The Joy of Scrambles

It put into context 2010, my first season, where I now realise I was lucky and blessed with good weather and good tracks to provoke my enthusiasm and interest in the sport. Had the Three Counties event come early last season, I may have though differently.

Don’t get me wrong, for good riders the conditions were great fun. For lesser mortals, slowing down and going offline meant simply a grinding hold as the bike was gripped in a clay like mud that encased everything.

As the girls were keen to camp, we’d headed over on Saturday night and parked up in the middle of the field. After erecting the gazebo and two tents, headed across to the excellent bar and (free!) hog roast for a chat and a beer. Crashed relatively early in the van and only to be woken by the forecast rain about 6am.

Rain and more rain

By the time Alan and Mark arrive around 8am, it had already begun to make the ground a bit soggy and the mud had start to cling to your boots. The gazebo has already paid for itself this season and breakfast on the barbeque was soon underway. Kevin arrive around 9am and the mud was beginning to manifest itself across the pits.

As the rain continued to fall, practice didn’t start at 9.30 and eventually a few keen souls made their way down through mud and rain to the start. The MX250 clutch wasn’t having any of it though and protested a lot on the start, dragging was a mild term. One the track itself, the bike didn’t really want to rev out (again the clutch) and the going could only be described as ‘heavy’. Went down on the SC500 later and forgot to turn on the fuel, so it wouldn’t restart (as normal) so managed to get it across the track and find some fuel to prime it with.

Fundamentally muddy

Still raining and the mud build up continued. The first pre75 250 race had 8 starters (from 19 on the programme) and like the other races soon came down to be a war of attrition, with mud/clay plaster bikes littered around the track with knackered riders. The good guys made it look good, really good and managed to slide and thread their way round the track without a problem.

Mark (aka Orville) trying to find his bike after practice

The sidecar race was an eye opener, with the race lasting 7-10 minutes or so and the clear up taking 20 minutes or more. I then fired up the 500 for the 1st race and after completing 2 (not quick) laps the bike was getting heavier and heavier and finally it became too much. Pulled over, spent 15 minutes pulling off the mud and then headed downhill and then up a side road back to the pits. Total nightmare and decided then that would be that.

Kevin's CZ after race 1

Watched Kevin and Mark in the Twinshock race and Wayde led for the first two laps until a puncture ruined his race. Getting traction and grip was getting harder as the rain continued to fall. Bank Holiday weather at its best ! They both decided to also call it a day.

And this is after one race

Took down camp and managed to spread mud through the van, over the tents and liberally coat the kids. Managed to blast the van out of the pits, which now had a number of abandon cars and caravans to add to the feeling of the destination.

Saffron spent a couple of hours cleaning

The trip home took 30 minutes or so and then out comes the sun. Took 2 hours to clean the bikes and pressure wash the kids, along with clothes, tents, BBQ and anything that was at Whitings Ash Farm.

Had a look at the MX250 later in the evening and the clutch was indeed locked solid. Need to debate the merits and thoughts about travelling to Border in two weeks or waiting for Narberth. Unfortunately, work will be getting in the way !

MC Lille, motocross not DJ

The MC Lille club has an impressive facility and an interesting track tucked into a small area of ground. It’s located in the sandy part of Belgium and thats the first thing you notice about the track, some big berms and some big jumps.

Nice, and did well in the evo class !

For their normal club meets they run two ‘classic’ races, for twinshocks, pre65 etc and one for pre90 (eg Evo class). Interesting selection of pre65 (Matchless, BSA and a couple of early CZ’s), some pre72 and twinshock bikes (Yamaha’s etc) but its not classic racing per se (this was actually on Saturday at Koningshooikt). The races are 12 minutes +2 laps, so a bit more tiring that the Welsh scrambles.

A mixed bag on the classic pre79 line

Some good races, though the jumps make it interesting (!) and the modern bikes are infact quick. A short chat to one of the guys in the paddock pointed me in the direction of Kate’s Retro Page which seems to be the location of all things classic motocross in Belgium including regs, calender. It’s in Dutch and French (like all things Belgian), but google translate does a good job.

Berms a plenty in the sand !

The modern guys later on the programme were quick; very quick. Sand technique, and track knowledge made for an impressive performance. Good afternoon’s intro to Belgian motocross.

Further work on the YZ

Firstly decided to clean up the frame prior to painting (using the Hammerite solution). First problem of the day was a cracked frame to the rear of the main top tube. One of the side stays had cracked at the base of the tube as it connects to the welded end. Needs fixing, obviously !

The frame tis cracked

Starting stripping the engine and first problem is that the drain plug had seen some action from the molegrips. Managed to hammer an 11mm socket onto it to undo it, but thats going to need to be replaced.

Off with the head and barrel and though the bike was running okay, with plenty of power (I didn’t check the compression), the rings are worn and there is clear evidence of them blowing down each side of the piston. No scoring on the piston, though the gudgeon pin holes are worn to an oval shape (?) Piston was at 70.25mm, therefore

Clutch side first and no problems with the getting the clutch bolt off (with an airgun !). The primary drive nut is a 26mm special, but managed to get it off with the long bar and a thin sided hex 27mm socket, saving another special trip to the tool shop.

The clutch basket has plenty of notching from wear, though the plates aren’t original and in pretty good condition.

Clutch basket wear

Removing the flywheel / rotor should have been straightforward, but like a few other things on the bike, it needs a specific M18 x 1.5mm RH thread puller. Alas the ones listed in most kits are solid and like the puller for the MX250 it needs to be hollow for a depth of around 22mm. Therefore drilled my puller with a 12mm bit down to 20mm and this did the trick, which amazed me. Off for a celebratory cup of tea.

Drilling the puller

Onward, and time to split the cases, still thinking about why the engine kept slipping out of neutral. No problems with the puller and again like the MX250 there are two handy M6 threads so the puller can sit on the primary drive end of the crank. Cases came apart easily, though they’d been put together with what looked like contact adhesive.

As it was apart, I’d got some new main bearings (as OEM, Koyo) and crank seals both of which were provided by Keith at Motolink. Heating the cases, popping out the old bearings with a couple of swipes of the hammer on a large socket and then more heat to the cases and the bearings just dropped in; easy. As seems to be the norm, as couple of shims were found on the bench under the engine. Did some checks on the parts diagrams online at North West Vintage Cycle Parts and managed to get it wrong a couple of times. Some input from Gavin and there still seemed to be too much movement in the clutch shaft, but I think is taking up by an external shim underneath the basket on the outside.

The reason behind the gearbox dropping out of neutral was also becoming clear; for the 1979 and 80 models, the neutral selector bolt and the drain bolt were combined (they were always separate on early and later bikes) and as mentioned above the one with this bike is knackered (internally and externally).

For torque settings:
|Cylinder Head bolts|25|
|Cylinder bolts|33|
|Clutch Nut|75|
|Drive Sprocket|75|
|Flywheel / rotor bolt|35|

Nothing listed in the Clymer manual for the primary drive bolt, which is interesting…well not really. I went to 75Nm for this also.

Cases split

Further inspection of the piston and ring showed it to be a 1st oversize Wiseco in old money (that 20 thou oversize, rather than metric), so again on the phone to Keith and a 2nd oversize piston kit with little end bearing acquired. Also, had a look at the Wossner options, which list a piston for the MX and YZ250’s; cheaper that Wiseco, available and seem pretty good.

Hammerite sprayed frame

Sprayed up the frame and got the compressor working a lot better than I’d done in the past, in particular managed to lay the paint quite thickly without the excessive overspray. Much happier with the result than from when I did the MX250 a couple of months before.

Time to order some bits, get the rear wheel sorted (a bit of a special saga all of its own) and move on to completing the bike. All great fun !

Slippery when Wet !

Up with the gazebo on arrival and by about 09h00 the usual suspects (minus Wayde and his teeth) were sheltering out of the rain. Kevin was making an appearance with his twinshock CZ and I’d managed to sort out the MX250 so had both bikes ready to race (well to go round the track).

As is normal the track was laid out on the side of the hill, making for some excellent spectator viewing and a good long course. The off-camber bends are interesting, and became a lot more interesting later on the afternoon.

Kevin managed to develop a fault on the CZ during practice and a sheared woodruff key was identified as the culprit. A search for a suitable replacement ensued and with some assistance, the bike was ready for the first race.

Hiding from the morning rain

Despite the rain, the 4 practice sessions had taken the top off the grass, the track was surprisingly good and by the time of my first race (the <250 pre74 race) it was good with a lot of the slippery bits taken out. A couple of the off camber corners were interesting, but track was riding well. Not the best start as got taken out in the 2nd corner by a rampant CZ handlebar.Quick remount and the bike was a lot better after the engine change (and frame change). The clutch was still sticking slightly but all was good. Sheared woodruff key

Out with the 500 and the bike was ballistic off the line, though only 4th into the first corner was down to timing on the tape. Lost a few places early on, but the track was much more suited to the 500 than Pontrilas but still need to tweak the bike around a bit. Suspension much improved.

Mike, Mark and Kevin all headed out for the 1st twinshock race, though a repeat shearing of the woodruff finished Kevin’s race early. Good riding from Mike on Alan’s XR500 kept Mark at bay, but problems with a spark plug cap meant that he was a lap down at the end.

The lady entrant

Before the interval and the 2nd 250 pre74 race, saw the the track in top form. Poor start but a consistent ride with again the bike going well, though may have to look at the gearing as dropped out of the power band a bit too often. Good fun though.

The interval saw some reflection and probably the most annoying PA system, which was way-too-loud and one they played Abba though. Actually, after 10 minutes or so it wore you down. The commentary of the races is a good idea, but shouldn’t forced on eveyone and broadcast for the whole of the valley to hear. Ah well.

Pre74 up to 250 race2

The first race after the interval saw the heavens open with an almighty shower. I decided to delay the trip up to the box, but it was wet. The exposed earth of the track was suddenly really slippery. Race speeds were down and the finishing corner was really slippery as I snaked my way through. One of the off camber sections was very interesting and didn’t get any easier for the last two races as it kept on raining.

After the last race...

Kevin hopped onto Alan’s XL350 for the 2nd Twinshock race and after a first lap misfire he managed to step on the gas to finish infront of Mark and Mike. Alan started the marketing campaign when he got back to the pits.

The track and weather got worse and though I did all 6 races, the last 2 were a bit of a war of attrition, but at least I was on the line; the Twinshock contingent decided to hide in the Gazebo rather than riding the last race.

Racing finished at 17h30 and headed back to Hereford; took 1 hour to clean the bikes up and longer to dry up all kit. Great track (when its not soaked), shame about the PA, but a good fun.

YZ250 strip

There were some obvious problems to be resolved:
– the rear wheel rim is cracked
– plastics need to be replaced
– clean up and possibly repair the petrol tank
– gear selection problems (doesn’t stay in neutral) and engine rebuild

Ready to be dismantled

The strip revealed a few other interesting things:
– the rear frame loop seems to be an ‘aftermarket’ bodge with a nice strip of aluminium bolted to the plastic
– an interesting spattering of 11mm bolts, along with the ‘normal’ 12 and 13mm selection.
– the ding in the exhaust was sizeable but tolerably. The end can was a Supertrap, probably off some four-stroke Honda.

Yamaha went monoshock in 1975

Took a couple of hours to strip the bike, taking photos and notes as I went. Managed to pick up a Clymer manual and wasn’t planning to strip the engine just yet.

Ordered some spares (like cables, bearings, seals and gaskets) from Keith Alderman at Motolink.


The wheel rim was going to be more of a problem that I thought as it seems not only are Central Wheels busy people, they seem to have a bit of a monopoly on the supply of rims, spokes and in particular drilling rims. Replacement Morad rim ordered, but there is a 4 week (minimum) wait for drilling and delivery.

CDI connectors

Rebuilding starts here.

Looking for performance

The main problems with bike were:
– the main mounting for the exhaust was missing and the combination of cable ties and lockwire wasn’t really doing a good job.
– the engine was running, but there was no low-down power at all and getting off the line was becoming a bit of a joke. Some playing with timing and carb didn’t seem to be doing the job.

So, prior to a trip to Belgium I spent a couple of hours stripping the bike down and prepping another frame, with a complete exhaust mount. Sprayed the new frame as before with aerosol black Hammerite Satin which seems to do a good job. Didn’t strip the engine, as I already had a spare engine following on from a rebuild during last season, so had one on the bench so to speak.

After a week in Belgium (good trip over on the KTM), back in the UK for the royal wedding and more importantly a whole day of bike rebuilding. A few issues needing resolving as a rebuilt the bike:

– steering head bearings, needed a new set
– clutch arm, during the strip I’d seem to have misplaced the connection from cable to clutch arm. Faffing with this and nicking one of the one of the TY250’s took about 1.5 hours, which is a pain.
– exhaust, the mounting of the silencer etc

Checked the compression of the old and the replacement engines, with old showing 75 psi, whilst the new 125 psi.

Existing engine, reason for poor performance

Removing the cylinder head and the barrel from the used engine revealed why there was loss of compression and power. The piston had cracked from the skirt up towards the rings (there are two rings on this piston). Might account for the problem getting from the line, but amazed that it was a least a little competitive and that it hadn’t completely broken up in the engine.

Starting up the new engine, it had slightly more than just a nice top end rattle with a metallic knock also. Though the bike ran okay and seems to have some power, decided not to continue the running in until I’d had a chance to resolve the noise.

Wire insert kit

Going through the piston and barrel selection (this new piston and barrel are 0.25 oversize), gave me a couple more options, but decided to stick with the existing piston as this had a new conrod, little end etc. Tried a different barrel (which seemed to a closer fit), but which needed more faff time to get ready as someone had butchered the exhaust bolt threads. Out with the new 6mm wire thread inserts, but took a couple of attempts, as the threads needed to go deeper than the tool would allow.

Used the same piston, ring, little end and gudgeon pin, the latter two of which were new…but same top end clatter. Time for a think and for a barbeque.

The thinkended up carrying on for another week and a trip to Madrid and Antwerp and with just the afternoon to go before the meeting at Abbeycwmhir decided to have another look. Some inspection of the top end components by neighbour Gavin identified the problem as being a worn gudgeon pin and a quick 15 minutes later, then engine was running again, though still with a slight knock. Also changed to another 0.25 piston and a fresh ring.

End can

Some further fettling and modified the exhaust rear can as it seemed to be restricting the engine. A quick run round the wet field seemed to indicate that there was some power and response. The carbueration was a little off, and I retarted the timing slightly and all seemed okay.

Will see what happens at Abbeycwmhir tomorrow….