1967 Triumph Mountain Cub restoration update

Starting to assemble the 1967 Triumph Mountain Cub. Every nut, bolt, and body part has been taken down and addressed aside from the original tank paint. Still waiting on parts to get the engine back together. The wheels are another area of concern. The front fender needs to be worked out. Small touches like a light weight tail light assembly and solo seat are also planned.

Getting a little farther into the assembly. The rear wheel has been a headache. The Triumph Tiger Cub is a little harder to figure some of the part numbers if you do not know the actual model you are dealing with. The Mountain Cub variety is even harder to figure out because there is not a parts catalogue specific to it (at least that I can find.) Perhaps this is because the model was produced at the very end of the Tiger Cub run, or because it was a US only model, but whatever the reason, there is some guessing that I have had to do. The bike came with a WM-3 wide wheel. After checking the latest Sports-model parts catalogue from 1965, there were two different wheel possibilities, but only one for a WM-3 width. After purchasing that specific wheel rim and lacing it multiple times, there was no way to get the spokes to fit correctly. After more research and hunting, the correct rim turned out to be the WM-2 width one. It appears the rims of both wheels were switched out at some point, and the WM-3 rim was substituted. Fortunately the wider rim can be used elsewhere, as it fits 63-70 650’s and other models. The front rim spoke nipples were way too small for the rim holes, and were swimming around in them. A new set of front and back stainless rims and spokes is on its way.

After the body work, the tank looks nice and smooth. It was primed and painted with rattle can enamel.

Nothing like fresh finishes on everything. Still not decided on the tank paint, but that decision can wait till the front fender is made, as it will probably get some paint as well. All the switches were cleaned and greased, connections were freshened up, and the wiring harness was restored. Some new sheathing and some missing connectors were replaced. The handlebar switches were also restored, and the wiring hidden inside the bars. A mounting bracket for the horn is all but invisible hidden behind the headlight. It uses the handlebar mount bolts to secure it. Since the original bracket was absent, and pictures showing it look like it was made for a different horn than the one with the bike, I just made something that worked in the space allowed. The wiring harness was modified to have a single sheath of five wires passing from under the tank to the headlight. Usually, there are connectors from the horn and kill switch that pass separately along side the main wiring harness. Instead, the ignition wire was added to the harness bundle, and routed to the headlight, where the horn and kill switch connections were made.

This tray was packed with hardware. As it dwindles in size, it makes me happier and happier.

Awaiting an oil level decal, and a final coat of clear on the oil tank. The air filter assembly and rear brake plate are ready to go. The air cleaner is another item that was different on the multiple Tiger Cub models. This one was also used on some pre-unit bikes. There are at least three different types used, as far as I can tell.

Only a few of the black parts were painted: the headlight bucket, horn bracket, speedo mount, and oil tank. The powder coating was done by Triad Product finishing in Lewisville, Texas, and is the best job ever! Not just hyperbole, the masking was impeccable, there were no runs, sags or bare spots, and the thickness was just right. In the past, I have used the powder coating as a base coat, and cleared over it, but this job was so good there is no need. The difference between the powder and painted parts is indiscernible.

An example of the wiring harness condition. Poor connections were cleaned, and the wire ends were freshened and tinned with solder. Dielectric grease was used on unexposed terminals as well as the bullet wire connectors on the wiring harness.

The wheel assemblies were taken down completely. The hubs and rear brake plate were powder coated, all the bearings were replaced, and the fresh hardware to finish it off.

The thirty-over piston is in place with new gaskets. Still waiting on the head.

A transmission main shaft bushing is back ordered from the UK, and the right side covers can’t be put on without it. The rest of the engine block is assembled. The clutch hub bearings and rubber cushions were replaced. The primary drive installation is waiting on the transmission assembly.

The crank shaft assembly was pressed together and then trued on a lathe. The roller bearing on the big end of the connecting rod ended up getting the nod after two successesive bronze bearings gave too much side play.

Making a rubber washer for the high beam indicator light, using an arbor press and punches.

And finally. My Buddy, Clinton rode up from Dallas, trying to get some miles on a fresh engine rebuild on his Norton Commando 850. Such a beautiful bike!

Rebuilding Honda Z50 Carburetors, and a pull start minibike for Skratch's Garage.

Two Honda 1970 Z50 minibikes were in need of a carburetor. With as many minis as there are around here, it pays to have one ready. Eight original carbs were worked over, with six of them completed, and a couple still needing parts.

This is a typical before picture. The choke assembly and any other steel parts have been stripped from the carb and sent out for zinc plating. The carb body is cleaned in an ultrasonic cleaner, with hot degreaser. Everything gets blown out, and put back together with new seals and gaskets. Some of these carbs were incomplete, missing floats, slides and fuel hose spigots. Replacements will be found, or they will stay as parts carbs.

All the parts ready for rebuild. The paper gaskets were replaced with new, and the nylon and rubber seals were replaced. The original paper gaskets are in remarkable shape for being over fifty years old, but the nylon and rubber sealing washers are cracked and need replaced..

The original plastic sealing washer on the choke lever is one of the impossible parts to find. Pictures of the part online look like it is made of natural nylon. The used washers, seen on the left, are somewhat puckered on the edges, suggesting they have shrunk after all the years, heat, and fuel. A piece of nylon rod was turned down on a lathe to a size slightly larger than the largest original one I could find (there were a total of ten measured to get the size.) Individual plugs were cut from that rod, with a 7/64” hole drilled in the center.

Getting the keyed opening in the nylon turned out to be easier than anticipated. Drilling the center hole is easy enough, but getting the exact dimensions needed to make for a tight seal around the shaft of the choke lever took a little figuring. A piece of steel rod slightly smaller than the shaft was ground down on the sides to the same dimensions as the original shaft. The end of the shaft was tapered to help it center on the pilot hole in the center of the nylon plug. After heating to cherry red, the rod is plunged through the plug until it pops out the other side( I did this over a slightly open vise, that allowed the rod end to poke through the opening.) After a quick quench in water, the nylon is solid and the flashing can be trimmed off with a sharp blade. Keeping the plug on the rod while trimming makes for more crisp edges.

The nylon washer on the left was the largest original I could find. The one on the right is one of the new ones.

Small sections of Honda tubing were cut to replace the rubber seal on the shaft, another part that is impossible to find in new shape.

Part of the way through the process. The bodies of the carbs were not refinished aside from the ultrasound cleaning. Some still had a fairly good original surface, but most were in some state of oxidation. Vapor honing gives a beautiful finish, that looks even better than original. That may be the way in the future, but for now, this will do.

The intake manifolds were bead blasted, and the studs and nuts were re-plated. New O-rings were used for the fuel drain needle, and manifold.

An finally… This DoodleBug minibike came from the same family as the 1967 Triumph Mountain Cub. It was hanging around the shop over at Skratch’s Garage in Haltom City, Texas, and I took it to do some mods and maintenance. It is being given a little refresh, with new bars, a mini Whizzer style tank, straight exhaust pipe, tires, chain, cables, and hand controls. She is a runner and rider, with a pretty mild engine. There may be an engine upgrade in the future…

The 1967 Triumph Mountain Cub Restoration Begins.

The Mountain Cub was broken down for restoration. Every part has been disassembled, cleaned, and inspected. New parts are trickling in. Mostly in a scattered state for now, with hardware out for cadmium plating, the head getting a rebuild, and the frame parts out for powder coating. A few aluminum parts have been polished, and dents were removed from the oil tank. There is always a learning process getting to know a particular bike. There is a lot of information available on the early years of the Cub, and more early used parts can be found as well. The information on the last two years of production (1966,1967) is scant, and things like the primary side cover are proving hard to find in good shape. The T20M Mountain Cub engine was produced during that last two years of the Tiger Cub run. There was a significant engine re-design in 1964 where the engine cases, crank, and side covers were modified enough that they are not interchangeable with later models. Other late model changes included a different connecting rod with a larger crank bearing and pin, something I found out disassembling the engine, as explained below.

The rust on the wheel hub was superficial, without any pitting, and cleaned up nicely after ultrasound degreasing and bead blasting. New bearings will go into the hub rebuild.

The frame parts all disassembled and degreased, awaiting bead blasting. Since acquiring an ultrasonic cleaner, the parts are cleaned in a water-based degreaser, opposed to the kerosene parts cleaner used in the past. The results are superior, and the process is less labor intensive.

The bead blasting is done, and any stubborn paint will be scraped or wire-brushed away prior to powder coating.

The factory brass-brazed frame joints are one of the cool things about Triumph frames. I have seen film of frames at the Meriden Triumph factory, where the frames are lying in a large bed of coals, being heated hot enough to apply the brass right there. While it seems a little crude, it is probably a pretty efficient way to get the job done. The frame was actually in very nice shape, without any significant alteration or distortion.

The crankshaft was disassembled, and it received a big-end roller-bearing conversion at some point. I have a new stock bearing and crank pin, but after disassembly, it seems the connecting rod is an early model with a small big-end bearing. A new rod has been ordered, with the bigger bearing found on the 1966-1967 engines. Given the copious smoke this engine produced when running, any non-stock parts are suspect as contributors, hence the conversion back to stock.

The sludge trap on Triumph cranks has always been a source of frustration. It is quite common for them to be badly chewed-up from previous removal (or perhaps, only attempts.) This one was no exception, and had to be drilled out. A 1/2” drill bit left just enough room to preserve the threads. This is the last little bit of the plug, wrapped around the drill bit. Fortunately, the threads were untouched during the process. Baxter Cycles had the new sludge trap replacement.

A couple of dents on the oil tank needed to be knocked out.

Some mandrels pressing the dents from inside of the tank through the filler hole, and a stud-gun to work out the rest, and its close enough for paint.

The replacement side cover was sanded and polished out. The case halves are clean, and all bushings and bearings have been replaced.

A new Morgo oil pump went in.Extra time was spent making sure that all the oil passages were super clean in the engine block, crank, and tubing, and especially the oil tank. There are many stories circulating amongst British bike owners about crankshafts and cams ruined after a rebuild because of a a dirty tank or sludge trap.

I left the head with Big D Cycles in Dallas, Texas, for new valve guides and valves. Once again, with everything else getting restored, and all the smoke it produced, it seems like it has to be done. This is the first time using an ultrasonic cleaner with a heavy-duty degreaser to clean parts. The finish was in surprisingly good shape on the engine center cases, given all the oxidation and wear on the side covers. There is a skid plate that goes on the bottom of the frame, and evidently it does a good job protecting the bottom (the thick layer of grease probably didn’t hurt either.) The new main bearings for the crank and tranny are in place, along with all the bronze bushings.

It’s a tedious process cleaning and working over the hardware prior to cadmium plating, but using the original hardware makes a big difference in the final product. Everything gets ultrasonic cleaning, degreasing, and wire brushing. Threads are chased and bends and nicks are repaired as well as possible Though there were some missing and incorrect pieces of hardware on the bike, a majority of the parts were there and in decent condition. The engine cheese-head Filson case screws had been boogered up a little, and were replaced with NOS ones. The heads of those original screws get hammered out enough to use again, but are still irregular enough to keep them out of this build. After all the prep, Texas Precision Plating in Garland, Texas does the cadmium plating.

The passenger pegs were removed by a previous owner, so the brackets were trimmed off to finish the job. The lug for the kickstand was kept, and a dome from the rear of a Norton feathered frame finishes off the end of the tube. There will be a solo seat on this bike, so the rear pegs are not needed. A new location for the brake light switch will have to be worked out. The location for the switch down low on the frame seemed a little vulnerable anyway, and could benefit from relocation.

The original white steel fender on the bottom, and an aluminum one to replace it. The fender was a clearance model from Lowbrow, that was sitting on the shelf. A little hammering and English wheel, and the crown was raised to more closely match the deep original. When the bike starts to go back together, the plan is to make a custom aluminum front fender as well. The modifications to the bike are all reversible. The old seat, fenders and tail light will be preserved should anyone want to restore it to original in the future.

The splines on the gear shift shaft were a little hammered. They worked, but look like a future failure waiting to happen. Baxter Cycle had a replacement for three bills, seen on the right. I was thinking a single-cylinder restoration might be a little less expensive than a twin or triple, but so far, that is not the case. A new shifter pedal will be used to keep everything as tight as possible.

New fork uppers are going on the bike along with new chrome locking collars, seals, gaiters, and bronze bushings. The restrictor cones are also being replaced, leaving the fork lowers, upper beauty rings, and tripletrees as the only original parts. Aside from the engine, suspension is one of the areas that I like to get worked out as well as possible, as it make so much difference in handling and comfort, and ultimately, safety.