dadof2

Some Betas suffer water pump corrosion needing a new primary case. Otherwise they are pretty well fault free but look out for stripped threads where fasteners go into alloy. Bottom end power is fairly soft but builds rapidly at higher revs. Flywheel weight and slow action throttle are common mods. Can't remember if the 09 has an ignition map switch. If the stator is movable you can get some of the effect of a softer power map by retarding ignition timing a touch.

Just because there is a single start time it does not mean there will be a MX type start, riders tend to head off at intervals with their friends.

Usually kickback on starting is caused by not pressing the kickstart firmly enough. Some people having had a kickback (that can hurt) tend to be a bit timid in future and that makes the problem worse. Strictly speaking a backfire cannot happen on a reed valve two stoke, the fire cannot get back past the reed valve. What people often call a backfire is a mistimed combustion in the combustion chamber or an unburnt fuel combustion in the exhaust. You need to know which it is before trying to fix it.

Boost bottles, perhaps better described as intake resonance reducers, did presumably work to some extent as several manufacturers, mainly Yamaha fitted them for extended periods. I have never seen independent test power graphs that showed after market bottles gave an overall power gain. Although a lot are advertised, I don't know what actual sales are. There is a lot of stuff offered for sale that does not actually work such as oil additives and magnetic fuel savers.

Firstly intake boost bottles. These appeared on Yamaha MX bikes in 1980s. An importer of another leading MX marque when asked when asked why their bikes did not have boost bottle replied "you would be better having a s??t before the race" The volume and shape of a 2T exhaust determines the power characteristics but as the exhaust is a fixed size optimum power is only achieved over a given portion of the rev range. If you had a variable length or variable volume exhaust you can extend the rev range over which power is produced. Hondas variable volume system was called ATAC and was valve operated. Other makers just welded a chamber to the exhaust pipe and relied on the speed of the exhaust gases to act as the valve to the chamber. I am not aware of any of these systems ever being fitted to a production trials bike. I would guess the volume of the resonator to be about 160 to 200cc on a 250 MX bike with connected close to the exhaust port with about a 20mm dia pipe 20 mm long. Low RPM scavenging is usually more to do with transfer port size / shape and expansion chamber outlet diameter / area. Water injection into the exhaust to control exhaust gas temperatures and volume can be used to give similar effects.

To list all my thought on this would result in an even longer post than I have written so far. If bikes were cheaper more would be sold. Reducing weight, especially once exotic materials are used adds significantly to cost. All other things being equal reducing weight reduces robustness, crash resistance, longevity and reliability. Weight reduction is a race no one can win it therefore represents a waste of development effort and adds to product price. To be competitive a bike has to be on or near the minimum weight limit, this means having a light engine or compromising the design elsewhere. If the minimum weight limit were higher the engine could be heavier. The need for a light engine means to be competitive a manufacturer has to develop a trials specific engine which has few or no other use. Low volume of trials sales does not justify development of such an engine or results in development costs having to be recouped over a small volume of sales. If engines could be heavier they (or near variants) would have other applications. This may tempt volume manufacturers like Yamaha, Suzuki and Kawasaki back into trials.

Yes there has been dangerous sections in the past but they were much less frequent. Lightness of the bikes may not be a major factor but it is a factor, even if just because a lighter bike is more capable and this leads to harder obstacles. Regarding spectacular sections, I get bored with them Bou and maybe one or two others have a clean or decent ride then the rest fail or barely attempt the hard bits. I would far rather watch the S3 championship riders in a tricky section where quite a lot ride it. Back in my TY250R (maybe about 1989) days there was a section in a North Yorks trial that consisted of about a 3 foot step followed by a 4 ft + step with not quite a bikes length between them. All riders did same course and I was expert at the time and riding regularly but even so was well pleased to clean it. Even if you failed all you did was hop off the back of the bike with it stood on end, no real danger. About 10 years later I was no longer riding regularly and had started doing the easier course which had been introduced. Instead of doing the double step the easier course turned left out of the beck, up onto the steep bank and along a sheep trod about 6 ft above the beck. Along the sheep trod I caught a protruding rock on the left and side of the sump guard stalled the bike and toppled into the beck as I had nowhere to foot with my right leg. I went a right purler, fortunately getting only bruises and a damaged throttle. Several other easier course riders fell off the trod in the same manner. I would have much preferred to tackle the steps. I have come across similar at several trials including as recently as last year. The CoCs in attempting to let lower ability riders ride round obstacles had actually exposed them to more danger. I know this is getting a bit away from WTC but CoCs probably need to set out sections with a bit more attention to what can happen if a rider fails. As for Neils comment about having a bike fall on them, a few kgs will hardly matter, its which bit hits you that counts. Digressing slightly to MX. So long as you were wearing body armour getting run over by a two stoke was usually no big deal, it had plenty of ground clearance and a smooch rounded "flexible" expansion chamber to cushion the blow. Modern 4 strokes are a lot worse to be run over by, they are 10 to 15 kg heavier, have less ground clearance and irregular shaped narrow sumps with sharp protrusions.

http://www.poetonaptec.co.uk/cylinder-repair.htm Have a look at the above

I have been to plenty of trials with a mass start. You sign on then can set off any time after the car horn sounds.

Consider Apico or Vertex for a piston. Could your barrel be repaired replated by Aptec Phoeton or Lancourts? Be a lot cheaper than new. I am guessing current situation at GG may make parts hard to get. It may be possible to use a piston from another bike if the barrel is bored / plated to suit. This may even mean fitting a bronze bush or different needle roller bearing to little end. Anyone know if Dynamin piston still available and if they might do one for GG?

Check plug colour and float level. Hard cotinual riding will empty a GG (and many other makes) tank in under 90 minutes, Gentle riding plus section inspection can get 3 hours from same amount of fuel.

First clean the points and set their gap, taking your time to get it exactly right. Then with a dial test indicator (DTI) in the plug hole turn the flywheel until the piston is the required distance BTDC. Where the flywheel is close to the engine casing "chisel" a very light slot in the casing. At the inner end of the slut centre punch a shallow dot in the flywheel. Fill the dot and the slot with black marker pen or something else so they stand out clearly. Using a strobe light check the alignment of the dot and the slot. Adjust the stator backplate until the marks align correctly under the strobe light. Having these permanent marks makes points and timing setting / checking easy in future. I used to find my Monts stayed in time for many months whereas Bultos used to go out of adjustment after about 6 trials.

I reckon Piebernat has it about right, much easier to keep control of a small enterprise. I also think he has so much experience of making trials type engines he does not need much R & D. Nice wide gasket faces on the engine for example. Why can't we do it in Britain? Several have tried (Armstrong, Hiro, CCM etc) but for some reason never sold in economic quantities. Spain probably has developed a cluster of competent parts supplies and expertise in the Barcelona area as well as necessary import contacts, bit like Oxford / Silverstone corridor is Heart of F1 engineering. I could pretty well source all the parts to build a trials bike within 40 miles of where I live and certainly within the UK or readily imported but the engine design and development costs would be the major obstacle. Perhaps someone could persuade Triumph to make a 250 4T engine that could have easy variants for Trials, Trail, Enduro, Commuters and Scooters

In my experience the clutch basket usually comes off fairly easily with a straight pull. Never had to use a puller, just gentle leverage on opposite sides at same time. Crank pinions can be very tight. I made a special two part fitting to insert under the pinion (puller claws would not fit). I then put a 3 leg hydraulic puller on my fitting.

My programming and operating experience is with punch presses, lasers etc not machine tools but as I used to design and buy in large numbers of machined components I had to have a fair idea of what our sub contractors machines could do. The Haas machines were multi axis machining centres and gave many years reliable service machining 316 stainless and P20 die steel both of which are fairly tough. I reckon machine tool reliability is much same as motorcycles, properly used and well maintained they generally give good long service, run too hot with dirty oil and they are soon scrap. I have also come across some Chinese lathes that are absolute crap, leadscrews just threaded rod and gears made of something like poor quality mild steel.

Fair bet it is the stator or HT coil even though plug sparks outside cylinder, it probably does not spark insidecylinder To rule out fuel shortage connect a 100ml syringe to the carb with a length of clear tubing. You can then see if fuel is flowing in correctly.

Very sad to read of Browns and Casales injuries. If browns injury is correctly reported he is likely to be out for 3 months or more, then there is the time after that to try to rebuild his confidence. Fujigas missed much of last year and even Bou was not exempt from injury. I feel the increased risk of injury is the inevitable consequence of ever lighter bikes, grippier tyres and more extreme sections. There is a trial on youtube (Germany I think) which shows riders riding across what looks like a concrete dam with a gap in it. No great skill required to ride across it but the penalty for wobbling off would be severe. Clerks of the course need to reduce the severity of sections and reduce the number which are steep rock hopping on dry grippy rocks. More loose soil, slippery rivers and mud needed. An increase in bike weight and reduction in tyre grip is unfortunately too much to hope for.

I would have a look back over all the previous times this issues has been raised. I was under the impression that the sport of motorcycles trials was about reliability, not stopping and not putting your feet down. Now the number of posters suggesting ever less amounts of oil in the fuel makes me wonder if we should have a separate branch of the sport, the aim of which is to see who can run the least oil in fuel ratio before the bike seizes.

First thing is to check woodruff key in flywheel has not sheared, and it and the keyways are in good condition. Next (using a dial test indicator in plug hole) mark TDC and 2.5mm BTDC on the flywheel. Attach a strobe light then spin the engine (battery drill is good for this) and see how far BTDC engine is firing. If it fires more than say 3.25mm BTDC then timing is almost certainly wrong. At this point you need manufacturers specifications or more advice.

This starting in reverse used to be quite common when points ignition bikes bounced back off a rock step. Ships 2 stroke diesels are designed to start in either direction, saves having a reverse gear. If it happens on a trials bike stop it immediately, running backwards could cause a nut on clutch, flywheel or primary gear to unscrew.

Thank you Zippy My point is that historically far east quality control has been very variable but they are capable of making quality items at low prices and are increasingly doing so. About 10 or 15 years ago a friend bought a Chinese trail bike, first time he jumped it the swinging arm bent, whole bike was pretty crap (typical at that time). I have looked at a couple of similar cheap Asian bikes recently and the quality is very very impressive. Regarding machine tools, the people I discussed this with had their expensive machines fully occupied and both bough cheap machines for alternative work they had chance of. They bought the cheap machines (taiwanese and chinese) in the expectation of them being suitable for wide tolerance work and writing them off at the end of the job. To their surprise the machines were very accurate, reliable and have hardly worn despite many years of use, performing as well as machines costing more than 4 times as much.

Quite a lot want a heavier bike - hence the escalating values of twin shocks etc. Never any problem enforcing weight limit at Karting, are trials types so thick they can't use scales. As trials bikes have got lighter, sales have declined.

#38 My general impression pretty well matches recession, so you conclusion that the facts undermine what I observed would seem to be some way off the mark. The threat of Greece leaving the Euro has not receded, it has come to the forefront again being reported in both left and right wing press this weekend. I suggest you also look at http://www.cnbc.com/id/102591625 If Greece's economy starts to grow after exit (historical precedence indicates this will be the case) then the pressure for Italy, Spain and Portugal to follow suit will grow. Sooner or later most will come to ask if the Euro was such a good idea, why are these recessions not ending? and from that point it is a near certainty that countries exiting the Euro is only a matter of time. Freed from the shackles of an overvalued currency companies like GG then may be able to grow again.

From # 362 Back to topic, Does the weight limit really do any good if the riders are just adding weight in the spots they want it, while keeping the bike itself light? If the above happens there is not much point. Its my view that a minimum weight limit set at the correct level means manufacturers do not have to waste money on lightweight product development or use exotic materials which often also results in more fragile parts.

What you should use depends on whether you want to lubricate or displace water and clean. None of these are heavy enough for chain lube. My favourite cable lube was Holts graphited penetrating oil For getting water off a chain and stopping it rusting I tend to use WD40 (the cheap version from Smith and Allan) I also use GT 85 for all round use, lever pivots, cables etc.