View Full Version : My 1938/39 Triumph. A Retrospective Review.

10-15-2016, 03:41 PM
By special request here is a retrospective Member Bike Build.

Axeric requested some more details and has suggested that others may be interested in my Speed Twin (also known as a 5T) so I thought I would post a short summary about how I got it from a few pieces in to a complete bike.

But first though a brief summary of the history of Triumph for those on here not familiar with the marque. My apologies to those of you who already know this, if you do please skip past it.

1887. Triumph Cycle Company Ltd registered and were selling imported bicycles.

1889 Bicycle manufacturing started. Company moves headquarters from London to Coventry.

1902 first motorcycle made using a clip on Belgian Minerva engine.

1905 First all-Triumph machine produced this was also the first 100% British motorcycle.

1915 to 1918, production became focused on the Allied war effort. More than 30,000 Model H bikes were supplied to Allied forces in World War I.

November 1940. The Coventry factory was destroyed by German bombers so production was moved to Meriden about 8 miles away and production resumed in 1942. Note, when this happened all of the factory records relating to individual machines before November 1940 were destroyed so there are minimal records in existence for before this date. (note this fact as it is relevant to my bike)

1983 when Triumph went into receivership John Bloor bought the name and manufacturing rights and set up what we know as the modern Triumph company based in Hinkley (about 16 miles from Meriden). This means that Triumph has produced motorcycles since 1902, making it the world's longest continuous production motorcycle manufacturer.

A note about British bike model years. Manufacturers showcased their new models for the coming year at the Earls Court Motorcycle show. This show is in autumn so the next years model is actually introduced in the previous year.

My bike was originally registered in October 1938 but it is a 1939 model.

My Bike

I acquired the first parts for my bike in the very early 90's. I got a frame, forks, wheels, brakes, seats and a small number of small parts. The main items missing were engine, carb, magneto, transmission, oil & petrol tanks, mudguards, toolbox, headlamp, handlebars and controls. Also there were no fasteners.

Its worth noting that in the UK a registration (title) is based on the frame number.

Quite a few people told me that an incomplete pre-war Speed Twin (pre WWII) was as hard as a basket case gets. They were probably right at the time. In very recent years there are some very good quality reproduction parts available so some items are not so hard now. There are still some very hard bits though even now.

At the time I got the bike it was pre-internet so I put some ads in magazines looking for parts as well as looking at autojumbles/swap meets. I ended up getting a 5T engine and a T100 engine, 2 gearboxes and primary drive plus a speedometer, all for what would now be considered bargain prices.

Fast foreward to the last few years and there is a guy who used to have a website dedicated to these pre-war Triumphs. He is considered to be something of an expert on Triumphs of this era and he has a database of frame and engine numbers, dates of registration etc. This is useful because, if you remember the text above, the original Triumph records were destroyed in 1940. These bikes did not have matching frame and engine numbers when they came out of the factory. Engines were taken off the pile in whatever order they happened to be in and put in the next frame on the production line. As it turns out there is a known original machine with a frame number 27 away from mine and an engine number 33 away. Amazingly, by total chance, I have got an engine that is exactly the right number for my frame.

Whilst I now had an engine and transmission I was still missing lots of stuff, lots of it 1 or 2 year only parts so I kept looking whenever I had a bit of spare cash (note its only in the last few years that I have a bit more spare cash). I turned up a couple of the items, most memorably an oil tank at a local autojumble (swap meet), the oil tank is a 2 year only item and as rare as hens teeth.

Around 2009 I decided to get stuck in and get the bike finished. I took some pictures and so here are a few.

First are some of the very few "before" pictures that I have.




This next one was taken in 2006 when I did a bit to get the frame painted and the wheels built but not much more.


Then the pictures pick things up in 2009




This rocker box needed replacing


I used this one but got the extra breather hole welded up that someone has added before I got it.


10-15-2016, 03:43 PM
Coming together.


I picked this chaincase up in the mid 90's and it is in good condition other than a small crack which i got welded at the same time as the rocker box.




You might wonder why I chose to highlight these oil pipes?

The reason is that they are a little unusual in how the rocker feed is controlled. Pre-war was different to post war in that pre war the feed to the rockers was from the oil feed to the crank. Post war it is from the scavenge side of the system.

You will see 2 pipes, one is the feed to the rockers and the other goes to the oil pressure gauge.


The smaller pipe is for the rockers but it needs a pressure regulator to make sure that the rockers donít get too much and the crank doesnít get starved. This is achieved by running the oil through the brass fitting with the banjo union then through the small round gauze filter and then through a screw thread inside the barrel shaped brass fitting. You can regulate the rocker feed by varying the amount of screw thread that the oil has to get through.

Its an unusual arrangement but it seems to work.



I thought that a new Morgo oil oil pump was a good idea.



More to come another evening.

10-16-2016, 01:15 PM
The engine came with a carb that looked at first to be the right type. When I had a closer look at the carb it was not in great condition. Also, on closer inspection it wasnít the right spec for my bike. As it happens a company called Burlen Fuel Systems own the brands Amal, SU, Zenith and Weber and manufacture new carburettors to the original specifications.



By now I was starting to become a pre-war Triumph geek and had gathered information from numerous sources and filtered it to get what I believed to be the correct specs for my bike. I had thought that Harry Woolridge's book was definitive and it mostly is and is mostly backed up by Roy Bacon's book. However it turns out that speaking to Burlen was a good move because they have copies of the original Amal factory records and the guy that I spoke to pulled up the original 1938 factory hand written spec sheet for the carb for my bike. They also told me that the carb that came with my engine was from a Matchless G3L from 1946 to 1950 based on the code stamped on it.

The carb that I required is a type 76, according to the Amal Spec Sheet, and is stamped with the number "76W/1DA". It is apparently unusual in that it has a 15/16" bore at the air intake end but a larger bore at the engine side of the carb. This size body is not available anymore but it would be an easy job to bore it out if you were that way inclined although I am not sure of the advantages of this. A lot of people are not aware of the differences between a type 76 and a 276. Most people call all of the pre-monoblock carbs Type 276's and are not aware of the type 76 that preceded it. Both carbs are similar but the type 76 has a different body which had air holes around the base. The 276 did not have these air holes and used a different method of drawing in emulsifying air.

The Amal record states a 107.5 needle jet but half sizes are not available any more so 107 is the closest current alternative. The spec for my 1939 Speed Twin is:

Type 76/ in 15/16Ē with a flange fit. The float chamber is on the right with a bottom feed nut & nipple connection. Float chamber tilted at 7 degrees. Jets are 140 main, 107.5 needle jet and a 3 slide.

So to cut a long story short, I was able to buy a brand new carb for my bike in a spec that is very close to the original.


The bike also came with the correct MO1 Magdyno which I sent to Tony Cooper to be refurbished.





The magdyno fits on a platform at the rear of the engine.


This is one of the distinguishing features between pre and post war Triumph twins. Post war used a separate mag and dynamo with the dynamo in front of the engine.

Here is the magdyno in place.



10-16-2016, 02:42 PM
What a great project John! Thanks for posting all this, it's fun to watch something other than an American bike come together....Triumph really was "modern" in the day!

10-16-2016, 09:27 PM
I have found that I really like these serial build threads. John does one of the best jobs I have seen in telling and offering photos but also mixing in questions that both get direct answers or that generate on-going discussion. Great job John.

Mike Love
AMCA # 19097

10-17-2016, 02:50 AM
Thanks for the nice comments guys. This thread will be shorter than the HD one because the bike was finished a while ago.

The next instalment will be tonight (UK time).


10-17-2016, 02:57 PM
When I got the mag mounted i came accross a problem. The mag pinion would not grip on the taper on the magneto shaft.

Offering the pinion up to another Lucas magneto it was fine so the problem is that the taper on my Lucas MO1 was very slightly undersize. The other problem (obviously) was that I had already had my magdyno refurbished.



The easiest solution was to get a small local gear manufacturer to make me a new pinion.



This led to another problem.

The gear manufacturer said that he couldnt cut the thread in the middle for the extractor. Instead he said he would just put 2 threaded holes in it for an more conventional extractor.



I offered the pinion up and it fitted fine. I screwed an extractor on (by hand) and removed the gear and saw that the case was broken. I couldnt believe it, I had not used any force. I screwed the screws into the pinion and then backed them off a couple of turns. I still cant work out exactly how it happened.



10-17-2016, 04:52 PM
First I did this:




Then I cut a thread in the centre of the new pinion for the correct extractor.

Then it was just a reassembly job. Whilst I was at it I changed the timing gears for ones that hadnít been drilled out like the ones that came with the bike.




And then, finally, I could time it.



10-18-2016, 01:05 PM
Here are some pictures of the seats.






Whilst going through my pictures I found a picture of this.


I took picture this from an ebay advert and then copied the pipe.

I found this picture of the new pipe along with some other stuff ready to go for plating. I am a bit paranoid about sending small parts to the platers so I do this with them and send an itemised list cross referenced to the picture. (Maybe I am a bit OCD?)


Here is a different batch of parts fresh back from the platers.



10-19-2016, 02:45 PM

I acquired this speedo in the 90's when I got the chaincase. I asked the guy with the chaincase if he had any more stuff and he disappeared into his shed and came back with this.


The speedo is not too rare although it was still a good find.

I got the ammeter with the bike. Whilst it looks similar to lots of other Lucas ammeters it is quite a rare item, 2 year only I think.


The oil gauge was an ebay item.



You can just see the faded WARNING sign in the second picture above.

It was miss described on ebay and I got it for (I think) about £100 which is a good price. It is a one year only item. Its made by Eureka but has the Triumph branding on it. The 1938 Speed Twin had a similar gauge but it only went to 120 psi. The T100 was introduced for 1939 and needed a higher pressure gauge and so both the Speed Twin and T100 were fitted with the same gauge. The post WWII bikes had a different gauge altogether which lasted until about 1949 (I think thatís the right date without looking it up) when the pressure gauge was dropped from the bikes because dealers were fed up with people coming along and saying that their oil pressure was lower than the gauge said that the minimum should be.

Note, after about 20 miles of riding my bike, when its fully warmed up, the oil pressure reads about 25psi at tickover and thatís with an upgraded oil pump so I imagine that the "minimum 35 psi" warning caused lots of queries for dealers.

I sent all 3 gauges to Ian Bartrum who did a great job. However when they first came back to me there was a problem with the oil gauge, can you spot it?


However I sent it back to him and he sorted it out straight away.



10-20-2016, 02:30 PM
The twistgrip was another ebay item and also quite rare. I had been looking for one for a while but they are not common. They have a spring loaded plunger (see bottom of second picture) that presses against a knurl inside the throttle to give a cruise control effect although mine is a bit worn so tends to slip off which is actually fine by me.



The Amal levers are also a rare item but there is a company in Czechoslovakia who make fantastic replicas so i went for those after 2 years of looking for originals.


By now its starting to look like a bike and these pictures were taken when I was wiring it.

The original looms were all black wires with coloured metal loops crimped to the ends to denote different circuits. I didnít have metal loops so i used coloured heat shrink and put a small loop at each end of a wire in similar colours to that described on a period wiring diagram.



Here is a detail that is a subtle difference between 1938 models and 1939 models. If you remember the rocker feed and oil pressure gauge feed that I mentioned above, you can see the oil pressure feed in this picture.


For 1938 models the oil pressure gauge feed went straight to the gauge with no breaks in it. The only way to disconnect it was at the gauge which made taking the tank or instrument panel off very awkward. For 1939 they added a union just below the tank so you could disconnect it easily.


10-21-2016, 02:18 PM
The tank was one of the last pieces I sourced. Before I got this one I was sold another one that turned out to be the wrong one for my bike. I then tried an Indian (the country) reproduction but the quality was awful so I looked for an original one.

I got this one which looked better than it turned out to be. I found it to have 2 issues. First the mounting holes should be threaded but were stripped to the point that they looked like they had been drilled out at a clearance fit. I didnít want to weld it because of the chrome and paint so I made threaded inserts. You can see one in the last of these 3 pictures.




The second issue was that when I put petrol into it it had pin holes. So I had to line it with POR15.



With a tank sorted out it was just a few last bits to do.



Here is a stop on the first ride in late May 2012.



More to come


10-22-2016, 10:49 AM
John: What is the brand of clamp that you used for your oil hoses? They look to be kind in not bunching the hose. Thanks

Mike Love
AMCA # 19097

10-22-2016, 11:06 AM
John: Looks like the Triumph branding is missing on the restored oil gauge? So you got a new needle as well.

Mike Love

AMCA #19097

10-22-2016, 11:31 AM
John: What is the brand of clamp that you used for your oil hoses? They look to be kind in not bunching the hose. Thanks

Mike Love
AMCA # 19097

Mike, I have no idea what brand they are I am afraid, they were just an online purchase from, I think, here (https://www.beal.org.uk/). I am pretty sure that you could find similar i the USA at a general workshop supplies place. Beal is more of a trade place rather than a big box store so not too many "general public" buy from them.

John: Looks like the Triumph branding is missing on the restored oil gauge? So you got a new needle as well.

Mike Love

AMCA #19097

The Triumph branding was missing from the gauge when it returned the first time but Ian Bartrum was very apologetic and fixed it straight away. See the picture of the gauge in place complete with Triumph branding . I am pretty sure that the needle was just repainted. Edit, you might be right, I was sure that the crescent "tail" on the needle was intact but I just looked at the picture again and you might be right perhaps I did get a new needle.


10-22-2016, 11:55 AM
Here is one for the oil pressure gauge nerds.

This is the "post war" oil gauge, you can see it is a different instrument altogether.




10-22-2016, 12:37 PM
The reason I took those pictures above on the first ride was because I had a breakdown. As I mentioned previously I entrusted some of the engine work to a "specialist" Unfortunately he put too little clearance on the valves/valve guides and I got a stuck valve. It was easily remedied by reaming out the guides to the correct clearance but it was a bit annoying.

After that I still had a couple of minor items to do like putting numbers on the front plate but for all practical purposes it was done.

I put a 500 hundred miles on it through the next few weeks. I would do a few miles and then iron out some issues then do some more miles then iron out some more minor issues etc. In August I took it to a VMCC ride out. The ride out started about 35 miles from where I live although I went there along the long scenic route and had done about 50 miles and had nearly got there when the bike stopped.

Here it is parked up waiting for the tow truck. I had tools with me and a few minor spares but not what I needed to fix this (minor) issue.



Here is a close up of the problem, if you look closely you will see petrol running down.


Its hard to see whats broken in the above picture but in this next picture its obvious.


The problem was caused by 2 things. First, the rear tank attaches to a flat mounting bar bolted to the frame. The bolts between the bar and frame had worked loose and so the tank had started vibrating badly causing the tap to fracture. This was easily remedied using Locite.

The second problem was my laziness. I had bought a new pattern tap for the bike from an autojumble/swap meet and it was made of some crappy metal. Also it is a later type of tap and so it is different to the one originally fitted to my bike. ( In hindsight I have no idea why I bought the pattern part but it has been a useful lesson)

I say laziness because I have this box in my shop.


I had an original one made from brass of the right type but it needed some work. It needed new cork, it needed a gauze filter adding and it needed the thread that screws into the tank reducing from 3/8" BSP to 1/4" BSP. An hour or so later had it sorted out.

The one on the right in the next picture is the correct tap and the one on the left is the correct thread for those not familiar with British Standard Pipe (BSP) thread.







10-22-2016, 12:39 PM
Other than those 2 breakdowns the bike has been good apart from one more issue. That issue is that I vibrated too much. I entrusted some of the engine work to a specialist but I only had the crank statically balanced and it was un-rideable above 55mph. This bad vibration led, at least in part, to the broken petrol tap.

2013 & 2014 was spent building an extension on my house so working on bikes took a bit of a back seat so it wasnít until 2015 that i got around to pulling the motor apart and getting the crank dynamically balanced.

What a huge difference that made to riding it. I recommend to everyone that if you are building a motor you need to dynamically balance it.

This brings us up to date on this bike except for that oil leak I mentioned a few weeks ago which i had lived with since last year (when I rebuilt the motor after balancing the crank) because I was so engrossed with the HD.

In hindsight I like to remember it as being an easier project than it actually was but in reality some of it was really hard work. Some parts were easy to find because they were used on bikes up to 1949 or even beyond but some were very difficult to locate.

Also it was a bit like a jigsaw puzzle without a picture so some of the small details were hard to get right and I would end up spending hours and hours getting some small part like say a bracket right. I am sure a lot of people on here have had similar experiences.

Something that I would do differently is the fasteners, remember I mentioned above that there were none with the bike. They are mostly Cycle Thread with some Whitworth. There a few firms that do fasteners to order in Cycle Thread but only in stainless steel. I opted for these stainless fasteners because this was much easier than making the hundreds of nuts and bolts and screws that I needed myself especially because lots of them are unique to this bike with domed heads or other unique features. I donít like how the stainless items look and also they like to gall which obviously I donít like either. Along the way I did collect a few original fasteners so at some point in the future I might start changing them out for steel ones and making the missing ones myself.

This point alone made the 20F so much easier to do. It came with most of the fasteners and I have probably only had to make 30 to 40 items myself and at least half of those were because the ones with the bike were too rusted but at least I had a pattern to work to.

Here is that picture of the 5T from my introduction again, its not a recent picture but its a good one. (since then I have put numbers on the front plate)


And thatís it. (well almost, I have vinyl letters on the number plates but having had the 20F painted by a sign writer I think I will do the same on my 5T at some point in the not too distant future because it looks so much better)

It starts mostly on first kick and compared to the 20F it is quite a modern bike. It does still have the odd oil leak so I can see why old British iron had such a reputation for oil leaks. I keep sorting them out but I donít think it will ever be 100% leak free. But it is a good bike and because I had it for so long before I managed to get it together and because it was so hard to find all of the bits I am quite attached to it so I think it will be a keeper.


10-23-2016, 08:07 AM
I enjoyed reading this, John. Beautiful bike! Dale

10-23-2016, 01:15 PM
Thanks Dale. I enjoyed the trip down memory lane, finding my old pictures and writing the posts.


03-14-2017, 09:04 PM
What a lovely job, you should be very proud.

Shaky Jake
03-14-2017, 11:42 PM
That's a beautiful machine. Lovely. Nice job.



03-16-2017, 03:45 AM
Thanks for the comments guys. I was just thinking about waking the Triumph up from its winter sleep. I have a couple of minor jobs to do so when I have done them I will post an update.


03-16-2017, 08:49 AM
I have a good friend here in Florida who is British, and a motorcycle collector. I have told him many times; how can a Brit, who loves motorcycles, not have a Triumph in his collection:)

John, your Triumph is stunning, and your documentation is excellent, as it was with your J model Harley. When you look at the beautiful lines of that bike, you wonder how modern motorcycle design got so out of touch with classic styling.

05-21-2017, 05:17 PM
Hello folks, I said I would do an update.

A few weeks ago I serviced the Triumph and did a couple of jobs i have been meaning to do for a while.

First up was the sump plate. There are 2 issues here. First, the standard plate is pressed steel and is prone to warping slightly and leaking. Mine is no exception. One remedy is to fit a machined alloy plate which is what I did. Also the studs go through the cases and oil gets down the threads and leaks. My remedy for this was to fit the studs using Delta 333 pipe sealant. I am a big fan of Delta sealants, for most applications they are as good as the equivalent Loctite product but much cheaper.

Old plate


Old vs New


However I ran into another problem. There is a gauze filter in the sump that the scavenge pipe sucks oil back to the tank through. When I took mine off I noticed that the gauze was starting to separate from the brass plate. When I investigated it came completely away with almost no effort. It seems that this repop filter is just glued together. The originals are soldered. I thought about soldering it back together but I couldnít get the glue off the gauze so i bought a better quality item from SRM made of stainless steel and it is crimped together.

Old one




New one


This is where it fits. You can just see the scavenge pipe.


I also needed to put a new gasket on one of the pushrod tubes.

Here is the front tube.


Gasket kits include rubber gaskets for top and bottom of the tube but I always had trouble sealing the top. Oliver Barnes at TriSupply advised me that the early bikes had a thick paper gasket (between 5/32" and 3/16") and he sold me some and it fixed them. However last time I had the top off the engine I reused a gasket and had a weep so i needed to replace it. Now the gaskets are, for what they are, not cheap. Ok they are not exactly expensive but I took the time to make a die and bought some paper and now I can cut as many as I like for the cost of a couple of bought ones (if you include the postage)

Here are 2 bottom gaskets to the left hand side, you can see that they are thicker. To the right is a modern top gasket and a paper one. The paper ones are, in my experience, much more effective.


Here is the die. Its just made from scrap and is in 2 parts which makes getting the gaskets out of it easier and also makes making it easier.


Last job is something that i do every year which is boil my petrol tap. These old Ewarts taps have a cork seal inside and they dry out and shrink, especially when I drain the fuel over winter. When they shrink they leak and the best method to fix this is to boil the cork for 20 mins. This usually make the cork OK for another year.



05-21-2017, 05:20 PM
Plunger with cork seal.




After boiling. You can see it has swollen up.


As I said this usually sorts it for a year.

I planned to go for the first proper ride out of the year today (Sunday) so I filled the tank right up and gave the bike a quick check over on Saturday. After I had parked it in the garage for a short time I could smell petrol. Turns out the cork has reached the end of its life. I have a new cork but the parts are riveted together. Looking through my box of taps I noticed I had another plunger that had been taken apart and soldered back together so I used that plunger with the new cork and soldered it together. The tap is now quite stiff but it seals fine and no boiling required. I think I could make a new plunger with O rings the next time I have a problem so that is a job for the future.

Close up of old cork on the soldered plunger.


Old cork. I forgot to take a picture of the old and new corks together. the new one is much bigger.


Replacement plunger, note solder.


As opposed to the original riveted construction.


So I went out with the local section of the VMCC. Liken that to your local chapter of the AMCA. It was a short run of about 35 miles although they were 35 miles of English lanes like this so even though it was a short ride it was nice. Also its about 20 miles each way from my mouse to where we met so I did about 75 miles all in.

Here is the sort of road for the most part of the run. The width is the same as the width of one car.


I didnt have a route holder so i had to follow someone who did. At first I was behind a 1918 Triumph doing only about 30 mph. Then a faster group went by so i tagged onto the back of them. They were much newer bikes, a 1970's 750 Honda, a Trident, another Honda etc. They were probably going at a comfortable pace for them but i had to work hard to keep up. I had enough GO but was lacking in the STOP department. Its fair to say that for at least 20 of the 35 miles I gave the Triumph a hard ride with a couple of "moments" when my muscle memory went for the gear change rather than the brake. It didnít miss a beat and is running better than ever.



Needs a clean


This afternoon I managed to do some work on a milling machine that I am doing up so all in all today has been a good day.