Bultaco Trials Models

Following a request from information on TrialsCentral , the thread produced a list of trials models

There are some Bultaco model lists, such as http://cemoto.tripod.com/bultaco.htm , but nothing with specific trials model information. Hopefully this list can provide some more specific information for Bultaco’s trials models.

The Trials Central thread included a post for Woody on the model numbers and some subsequent comments from other posters.

M10 – original 250cc 4 speed radial head 1965/66

M27 – next version 250cc (may have been the first 5 speed, can’t remember) 1967/68

M49 – 5 speed 250cc 1968/70

M80 – Updated M49 250cc with slimline one piece tank seat (available as a kit on the late type 49 before Bultaco standardised it on the 80) 1971/72

M91 – updated M80 250cc with new small front hub, new arched bottom fork yoke iin alloy (previous models steel) 1972/73

M92 – as M91 but first 325cc engine

M124 – updated M91 250cc with different exhaust and rear wheel, new forks no longer tapered fit into top yoke, new shape clutch cover 1974

M125 – as M124 but 325cc

M150 – updated M124 250cc with different exhaust 1974/75

M151 – as per 150 but 325cc

M49 to M151 were essentially a continual design of the same bike. UK models from late 91/92 through to 150/151 were fitted with alloy blue/silver homerlite tanks seat units (homerlite = company that made them in Wolverhampton)

M158/159 (250/325) 1975/76 through M182/183 1976 to the M198/199 1977/78 – New model (the one that Martin Lampkin is usually associated with) with different frame, seperate tank and seat, new exhaust, rear wheel, 250 downsized to 238cc (French tax laws) engine internals and frame changes along the way.

All bikes red with silver frame up to this point (from the factory)

M198a – Now all blue in colour with seperate bashplate, new timing cover with thumb logo, reinforced swingarm with big gussetts up to shock mounts 1978/80

M199a – as 198a but 325cc

Somewhere along the line a 250 model got it’s own frame design but then reverted back to a common frame for both, can’t remember which model this happened on

M198b – Basically a remodelled 198a with new square section swingarm and rear frame loop cut off – white frame/mudguards, blue tank/sidepanels/yokes/forks 1981/83

M199b – as per 198b but engine overbored to 340cc with Pursang piston and fitted with 6 speed gearbox

There were some other comments and I’ll update the file accordingly

The Robot Observer

One of the perennial problems with running trials events is observers. Its not that they are crap, its just there are not enough of them.

I’ll observe trials myself and I enjoy it, but partly in the knowledge that I know I can ride an event at another time. If its raining and cold, it can be a bit tedious.

So , like Hawkeye in cricket and tennis, is there a technical solution to the lack of observers ? If not a direct replacement, some form of technology aids to observers would potentially be interesting

The problem
Not enough observers for the bog-standard club trial. You want to run a 20-section 2 lap trial and end up running a 20-lap 2 section trial as you’ve only got 2 observers. Its November, its raining and The Great Escape is on TV.

Robot Technology

In theory there are potentially a number of ways of implementing a technology based robot observer.

video: use a well positioned video camera to record all the riders. The problem will tracking the bike in the section as you’ll need some form of image sensing technology to track the moving image (ie the bike and rider). Most observers turn their head in a section and will also potentially move around, so as to get the best view

sensors: this would need to be a combination of section-based sensors (such as the start and end cards) and a sensor on the bike and/or rider.


Video has the advantage of still allowing human intervention to view the action and apply the power of the human brain to interpret what is going on in the section. The disadvantage is that someone has to sit and watch all the action from the trial (each rider, each section) after the event. Its going to delay getting the results out. There is some cheap web-based technology and it would be best to write to local disk (to ensure data recording and integrity). It could be a good evening in the pub doing the results and it would be a good training aid.


Sensors would have to have the ability to interpret the actions of the bike and rider directly, that is without human intervention. This would need to work out each footing, the boundaries of the section (ie markers etc) and the movement of the bike (for TSR22B for example). This would be non trivial, but would allow for real-time results to be displayed for any specific rider.

The challenges would not be straight forward, but would make for an interesting experiment.

Technology Aids

Not thinking of replacing observers, which would be nice, it would be good in some respects to improve the recording and calculation of results. With the recent Wye Valley trial, 35 sections scattered around a 30 mile lap can make for an interesting exercise in collecting the observer sheets. It also means that though results can be done quickly it can require additional resources.

Logging via mobile phone (ah not many places with a signal in south Herefordshire) or directly in a format the removes transcription errors etc would also be useful.

Head mounted cameras for observers, would also make for interesting viewing.


Video based robot observing potentially gives the affordable short-term solution to the lack-of-observer problem. Investigating the practicalities of recording and interpreting the video is the next challenge. Something that detects movement, is weatherproof and affordable seems to make the best sense.

All good fun !

The Jumbo bites back….

Since I started riding a couple of years ago, I’ve had the odd bang and bruise but the latest injury didn’t actually occur at a trial, but in the shed…..

The SWM Jumbo build project was nearing completion and I’d the bike re-assembled with the right piston etc and was attempting to kick it over in the shed. The combination of lots of compression at the wrong time (still learning how to use the decompression lever at the right time) and a kickstart with some worn splines resulting in the Jumbo biting….

Jumbo leg