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Bike Review - Posted 29th October 2012
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MZ ETZ 250 Trials Conversion - Part Two

Rick Howell gets his classic MZ ready to ride off-road in the long-distance trials organised by the MCC...

I didn't want to lose the basic look of the original bike so I have only modified it lightly - with the intention that all (well, most) modifications can be reversed with little effort. There were some that are essential and there are some that just make life easier in the saddle on a long and potentially rough event.

Note lack of engine cradle... MZ ETZ250

First off in the essential list are changes to gearing. MCC trials involve a fair bit of climbing hills in a controlled manner (hopefully) and lowering the overall ratio to accommodate reasonable upward progress without completely ruining road speed is a balancing trick that needs careful consideration (or literal trial and error).

My fellow MCC MZ rider Mick Jeffries suggested some parts available to help here - MZ spares dealers Burwins stock 15T gearbox sprockets (standard is 19T), and the Honda CG125 sprocket is a 14T fit but needs a spacer to match the integral boss on the MZ part. There are 13 and 12 tooth sprockets similarly available from Talon.

I've fitted a 14T and that gives a top road speed of about 60, but the lack of torque at low revs means that restarts (pulling away cleanly from a standing start on a steep and often loose surface) aren't very easy.

MZs on

The chain is 428 size and is shrouded by that unfashionable but very sensible chain-enclosing guard which keeps the majority of the muck well away. Alongside, the swinging arm and 18-inch alloy rimmed rear wheel accepts a necessary Pirelli MT43 Trials tyre without protest, and an aftermarket sidestand is fixed to the rear wheel spindle in place of the standard spacer. This allows the centre stand to be removed, for ground clearance.

Note enclosed chain, serrated footrests and rear brake 'tube'. Strap is holding engine in place. Temporarily, hopefully...

The standard footrests are quite high and set forward and, I find, uncomfortable. MZ didn't spend too much money on procuring them - it's a bent tube bolting underneath the frame which flexes when one is standing on them. Not good, or confidence inspiring, so I ditched them and decided to just use the pillion rests instead. Actually they're quite comfortable though the springy originals have been changed for modified Bantam ones with suitable serrations. They work a treat with muddy boots, and need to be pivoted for use of the left-hand kickstart.

This does mean that the equally cheap rear brake tube (lever is too flattering a term) needs to be shortened, but with a footrest rubber jammed on the end it works quite well. The gear lever ends up in space but heel changes are ok, like on an old BSA Bantam, and anyway mid-section changes aren't usually necessary or desirable. And I keep to the old climbing maxim about three points of contact at all times. The proof is there - I haven't fallen off yet.

Single seat leaves room to strap tool bag in place. Note emergency rear light on grab-rail...

Strictly speaking, only one set of footrests means a single saddle, so I fitted one I had bought at Malvern years ago, onto a base plate of bent alloy which covered some of the bombproof MZ electrics and also leaves room for carrying stuff. I also fitted a pair of braced trials handlebars from Hitchcocks to give a bit more control and height.

Further forward another essential, well I consider it so, is a 21-inch front wheel. This required the mudguard to be replaced but that created a problem with the exhaust. Apparently the solution is a TS250 barrel and head and header pipe which is of a tighter bend. Being a cheapskate I just hacked off the bottom of the guard where it fouled and put up with the spatter for a day or two, and then got fed up and fitted a flexible mudguard. This worked fine until it started to melt when in contact with the exhaust, so I added bits of aluminium - and although it's a bit of a dog's breakfast it worked well on the 300 miles of mud and road muck that was the Exeter Trial.

In the desirable range - the flexible mudguard/flap thingy is on this list - are items like the route card reader, emergency lights and spare cables. The route card reader is something knocked up by many of the riders on these events. Some of our wealthier MCC members purchase proper wired-in, thumb-switch operated electric gizmos for attaching to their KTM Super-Motards, while some of the less-well-off purchase the plastic rollers with a covering sheath (not enough room generally for the many pages of instructions beloved by the MCC). The rest of us make do with a wide variety of butchered sandwich / bacon / food storage boxes with bits of dowel attached to provide an 'information platform'.

Butchered sandwich / bacon / food storage box with bits of dowel attached provides an 'information platform'...

Since half the trial is in the dark, some form of lighting is then dangled by more or less precarious means to illuminate said information whilst on the move, though I favour backlit data using strip LEDs.

Emergency lights can take many forms but the LED has been a godsend. Additional proper headlights are frowned upon by the rule makers but a spare rear light is very useful. In the - very annoying - event that the rear lamp filament blows during the night section, a spare lamp is necessary to be fitted to be legal, and this can become tedious. If there is an intermittent fault which keeps blowing the lamp (such as water, or mud, or vibration - usual ingredients to a bike fitted with trials tyres) then the machine could fail scrutineering either at the start or after the 100 mile assembly ride to the actual start of the main event.

A cycle lamp acts as an fill-in until time permits a proper repair, and fixing can be rudimentary using cable ties (always carry a selection). Many riders carry a headtorch too, as roadside repairs in the depths of winter are seldom suddenly required in the middle of Exmoor next to the only streetlight for 25 miles. I exaggerate, of course; there are no streetlights. Headtorches are good.

I also attach a clock. These trials are run to timings and on some events the organisers will enforce the various regulations concerning keeping to time rigidly. It is supposed to help to move the peloton along in an orderly manner and therefore minimise the length of time sections need to remain open and therefore marshals need to be on open hillsides in potentially hostile weather. A clock allows one to keep an eye on progress relative to each competitor's published time (every competitor is different as they are started at one minute intervals). Lateness at key points can downgrade the award you qualify for, so 10 minutes late at a control stage could downgrade a Gold performance to a Silver, for example.

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Next time: what to pack, and how Rick's MZ performed in the Exeter Trial, in the middle of winter.

Read more at www.themotorcyclingclub.org.uk

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