Restoring & Modifying 1971 OIF TR120

[speedrattle]

the GT style is the next best thing to the old donkey dicks.

i use em on everything

 

[NM Bonny]

the GT style is the next best thing to the old donkey dicks.

i use em on everything

Cool, glad to hear you like them and I didn't make a bad purchase. I don't want my hands falling asleep on longer rides.

 

[NM Bonny]

Ahhh... that's better! Here are before and after shots of the kicker cover... man oh man, that thing was beat up! Fortunately, the primary--with much larger surface area--only has small scratches and bad oxidation, so I'm hoping it will (only) take a day. Then, there'll be the hubs, rear brake backing plate, and fork sliders, oh my!

UPS says the fasteners for the front disc brake adapter will be here Tuesday. Tuesday! They must've entrusted delivery to a kid on a skateboard...

Ah, well, at least I'll have the R/H covers buttoned up and can dive into the primary, clutch, alternator, and sprocket work in the meanwhile.

 

[NM Bonny]

I've got a question that I hope someone can help me with.

On my '51 FL Harley, which has a superficially similar clutch setup and release design, there is a throwout bearing on the tranny side under the kicker cover. This Unit 650, however, has no throwout bearing--and yet the clutch actuation rod doesn't get melted (at either end) as will the Harley's (and in very short order) if the throwout bearing is bad.

I found this explanation of how the Unit 650's clutch release works:

"When the rider pulls on the clutch lever, a ball & ramp mechanism at the opposite end of the clutch cable forces a shaft to release the spring pressure at the clutch pressure plate, freeing the connection between the drive (friction) and driven (plain) clutch plates; this disengages the connection between the engine’s “power unit” and transmission. As the clutch lever is released, the pushrod retracts, allowing the spring pressure to be fed through the pressure plate into the clutch plate stack, resulting in the power unit once again driving the transmission mainshaft."

This makes perfect sense--but it doesn't explain why neither of the pushrod's ends gets destroyed when it is shoved against the clutch pressure plate, which presumably is spinning away.

The Harley uses a fork under the kicker cover to move the pushrod toward the L/H side, whereas the Triumph uses a ball-and-ramp mechanism. But in the Harley, the fork moves the throwout bearing which in turn moves the pushrod. On the Triumph, the ball-and-ramp directly actuates the pushrod--with no bearing at either end.

How does the rod escape damage? Does the pressure plate stop spinning when you actuate the lever? Can it be as simple as that?

 

[Rudie]

doesn't explain why neither of the pushrod's ends gets destroyed when it is shoved against the clutch pressure plate, which presumably is spinning away.

Both ends of the T1736 clutch pushrod are (should be) hardened (something that has to be redone if a rod is shortened).

When the Triumph multiplate clutch is adjusted, is why you have to tighten the T2159 "Adjuster pin" in the the centre of the pressure plate very carefully, so that the play between the various clutch actuation parts is just taken up; then, when the Adjuster pin is turned anti-clockwise half a turn or so, that gives a small amount of play between the normally spinning clutch and the not normally spinning pushrod.

When the clutch is operated and the rod is pushed against the Adjuster pin in the pressure plate, the Adjuster pin should spin only briefly on the hardened end of the pushrod, because the pressure plate stops spinning. The Adjuster pin will spin longer on the pushrod when pulling away from a standstill but, as long as that is not excessive, the Triumph parts seem to work well, last a long time.

A mod I have known some twin owners make is cut a clutch pushrod half, shorten the two halves to accommodate a small bearing ball in the mainshaft between the two parts of the pushrod.

 

[NM Bonny]

Both ends of the T1736 clutch pushrod are (should be) hardened (something that has to be redone if a rod is shortened).

When the Triumph multiplate clutch is adjusted, is why you have to tighten the T2159 "Adjuster pin" in the the centre of the pressure plate very carefully, so that the play between the various clutch actuation parts is just taken up; then, when the Adjuster pin is turned anti-clockwise half a turn or so, that gives a small amount of play between the normally spinning clutch and the not normally spinning pushrod.

When the clutch is operated and the rod is pushed against the Adjuster pin in the pressure plate, the Adjuster pin should spin only briefly on the hardened end of the pushrod, because the pressure plate stops spinning. The Adjuster pin will spin longer on the pushrod when pulling away from a standstill but, as long as that is not excessive, the Triumph parts seem to work well, last a long time.

A mod I have known some twin owners make is cut a clutch pushrod half, shorten the two halves to accommodate a small bearing ball in the mainshaft between the two parts of the pushrod.

Ah, so indeed it is Triumph's elegantly simple design that obviates the need for a throwout bearing: the pressure plate stops spinning. I like that better than the Harley setup. Thank you.

Kicker cover bushes are sitting in my mailbox, evidently, so I'll hike down and retrieve them, and get the R/H side buttoned up at last! Also, the 3/8-20 fasteners should arrive today. If so, I'll run them over to the machinist and find out when he'll make the prototype caliper adapter.

 

[speedrattle]

i once welded both ends solid pulling in the clutch and holding it at the end of a dyno run. my mistake, not the fault of the design.

i cover the pushrod in white lithium grease too before i slip it into the mainshaft, just in case things do spin. even after a hundred miles or so the grease is still there.

 

[NM Bonny]

i once welded both ends solid pulling in the clutch and holding it at the end of a dyno run. my mistake, not the fault of the design.

i cover the pushrod in white lithium grease too before i slip it into the mainshaft, just in case things do spin. even after a hundred miles or so the grease is still there.

Yeah, I once welded the pushrod on the '51 FL to the adjuster screw, shortly before the throwout bearing (the size of a child's fist on that bike) exploded. The 'mousetrap' lever effort reducer works well but has a complex adjustment sequence that you depart from at your peril... and even if not, the thing constantly goes out of adjustment as the cable stretches, humidity varies, the earth turns on its axis, etc...

Good idea. I'll do that. Thanks.

 

[NM Bonny]

The tranny drain plug and level tube arrived, and it's better in two regards: the flats are bigger, so it won't get rounded off as easily, and the threads are slightly longer. (Crummy photo, as the flanges are not quite even.)

However, the length is substantially longer. Does anyone know if the longer tube superseded the OEM shorter one? Perhaps to bathe the ball-and-ramp mechanism or better lubricate the gears...?

 

[NM Bonny]

Hmmm... no, immersing the ball-and-ramp can't be right based on this photo... however, the manual says maintaining oil level properly is important to achieve long wear in this component.

 

[Rudie]

tranny drain plug and level tube
better
threads are slightly longer.

Only better if the length of thread on the plug is more like the length of thread in the crankcase. If more, it is just metal protruding inside the crankcase towards a spinning gear ...

length is substantially longer. Does anyone know if the longer tube superseded the OEM shorter one?

Yes (I know); no longer one - the latest 750 twin manuals readable online are '78 T140E Owner's Handbook and '73-'78 750 twin workshop manual, both have the same 500 cc gearbox oil quantity as your bike. If you put in much more, when you lean the bike on the sidestand, gearbox oil runs out over the gearbox sprocket ...

Having a lengthy association with Triumphs, I regard the drain plug with the level tube as the devil's invention - having seen too many tubes rolling around in the bottoms of gearboxes and one set of crankcases where the loose level tube had been picked up between two gears ... I do not know whether that bike's rider survived.

Regrettably, the 650/750 twins are the only Triumphs that did not get a gearbox cover modified for a dipstick, a standard bolt substituted for the level tube drain plug. Nevertheless, for the above reasons, I would never use a level tube drain plug (particularly one possibly as badly made as your new one). The gearbox oil quantity is 500 cc (here, that is a standard bottle of gearbox oil); I do not know anyone who does not have a measuring container of some sort in their garages, workshops, sheds; if I tip the correct measured oil quantity into a gearbox, why would I need that horrible level tube? I can see if any oil subsequently leaks out; if I am concerned about the gearbox oil level, it is not difficult to drain it into the measuring container to check?

 

[NM Bonny]

Only better if the length of thread on the plug is more like the length of thread in the crankcase. If more, it is just metal protruding inside the crankcase towards a spinning gear ...


Yes (I know); no longer one - the latest 750 twin manuals readable online are '78 T140E Owner's Handbook and '73-'78 750 twin workshop manual, both have the same 500 cc gearbox oil quantity as your bike. If you put in much more, when you lean the bike on the sidestand, gearbox oil runs out over the gearbox sprocket ...

Having a lengthy association with Triumphs, I regard the drain plug with the level tube as the devil's invention - having seen too many tubes rolling around in the bottoms of gearboxes and one set of crankcases where the loose level tube had been picked up between two gears ... I do not know whether that bike's rider survived.

Regrettably, the 650/750 twins are the only Triumphs that did not get a gearbox cover modified for a dipstick, a standard bolt substituted for the level tube drain plug. Nevertheless, for the above reasons, I would never use a level tube drain plug (particularly one possibly as badly made as your new one). The gearbox oil quantity is 500 cc (here, that is a standard bottle of gearbox oil); I do not know anyone who does not have a measuring container of some sort in their garages, workshops, sheds; if I tip the correct measured oil quantity into a gearbox, why would I need that horrible level tube? I can see if any oil subsequently leaks out; if I am concerned about the gearbox oil level, it is not difficult to drain it into the measuring container to check?

Huh, okay, thanks for that brief history. Well, since I just bought the darned thing, what I'll do is install it for now, add the 500cc of gear oil, and see if any is coming out the tube. Presumably, it shouldn't as the tube is a touch longer than the OEM one in the photo.

Regardless, I will for sure put it in gear, pull the plugs, and rotate the tranny to make sure I don't hear anything grinding. I did not hear or feel anything amiss when I screwed it in. I assume they designed it to protrude up between or away from any cogs...? Oh, I can also try to peek inside through that hole with my inspection cam to see the pipe if possible...

Then, next time I change the gearbox oil, it's easy-peasy to just saw off the tube if I don't want it. Voila.

Front brake: the fasteners arrived, so I'm waiting to hear back from my neighbor/machinist about a time to make the prototype adapter!

 

[NM Bonny]

Question:

I installed the gear change lever and kick starter bushes (went in easy after a little torching per the manual). The former's I.D. is spot on for the O-ring and shaft fit, but the latter is too tight for the new kicker shaft. I do not see a reamer in the tools section of the manual.

Is anyone aware of someone who sells one for this application? If not, I'll just use one of my adjustable reamers, if I have one that small... or carry it over to the machinist while we're working on the caliper adapter.

I have to bead-blast the top triple clamp for repainting before pressing in the new handlebar bushes and installing the steering lock, too...

 

[NM Bonny]

Here you go... that level tube is in a pretty benign position, up forward of the gear clusters, if I'm envisioning the mechanism correctly. This view is in alongside the gear-changer thingy.

Of course, if the darned thing fell out, it'd be difficult to get out without dismantling the tranny...

 

[NM Bonny]

All rightee then...

The bushes were both undersized and needed to be reamed--significantly for the kicker shaft, and just a graze for the shifter, which worked well until just before full insertion, indicating a slightly conical I.D. or perhaps some compression at one end when driven into the cover--which would indicate that the hole in the cover tapers slightly.

Luckily, I had bought a set of adjustable hand reamers a while back and they worked perfectly. The kick starter feels great, and the shift ratchet & pawl setup seems like it'll be smooth and crisp now. Hope so. I'll get the R/H side buttoned up mañana.

Brakes: met to approve the final drawing for the caliper adapter. He stayed true to my design but for altering a few radii to allow for variation in the fork slider castings and the Wilwood calipers.

Should be building the front wheel and reinstalling the fork soon!

 

[NM Bonny]

Well, if I don't say so myself, that is one sexy part! Deceptively complex, and I'd argue even harder to design than my Creative Spridgets rear disc adapters--which were not an easy task, either. (The inward aspect which doesn't show is very complex.)

My self-congratulation aside, the design is a success on every level: strong as a house from 6061-T6 aluminum (over-engineered re: thickness, as I like to do with brake parts for safety's sake), a sleek profile that tightly nests the caliper in the direction of rotation (which makes the design far stronger than the hardened 3/8" screws retaining it), very light (barely 7 ounces), and entirely form-follows function engineering.

My machinist is very grumpy from trying to make custom soft jaws just to machine the thing, but he's also excited about how the part came out (he did a fantastic job). It's hard to see but the fasteners on the part are flush with its outboard surface and don't protrude out the back side of the slider's caliper ears. Also the part itself is flush with the caliper. Very clean and integrated looking, I think.

Anyway, I'll now reassemble the forks with those nifty 'low stiction' damper seals Rudie alerted me to, install the new headset bearings, R&R the hub bearings and lace up the front wheel... and set her on the suspension to have a look see. I think it'll be handsome with the dual 5-spoke rotor, which I believe should give the bike a neat '70s look.

Should I end up making a production run of these for those who want to do the conversion, I'd probably anodize them in black--though mine will be polished to match the sliders and Sporty hub. Well, though they'd be cheaper without anodizing... regardless, I will apply catalyzed clear coat to mine to retain the shine without maintenance.

She should now stop on a dime. Very exciting.

 

[NM Bonny]

For the axle on this conversion, since the Sporty hub and Triumph disc brake sliders both take a 3/4" O.D. spindle, one could either buy a later model T140 axle for $65~$70 and pay a machinist to turn down the unnecessary feature, or...

...just buy this carbon steel linear motion shaft for $10.46 (see pic). It's 8" length is just about perfect, so no work needed at all--and as discussed earlier, the same outfit sells the inexpensive steel shims I used to center the hub...

...nope. I need 8.25", so will order the 9" shaft for $11.64 and cut it to length. But well worth the effort to save so much over the T140 axle plus machining.

 

[Rudie]

For the axle on this conversion, since the
Triumph disc brake sliders
take a 3/4" O.D. spindle, one could either buy a later model T140 axle

More subtle than that ...

While the conical hub spindle takes two W653/37-0653 bearings, disc brake spindle takes only one, and they are nominal 20 mm i.d. bearings (the bearing i.d. is slightly smaller, the spindle o.d. is slightly larger.

Between where the bearing fits on the spindle and the end of the spindle is slightly smaller than the bearing i.d. but is still larger than 3/4" (I measure 0.780"/0.785").

The 57-1070 captive bearing on a Triumph disc brake spindle is 25 mm i.d. nominal.

The "shoulder" on all Triumph spindles is for the captive bearing inner race to bear against.

 

[NM Bonny]

More subtle than that ...

While the conical hub spindle takes two W653/37-0653 bearings, disc brake spindle takes only one, and they are nominal 20 mm i.d. bearings (the bearing i.d. is slightly smaller, the spindle o.d. is slightly larger.

Between where the bearing fits on the spindle and the end of the spindle is slightly smaller than the bearing i.d. but is still larger than 3/4" (I measure 0.780"/0.785").

The 57-1070 captive bearing on a Triumph disc brake spindle is 25 mm i.d. nominal.

The "shoulder" on all Triumph spindles is for the captive bearing inner race to bear against.

Ah, I see - thank you! Well, thankfully, this is less complicated, as the Sportster hub (for this year range) just has two bearings pressed in from each side against a central tubular spacer.

However, my machinist said the linear motion shaft I am using is so hard that although he can cut it to length and radius it on the lathe, a DIYer would not be able to cut it with a hacksaw, as it would just remove the blade's teeth. So, should anyone wish to replicate this conversion, he'll recommend a material that is strong enough but not so hard as this--and it'd be even cheaper, too.

Today, I hope to get the forks reinstalled with the new headset bearings and resolve the controls, wiring, and order a brake hose. Then it's on to building a wheel, so I can set her down long enough to fix a flat on the '51 FL...

 

[Rudie]

thankfully, this is less complicated, as the Sportster hub (for this year range) just has two bearings pressed in from each side against a central tubular spacer.

order a brake hose.

Given all the other work you do yourself, surprised you do not make it yourself? I have made my own braided brake hoses for years, using Goodridge stainless parts, very simple, very foolproof, very long lasting. Happy to suggest Goodridge and standard Triumph parts to use, if you wish?