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The 'Yamaha Enduro'

1975 Yamaha DT125/175MX Hybrid

Entry 01: Saturday 20 August 2011


Well, with ’The Corporal’ having gone to a nice new home, I can FINALLY get on with the bike I REALLY wanted to ‘Do’ before all of this Super-Dream nonsense began! (And TRY and 'blog' it in 'real time' as it happens! HOPEFULLY, this one wont drag out too long....... He SAYS, ever the optimist; but to long in the tooth to truly believe it!)

  It’s a mongeral ‘Hybrid’ Yamaha ‘Enduro’ 125/175, and this is what it looked like a year ago, when I first acquired it.

 Yamaha DT175MX 'Barn-Find' Yamaha DT175MX 'Barn-Find'

 Yamaha DT175MX 'Barn-Find' Yamaha DT175MX 'Barn-Find'

Yamaha DT175MX 'Barn-Find'

In short… RUSTY! But it has a few good points.

Why I bought it.

It’s a ‘Classic’! A bit of two stroke lunacy, from another age. And it was CHEAP! I cut my teeth off road, riding air cooled Yams; the TY trials variant, in various capacities, and my first road bike was a twin-shock DT50E… which convinced me that my idea knobbly shod road bikes were neither fish nor foul was not far from true! And I decided very early on, dirt bikes for dirt, road bikes for road, race bikes for the track; horses for courses, and all that.

Twenty odd years on, and I am struggling on half crippled legs to hold up my CB750 road bike…… Looking around for ‘tiddlers’ for Donna, after her cruiser was stolen, I spotted this thing, and just couldn’t resist it! At under 100Kg in street trim, its 20% lighter even than a CB125 Super-Dream, and with a 2” lift kit, the thing has a seat height taller than either my 4” jacked 750 or VF1000! As well as being less than a third the weight!

I can sit the saddle of this thing, and hold it up, legs straight, knee locked, and there’s bog all of it to hold up; So if it did fall over, pick back up again!

And unable to ride competitively in my favoured discipline of trials, maybe attempt a little ‘Green-Laning’! Which was what immediately went through my mind when I first sat on it, while looking at a rather sad NS125 Donna was interested in, being sold by a chap clearing out his unfinished projects from his sisters garage, where they had been shoved after he’d divorced, and from where they were being evicted, as sister was moving house.

Chap fiddled a bit and fired it up for me, and I promptly wheelied it across his sister’s front lawn….. BIG GRIN on my face…. SOLD!

NS was a waste of time though; engine didn’t run, forks had no damping, headstock wobbled, rear suspension hardly moved, and it had no screen. UK clocks belied suggestion it was as suggested the ‘Full Power’ Italian market variant, with the ‘full 33bhp’ he claimed a de restricted 125 should have, while lack of ATAC bits kind of concluded the suggestion…. and no amount of fault finding would convince the bloke it wasn’t worth at ‘least’ £500 for the (non running!) engine alone!

But he was not so optimistic about the DT… listed on e-bay, as a DT125, it had failed to grab the imagination of a generation of modern teen learner, whose DADS probably thought an air cooled DT was ‘old fashioned’, and just saw a heap of rusty junk! Consequently, I snaffled it for about half what DT175’s were fetching, incomplete, without documents as ‘barn find’ field bikes, for spares or repairs! And was even happier when I went to collect it, and while sorting the straps to load it on the car to take it home, chap starts coming out of the garage with boxes of ‘bits’ to go with it, including the original engine, and a spare exhaust and lots of electrical bits!


When I first stuck pics up of this bike, more observant, and more knowleagable two stroke nuts, observed that this bike where’s a ‘P’ suffix registration. One of them, even went as far as to run it through the DVLA checker and reminded me that this index was issued to a Yellow Yamaha 125 in November 1975. While the bike, as shown in the pictures, is to all extents and purposes, a Yamaha DT175MX or approximately 1978 vintage, a very early mono-shock, with tubular swing arm. And I wont disagree. It is.

Yamaha DT’s are commonly nicked bikes, and if this one had been ‘ringed’ might make sense of why it was so cheap… YES, it did all ring ‘alarm bells’. But there are other reasons to try and register a DT175MX as an earlier DT125, and that was the 1982 125 Learner-Laws.

When introduced, Yamaha 175’s (and 200’s and 250’s!) dropped in value, to ‘almost’ worthless, because you couldn’t ride them on a provisional licence. The Yamaha DT175, had been far more popular than the DT125 or DT250, when learner legal, because it had a bit ‘more’ oomph than the 125, and was a lot more manageable, as well as a lot cheaper to buy and run, than the full 250; but when learners were restricted to 12.5bhp 125’s, they didn’t offer much more than a 125, and many wound up hacked and abused ‘Field Bikes’, thrashed over waste land by kids.

Pre 1982 125’s on the other hand, suddenly became quite sought after. A loop-hole in the Learner-Laws provided pre ’82 registered 125’s need not be restricted to 12.5bhp, and where ‘tuning’ or ‘de-restricting’ a post 82 bike made it illegal to ride on provisional entitlement, rule didn’t apply to pre 82 registered bikes. Hence in my youth, pre ’82 125’s were quite sought after, as many of them had more power than new bikes to begin with, and could easily, and legally be tuned for even more, and still ridden on L’s.

Some took the idea further than others, and dropped RD200 engines into RD125 frames, or X5 lumps into X3 frames, that kind of thing… other simply got the log-book for a smashed 125, got a number plate made for it, and slapped it onto a 200, with 125 side panels or just decals! I think that THIS bike is possibly of that veriety of post ’82 learner ‘cheaters’.

HOWEVER, not crudely ‘ringed’. Engine that came with the bike, missing its barrel, is a 1975 125 bottom end, and matched that which would have been in the bike originally registered. Possible in those days, to build a ‘special’ and use the registration from the engine donor, and I suspect that was the way it was done; the frame, possibly a new replacement from Yamaha, stamped up with matching numbers, and no signs of grinding, welding or tampering around it on the head-stock. And stripping it down, more I find that supports this idea, until a later 175MX engine dropped in at a later date, possibly when the original 125 motor needed a re-bore; hence missing barrel. (I actually have the barrel, and a brand new piston amongst the bits, but of course hole in barrel is too small for piston!)

Anyhow; doesn’t really matter what it was; what it IS is a very un-original Yamaha ‘Enduro’, conforming to neither early T-Shock Spec nor later Mono-Shock Spec. Only ONE thing to note, it is NOT a ‘DT’….. well it IS…. But it isn’t!

he DT series was named after the engine coding used for the ‘big-block’ 250 & 400’s, given six speeds, when they gained the ‘new’ moto-cross inspired mono-shock rear suspension. Previous ‘Street-Scrambler’ models in all capacities had, until then simply been badged ‘Enduro’, as were the early ‘DT’ series 250 and 400’s, which gained ‘DT’ badges to denote the DT series engine!

Marketing men later decided to use the DT badging to denote the entire range of ‘Street-Scramblers’, and in about 1981, when most of the ‘Enduro’ models gained the cantilever monoshock rear suspension, it became ‘officially’ the model designation.

Badging HAD been used on some earlier ‘Enduro’ models, and not necessarily the 250/400’s, or even just the mono-shocks; some-times from the factory, some-times from the dealers, but quite commonly by early owners.

The ‘Triggers-Broom’ of a Yellow Yamaha 125, originally registered, would almost certainly NOT have been badged a ‘DT’ but an ‘enduro’. The sole or possibly numerous, later DT-MX, that donated ‘bits’ for the bikes metamorphosis, may have been badged DT, but the three model years of bikes given the tubular swing arm, rarely wore DT badges from the factory, and the livery that corresponds to the very early, flat ‘side-panels’ and rounded, unvented mudguard, simply provided YAMAHA on the tank, with either 125 or 175 capacity badging, and an ‘ENDURO’ badge as model identifier.

It’s a DT…. But its NOT a DT…… Meanwhile; however it got to be a mono-shock from an earlier twin shock; pitty is, earlier twin shock Yamaha ‘Enduro’ models are now far more sought after restorers and collectors bikes, worth far more than the, later, early mono-shock models!

What I intend doing with it

Fix it and RIDE it!

This one is a keeper, Basically! This is NOT a sought after ‘collectors’ bike. If it was a relatively unmolested Twin-Shock ‘Enduro’ might need a little more contentious care to restore it as authentically as possible, to preserve both historic and financial value. If it was a fairly complete DT175MX, again, may need a bit more thought.

Perversely, at the time I bought this one, and still; the later, and much more common square swing-arm 175’s, without any registration, often not as complete, and in worse condition, are fetching much more than I paid for this one. Which did prompt thoughts as to whether to restore it utterly as an early DT175MX, and attempt to re-register it on an age related plate, or break it for spares, and attempt to restore it, with the second engine, as the bike originally registered, a more valuable still, DT125E.

Nope….. too synical! I got it because it was cheaper than a pair of tyres for the CB750, and offered big grins, for little bucks!

SO, back to very initial intent; a low rent renovation, to create a pocket money ‘toy’ bike for fun and frolics, with a bit of history and classic cudos.

Padding that out a bit; what’s ‘pocket money’, and what’s a renovation? How far do I take it, making it ‘nice’ how far don’t I take it? What are the boundaries? So, pondering starting points; ideas about powder coated frames, Hagon shocks; rebuilt wheels with stainless spokes and ali rims, big-one exhaust, fibre reeds all brought into check….. Brakes, Steering, Suspension!

As always, lets get the basics ‘sorted’. Lets be sure we can stop, before we go…. Err, embarrassed admission! Actually I didn’t! Breaking my own rules, prodding and poking, I fitted up the ‘spare’ exhaust and tried cleaning the carb, to assess the engine, to be able to decide whether to do anything with the one in the frame, or put attention into the one in the back of the Range Rover. Fired it up, found a gear, and promptly wheelied the length of my lawn, got it down as I reached the patio, hauled in the brakes, and sailed straight on into the back wall of my house….. LAUGHING MY HEAD OFF! Yup… that’s what Y?amaha dirt bikes are all about! SHEAR STOOOOPIDITY!

So, bolting serious head back on for a moment; the usual suspects vis mechanical integrity. Sort the brakes…. We now know NEED some fairly serious sorting, steering and the suspension….. THAT is a case of ‘whatever it takes’… we don’t stint on these bits.

Engine It has one. It runs! That’s ’good enough’! So, no getting carried away; sort what we got, scrub, fettle and make as good as. When we get to it, IF it needs more, we’ll wait and see. For now. Exhaust can have a bit of paint; engine can have a bit of paint. Carb can be cleaned again, and if its LUCKY I’ll treat it to a new spark plug!

Frame & Cosmetics Lots of deliberation on this one. Idea of having frame powder coated as good ‘base’ for anything else I do was pondered very seriously. In all though, while the frame would only cost £40 and the swing arm £25, how far do I go? Adding in the fork yokes, lifts that £10, then there‘s the brake lever, another £5, and the footrests, what about the fork sliders…. And so it goes on, and on and on. So hold the ‘phone! I have had my Montesa since 1985. It got sand-blasted that summer, and painted in Red Smoothrite… it has lasted over quarter of a century of competitive trials action, with ME riding, or more often falling off it, taking chunks out of the paintwork! It’s had the occasional clean down and another coat chucked over, and had some of the bigger scratches or patched touched up between times. If the bike I have had a life time has survived without plastic coating, can I really justify shelling out that kind of money, on a ‘pocket money toy’. Short answer NO! So, Black Smoothrite, a brush and a tin of thinners! Which leads me to the tank and panels, which, scruffy, I could probably get away with, ‘as is’… but the paint is cracked and flaking off the mudguards, and there is a bit of rust round the seam of the tank…… and Donna reckons it needs ‘painting’, so OK….. maybe just to smart it up….. but NOT going to town on it with five base coats and three colour coats, custom decals and lacquer again! Seen some nice Plasticote for £3.99 a can, in a sort of orangie yellow…. Maybe that will ‘do’, possibly some period ‘pre-DT’ decals.

Electrics & Equipment It has a lamp on the front, and another on the back, and there’s some wires poking out the magneto cover….. Hmmmm…… by Construction & Use regulations in force when first registered, doesn’t ACTUALLY need any lights or stuff…. COULD for the use I’m likely to give it, get it tested with no lights, under both granddad rights and exemptions for ‘machines adapted for off-road use’. Nope. Think I need lights at least. Especially as its already starting to get darker earlier. Donna reckons I ‘ought’ to have indicators, and I’m sort of in agreement, but hey! Got to make from scratch whatever its going to have, so ‘we’ll see’!

And THAT is about it; the ‘plan’ as it stands right now.

So lets get on with it!

Well, in a hiatus during the Pup-Project, I DID have a little poke and play. Had to pull it out of the stack to move some bikes about, and couldn’t resist having a bit of a mess…. Which was when the afore-mentioned incident wheelieing into my house wall occurred!

 Yamaha DT175MX 'Barn-Find' - initial poking Yamaha DT175MX 'Barn-Find' - initial poking

Basically, the exhaust on the bike had more holes around the header than metal, so I swapped it.

 Yamaha DT175MX 'Barn-Find' - rotten exhaust

Then I cleaned the carburettor, got it started….. CRASHED IT… so did what I OUGHT to have done right at the beginning, and started looking at the brakes!

 Yamaha DT175MX 'Barn-Find' - Dirty Carburettor

Also discovered that there was no Two-Stroke oil reservoir, and no battery, and had a general ‘poke’

 Yamaha DT175MX 'Barn-Find' - missing oil tank

Got as far as taking the brake cable off, and Donna, getting annoyed with me, made me put it away! So, ’The Corporal’ Done, and Gone; pulled it back out the stack, moved some bikes around, ignored the pile of Super Dream bits in the kitchen I ought to tidy up, and carried on!

 Yamaha DT175MX 'Barn-Find'

Hydraulic bike stand, finally getting used for what it was intended!

 Yamaha DT175MX 'Barn-Find'

And a snap of the front end, where I intended to start, and that rusty front wheel.

Yamaha DT175MX 'Barn-Find' - Rusty Front Wheel

Lots of rust, on the fork jokes and bracketry to be dealt with, and that headlamp, is, well… it LOOKS like a headlamp! Lens doesn’t seem to be pointing in the right direction, and I haven’t a clue whether there’s even a bulb in there! Interesting feature is the shrodiner (car tyre!) valves on the fork caps. These conform not, to any likely Yamaha fork of that era. Neither early 125 ‘Enduro’, nor DT-MX, nor the competition variant IT175… I THINK they may be a home made ‘modification’…

Yamaha DT175MX 'Barn-Find' - Rusty Fork Yokes

‘Flat’ side panels are very early DT-MX. Later ones had a diagonal step. They have been re-painted though. Seat base looks quite useful, though, if a bit dirty. Seat cover, is also surprisingly serviceable, though not perfect.

Yamaha DT175MX - Original '78 model 'flat' side panels

Under the tank, its starting to look more promicing. For all that VERY rusty exhaust and abortion of wiring, its mucky, but the paint is surprisingly ‘mot bad’ considering rust everywhere else!

Yamaha DT175MX 'Barn-Find' - Grot under tank & seat

OK, enough faffing abouit admiring bits, lets get on with some ‘real’ work!

Yamaha DT175MX 'Barn-Find' - Rusty Front Wheel

Front wheel out, lets look at them brakes! The Shoes will probably be replaced as a matter of course, but needed to inspect the drum itself, and the shoes. If the drum is ‘gone’ then I need a new wheel, and there’s little point trying to clean up the rusty spokes or anything on this one. However, more importantly, I need to check what the shoes look like, because this is NOT a DT-MX front hub. We think that the bike has the whole front end, wheel, brakes and forks from the original ’75 Enduro, but it might NOT be, so want to check sizes and form before ordering ‘bits’ that might not fit.

Yamaha DT175MX 'Barn-Find' - Brake Shoes

Shoes aren’t actually as bad as I had imagined, but they are pretty badly worn, so will be replaced. A ‘Bits List’ is starting to be put together now!

Yamaha DT175MX 'Barn-Find' - Cleaning wheel spokes

So, quick attack with sand-paper to see how the spokes clean up….

Yamaha DT175MX 'Barn-Find' - Rusty Exhaust

Needed REALLY to get stuck in to stripping down the front end, and finding out fork seal sizes, and looking at headrace bearings and ‘stuff’….. but what the heck! LETS PAINT SOMETHING! Always makes you feel like you have achieved sommat!

Yamaha DT175MX 'Barn-Find' - Cleaning Exhaust

First hit on the tail pipe with the rotary wire on the drill.

Yamaha DT175MX 'Barn-Find' - Cleaning tail-Pipe

Second hit with the rotary wire on the angry grinder. Never want to go straight in with this tool, it’s a bit fierce and can chew aluminium up in moments. But on stubborn rust like this, LOOK at the difference. Incredibly there is STILL metal under all that rust! (Yamaha used to make their off-road exhausts PRETTY thick, in them days) Lets get some paint on it!

Yamaha DT175MX 'Barn-Find' - Painted Tail Pipe

I had the last can of PJ1 ‘Ceramic Hard’ from Busters, and apparently the importers have 5000 and H&S wont let them sell, because they don’t have a warning on the lable, and are insisting that the cans are all re-labled, a sticker on the existing lable wont do! What the heck! This is a low rent renovation, not concourse d’elegance! And its NEVER going to be pretty with all that rust pitting and aged braze! Plasticote BBQ paint, £8.99 a can, JUST the job! Don’t look TOO bad, does it? OK, lets leave that to dry, and get on with some ‘propper work’.

Yamaha DT175MX 'Barn-Find' - Forks stripped for overhaul

Forks took some bashing to get them out the jokes, but I DO like Yamaha mechanics! Once out they just slide apart like a dream. Curiously I have TWO fork springs in each leg! More precisely, as one end of each spring lacks the wound termination, two cut down halves of two springs. Think I might have to do some measuring and see what Alf Hagon has to offer.

Yamaha DT175MX 'Barn-Find' - Fork Slider stripped for painting

Wearing out rotary wires! Sliders cleaned up ready to take paint

Yamaha DT175MX 'Barn-Find' - Forks stripped for overhaul

Forks all stripped, seals popped ready to measure up.

 Yamaha DT175MX 'Barn-Find' - Fork Stancions polished

Stanchions polished up. Rust and pitting between the yokes is still pretty bad, cosmetically, but ‘wiped’ area under the gaiters isn’t so ‘bad’….

Yamaha DT175MX 'Barn-Find' - Part stripped for renovation

Front end starting to look a bit ‘bare’, but strip down well under way, and looking like progress!

Yamaha DT175MX 'Barn-Find' - Part stripped for renovation

Enough seriouse stuff, LOOK at that exhaust! Lets Paint it!

Yamaha DT175MX 'Barn-Find' - Rusty Exhaust to be cleaned

Straight in with the wire on the angry grinder now, only a few bits to do with the drill, where you cant get in on the bend.

Yamaha DT175MX 'Barn-Find' - Rusty Exhaust being de-rusted

Very conservative ‘taper’ and not a large amount of ‘expansion’ on these early expansion chamber exhausts; suggests good mid range. Explains why so many put aftermarket spannies on them!

Yamaha DT175MX 'Barn-Find' - De-Rusted exhaust

Old Gianelli ort Fresco pipes released an awful lot of hidden potential, AND saved a shed load or weight! BUT seem to recall they had a habbit of rotting within a year or two, and denting around the header area if hit by a stone of the front wheel. THIS thirty year Yamaha pipe shows how much metal they put in them to begin with, against rust and dents! Amazing to think that at the time this bike was built, people grumbled about Japanese bikes, like they do Chinese ones, today, “Not built to last!” they said. “Made of Monkey Metal!” they explained. Hmmmm thirty years on, and THIS thing is in better shape than the 1963 BSA c15 I got to ‘trials-chop’ in 1984…. THAT bike was then, barely twenty years old!

Yamaha DT175MX 'Barn-Find' -De-Rusted Exhaust

Bit of brazing revealed around the port flange, where they all tend to rot, but it seals, I’m not complaining!

Yamaha DT175MX 'Barn-Find' - Repainted Exhaust

So, douse of BBQ paint, and hand to dry over a camping stove to help ‘cure’ and I’m happy. Amount of ‘pitting’ on both pipes, though, could probably have got as good a finish brush-painting them, however. But with the paint ‘thinning’ over the rough metal, given both pipes two coats, and probably give them a bit more before they are ‘done’, which might smooth them out a bit more, but basically just to make sure of even coverage over the metal, and avoid porosity. So, back to mechanics, and a look at the head-stock… but that can wait until NEXT time!





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