Another T120 added to the fold

Guys, I bought this T120 (1967) recently. Needs a lot of work. I trawled the Net for sources of information but hope that some of you who are knowledgeable can advise.

The previous owner rebuilt the motor, so I hope I'm starting from a sound base. I've ridden it around the block and there's zero damping in the forks, so a complete front end overhaul is needed. No nasty noises, idles evenly, missing/hesitating under load but does rev out. I'm not too worried about that (Boyer ign). "Under the hood" it has a belt drive and SRM clutch.

Clearly, it's missing a complete exhaust system, centre stand, speedo and cable, clock mounting bracket, and chain guard. The side stand doesn't look like it's from a unit twin, or is it even in the right position? The petrol tank is the larger (UK?) tank. Looks like it has the wider US handlebars. And looks like it's also missing a steering damper. Was that standard fitment on the T120R?

I understand the TLS front brake was added in 1968 but should be a useful mod. The rear light mounting looks like it's from a later US model year. The tank is 'sort of' painted in 1966 pattern and colours, but I think the orange should be grenadier red? What is the lug for on the front of the headstock (last pic, at 7 o'clock under the steering lock as viewed from this angle)?

The log book says January 1967, engine and frame numbers match (DU52907), so I guess it would have come originally with Monoblocs and SLS drum? I have seen what are claimed to be authentic restorations with Concentrics, grey seat tops and TLS front brakes and a variety of paint jobs. Was the factory paint job aubergine and white (US), or aubergine and gold, (UK) with chrome/ss fenders or painted? Can anyone please clarify? I don't mind too much if the final outcome is UK or US spec.

My aim is to make the bike complete, ditch the TT style pipes, fix the slight oil leaks, have a bit of fun with it, and get it to a stage where I can hand it on to someone else in good fettle.

Your comments would be welcome!

Dave

Nice enough bike to look at, but it's a bitsa.

I'd keep the 69/70 front brake, it's the best on a Bonnie.

If you check the serial numbers, and it is actually a '67, there are variables

Early-
Aubergine & White, all laid on Gold sheen
Monoblocs
Gray-topped seat

Late-
Aubergine & Gold
Concentrics
All black seat

It's got a hacked meter bracket, needs to have the duals with gray faces.

Should have a chain guard with the rear brake light switch mounted nearer the front.

Should have shrouded shocks.

Definitely needs the earlier alloy bodied tail light housing, my favorite.

Keyswitch belongs in the left sidecover at the upper front.

There is nothing "wrong" with it as-is (apart from needing a speedo and chain guard). It'll get it's fair share of compliments just as it is (well, fix the oil dribbles, or you'll get all the usual comments on that note)

"Far from perfect", but I like it.

Still among my top 3, and I've owned 163 bikes...



I went with gray-topped seat, monobloc carbs, stainless fenders, and Aubergine & White paint. It already had the '70 style grab rail when I bought it.

Putting oil into the forks may restore the damping.

That wiring, with silly red and blue crimped terminals, will give you trouble.

Thank you Grandpaul and Triton Thrasher.

Indeed, that wiring is awful and I aim to sort it properly!

Thanks for the info on paint schemes. I think the paint will be the last on my list of things to do but still good to know. How about a brighter shade of red and white but to the factory pattern - colour above, white on gold sheen below? and with white fenders and a stripe down the middle? Or would that upset people?

Ah, didn't know about the ignition switch position. Is that from a later model year? The US style tail light mount looks neat and I will get that.

I haven't visited this forum much in the last few years, but there used to be a member here and on a BSA singles forum (Kommando) who devised an ingenious damping mod for external spring Triumph forks. Is he still about?

Cheers,

Dave

I should have noticed your location, of course your paint scheme pattern will be different from my U.S. variant.

I think the '66 paint scheme you have looks very nearly correct to my eye, but may look different enough in person that it puts you off. I like it just fine on my '66...

grandpaul said:

I should have noticed your location, of course your paint scheme pattern will be different from my U.S. variant.

I think the '66 paint scheme you have looks very nearly correct to my eye, but may look different enough in person that it puts you off. I like it just fine on my '66...

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She looks very nice indeed, Grandpaul. Thanks for posting.

Some good info here Dave:

https://triumphbonneville120.co.uk/pain ... ations.php

Hi Fast Eddie - I have followed your build threads on the main forum with great interest, and thanks for the link. I had seen it before and I have to admit disappointment at seeing that aubergine was the official factory colour that year! Still, I think that, overall, Triumphs had the best and most flamboyant paint schemes of any factory in the 60s.

Cheers,

Dave

daveh said:

Hi Fast Eddie - I have followed your build threads on the main forum with great interest, and thanks for the link. I had seen it before and I have to admit disappointment at seeing that aubergine was the official factory colour that year! Still, I think that, overall, Triumphs had the best and most flamboyant paint schemes of any factory in the 60s.

Cheers,

Dave

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Some of them are too flamboyant for my simple tastes, that's one of the reasons the '68 T120R (ie US spec) is my favourite. To my eye, it lets the design speak for itself, rather than rely on fussy paint schemes.

But, IMHO, unless you're aiming for a conkers trophy winner, then just choose the Triumph paint scheme you prefer. Sure, some folk at club nights will delight in telling you that your '66 has a '67 paint scheme (or whatever) but you can take delight in telling them "I know... Lovely innit"!?

Fast Eddie said:

daveh said:

Hi Fast Eddie - I have followed your build threads on the main forum with great interest, and thanks for the link. I had seen it before and I have to admit disappointment at seeing that aubergine was the official factory colour that year! Still, I think that, overall, Triumphs had the best and most flamboyant paint schemes of any factory in the 60s.

Cheers,

Dave

Click to expand...

Some of them are too flamboyant for my simple tastes, that's one of the reasons the '68 T120R (ie US spec) is my favourite. To my eye, it lets the design speak for itself, rather than rely on fussy paint schemes.

But, IMHO, unless you're aiming for a conkers trophy winner, then just choose the Triumph paint scheme you prefer. Sure, some folk at club nights will delight in telling you that your '66 has a '67 paint scheme (or whatever) but you can take delight in telling them "I know... Lovely innit"!?

Click to expand...

+1 ... cool as is 8) ... I wouldn't bother changing a thing.

Fast Eddie said:

Sure, some folk at club nights will delight in telling you that your '66 has a '67 paint scheme (or whatever) but you can take delight in telling them "I know... Lovely innit"!?

Click to expand...

Ha, yes, I wish there wasn't so much of this pc attitude.

+1 ... cool as is 8) ... I wouldn't bother changing a thing.

Click to expand...

Thanks, Nortribuell, which by the sound of your moniker means you are a Triumph owner, among other marques? What do you have?

More seriously, though, the forks need a complete rebuild, probably new stanchions and bushes, and I'm planning some damper mods. The ovality needs to be machined out of the front brake drum and oversize proper decent linings machined and fitted. Swinging arm pivot is worn, a few oil leaks here and there, and probably a new wiring harness needed. I need to delve into the carbs to check the jets and sizes and go over the connections to the Boyer ignition.

The paint will be the last consideration because I want to get it fully operational first. I might make some moderate rear sets to go with lower bars and a reverse gear shift lever which would make it one up, three down - a better way to shift. Any mods I make will be reversible to stock.

Question: Since I'm new to these motors, how does it breathe - through the primary case? Is this adequate and can one avoid oil dribbling out? Could you hook up a reed valve crankcase breather, is it worth doing, and could it be reversible to stock? The XS 650 breather mod for my Commando and Ducati 450 worked a treat.

Dave

The engine breathes through a timed breather, same as early Commandos. The exhaust pipe is WAY up under the engine, above and ahead of the drive sprocket where it is extremely hard to get to unless you lay the bike on it's side.

It is reasonably effective, and doesn't benefit as much from a reed valve as a Commando.

That exit pipe joins the tank vent at a curiously shaped y-pipe in the battery area under the seat, then exits out a long pipe to the rear fender near the tail light.

grandpaul said:

The engine breathes through a timed breather, same as early Commandos. The exhaust pipe is WAY up under the engine, above and ahead of the drive sprocket where it is extremely hard to get to unless you lay the bike on it's side.

It is reasonably effective, and doesn't benefit as much from a reed valve as a Commando.

That exit pipe joins the tank vent at a curiously shaped y-pipe in the battery area under the seat, then exits out a long pipe to the rear fender near the tail light.

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Ah, excellent, thanks for filling me in, Grandpaul. I must delve inwards and find the exit of the crankcase breather and the Y shaped pipe. May I ask a further question - later pre-OIF twins had that vent hose from the oil tank along the left side of the rear mudguard but I haven't noticed it in photos of earlier years like mine. Since I'm not sure if the venting arrangement on mine is stock or what I will find when I get underneath, where does the oil tank vent to on your '67, or have you modified yours?

Dave

It was/is just a plain rubber hose 'till the D-shaped ones came out (69/70?)

grandpaul said:

It was/is just a plain rubber hose 'till the D-shaped ones came out (69/70?)

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OK, thank you.

I have another question for Bonnie experts, especially Grandpaul.

Since my Bonnie is a '67, it should have the ignition switch mounted in the left hand side panel. Mine has the later side panel, without a hole for the switch. Looking at the 1967 and 1968 Parts Books, I see that the '67 side panel has two lugs at the top. My side panel has two rubber grommets and mounts on two pins on the rear frame rail and a screwed knob at the top and front.

My question is: is the '67 rear frame (or subframe) different to the later subframes? If so, are there additional brackets on the rear frame to mount the side panel which is correct for that year? And if there are additional or different brackets/mounting points, could someone post some photos, please?

I could leave the existing arrangement as is, but I have a new '67 wiring loom so I might as well get the correct side panel.

Dave

I'd have to go back and compare details, they did change from certain years to subsequent years.

You can always just drill a hole in the sidecover you have, if it's not a concours 100 point bike...

grandpaul said:

I'd have to go back and compare details, they did change from certain years to subsequent years.

You can always just drill a hole in the sidecover you have, if it's not a concours 100 point bike...

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Thanks Grandpaul, I will wait to hear back from you at your leisure but will explore making a hole in the existing side cover.

Time flies. Nearly four years ago since I last posted here. I hope you guys will still speak to me!

I decided to do a (fairly) authentic rebuild of the poor old 1967 T120R you saw above. Here she is now. Lots of delays because I was busy with other things, the pandemic happened and I snapped my Achilles tendon, and that's put paid to kickstarting anything for a year.

The bike was not finished when I took the pics. The purists will note the unshrouded rear shocks (I have them and will be fitted), Amal Concentrics (should be Monoblocs), the later TLS front brake, and a few other things. I like the TLS brake. I had the drum skimmed and Villiers Services made the new linings to size. The brake action is firmer with flatter handlebars but surprisingly, the cowhorns make the bike quite a comfortable ride. The paint was supplied by RS Paints in England.

As any of you who know these machines well will attest that there's often a lot of work involved to make them run and ride well. Everything electrical is new. The cases were cleaned manually, not blasted. Lots of fitting and fettling to get new and old stock cycle parts to fit and function well. The engine took some time to complete but was mostly straightforward and too much to list, but most of the usual wearing parts were replaced, repaired or re-made.

I took it for its first proper shakedown run in late May last year and it ran really nicely. Easy to start, a nice midrange and steering is light and flickable but stable. I now appreciate why the kids back in the day wanted them...