Restoring & Modifying 1971 OIF TR120

[NM Bonny]

Well, I'm a little behind the curve due to other commitments, but hope to get the tire fitted and wheel mounted this weekend. I had a go at it yesterday but was having trouble with the Battlax's bead and didn't want to bugger up my shiny aluminum rim, so am taking it to a shop this a.m.

I'll post some pics--and will be able to provide an unsprung weight comparison: caliper is 29 oz, and will have to be added to built wheel weight (plus axle) to net a 1:1 comparison to stock, which is 31 lbs.

In the interim, while looking at an earlier post, I realized that someone wanting to do this conversion as a straight bolt-on (i.e., without having to lace up a wheel) could just buy a new (or used) 19" x 2.15" front Sportster wheel. Chrome steel (aluminum hub) is available for $170~$250, depending on vendor.

I haven't (yet) found a built wheel with an aluminum rim fitted to the second-generation hub used on this conversion, so the concession would be more unsprung weight. My goal, in case it wasn't obvious, was to increase braking force without overwhelming the dampening specs of the OEM Triumph sliders. We'll soon see if I was successful!

 

[atomsplitter]

Depending on what weight oil you put in the forks will determine the damping characteristics. If you want to ensure the forks don't bottom on hard braking put in stiffer springs. I recently changed the springs in my 2017 T-120 and added preload adjuster caps. That may not be an option for your bike due to age but if you could get someone to machine adjuster caps that would help solve the front end dive on hard braking.

 

[NM Bonny]

Depending on what weight oil you put in the forks will determine the damping characteristics. If you want to ensure the forks don't bottom on hard braking put in stiffer springs. I recently changed the springs in my 2017 T-120 and added preload adjuster caps. That may not be an option for your bike due to age but if you could get someone to machine adjuster caps that would help solve the front end dive on hard braking.

Funny, I hadn't thought of that but it's an obvious consideration now that you mention it. This thing should have markedly improved braking over not only a stock '71 but also an '80 with the smaller OEM disc brake (we're assuming both bikes would have an upgraded tire like the Battlax BT46 I've chosen: no way the Dunlop K70 is going to provide the stopping power this tire does).

I bought 5W Belray fork oil to see how it does.

I just picked up the wheel but it's too bloody hot right now, or I'd be out there installing the rotor and weighing the wheel for our comparison, balancing and installing it on the bike... what fun! Tomorrow morning for sure.

A quick glance suggests the preload caps on the market are for the 'new generation' Triumphs. But, yes, my neighbor/machinist could easily turn some adjusters. We'll see how she does with the increased braking force. Who knows? Might be fine...

Question: if you recall, how much adjustment is built into your new caps, as measured in [x] inches of movement along the long axis of the springs? That data would be very useful--i.e., how much preload one has to add to net a useful benefit, and at what point does the thing just become too harsh.

I get that you've got stiffer springs, which would (especially) affect the second data point, but it'd still be useful to know the adjustment range.

 

[NM Bonny]

This post is just a placeholder for data, like some of the others...

Bridgestone Battlax BT46 in stock OIF sizes with O.D. and standard rim size (what I'm running with the Borannis):
- 3.25-19 54H TL - 665mm; rim 2.15"
- 4.00-18 64H W - 673mm; rim 2.5"

However, a question:

As for tire pressure, all Bridgestone says is not to exceed 57 psi on their motorcycle tires, but otherwise to defer to manufacturer's specs.

I'm not inclined to use the same pressure in the '70s literature with the Dunlop K70s in use back then. Any suggestions for these tires on this OIF bike, for one-up riding? Absent any direct experience, I was going to start with 30 psi and go from there...

 

[atomsplitter]

Funny, I hadn't thought of that but it's an obvious consideration now that you mention it. This thing should have markedly improved braking over not only a stock '71 but also an '80 with the smaller OEM disc brake (we're assuming both bikes would have an upgraded tire like the Battlax BT46 I've chosen: no way the Dunlop K70 is going to provide the stopping power this tire does).

I bought 5W Belray fork oil to see how it does.

I just picked up the wheel but it's too bloody hot right now, or I'd be out there installing the rotor and weighing the wheel for our comparison, balancing and installing it on the bike... what fun! Tomorrow morning for sure.

A quick glance suggests the preload caps on the market are for the 'new generation' Triumphs. But, yes, my neighbor/machinist could easily turn some adjusters. We'll see how she does with the increased braking force. Who knows? Might be fine...

Question: if you recall, how much adjustment is built into your new caps, as measured in [x] inches of movement along the long axis of the springs? That data would be very useful--i.e., how much preload one has to add to net a useful benefit, and at what point does the thing just become too harsh.

I get that you've got stiffer springs, which would (especially) affect the second data point, but it'd still be useful to know the adjustment range.

My T-120 caps have about an inch of threads. You can also investigate progressive springs so it transitions to the fixed spring rate. I kept the stock oil, changed to progressive springs and adjuster caps and the ride is now smooth as butter.

If you want fully adjustable then you'll have to find someone that makes emulators for your forks. I did that with my Triumph Bobber so left leg handles compression damping the right leg rebound. Progressive springs and the preload adjusters are the star wheels: The allen screw in the center adjusts the damping rates.

 

[NM Bonny]

My T-120 caps have about an inch of threads. You can also investigate progressive springs so it transitions to the fixed spring rate. I kept the stock oil, changed to progressive springs and adjuster caps and the ride is now smooth as butter.


If you want fully adjustable then you'll have to find someone that makes emulators for your forks. I did that with my Triumph Bobber so left leg handles compression damping the right leg rebound. Progressive springs and the preload adjusters are the star wheels: The allen screw in the center adjusts the damping rates.

Okay, thank you for this. Yes, I'll look into this if things aren't working well--but see the next post for this morning's data (in a moment), which suggests that fork performance in general should be improved over stock...

 

[NM Bonny]

So, I got the wheel mounted, with a few minor hiccups.

First thing was that I had fastened the fender onto the sliders, and the wire fender mounts pulled the sliders together and rotated one slightly, so that the hub wouldn't slip between without damaging the shims. Easy-peasy: loosen the bolts up and install the wheel and axle, then tighten the fender mounts last.

Second thing--a perfectly fine development--was that somehow my lateral hub end-play measurement was off: I will need another pair of thicker shims, as there's too much freeplay. I'll check McMaster Carr, but I might be able to have just one thick shim on either side--much better than a jumble of thinner ones for R&Ring the wheel.

Finally, the lateral fender clearance is close, but it's easy to yank the fender into alignment on its wire mounts. Once that's done, as you can see, the tire is neither too close, nor riding too high above the tire. It looks proportional--though I could mash it down closer to the tire if I wanted. The wire mounts are very forgiving (and might have gotten a little distorted during the bodywork process.

At any rate, as you can see, the conversion looks much as I'd envisioned it: clean and elegant, and (to my eye, anyway) not at all out of place, given the lines of the machine and overall mass of the caliper and rotor to the wheel and fender. Compare to the stock rear wheel and tire... looks better to me.

Unsprung weight comparison - bear in mind these are with a bathroom scale, so not very accurate--save for the caliper weight, which I measured with my digital mail scale and added to the weight of the built wheel:
- Stock wheel w/axle, brake parts, and inflated Dunlop K70 in 3.25-19: 31 lbs
- New wheel w/axle, rotor, caliper, adapter, and inflated Bridgestone Battlax in 3.25-19: 27 lbs
= Savings ~ 4 lbs of unsprung weight

That means, of course, better tire adhesion and braking over uneven pavement, all other things being equal re: the OEM dampers and spring ratio.

But they aren't equal, of course: the 4-pot Wilwood caliper and 11.5" rotor should net dramatically more powerful braking with less fade and better modulation.

I need a break but when I get back at it, I'll tackle sanding and polishing that big conical rear drum, R&Ring the bearings, and lacing up the rear rim... and before reinstalling the wheel, rebuild the swingarm. Then set her down on the tires for good!

The website (for the first time) wanted me to shrink the images way down, so sorry if these don't look great...

 

[atomsplitter]

Purists might think it's sacrilege to put modern disk brakes on an ancient scoot, but then they don't mind a horrible ride, marginal brakes, and limited performance for the sake of authenticity. Me, I like what you've done. Old school charm with modern paerformance. Kinda reminds me of my Thruxton R: looks old, it just isn't

 

[NM Bonny]

Purists might think it's sacrilege to put modern disk brakes on an ancient scoot, but then they don't mind a horrible ride, marginal brakes, and limited performance for the sake of authenticity. Me, I like what you've done. Old school charm with modern paerformance. Kinda reminds me of my Thruxton R: looks old, it just isn't

Yeah, that's a cool bike. Too new for me, but then I'm a complicated monkey...

If folks want to rigidly adhere to some corporate exec's self-serving decisions re: how to configure a product for [x] market during [y] year, that's up to them.

But I've never understood the smug superiority of people who genuflect before a parts book. It's not scripture, for heaven's sake...

 

[sikatri]

Yeah, that's a cool bike. Too new for me, but then I'm a complicated monkey...

If folks want to rigidly adhere to some corporate exec's self-serving decisions re: how to configure a product for [x] market during [y] year, that's up to them.

But I've never understood the smug superiority of people who genuflect before a parts book. It's not scripture, for heaven's sake...

This thought pretty much goes along with my thoughts on my 2005 Thruxton and starting to mod it to be mine. Previous owner had already started the process and I didn’t see the point of putting money into making it “factory” at that point. I do like the look of the old drum brakes, but I certainly wouldn’t put them on my Thruxton to complete a 1960’s retro look, but I will yank out plastic bits that will feel and look better as aluminum. It all goes to what your intent is for a bike. A restoration of a classic to original is of course a great idea when a motorcycle is a rare specimen or just your thing. But, if a classic has lost a significant number of its original parts I doubt I’d be very inclined to go that route. In the end it’s your motorcycle do as you wish.

 

[NM Bonny]

This thought pretty much goes along with my thoughts on my 2005 Thruxton and starting to mod it to be mine. Previous owner had already started the process and I didn’t see the point of putting money into making it “factory” at that point. I do like the look of the old drum brakes, but I certainly wouldn’t put them on my Thruxton to complete a 1960’s retro look, but I will yank out plastic bits that will feel and look better as aluminum. It all goes to what your intent is for a bike. A restoration of a classic to original is of course a great idea when a motorcycle is a rare specimen or just your thing. But, if a classic has lost a significant number of its original parts I doubt I’d be very inclined to go that route. In the end it’s your motorcycle do as you wish.

Yes - and all those nifty OEM parts I took off that are in great shape will make someone's day if he or she is trying to restore a '71-72 OIF to original condition. Once this is running, I'll be selling them off on the forum's classified section...

I will be interested to see the choices you make and hope you'll share them with us. But, yeah, I've had the twin-leading-shoe, air-cooled drum brake, gray-hair-generating experience, and once is enough.

 

[sikatri]

Yes - and all those nifty OEM parts I took off that are in great shape will make someone's day if he or she is trying to restore a '71-72 OIF to original condition. Once this is running, I'll be selling them off on the forum's classified section...

I will be interested to see the choices you make and hope you'll share them with us. But, yeah, I've had the twin-leading-shoe, air-cooled drum brake, gray-hair-generating experience, and once is enough.

Well there’s a number of threads already on here with the mods I’ve made so far. Not done yet, so stay tuned, I’ll post new items as I go along. Of course it won’t be in this classic section.

 

[Rudie]

tire pressure, all Bridgestone says is not to exceed 57 psi on their motorcycle tires, but otherwise to defer to manufacturer's specs.

I'm not inclined to use the same pressure in the '70s literature with the Dunlop K70s in use back then. Any suggestions for these tires on this OIF bike, for one-up riding? Absent any direct experience, I was going to start with 30 psi and go from there...

Not even Dunlop still advises "the same pressure in the '70s literature" (24 psi front, 25 psi rear iirc?), their current advice is (has been for many years) 28 psi front, 32 psi rear.

This is similar to makers of relatively 'modern' tyres for old bikes, such as Avon for Roadriders - 2 bar (29 psi) front, 2.2/2.3 bar (32/33 psi) rear - so starting with 30 psi - in the front, a couple more in the rear - is about right.

For two up riding, increase both front and rear pressures (by about 4 psi, rear maybe a couple more). Many years ago, quickly preparing my T160 for a trip, I increased only the rear tyre's pressure, Japanese style. The resulting handling when lane splitting in home bound London commuter traffic made a great natural laxative ...

 

[NM Bonny]

Not even Dunlop still advises "the same pressure in the '70s literature" (24 psi front, 25 psi rear iirc?), their current advice is (has been for many years) 28 psi front, 32 psi rear.

This is similar to makers of relatively 'modern' tyres for old bikes, such as Avon for Roadriders - 2 bar (29 psi) front, 2.2/2.3 bar (32/33 psi) rear - so starting with 30 psi - in the front, a couple more in the rear - is about right.

For two up riding, increase both front and rear pressures (by about 4 psi, rear maybe a couple more). Many years ago, quickly preparing my T160 for a trip, I increased only the rear tyre's pressure, Japanese style. The resulting handling when lane splitting in home bound London commuter traffic made a great natural laxative ...

Yikes... lane-splitting while negotiating intestinal challenges = no fun.

Okay, thanks for this info. I suppose at my glacial pace this all seems academic, but it's a lot of fun anticipating that first ride, and I want it to be as drama-free as possible.

 

[NM Bonny]

Grabbed some time to install a line and bleed the system... man oh man, this is going to stop on a dime.

I used a R/H caliper because I didn't want the line coming all the way up from that bottom surface, so the simple bleeding procedure is to set the caliper on a cart as I did, slip a 1/4" shim in between the pads so they don't over-travel, bleed it, and bolt it back onto the adapter.

As you can see in the next few photos, the lever travel on this master is just about spot on for the Wilwood caliper's volume. Feel is very crisp, pistons retract nicely for no brake drag while paddling around the garage.

I'm eager to test it on the road, re: modulation, but it feels like it's going to be a two-finger affair for most braking situations. I'll pop on the GoPro when I try it out so folks can come along...

 

[NM Bonny]

I keep finding myself ogling this polished aluminum fairing, which is based on the '70s 1/2 fairing fitted to the Ducati 900SS... and glancing back-and-forth at the second photo.

The polished aluminum would match my soon-to-be polished aluminum side covers--and the manufacturer will widen the headlamp hole to fit a 7" bucket, which has the effect of making the front of the fairing look even narrower and more bullet-like.

It's possible with the flat bars I have on hand, that it'd work without trimming the cutout, just by lifting it an inch or so.

Ruh-row...

 

[Qship]

Your bike is really coming along nicely. Love the color and that nice shiny new stopping appliance looks great on there.

 

[NM Bonny]

Your bike is really coming along nicely. Love the color and that nice shiny new stopping appliance looks great on there.

Thank you, Sir. My progress has been near glacial in its pace, but the project is immensely satisfying in ways that are hard to describe--though I may try in an essay based on journal entries penne during my first bike camping trip up into the Jemez whenever it's running. I'll take along the GoPro and 35mm with a big lens or two.

 

[NM Bonny]

As a follow-up to #296, here is the owner of Omega's response:

"Thank you for your email.
"We can make the headlight cutout according to your measurements. The look will remain the same, only the diameter will change. The modification is free of charge.
"The bracket that holds the headlight (A) will be larger."

I am seriously considering buying this fairing, because even if I decide not to use it once in-hand, I could always sell it to a 'modern' Bonneville owner here in the states, as that's the bike for which the mounts are configured (and which I'd modify if fitting it to my bike). So, I wouldn't be out a dime.

 

[sikatri]

As a follow-up to #296, here is the owner of Omega's response:

"Thank you for your email.
"We can make the headlight cutout according to your measurements. The look will remain the same, only the diameter will change. The modification is free of charge.
"The bracket that holds the headlight (A) will be larger."

I am seriously considering buying this fairing, because even if I decide not to use it once in-hand, I could always sell it to a 'modern' Bonneville owner here in the states, as that's the bike for which the mounts are configured (and which I'd modify if fitting it to my bike). So, I wouldn't be out a dime.

I installed an Omega fairing on my 2005 Thruxton. Get the polished one even if you decide to paint. I made the slight mistake of getting the non polished and ended up polishing by hand. LoL.

Here’s the full thread if you’re interested:
https://www.triumphtalk.com/threads/fairing-mod-coming-soon.58075/page-5

The full thread might give you ideas on how it attaches to the frame and what modifications you might need to do.