Llanthony Classic Scramble : Clyro

After suggestions and persuasions from the Tredegar contingent and some planning aforethought it was time for my first scrambles event. The weather had been excellent for a couple of weeks and the day bode well as I drove up from Clyro on the road over to Newchurch. Nice spot, high on the hills, with some great views looking back to the Black Mountains.

Turned up early and about 5 minutes ahead of Alan and Mark. Quick chat and then off to walk the track, ie one big section. Some tight turns, some steep slopes and an off-camber straight down the back of the course. Looked fairly smooth and fairly fast.

Not have ridden any scramble or motocross before, it was all a bit of blur. Back for some tea and the arrival of Kevin in his new Series II Landrover at a top speed of 50 mph from Tredegar.

Mark starting the Cappra

The Yamaha needed a bump start to get going and wasn’t running that well to start with, all a bit strange. Anyway, out for my first practice and going down to the start and then on the track was a bit of a nervous moment. Got going okay and didn’t seem too slow and didn’t drop the bike. Did 4-5 laps (I think) which was great fun and seemed to be in the groove. Not used to riding off-road with so much kit (armour, full-face lid etc) and also keeping the bike on-song and in the power band; quite easy in places, especially coming out of corners and up the slopes. Picking the line into corners was also something I needed to work out.

On the Twinshock side, the competition was warming up between Kevin and Mark, with Kevin having the CZ and the Beta to choose from, to face up to Mark’s Cappra. Dave’s TM400 Suzuki has also arrived and was looking pristine.

Dave's Suzuki TM400

Graham arrived to spectate and provide moral support. It was needed, as trying to start the Yam for a second bit of practice, found there was no spark. Checked the dodgy connectors and the kill switch, still no spark. Graham moved into gear in his role as pit crew and tracked down the problem to a dodgy plug cap. No spare available, so bared back the cable and screwed the plug cap to lock it in place and then out with the lockwire pliers and electrical tape to finish the job.

No large motorhome ?

Walking around, you notice that just like trials, there is plenty of money being thrown at bikes, including the pre74 and Twinshock machinery. Lots of trick kit and the accompanying discussions on the rules and regulations. As with my riding, the politics in the scrambles scene are also going to take a while to work out.

Race 1
Not a bad start and gained a couple of places in the first corner, however then dropped it in the second corner ! Took a couple of kicks, but then at the back. Overtook a couple of other riders before the engine died on the second lap. This was the CDI connectors coming out (not for the first time) and a couple of attempts to put them in place meant I got the bike round for another lap. Not the best start.

Hilltop : a great venue

In the Twinshock race, Mark managed to pip Kevin to the line in the last couple of corners, so 1-0 to Mark.

More bike fettling during the lunch break and I cable tied the electrical connectors together after electrical tape was wrapped round. Then reconnected the kill switch on the bike. Good to see lots of other people putting bikes back together after the first race.

Turn 1

Race 2
Still had to bump start the bike, but away if went and up to the holding area prior to the start. Had a crap start away from the line with the engine bogging down. With the track cutting up a lot now, it was more challenging and still had issues getting the power down. Didn’t come last and didn’t get lapped, though again did stall the bike on the last off-camber corner. Good fun and a completed race with the bike performing well, even if the rider wasn’t

In the Twinshock race, this timeout on the Beta, Kevin managed to get well clear after Mark had a good start. Alan battled it out on the XL350, getting the better of a couple of Maico’s at the back of the field.

More fuel in the bike and then with only time to watch a couple of races, it was time for the next race.

Race 1

Race 3
Better start and made it through the first couple of corners unscathed until getting squeezed on the inside of turn 3. Back of the field again and with advice not to use the clutch so much, seemed to be getting a better pace and feel for the race. So were the other riders, and as the track was getting more cut-up it was clear their skill and lines were making a lot of difference. Plenty to learn on getting round the track.

Away for Race 3

Once again, Kevin got the better of Mark, though a bit closer this time round. Kevin staying with the Beta after changing the rear sprocket during lunch.


Race 4
With a non-serviceable Tannoy, it was difficult to work out what was going on, but a couple of open races at the end, same me line up with the Tredegar Twinshock contingent. After a lap staying in touch with Alan, saw me lose ground and then go lapped by a speeding Maico on the final lap.

Once again, after some handlebar to handlebar racing, Kevin came out on top, leaving Mark rueing his chances on the Montesa.

All-in-all a really great day out; glorious weather. Maybe not the most competitive in terms of racing, but managed to make it round without being too dangerous.

Queuing for the start

In terms of the bike, it was a good shake-down, in particular exposing the paucity of the original electrics. These need a refresh, with new plug cap, poss coil and HT lead. Also may replace the connectors which aren’t the best.

There are some issues with the fueling as though the carb seemed to run okay when out on the track, it still doesn’t seem spot on. A lot of this may be my own style on the bike and in some cases I wasn’t quick enough through the gears (ie using the clutch) and also feathering the clutch in corners to keep the revs up.

Kitchen installation may come in the way of an early return to the track and it took about 3 cups of tea to get the dust out of the system. Excellent fun though.

Yamaha MX250 Spares

List of Yamaha MX250 spares, I’ve not listed any prices, but please get in touch on 07720 079845 for more info.

|Mikuni Carb 30mm internal inlet diameter, used (gunky) but complete and will clean up.|IMG_0561.jpg|
|Seat Base, foam decayed and will need replacing, but base in good condition|IMG_0567.jpg|
|Wheels, front and rear, couple of broken spokes and a dent in the front rim that may knock out. Hubs not too work and useable|IMG_0568.jpg|
|Throttle body and cable, original in worn state|IMG_0570.jpg|
|Rear Shocks, original. Work and not too untidy|IMG_0571.jpg|
|Crankshaft Bearings and Seals, used but not worn, just replaced them anyway whilst doing little-end|IMG_0572.jpg|
|Throttle Body and Cable, also used | IMG_0573.jpg |
|Clutch Cable, used | IMG_0574.jpg|
|CDI unit, working| IMG_0575.jpg|
|Assorted fastners, for the original finish|IMG_0576.jpg|
|Rear brake plate, with arm and rear wheel spindle | IMG_0578.jpg|
|Front wheel spindle|IMG_0579.jpg|
|Front brake plate, no brake arm|IMG_0582.jpg|
|Front forks, complete. Some marking on tubes, where they sit between yokes where someone tried to weld on a bracket|IMG_0583.jpg|
|Plastics, faded due to Californian sun no doubt|IMG_0584.jpg|
|Yoke, top and bottom, with nuts but no bearings|IMG_0586.jpg|
|Autolube pump and tank, with hole in it|IMG_0588.jpg|
|Decompressor lever and cable|IMG_0589.jpg|
|Another set of rear shocks, more corrosion on springs of this set|IMG_0590.jpg|
|Exhaust, not including tail pipe, some surface corrosion but very useable|IMG_0592.jpg|
|Handlebars, period set in useable condition|IMG_0593.jpg|
|Frame and engine bottom end, without clutch side. Frame has correct 1974 numbers, whilst 60% of engine bottom end is there, needs stripping|IMG_0593.jpg|

Completed Bike and notes for restorers

Completed bike

Some final adjustments during the day, in particular setting up the carb, as the bike felt lumpy as it pulling away.

After adjusting the float height

Panels in the right place

|Bike 1|Acquired from a garage in Tredegar from Kev, running but needing some attention (ie complete rebuild)|
|Bike 2|Second bike came AP Motorcycles who are serial importers of cars and bikes, and the good thing is they know their dirt bikes. |
| Piston Kit | Got an original 0.50mm (2nd oversize) piston kit from Keith Alderman at Motolink . There are plenty of OEM Yamaha pistons and Wiseco piston kits on eBay in the US, though you need to take into account shipping and the exchange rate. |
| Crank bearings, seals and gaskets | Also from Motolink as well as lots of information on the MX250. |
|Tank Decals| These came via Speed and Sport Yamaha’s ebay shop and were the only place I could find who did them. |
| Plastics |The front and rear mudguard as well as the side panels came from [ Reproduction Decals ->
http://www.reproductiondecals.com/default_frameset.html?content.html~main ] in Canada however these came from DC Plastics who indeed sell a a complete plastics set for the 1974 MX . The parts from Repo Decals were cheaper than the set on the DC site (I think?) |
| Front number plate | I got from Yuniparts who are mainly on ebay UK and specialise in XT/TT 500 parts. Luckily the TT parts also fit MX250/360 and SC500’s. |
|Seat Cover | Came from Pit Replica in Thailand, and arrive in 10 days |
|Handlebars and Levers| I already these from an incomplete trials bike project. I used standard Renthal bars and a pair of the excellent Domino levers, which are cheap but are pretty durable. These originally came from BVM in Stroud, but available from anywhere. I also got a set of pattern copies of the original fitment bars, again from Yuniparts as they are like the TT/XT fitment of the day. |
|Throttle and Cable| A nice quick action set from Motolink with the appropriate cable to match |
|Clutch Cable | A pattern copy of the original cable, again from Motolink|
|Brake Cable | After some searching and thoughts about modification, ordered a good value one from Yuniparts (for £7.65) though it was listed for the later MX250B. It fits the earlier MX250’s equally well. Yuniparts also stock pattern brake shoes (front and rear) for the MX250, as they are the same hubs as for the TT500. |
|Spark Plugs| From the ebay seller in Alderney, both standard and Iridium plugs|
|Tyres| From my local offroad supplier in Pontrilas, LG Racing Gone for medium compund set of Michelin Cross AC10 |

Did the numbers last


As well as the parts, I got some of the work done, ie the bits I couldn’t do myself (like the rebore and the rechroming). The rebore was done locally (to a very high standard by Russ Tyler, whilst the forks went to [ A M Philpots ->
http://www.amphardchrome.co.uk/ ] who do an excellent collection and delivery service.

I decided to paint the frame myself, rather than powder coat it and did this with Hammerite Satin paint (from aerosol cans). I was really pleased with results and would do this again with any bike I could get the approx paint colour for.

The wheels were respoked (with galvanised rather than stainless) by Gerard Pettit done in Caerphilly and again excellent service for reasonable money. I’ve heard that Central Wheels are pretty good and they can also potentially polish the hubs etc if you want (I didn’t)

Some more notes of restoration

What’s good about the MX250 and the MX250A is they are pre74 eligible (the MX250B was monoshock) and though never imported to the UK there are loads of bikes and spares in the US (and also AUS and NZ it seems. There are common parts with the Yamaha DT250 and DT400 of the same period (not the later ones), both engine and cycle parts and lots of cycle parts are interchangeable with the Yamaha TT500 (lightweight version of the XT) which are currently massively popular in the UK (and silly money).

Restoring a silver MX250 (1973) or a yellow MX250A (1974) should both be straightforward and plastics and decals are available for both. I must admit the Yamaha US yellow wins for me.

Make sure you get hold of the right MP7 flywheel puller M20 1.5mm RH thread as you’ll need it and won’t get the flywheel off without it. It fits only a few CDI / small flywheel bikes and I had to order one from the US, which turned up in 10 days [[I can now recommend international eBay to anyone after completing this restoration, with parts from the UK, US, New Zealand and Thailand being ordered successfully without hassle ]].

Before my first race, I’m already happy with the project and working on the bike. Its easy to work on, and the engine strip was relatively straightforward (to a four-stroke and a Rotax trials engine) and would make a good first project. Spares are not a problem and you just need to plan up front on what you need and when.

Maybe a MX360 next (have some spares now) but lets wait till the first meeting and see how i get on.

Digging out the SWM TL320

This was my first SWM and its unrestored and in its original condition. Before the Jumbo, did two years of Sammy Miller rounds on it, but have never really written up much about the bike.

Chickens were more interested in the cut-up ground

I’ve not ridden the bike much recently, especially with the Beta going so well, so need to decide what to do with it; ie ride it in a couple of events, or potentially sell it.


It’s had the best engine of all of the SWM’s and though Gavin sheared a Woodruff key on it on the Harry Perry trial a couple of years back its been really reliable. The electrics are now sorted with the condensor up under the tank and out from behind the flywheel.

Nearly there…

Some more photos of the nearly completed bike. The side panels are done, though the numbers I have are too large for the black vinyl ovals. The seat has been recovered (which was straightforward).

Still need to improve the the attachment for the exhaust rear box and trying to work out the best way of doing that, as will need some engineering modification.

Some tweaking to the carb stopped a fuel leak and the idle screw from the ‘spares’ bike was longer (??) and now seems to work correctly. Plenty of go on main jet though will clean up the rest of the spare carb just in case.

99% complete

The field wasn’t in such good form as the previous weekend with all the recent rain and the bottom corner had cut up pretty badly. Need to find out the best way of getting grip !

Hopefully the rider can match the looks