Honda MT125R

Honda MT125R

Honda MT125RSimple and cheap, yet a staggeringly effective package

The MT 125 is a factory produced race bike quite unlike any other with its road going brakes and motocross engine. Contrasting virtually every other race or indeed any form of bike that had previously left the Japanese Honda factory the MT uses many components from a variety of road and MX based machines. The original cable (affectionately known as a string stopper) front brake is lifted straight off that unlikely track god machine, the CB200, the rear wheel hub is directly off the ST90 while the rear brake and sprockets are XL100. The frame is largely unique however as are the front forks but wherever possible freely available parts have been used by Honda in the making of this quite extraordinary machine.

The port timing of the air cooled motor is unchanged from the CR125 MX racer just a slightly larger volume inlet port to marry with the bigger diameter carburettor required for high speed runs. The gear ratios where also altered to suit the higher speeds encountered in track racing making slipping the clutch a necessity at all times in first gear. The clutch is the standard MX wet multi plate unit and appears to be up to the job of handling the constant abuse that the Cadwell full circuit meters out with its tight hairpin, steep mountain and of course the new chicane all requiring a seemingly un healthy amount of slipping in first gear to negotiate correctly.

MT125Punishment aside the tiny buzz bomb of a machine just kept going lap after lap there was a perceivable drop in power after five or so hot circuits due to the air cooling and being trapped within the all encompassing and restrictive fairing. This was addressed two years after the MT’s introduction with the release of the water-cooled version, enabling race long full power to be reliably maintained.

The simplicity of the design was demonstrated during the day when one of our trusty mounts nipped a new piston potentially ruining the test but no worries, within minutes the top end was off thanks to the four 12mm nuts that hold the barrel by its base and the two springs that hold the exhaust on, and the problem was easily solved.

The iron lined bore can be simply sanded back to usefulness with most seizures as in this case the original components were reused, just rubbed up a little and re fitted.

Mastering the tiny machine

Thanks to the UK’s leading MT125 protagonist Jerry Lodge we had a whole line up of race ready 125’s to play with.

MT125RThe air was warm, the sun shone and strangely the track day was not a hugely attended one, meaning lots of open track to stretch this machine fully.
The Cadwell full circuit may be a daunting task to all but the most highly sorted of race machines, but the diminutive Honda made light work of the many bends and undulations that characterise the Lincolnshire circuit, putting to shame many a larger machine in the process. The bike is unfeasibly light and, upon first impressions at least, not up to the job forcing one to take the first few laps very steady indeed, that is until the first couple of corners have been negotiated and you realise the thing isn’t going to snap in half from underneath you. 26 BHP doesn’t sound like a lot but when it is in such a tiny package, every single one packs a mighty punch. Not one single component looks capable of performing the job of hurtling around racetrack at 110 mph plus. Nothing could be further than the truth how ever, and the MT makes light work of getting around any bend, no matter how demanding.

The spindly looking chassis can easily tame the 26 or so horses put out be the air cooled Elsinore engine and the narrow tyres grip way beyond what is ever imaginable to create some huge corner speeds. The whole lot can be ridden around on the front tyre, hard on the brakes, ignoring accepted braking markers and diving well into the apex of bends before cracking that throttle open to make the most of the exaggerated speeds that this process creates. Its an intense and enjoyable ride that, after riding bigger less agile machines, takes a bit of getting used to before becoming the norm. Even the abridged riding position becomes comfortable after a short while and strangely for such a small machine hanging off works really well. Just like the more well known TZ250 and 350, the MT would adequately teach the club and national rider all he needed to know in readiness for their move on into international and even GP rankings. It looks little more than a toy but the Honda is as much a real race bike as any exotically designed and expensively built machine.

Honda MT125Once into a bend the lightweight tubular chassis holds firm and true enabling very accurate riding and superb confidence to be built up especially in the front end. Accurate riding is the order of the day to maintain speed and lap times, even more so when surrounded by thirty or so other riders on identical machinery and with the same desire to finish first. The slightest mistake will cost your dear, wander off line just a tad, or force the machine away from its natural trajectory and the clock starts going backwards as a swarm of buzzing MT’s pass your elbows on their way to the finishing stripe. Just the sort of thing that makes for close and exciting racing and with £500 a win in each round (I was on £20 a week back then) more than enough to fully concentrate a young racers mind.

As the speed drops down and you eventually run out of gears to downshift it is necessary to dip the clutch a wee bit to get the engine buzzing up into its relatively narrow power band. This does feel unnatural at first especially when at full lean but the rear tyre is a canny beast and hangs on whatever the abuse you may throw at it. If the power is allowed to drop below the power band it will not pull back up into it with out provocation no amount of throttle control will get the MT back up onto its pipe.

Once back singing its high-pitched song, after the short and hollow “ your going nowhere refrain”, the engine pulls very strongly and soon disappears up the track with gusto. This is the harsh world of piston ported, short stroke two strokes, no power one minute the ride of your life the next. Not quite as fast as modern tackle but don’t let that worry you as other bikes brake for corners, generally the MT doesn’t need to do so anything like as often.

MT125 HondaTwo years after its inception the MT did get a reed valve, making low down power a bit more manageable along with watercooling enabling a decent hike in power too.
The race series

It is not clear exactly why the MT was first introduced, it was slower than most 125 race machines currently around and if thrown out into the big wide world unprotected would have been blown away completely. However, its conception and subsequent production proved prudent, when Honda Japan first announced the motocross engined race machines the UK importers ordered 45 straight off with a view to organising a one make race series. The plan was to let 30 Honda dealers sponsor a rider each with around £500 on offer for a race win guaranteed along with country wide coverage and un doubted notoriety for the leading combatants.
The plan worked and the big Honda name which had previously been unrepresented on the UK scene was suddenly very much in the frame of things.

The rules, requiring absolutely no modifications from the original specification, were very forcefully applied, one competitor for instance was completely banned from the first series simply for drilling the front disc. No tuning other than jetting and gearing was allowed and this provided very close racing throughout the eight rounds. The eventual victor Clive Horton, like several of the front runners in that first year, was already one of the UK’s leading riders but he feels the Honda series gave his career, and most other rider’s involved, a healthy shot in the arm.

Clive Horton

MT125R Honda“The Honda MT 125, a great concept, dead simple, dead cheap, the dealers were encouraged to buy and supply them to their own chosen riders. I had an interview with Ken Foster of Fosters of Chorleton cum Hardy Manchester. He offered to support me supply the bike, spares and a mechanic. what’s more I could keep all the prize money. That statement alone more than squared it for me. We arranged a test day at Oulton Park a week or so before the first round of the championship.

I remember the bike as a totally adequate piece of equipment simple strong reliable and whilst not as fast as the Brader Brothers Maico I was riding at the time certainly effective at whipping round Oulton at a decent lap time.

The beauty of the MT125 championship was the 1 rule, STANDARD UNMODIFIED MT125s except you could use what tyres you liked, change gearing and carburation. Rules applied with a rod of iron and no recourse to the court of human rights or anything like that. Everyone knew where they stood following the drilled disc episode, I’ll tell you.

I think there is room for another championship just like it, the R6 cup gets close but is not cheap. However the best rider will always emerge when you have well applied rules”.

70’s 125 racing in the UK was not in a good situation with poor grids and low spectator interest so the Honda series certainly gave the race viewer something to look at for a change. The series gave many a rider the leg up into GP’s and international racing, often with more than a few quid in their back pocket to help along the way.

The series ran at top UK level for five seasons during which many of the stars of the eighties featured in the results sheets, the bike changed a couple of times too with the switch to water cooling in 1980 along with a stronger chassis. Yamaha stole much of Honda limelight when they introduced the televised Pro Am series, the big H retaliated with their own roadster based race series but never eclipsed either the LC or their own earlier attempts. The original air-cooled MT with its comparative low power output had grown into a bike that was competitive against the pukka GP bikes and yet remained cheap to run. The single cylinder concept became the norm in eighth litre racing and the MT’s off spring have since won countless titles both nationally and at world level.

Honda MT125R Specifications

  • Engine – 123cc aircooled piston port
  • Bore & Stroke – 56mm x 50.7mm
  • Power – 25bhp@10,500rpm
  • Torque – 12.2ftlb@10,500rpm
  • Transmission – 6 speed wet clutch
  • Carburettor – 34mm Mikuni
  • Ignition – Honda CDI
  • Chassis – Steel tube cradle
  • Suspension – 32mm telescopic forks twin shock rear
  • Tyres – 3.75x 18 front KR 3.25/4.58 x 18 Rear
  • Brakes – 220mm disc front, 110mm drum rear
  • Wheelbase – 1220mm
  • Weight – 77kgs
  • Top speed – 120mph

Honda MT125 Gallery

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