The second bike and the work continues

Picked this up from AP Motorcycles who bring in classic cars and bikes from the US. I’d bought some spares (I think an XS500 / TX500 engine) from them years ago and as the hunt for an airbox took me to Ellastone Offroad in Uttoexer, it then took me onto Richard in Ashbourne.

In the process of picking up the MX250, managed to take a look at a few bikes and the hordes of engines in the sheds there. Plenty of twinshock and evo motocross machinery, as well as XT500’s and parts. A short hunt for an MX360 engine wasn’t successful, though subsequent research indicated it might not be worthwhile as in investment.

MX250, the 2nd bike

The bikes not a stunner, but very original and though there’s some bits missing (llike the clutch side of the engine), there are also bits I needed, including the airbox and a decent front wheel rim. Also a 1974 yellow tank, though its got some large dings in it. This bikes in very original form, as the autolube and oil tank are still on the bike. That rolling it out of the van and onto the drive did catch the eye for looks and general set-up.


Time to strip this one down also and this should give me a good basis for me to start on actually putting it all back together.

This week also saw a trip to the AGM of the Llanthony Classic club at the Rising Sun in Pandy and the membership fee duly paid and an AMCA license form grasped. First meeting is 18th April, so 3 months to get the project done and up-and-ready to race.

Lots of good conversation, including some further chat on MX250’s and what to look for and what to work on. It seems that MX250’s share common engine parts with YZ250 C’s and D’s (though not the earlier exotic A’s or B’s).

This was confirmed later in the week whilst talking to Motolink Yamaha , who races Yamaha’s, currently a modified MX250. Hopefully some cables and airbox cover coming from there. Also managed to track down the tank decals on Speed and Sports shop and so thats now been ordered.

The rear shocks arrived from Norman Blakemore , for whom again there was further agreement on the quality of the product. Also arrived was the seat cover from Thailand (only 10 days from ordering) and the steering head bearings and fork seals from Pyramid Parts . The (thin) Clymer manual arrived also, but strangely from Amazon, though thats not where I ordered it from. Further investigation required as Amazon UK don’t list it….

Finally dropped the wheels down to Gerard Pettit in Bedwas for a rebuild and then went to talk to bikes and watch classic motocross Youtube with Graham. Watching a clip from Farleigh Castle 2009 does remind you that you rarely come a croppr riding trials, classic motocross if different…

MX250 strip

Only had the bike a day, but time to strip it down and start the process of restoration.

Whilst I’d worked out what was missing time to work out what was broken and needed fixing.

Ready for dissembly

The bike was wheeled up on the stand and whipped off the tank and exhaust fairly quickly. The exhaust system is complete, with the rear box and is in good condition with no corrosion. Not sure how the system is attached to the barrel but there was one spring holding it in place; no gasket etc,

CDI and Ignition

Joy of joys, the bike is electronic ignition though the CDI unit is about the same size as a modern one-bedroom studio apartment. Simple wiring layout and the original connectors (nice and chunky and good condition), The coil, cables and spark plug lead and cap all also seemed serviceable, didn’t check the spark, but the bike seems to fire up easily and there’s good compression.

Ignition Coil


Removing the front end revealed the true horrors to the weld to the chrome (what posses some people ?). Forgotten about the joys old fashioned steering head bearings, that was until I sprayed ball-bearings across the workshop.


Engine in frame

Didn’t take long to be in a position to remove the engine.

Broken engine mount

Removing the engine mounting bolts revealed one problem, a broken mount, where it had snapped off where it connected to the frame. Some remedial welding required here, but apart from that the frame looks straight.

Front wheel

The front wheel rim is original, though the large dent may mean it won’t be for much longer. The forks are straight and once I work out how to get the forks out of the bottom yokes (the Weld from Hell is in the way) I can strip them down and think about re-chroming. The forks seem to work (though there is a hint of no oil) but as with the trials bike, setting them up to work correctly may be more of a challenge.

The rear shocks are original, work (to some extent) and really need beefing up for competitive action. They are serviceable and that’s another decision to make as new replacements may be a far better alternative.

Engine on the bench

The engine looks complete and even the (broken) front sprocket cover is there and in place. There is a top end rattle (but hey, its a Yamaha) so may not be too bad as it seemed to run without too any crunching noises or oodles of smoke. Its funny how all these engines have the autolube housing in place, though there are pre-mix

There is now an MX250 space on the shelf and the parts, bolts and other sundries now occupy the space (left my off-loaded SWM parts).

Ok, what is it and what year ? Also what do I need ?

The detective work, both on what it is and where do i get what I need starts here.

Engine Numbers

First up, closer inspection of the engine numbers may show them to match, but for sure they aren’t original Yamaha numbers, Not-so subtle use of a file and poor aim with the number punches show the numbers on the bike ‘3(or 5)15341045’ not to be related to any known Yamaha. Ah.

There’s a good article with the Yamaha dirt bike engine number ranges which show that Yamaha 250 MX bikes should have the following ranges.

| Model | Year | starting engine number |
| MX 250 | 1973 | 364-000101 |
| MX 250A | 1974 | 364-020101 |
| MX 250B | 1975 | 509-000101 |

So working out what year specifically the bike (and which model it is) becomes a little more tricky and I’ll have to look for subtle differences, if there are any.

The CycleChaos – wiki site has some good pictures of the MX250, A and B where the 1975 B model is actually a monoshock. This narrows it down a bit, so the bike is either a 73 or 74 model and for both the exhaust system and cycle parts seems to be similar, just the plastics and paint-work being different (I think).

Looking for Parts

The search for parts and a strip down of the bike begins here:

airbox, its missing
wheels, spokes and rims. Both rims look well bashed so may need replacing if they can’t be straightened.
front brake, missing front brake arm. Also need to look out for brake shoes.
mudguard / fenders [[already getting use to the language changes for search]], none on the bike, some choices here including some YZ copies in yellow available in the UK, they’ll look the closest.
sidepanels, none
tank, need some decals for the tank, when its resprayed and filled
chain & sprockets, the sprockets look ok but may need to be replaced.

Ordering Parts

The good thing about Yamaha’s is that there are lots of parts to choose from and availability is pretty good. Also, although the MX was never a UK bike, you would hope that lots of the bits from the DT (which was a UK bike) should fit. Anyway, the search and ordering starts here.

|Part|Comments|From Where|
|Airbox|Ebay is going to be the place, as its a deleted item on the Yam spares list |The fibreglass airbox will be a challenge, though there is one on ebay in the US, will look for local options|
|Brake Shoes|Based on a US listing for a pair of Yam brake pads, DT250, 400 (and lots of other models) fit|Ordered from Yambits on ebay UK|
|Cables|They all need replacing| Venhill website doesn’t list specific MX cables, but either DT or universal cables should fit |
|Chain|Should be a 520 – 106 chain, can get that locally|LG Racing are local |
|Controls|Not so worried about originals| Again, will look at LG Racing |
|Electrics|All look ok, including the CDI and cabling.| |
|Fork Seals|Will need replacing|Like the head bearings, from ebay and p.k.n |
|Handlebars|Looking for some original looking bars|Found some reasonably priced chrome bars from Yuniparts |
|Manual|There’s a Clymer 68-76 Dirt Bike Manual and I think a Haynes Trail Bike alternative|Couple of download options, but I’m a fan of the real thing. Will see what’s on ebay US|
|Plastics/Mudguards/Side Panels|Will look at pattern options from UK and US|Yuniparts in UK do a yellow front, but not rears. Reproduction Decals in Canada do all the plastics for the 73 and 74 MX250’s|
|Steering Head Bearings|These are originally ball bearing races and need replacing the more modern taper roller bearings|Listed on ebay and are from Pyramid Parts in the UK |
|Seat Cover|Replacement covers available in the US and er. Thailand|Ordered from Pit Replica ebay shop in the US, from Thailand, so we shall see|
|Shock Absorbers|Could go for a shock rebuild, or a new set| see table below|
|Tank Decals|Harder than I thought|There are some NOS decals on Speed and Sports extensive spares list for Yamaha dirt bikes, but maybe not a $60.00|

The hunt continues for the other parts and the bike strip-down is also happening

Shock Choices

Did some shock absorber research….

|Falcon | List a fitment for the MX 250 , but at GBP 190 for the steel and nearly £300 for the aluminium bodies, there not cheap |
| NJB | Offer clubman and expert scrambles shocks |
| Road and Race Suspension | Offer a twinshock rebuild service though the OEM shocks on the MX aren’t rebuildable AFAIK |
| Betor | MX and Enduro shocks Got these on a couple of trials bike and whilst ok, aren’t stunning. Haven’t tried the newer Aluminium version |

Decision in the end, after speaking to Norman Blakemore on the phone at NJB Shocks was to go for the expert scrambles shocks, at GBP 103. They are 330mm, so just over the original 320mm.. Will keep you posted on performance.

A slightly different project, introducing a Yamaha MX 250

What I think is a 1973 Yamaha MX250, though further investigation is needed to work out exactly which year.

Picked up from Kevin’s collection of bikes of bikes in Tredgar and this was there next to an original (but pretty rotten) 1971 Honda XL 250 Motorsport, I bike I’ve also always fancied.

However, with an interest in getting an early 70’s, preferably pre-74 motocrosser, the Yamaha was my target bike for the trip into the wintery wilderness of the Gwent valleys. Its a US import, thought to have come via Ellastone off-road in Uttoxeter. It has been pretty well mangled in terms of looks, though the frame is straight in good condition and the frame and engine numbers match. Also it runs, with that standard Yamaha top end rattle. The exhaust system also is complete and in very good condition for its 35+ years.

Yamaha MX250
Yamaha MX250

Not so good, is the large ding in the front wheel and also where someone has tried to weld something to the top of the fork tubes (??) but the rest of the fork chrome where it matters looks fine and they seem to work pretty well. Rear shocks, with reservoirs are original and also seem to work ok, but will probably need new ones for any racing.

What’s missing, ah well. There’s no plastics, mudguards or side panels, and there’s no airbox. Whilst you could get away with a clip-on K&N filter, sometimes difficult to get the same performance than with an airbox. Also missing the front brake arm, but something from DT should fit. Also will need new cables across the bike.

The engine runs

Also, need to work out the year exactly. These bikes were primarily silver in 72 and 73 (with red and then yellow graphics) and then yellow in 74. Will have to remove some of the red paint from the tank to see what lurks beneath.

Having no plastics at least gives me the choice on what to get in terms of which colour (and therefore which year) to make the bike. Some research on t’Internet in front of the fire, instead of the sub-zero shed seems to make sense.

Anyway, after being stalled on the Transalp rebuild for a while, nice to have a restoration project to do for 2010.

What tyres for snow ?

With the current ‘coldest-since-1963’ winter conditions, no time to stop riding the bike. But what tyres to choose.

The mixed conditions in Herefordshire (ie snow, ice and slush) means the biking is currently fun ! Whilst the KTM has stayed in the garage, the Pampera is an ideal tool for splat round the field or a trip into town or to the shops.

Snow, dark and -10 C

Tyre choice is interesting, but i’ve ended up with an enduro rear and trials front, basically to get drive on snow and the packed snow on the untreated rodes. The Michelin trials front steers okay, but still quick to wash out on the roads. Keeping your hand off the front brake is also essential and the good thing about the Pampera is a useable rear (ie disk).

Herefordshire Classic, Clyro Trial

After missing out on trials over Christmas (a lot cancelled), braved the icy roads and sub-zero conditions to head over to Clyro for the Herefordshire Classic Trials Club event.

Its an AMCA club, and only a tenner for entry. No observer, so riding as groups, but an excellent venue at Clyro in the woods behind the Baskerville Hotel. Its was cold and the car park a skating rink, but apart from the track, the sections benefited from tree cover and rode really well.

Mark and Kevin were up from Tredegar and along with Andy Morgan we rode round as a group of four.

Around 30 riders had entered, including some modern bikes. Entry not the same level as last year, but crazy roads and temperatures more Nordic than Welsh were probably a factor.

Andy Carter on Section 1

The first section summed up the action for the day, as Kevin on a Beta Alp (recently acquired) stormed up a slippery climb on Section 1 for a clean. Kevin rode like a demon all day and only dropped one 5 on the last lap, at the relatively easy section 3. Mark and I managed 3’s on the first section and this also set the tone for the day.

Section 2 was a bit more nadgery round trees and across a few routes; still managed to screw it up on the first lap but straightforward later on. Kevin cleaned this as well, and it was clear that the Alp, with only one useable gear in sections (ie bottom) suits his riding style (quick and just hang on). Section 3 was up the first stream and slightly more awkward than normal with a couple of deviations round trees, before tackling the steps in stream.

Andy Pitt on Section 3

Section 4 was the usual climb up the stream, but included the the turn out to the left at the top, making it a tricky finish. Watching a few on the monoshock riders showed that it wasn’t easy. Up steps Kevin on the Beta and low and behold he cleans it….Woody then does the same, showing the line and approach in doing so. I managed to get round for a dab (on all 3 laps).

Kevin, after cleaning section 4

Sections 5 & 6 were in the next stream, with the rock steps not really presenting too much of a problem, though plenty of loose rocks to catch the unwary. It was in section 5 that Kevin dropped his first marks of the day with a loose couple of dabs. Section 7 was up the bank to the left and up and around trees with a slippery descent. Section 8 was straightforward, though could have been more interesting had the end cards been at the top of the slope rather than only halfway up. Mark continued his pattern of dropping inexplicable 5’s here though a trip back to the van at the end of lap 1 seemed to bring some improvement.

Section 9 was one the harder ones of the day, with an awkward step up through some trees, especially after the early riders moved a large rock. This changed the line in the section and required some pace to get over the gap the rock had left. I struggled here on each lap, taking a 5 on lap 1, with the best a dab on the last lap of three.

Section 10 was another one up and around trees and I managed to take a dab on each lap, in a different place each time. Nice section though and one that was good for practising control, especially the twisting exit up and though the trees.

Dave Wood, Section 5

Section 11 was straightforward (which means Mark can find a way of getting a 5) though a tight route up through the stream. Section 12 saw my 5 for the day on the first lap and was my worst section; just couldn’t get the bike lined up correctly to tackle the steep climb up the stream to the exit. Frustratingly a two was my best score.

A good trial and considering I’d not ridden for a couple of months, pretty enjoyable. Could have ridden better, but thats always the case. Kevin’s performance on the Alp was put down to riding a monoshock at a classic trial and all the advantages hydraulic brakes provide (the rear wasn’t working) and also that some of Bill Myers skill (previous owner of said bike) must have been left on it. Mark and I managed a few excuses about bike trouble and lack of riding but had to admit it was a good ride.

The Beta would idle and kept cutting out when idling. I’d noticed that the spark on the bike was pretty poor recently and I also need to look at the carbuerration. Time for some shed time and a service of the bike. It was -7 in Hungerstone this morning, so it might wait till it warms up…..

Modifying the electrics

Finally got round to moving the condensor on the SWM

After frying yet another condensor at the Stump Wood Hill Climb, thought it was finally time to move.

SWM / Rotax stator plate

Like a lot of points-based bikes seem to mount the condensor between charging coil and the points, that is behind the flywheel, otherwise known as the hottest and least accessible place on the bike.

Condensor next to ignition coil

Watching the clip of the 1968 Scottish (on the the Duke 6 from the Scottish DVD), it shows Sammy Miller in-prep with two condensors and coils mounted under the tank. Anyway, with some inspiration from Guiildford and a kindly donated condensor with a tail, it took about 30 minutes or so to make some alterations to place the condensor on the mounting next to the coil. This seems to earth ok and immediately got a spark, so all good and no problems..

Running well

Hopefully this will remove the issues with failures at trials and with a good tighten on the flywheel bolt (hmm, maybe loctite also) should also prevent the other SWM problem of note.

Some other considerations for mods on the TL320, again taking some inspirations from Pete’s bike in Guildford
– rear box on the exhaust system. One of the WES TY250 twinshock exhausts should go with only slight modification
– footrests, they need to wider and also potentially move them down and back from the current stock position. I’ve a spare frame so may do this here, rather than on the untouched original
– carb and jetting has always seemed pretty good but there is probably some room for improvement.

Taking the bike for a spin round the field, moving off of idle is pretty lively and i need to remove some of the snap to make it more controllable (throttle adjustment) and also get the currently cheap (Vee Rubber) rear better placed on the rim. b

First ride….

My daughters first ride round the garden didn’t last too long

It wasn’t the longest ride on Christmas morning, but managed to prove the strength and reliability of the Beta Minitrial 50cc twist-and-go.

After a couple of controlled laps of the garden, a demonstration of stopping and going, my daughter got a rush of blood (and a bit too much right hand) took out the climbing frame.

The remains of the climbing frame

Not that it was a cheap frame (TP Activity Toys, who I recommend). Saffron was okay, more shock to mother and sister and the bike was pretty unscathed though needs a new brake lever; the design of which sort of guarantees a failure.

Replacement lever on the way; lets see how she gets on …..