feetupfun

I think you should consider the broader motorcycling market before thinking that the Spanish makes folded because of Fantic. Sure enough the Fantic was a more modern design than the Bultacos of the same year but the seeds of what happened to the Spanish makes were planted 10 years before the Fantic 200 came out. As popular as trials was and still is in Europe, trials bikes were and still are only a small part of the motorcycle market worldwide. Think about the big sellers ie Road bikes, Trail bikes and Motocross bikes. During the 1970s the Japanese makers took over most of the world market in these fields which had been previously dominated by European brands. With reduced sales, product development was limited and so the Spanish bikes fell behind others in the race for technological improvement. There were also significant political changes happening in Spain at the time which led to increased labour disputation issues in the Spanish workforce.

To answer the question about riding it with oil leaking, if it goes bang (noise and jarring felt through the grips) on landing, you are doing damage to the fork internals. Also if it is low on oil it will probably also go bang as the front comes off the ground. If you don't get a bang, you have not lost enough oil to make a difference yet.

Hello Patrick Thanks for the great photos of you and your fine M49. I had a bit of trouble reading your web page (we Aussies only get a small amount of schooling in other languages). Did you say the restoration cost 4500 Swiss Francs? Mine is also an early M49(M4900100). You may weep if you saw how unusual mine looked when I bought it so I won't send you any photos until it looks more like a M49. It had been fitted with a road bike dual seat, huge front and rear road-bike type footpegs mounted on heavy steel frames, the rear frame loop had been bent down to allow the double seat to fit better and the tank and side covers had been painted pale blue with a white flash to resemble a 1978 Pursang. The good part is that the bike is generally in quite good undamaged condition and runs well. It still has an old chevron pattern trials front tyre and the original aluminium front mudguard and mounting stays. I was able to buy a correct seat with a good base and a spare tank and set of sidecovers and am still deciding which tank to use. It is very good to see such clear photos of a bike such as yours for when I paint the tank and sidecovers. Yours is the first I have seen with "BULTACO" on the sides of the fuel tank. Was that standard on yours? I can't quite see what footpegs you have used on yours. Where I ride the safety rules require folding pegs so I will probably make up a set to fit the standard mounting locations for Post Classic competition events. More news later Bye for now Regards David Lahey Australia

Thanks twinnshock, I hadn't seen the trialclasico.com site before. There was a good closeup photo of their replica muffler for the M49 so if I want to make one it will be easy to get it looking right. They certainly are expensive to buy. I agree that they are not the most practical type muffler to use but the old Bultacos look a bit strange with cylindrical mufflers. If you want a good practical cylindrical end muffler for old two stroke trials bikes, I suggest that a Suzuki RGV250 end muffler from a wrecker is a good starting point. They are light, cheap and look quite good. David

My Sherpa M49 came without the (top-in bottom-out) triangular box end muffler. I have not seen them for sale anywhere so am guessing will need to make one. I don't have any decent close-up photos of an original muffler to help with this. Maybe the replica triangular muffler (bottom-in top-out) as sold by Sammy Miller can be easily modified. Can anyone help me with this issue? Thanks David Lahey

Things to check: 1 The vertical rotating shaft tends to develop a rounded pit where the end of the pushrod bears on it. This increases the surface area in contact with the end of the rod which increases the friction. It can be restored by welding and refinishing or they are available from Yamaha. Make sure that the point where the pushrod bears on the flat surface of the vertical rotating shaft is well lubricated with a grease containing a high pressure additive such as molybdenum disulphide to resist galling. 2 The action of the TY175 clutch mechanism is affected when the flat face of the rotating shaft that pushes on the pushrod is not at 90 degrees to the pushrod in the middle of its movement. If yours is not at 90 degrees, you will need to make changes to the clutch components to get it there to optimise the action. Things that affect this angle are: Incorrect adjustment of the rotating shaft height, clutch plate wear, pitting of the flat surface of the rotating shaft, wear of the end of the pushrod and wear of the ball. If the angle is significantly less or more than 90 degrees, the end of the pushrod will be getting pushed sideways which will greatly increase friction and wear in the mechanism.

Rob Welcome to the Oz twinshock trials fraternity. Great news. Does this mean you have given up the idea of getting a KTM trials bike? David

Neonsurge This problem never happened under acceleration hard or gentle. It was when the throttle was being closed and this is what BATRIAL seemed to be saying also. Yes a larger pilot jet will halp with pinging under acceleration but I don't think that is the problem here. David

Dear BATRIAL My 2003 REV3 200 used to make the same noise at the same time as what you described; just as the throttle is snapped shut. I tried different fuels, different jetting ie needle position, needle shape, pilot jet size, main jet size, float height, spark plug temperature rating and oil/fuel mix ratio. When I advanced the ignition timing a bit, the noise you described disappeared. The place where my bike runs so nicely is with the stator screws in the middle of the adjusting slots. In case there is confusion about what is advancing the ignition, it means to cause the spark to occur earlier ie to rotate the stator in the opposite direction to the direction the rotation of the rotor. I hope this is of use to you. David Lahey

Betas are known for sometimes developing corrosion that lets the coolant get into the gearbox oil. Have a close look inside the water pump cavity.

Chunky, If the red frame is original colour I would be guessing it a 1984 or 1985 model which would be called a TY250N here. I see the wheel rims are different colours. I suspect the rear wheel with gold rim is original and the non-standard front wheel has been fitted as part of the disc brake conversion. I don't know what bike the fuel tank is from. David

A photo would be pretty useful for identification.

Apart from reduced risk of melting ones wellies, can someone explain why reducing the temperature of the outside of the exhaust pipe on a 4 stroke is important? I would have thought that cooling the exhaust gas as quickly as possible to reduce its volume (by dissipating heat through the wall of the exhaust pipe) would mean the exhaust system could be made smaller diameter than if the exhaust gases were kept hot by coating the header with an insulator. Advocates of ceramic coated headers on trials bikes please share the reasons for doing it. By the way I'm not asking about turbocharged diesel truck headers because they are coated to keep as much heat (energy) in the exhaust gas as possible between the head and the turbo.

Mike The 51T rear will be fine but I suggest using a 12T front. Using 51/13 means that second is a bit too fast for most competition sections and first is a bit too fast for extremely tight stuff but OK for most sections. Using 51/12 is better for competition because it allows the choice of using first or second gears in sections and makes first nice and slow. The penalty is that a TY175 with 51/12 gearing will only do about 50-60km/h flat out so might be a little slow if you do much trail riding. David Lahey

Ishy what I see in your results is that: The outside temperature of an air cooled (4 stroke) motor is generally hotter than the outside of many water cooled (2 and 4 stroke) motors The water cooled motors had narrower operating temperature ranges than the air cooled motor (ie their thermostatic control systems were working) Both are totally expected results I would also expect that: If you tested an air cooled 2 stroke motor under the same conditions you would get a result similar to the Scorpa 125. If the ambient conditions of the test were very cold or very hot instead of the 30 degrees C, the benefits of water cooling would be even more apparent ie the water cooled bikes would have the same operating temperature range as for 30 degrees but the air cooled bikes would be correspondingly hotter in hotter weather and colder in colder conditions and would continue to see a wide temperature range at any given ambient conditions. BTW I'm assuming you did the testing in conditions considered hot in most of the trials riding world. In most of Australia the normal summertime day temperature is well above 30 degrees C. Where I live it is usually 33 in summer and 27 in winter. Further North and away from the coast summer days are normally around 43 degrees. This why I am an advocate of thermostatically controlled water cooled trials bikes be they 2 or 4 stroke.

Steve, is that Bundaberg, Queensland, Australia? Yes you are on the right track about the kicking it over compression. I have a M138 (350) Alpina which certainly warms you up kicking it over. If you are from this Bundy, there are well stocked Bultaco parts suppliers much closer than the UK ie Don and Marie Newell in Brisbane and Peter Schoene in Melbourne. Please reply if you want phone numbers. Sorry if you are from a non-OZ Bundaberg. From David Lahey, Gladstone (just up the road from the Bundaberg famous for Bundy Rum).

Is this a trick question? If they are your spoke nipples, why are you asking for someone else to tell you how big they are? More info please

What's the clutch slipping for? Yes fourth gear Yes feet on pegs If you are doing the wheelie on the flat, rest your backside up against the rear guard high enough to get your toe low enough to touch the brake pedal. If you are doing it uphill you can do without the rear brake. When you are ready, maintain mid RPM and feed out the clutch to get the front up. Starting speed can be almost stopped. The slower the better for starting as you will accelerate as you bring the front wheel up under power. As the front comes up, move you shoulders and head to one side so you can see where you are going, looking past the front wheel. The lower you sit, the more vertical the balance point will be. While the front wheel is still spinning you can get a strong steering effect by turning the bars opposite to the way you want the bike to turn. Old twinshock bikes with a higher centre of gravity are the best to learn on because they are less vertical at the balance point and have higher seats. This makes them easier to steer during the wheelie. Keep your torso and legs as still as possible. Some people prefer to hold the inner section of the bars or the top of the left fork leg with their left hand once the bike is up to get their arm out of their field of view.

In case you are still looking, there is a white Italjet 250 for sale in Australia. It has just been listed on the Australian Trials website. www.trials.com.au

Asking what is the best trials engine is a lot like asking someone "what is the world's coolest car?" It's so tempting to say "my car" But naming the worst trials engine is another thing altogether. For now I reckon the worst trials engine is simply the one that is not suited to the skill level of the rider using it.

Sounds a lot like an air leak. Check for air leaks at: The cylinder base gasket. The crank seals. Are they fitted the right way around? Are they the right type? The reed case to crankcase joint. The carby to reed case connecting piece. Did you take the throttle slide out to fit the carby to the bike? If so is the slide in backwards? Were the sealing surfaces of the crankcase halves OK? David

Hi BJ downunder. What you have pointed out about the difference in the finning design of 1970s two and four strokes is interesting but I'm not sure that it means that the two stroke has more problems keeping cool on a hot day (which we certainly get plenty of here down under). The main reason that 1970s Honda XL250 engines have less finning than air cooled two strokes of the same era is that it is all to do with surface area available for heat transfer. Because of the location of the cam, rocker gear and cam chain case inside the 1970s XL250 Honda engine, the external surface area of the engine available for heat transfer ends up almost large enough even without fins - hence stubby finning. In the case of a two stroke motor, the surface area of the head and cylinder without fins would be way too small. Hence a two stroke of the same power output as the XL250 would need more fin area. In reality the comparison between these two particular engines is problematic because the H6360 Monty motor would probably be able to produce about twice the power of a standard XL250 so there is a need for additional finning by comparison for that cause as well (waste heat produced increases with increased power output). Remember that the sizing of the cooling surface area is not only designed to prevent overheating, but also to prevent the engine getting too COLD in service.

My Cota 348 came with air valves on the fork caps. They are intended to be used as a tuning tool for fork action. The standard steel springs inside are a bit soft on their own. About 3psi with the forks topped out works fine for me as far as spring rate goes, but it does cause a bit of additional friction at the fork seals. If I could buy stiffer steel springs and run without the air pressure I would. Unfortunately I haven't found a replacement yet. BTW is your Cota really a 349 or is it a 348? They are quite different in the frame, engine, triple clamps and seat/tank. Where I live the 348 was sold 1976 to 1978 and the first red 349 came out in 1979. Keep on trying to get the front brakes to work well. Its worth it. The 348 has very good brakes when set up properly.

The measured weight of my Cota 348 ready to ride trials (no lights and half a tank of fuel) is 93kg. Others in the same stable also ready to ride are: TY250B 93kg KT250A2 94kg TY175B 83kg I would have hoped that a bike made 10 years after these bikes (the TLR250) would be lighter than a Cota 348.

Yes the Barnett fibre plates work great in Bultaco Sherpas. The takeup becomes silky smooth and the clutch spring preload can be backed off to provide a lighter pull yet retain the required resistance to slipping (they have a higher coefficient of friction than steel on steel). I just wish Barnett made them for Montesas as the sudden and jerky takeup is the main weakness with my 348 Cota in competition.