the slop in the bottom mounting (I need that to permit shaft alignments using the top mount), and had the top hole sleeved closely for the new st/st stud, and aquired an adjuster for the left side. This should enable accurate parallelisation of the crank and g/box shafts, then I will have to do any necessary adjustments/shimming at the engine sprocket, for final chain alignment.
I'm almost looking forward to primary chain adjustments now, infrequent as they were, for 30+ years they have involved levering the left end of the g/box about until getting both alignment and tension right, in combination with the right adjuster, then nipping it up, finding chain too tight/loose, doing the misery again, etc!!
Only now do I realise how much patience I have expended!