Rings and Carburetors: Swimming Upstream on this Vintage Motorcycle Restoration Project

The never ending winter drones on up here, so I'm putting my back into getting the '71 Triumph Bonneville project closer to a state of mobility.

I have a new 750cc head and pistons on hand, so I gave the piston rings a go. Installing them is pretty straightforward and the first set went in no problem, but as I was compressing the second set into the cylinder sleeve it didn't feel right, so I backed everything out and the bottom ring came out in pieces. I can only think it was already compromised in the package.

I sent Britcycle an email and they looked through the warehouse to see if they had any extras laying around, but I was out of luck, so it's a $100 failure (new rings, taxes, shipping). Ouch. This got me looking at costs for this vintage project. The last one I did was the Fireblade. Those are my favourite kinds of restorations. Parts are easy to find and relatively inexpensive, the bike is rideable fairly quickly and, after riding it for a season, I can turn it over for at least what I put into it (or with a small profit as was the case with the Fireblade).

New cylinder heads and cylinders... and broken ring.

 

I think I'm still right way up on the Bonneville simply because these older bikes seem to work under their own economy. I was looking up prices of what I've got on eBay this evening and the frickin owners manual that Bryan threw in at the last minute is $50US! A used top end is $500US (and Bryan gave me 2 of the things!). I imagine I could double my money just parting it all out, though dealing with people doing that would be a giant pain in the ass - at least it has been with the newer bike crowd, maybe the vintage types are less adversarial.

I had a couple of choices when I was considering going old school, and I think I picked the hardest possible one to bring back to life. The technical side of it doesn't bother me, but with costs increasing all around I'm bothered more about the high prices and difficulty finding and shipping parts than I am with what I've got to do to bring it back. That old BSA would have probably been a better choice for my first vintage resto, but it (and alas, Bryan) are long gone.

I've got what I've got, and I've got a lot of it, and I'm crafty. I'll see what I can do about replacing fasteners and the other bits and pieces I'm missing without it breaking the bank, those these strange old British pre-metric fasteners are a story unto themselves. The goal right now is to rebuild the bike to an operational state and then maybe ride it for a bit before putting it up for sale. I still need a seat and exhausts and I'll need other odds and ends like control cables. If I can get it back to a state of play, I think I can cover costs and move it along, then I'm thinking I'll go back to my favourite hunting grounds: forgotten bikes from the 80s, 90s and 00s that I can turn over for next to nothing while giving me a chance to ride something different for a little while.

When the ring crumbled on me I changed gears and rebuilt the Amal carbs. That went well, but I'm missing two of the bolts to put the second carb back together - they weren't on it when I wiped the mud and rust away. It's these little setbacks that stall things, and it's not like I can grab a couple of replacements out of my big tray of bolts (most of which are metric).

 

How simple can you make a carburettor? These old Amals are pretty close to first principles. The combination of archaeology and simple mechanics is very appealing when everything else I ride carries a computer and my day job is all about them - it's nice to be fully analog!

I'd broken down the carbs in the fall and left them packaged in a segmented toolbox. Putting them back together was problem free and the kits I got from Britcycle replaced all the gaskets and rubber grommets in them. The old rubber bits were really showing their age.

Guess which one is the 50 year old ring (I;m assuming they're original)?

Just need some bolts (at $3.50US a pop)

If money and time were no object I'd dig deeper into this vintage resto thing - I dig the mechanical simplicity and I enjoy seeing how mechanical evolution happens over time. As a hobby in retirement, it has great appeal, but I'm some years away from that much free time on my hands.

I'll see this one through and then refocus on the SPQR-WRO (small profit, quick return - with riding opportunities) side of it where the costs and time commitments aren't quite so demanding.

 

 

 

1971 Triumph Bonneville T120 Sensible Bodywork Bolt Replacements

I'm in the process or stripping the last bits of hardware from the frame and bodywork in order to clean up and paint the frame and bodywork on the 51 year old Bonneville project bike.  The bolts holding the licence plate holder onto the rear fender were 4 different sizes with the longest ones protruding so far toward the wheel that they'd be a safety hazzard on a big bump (the tire would make contact with them on full suspension compression, especially with me on it).

I was talking to a friend online who made a career out of flying helicopters for the military and he said he's found wrong sized hardware in controls that have actually jeopardized flight safety.  One of the rhings I enjoy about motorcycle mechanics is that it feels closer to aviation than four wheel appliance repair where an error like this might cause you inconvenience as you roll to a stop on the side of the road.  If you're up in the air or out on a bike and you have a catasrophic mechanical failure, it's a very different consequence.

Another pilot friend (the perils of being an air cadet), when we were going up for a flight in a Cessna, brought it back around and landed when the engine didn't feel right.  Everyone was impatient at the delay, but he said something that is simply true that many people don't consider when their flight is delayed:  "it's better to be down here wishing you were up there, than being up there wishing you were down here."  It's a shame more people who work on bikes don't think the same way.  I've seen even professional work that was half assed to save time/money.  Incompetence like that puts a rider's life at risk needlessly.  It can end up costing you far more than you saved.

Pretty sure that last one isn't a stock Triumph bolt.  These'll all get replaced with metric bolts because they're easier to find, but they'll be the right length, matching and be staineless steel.

The 14-0101 bolts used to fasten the fenders on the '71 Bonneville are 1/4" X 1/2" X 28 UNF, which are a bugger to try and find a match for.  The longest bolt on the bike was an inch and a half - way too long for where it was.  Working with SAE/imperial sizes on this bike makes it a real pain to match hardware out of what I have on hand, but stuffing a bolt that long onto a bike where it can interfere with the wheel isn't sensible.

SAE Wrench Size	Bolt Size (SI)	Metric Wrench Size
5/16″	1/8″	8 mm
3/8″	3/16″	10 mm
7/16″	1/4″	11 mm
1/2″	5/16″	13 mm
9/16″	3/8″	14 mm
5/8″	7/16″	16 mm
3/4″	1/2″	19 mm
13/16″	9/16″	21 mm
7/8″	9/16″	22 mm
15/16″	5/8″	24 mm

1/4" bolts can be replaced with an 11mm metric option and finding stainless steel versions of these are easy.  I can also get four matching that are the correct length for the job at hand rather than bunging whatever I have in the toolbox onto the bike.  Compared to other costs in this restoration, hardware costs are trivial (for under $40CAD I can get a 900+ piece kit).  When I'm dropping $600+ on a new head, spending a bit on properly sized bolts seems like a no-brainer.

Of course, body panel fasteners are a different proposition to what you put into a motor or transimssion - in those cases I'd always use stock pieces to manage the heat and pressures involved as decided by the engineers to designed the thing, but for bodywork there is a bit more latitude, you just don't want to be a pratt about it.

While sorting the
frame I've cleaned
up the oil in frame
drain system.

The Amazon bolt set arrived in less than 24 hours.  It is (of course) snowing today in mid-April in Canada, so moving the other bikes out of the garage to paint things isn't likely, and I can't paint outside if it's snowing.  You need 10°-30°C temperatures, no direcf sunlight and good ventilation.  If I can get the other bikes out of the garage, open the door a foot and run the fan, I might be able to retain enough heat to do it, but Canada's 'spring time' isn't helping things along.

If had a wee outdoor shed I'd use it as a paint booth, heating it to the required temperature and then having a fan to move the overspray out.  This DIY paintbooth would be a thing if I had a larger workshop, but a shed outside is a real possibility.  It could provide storage, freeing up space in the garage, but with some crafty ventilation it'd also be a paintbooth.  If I don't get to painting today, I can at least finish prepping the frame and body panels and hope for warmer temperatures later in the week.

New tires and innertubes are on hand.  The frame is being prepped.
I've still got some other body panels to clean and prep for painting.

1971 Triumph Bonneville Restoration Project: Frame Breakdown & Rear Brakes

I'd initially planned to do a rolling restoration of the 1971 Triumph Bonneville project, but the state of the engine and my desire to get it back to a place where I can enjoy an updated, dependable but mechanically sympathetic restoration (I want the bike to retain its patina, but I also want it to be dependable) made a rolling restoration impractical.  The engine is lined up for a new 750cc head and electronic ignition system, but before all of that I have to get the frame and wheels sorted out so that I can put the upgraded engine back into a sorted rolling chassis.

To that end, it was finally time to take it to pieces, which also gave me a lot of space back in the one car garage once the bike stand was stacked to the side:

The frame out means I don't need to fill half the garage with the bike stand.

Black rubber bands cover the frame to swingarm joints (to prevent water getting in?).

Way more space in the garage with the Bonnie in pieces.

With the bike in pieces, I'm restoring all parts that I can reuse.  This usually involves some WD40, a toothbrush or wire brush depending on how filthy it is, and then a dip in a hot ultrasonic bath for small pieces to get them back to fresh.

The front wheel Smiths speedometer.

Into the rear brakes. Like everything else on this old bike they are much simpler than modern hydraulic brakes.

Bringing old parts back from the brink is very satisfying.

The entire rear brake system - the brake lever is so long because it is the only mechanical advantage you have when applying the rear brakes.  Instead of using hydraulics to amplify your push on the pedal, the old Bonnie is a simple mechanical system.  You press the brake lever which pulls that long metal bar which rotates the top of the drums, pressing them into outside of the drum.  No hydraulics, and I bet you have to press that lever like you mean it to lock the rear wheel.

1971 Triumph Bonneville Project: Engine Out

The weather's all over the place at the beginning of March this year.  Last weekend I had both road-ready bikes out for a shakedown, this weekend we're skiing in -20°C windchill; that's the road I was riding on last week.

As GP from Hammy Hamster would say, 'the elephants are against us.'  With the outside trying to kill us again, I'm focusing on doing a complete tear down of the 1971 Triumph Bonneville project.  I was originally going to see if I could get the bike in motion as it is, but a combination of factors including 1971 Triumph build quality and the early 80s muppet who tried and failed to turn the bike into a chopper's spannering skills have me now approaching this as a frame up restoration.

I've been working around the edges which has been good for reconnaissance in determining what state the bike is in, but now that I'm committed to doing the bike from the frame up the first job was to remove the bottom end of the motor and clear the way for a frame restoration:

The bottom end was surprisingly light and easy to lift out of the frame and none of the frame to engine bolts caused any problems.  Some were quite loose, so a frame up resto is making more and more sense as I don't trust anything the chopper muppet did to the bike circa 1983.

It was my first time into the rear drums and, like the fronts, they were age seized but otherwise not in terrible shape, though whenever I get into the dark places on this bike it looks like a scene out of Indiana Jones.

I've left the frame on the bench as I continue to strip it of accessories.  The last time I did some coating work on a project bike it was with Fireball Coatings in Elora but seven years on they seem to have evaporated.  I've been looking for alternate (and hopefully better) options and KC Coatings in Guelph looks promising.  I intend to get in touch with them and see if we can shot blast and powder coat the Bonneville frame, I just have to make sure they can do it on a complicated oil-in-frame design like this one.  Powder coating adds thickness and can cause problems with fasteners and fitting things back together so I need to find out if KC understands that and can can work with this one so that its mechanical pieces will still fit back together.

Following the frame I'll sort out both wheels (bearings, tires and inner tubes) before getting the rolling chassis back together and then rebuilding the motor with my swish new 750cc head.

Motor out and on a pop up workbench by the window.  It's lighter than it looks.

I set up the Black & Decker WorkMate by the back door to the garage to give me somewhere to work on the bottom end of the motor.  With the engine split and out of the frame, I can lift the parts off the bike around easily.  I might put the bench away and make some space while the project is in pieces.

Resources & Links

Power-coating Specialist in Guelph for the frame:

https://www.kccoatingsltd.com/contact

Where to find tires:

https://revco.ca/

Revco is fantastic at shipping (even during a pandemic) and very transparent and communicative with delivery times.  Everything I've gotten from them has been expertly packed, is new stock (no old/new tires).  They know what they're doing with motorsport tires.

How to DIY your own fender: 

https://purposebuiltmoto.com/how-to-make-a-diy-motorcycle-fender/

If I had more space I'd have welding kit and an English Wheel set up in the workshop and get into a lot more fabrication.  I'd go digital too.  A industrial sized 3d printer would make me dangerous:  https://tkmotorcyclediaries.blogspot.com/2015/11/iihtm-digital-workshop.html

1971 Oil In Frame Triumph Bonneville Restoration: Tire Choices

The old Bonneville needs new tires and inner tubes so I'm wrapping my head around olde fashioned, pre-metric motor-bike tyre sizes.

Those would be the Dunlop K70s that came with the Bonnieville back in the day.
Fortunately Dunlop is still looking after the bike they designed the tire for.

The '71 Triumph Bonneville came with 3.25 X 19″ front & 4.00 X 18″ rears and used Dunlop K70 tires as standard equipment.

It looks like there are modern Dunlop options for vintage SAE (non-metric) wheels at Revco where I've gotten my last two sets of tires.  The handy chart below shows metric and imperial conversions but after some digging I was able to find SAE/pre-metric modern Dunlop K70s that are the exact fit for the bike.  Using recent versions of original equipment that give me the benefit of modern rubber durability and grip while still keeping close to the originally engineering intent in Triumph's tire choice is fantastic.  I'm not trying to recreate riding in 1971, I'm trying to start with that technology and update where prudent for 21st Century use.

  Tire Charts                               Motorcycle Street Tire Size Conversion Charts

Metric 80/90 90/90 100/90 110/90 120/90 130/90 140/90	Alphanumeric - NA- MH 90 MJ 90   ML 90 MN90/MP90/MR 90 MT 90 MU 90	Inch-(Series90) 2.75 3.00/3.25   3.25 3.50 4.00/4.25 5.0 - NA-	Inch-(Series82) - NA- - NA- 3.60 4.10 4.25/82/4.40 5.10 - NA-	Front Tires: Metric 80/90 90/90 100/90 110/90 120/80 120/90 130/90 Alpha MH90 MJ90 MM90 MN90 - NA- MR90 MT90 Inch 2.50/2.75 2.75/3.00 3.25/3.50 3.75/4.00 4.25/4.50 4.25/4.50 5.00/5.10	Rear Tires: Metric 110/90 120/90 130/80 130/90 140/80 140/90 150/80 150/90 160/80 180/55 200/60 230/50 Alpha MP85 MR90 - NA- MT90 - NA- MU90 MV85 MV85 - NA- - NA- - NA- - NA- Inch 4.50/4.75 4.50/4.75 5.00/5.10 5.00/5.10 5.50/6.00 5.50/6.00 6.00/6.25 6.00/6.25 6.80/7.00 7.00/7.25 7.90/8.00 9.50
Size 120/80V16 130/90H16 130/90V16 500S16 MT90H16 3.00 130/90H16 3.00 140/90H16 140/80VB16 140/90H16 150/80V16 160/80H16 160/80H16 200/60VB16 120/80V18 120/90V18 120/90H16 130/80V18 130/70VB18 150/70VB18 140/70V18 170/60VB18 180/55VB18 230/50 X 15	Rim 2.75 3.00 3.00 3.00 3.00 3.00 3.50 3.50 3.50 3.50 4.00 4.00 5.50 2.75 2.75 2.75 3.00 3.50 4.00 4.00 4.50 5.50 7.00 to 8.00	Overall Width 4.7 5.00 5.2 5.2 5.3 5.4 5.8 5.9 6.0 6.2 6.4 6.8 7.9 4.8 4.8 4.9 5.2 5.4 5.9 6.1 6.9 7.0 9.5	Overall Diameter 23.8 25.4 25.0 26.4 25.3 25.6 25.6 24.8 25.8 25.4 26.1 26.1 25.9 25.9 26.4 26.3 26.3 25.4 26.2 25.7 26.0 26.3 25.3

Note: Measurements are based on the given rim widths. A rough rule of thumb: Each additional 1/2-inch of rim width will be approximately 1/4-inch more in each tire width.

The K70s at Revco are just over a hundred bucks a pop and Counteract Balance Beaded inner tubes are actually cheaper than name brand plain old rubber inner tubes. I've been using the Counteract beads for years to great effect so they'd be my first choice even if they weren't cheaper. All in I'm looking at about $320CAN ($250USD) for new rubber for this vintage restoration project, which considering the price of some of the other parts is pretty reasonable.

In order to rebuild the wheels I'll need to replace the bearings and clean up the brakes before putting new pads and hydraulic brake cylinders back in them. All that and getting the frame sorted out will get me back to a correct rolling chassis ready for the upgraded engine.

Somewhere at the end of all of this will be a road worthy '71 Triumph Bonneville, but it's a lot of parts to find and get in and then a lot time in the garage to get there. I'm hoping it'll be on the road for next year's riding season.  As we thaw out here in Canada I'll be out on the Tiger and GTR and not spannering so much.

Meanwhile, here are some more motorcycle tire sizing reference charts found on the interwebs: