feetupfun

This is what the Aussie 1976 C model looked like when new http://www.bikepics.com/pictures/763083/

Inside the carby is a device that controls the level of fuel in the bowl. It consists of a float and a valve. The float pushes the valve shut when the fuel is deep enough in the bowl. As fuel is used, the float goes down and lets more fuel in from the tank to the bowl, restoring the level. For some reason that valve in your bike is not stopping the fuel from overfilling the bowl. You will need to pull it apart and work out why that is happening. It might be as simple as the valve being stuck open, or it might be something else.

Your footpeg mounts are standard TY175 but the footpegs are from something else 525 - 00..... is B model 1975 525 - 10...... is C model 1976 Standard fork tube protrusion for TY175 is 22mm.

As far as viscosity goes, SAE 10W40 will be OK in the gearbox. The important thing with gearbox oil in wet clutch bikes is to avoid oils that contain friction modifiers or extreme pressure additives because they will cause the clutch to slip.

There were plenty of the red coloured first model Shercos sold here and one of them is still being ridden in our local trials. I will be able to get high quality photos but it will be a while as our riding season has just finished. I am pretty sure I have magazine photos of that model and I think there might be a close-up of the thumbs up graphic in that. I'll have a look later today. When they were advertised they were referred to as the "Bultaco Sherco" which was very hard for some of us to pronounce after thirty years of saying something very similar but different.

Rev 3 is the model series that followed the Techno series ie Beta Techno, Beta Rev 3, Beta Evo

1968 Sherpa T (model 49) triple clamps are different to model 125 triple clamps in many ways, if they are indeed the originals on the model 49 or even on your model 125. It has been so many years since new that your bike or the one that the 1968 clamps came off may not have the original triple clamps. The model 125 Sherpa T does share triple clamp type with many other model Sherpa Ts so you stand a good chance of being able to get some to replace yours. I hope you have considered straightening them because it may be possible and easier. Sherpa T triple clamps are unique amongst Bultacos so you can rule out triple clamps from Alpinas, Matadors, Fronteras and Pursangs. For a model 125, you should be seeking triple clamps from a Sherpa T from about 1974 onwards (model 124/125 onwards) Eariler fork tubes and triple clamps were different to what should be on yours.

It only takes a tiny amount of water in the oil to make it go grey. There is no reason for the gearbox oil to go whire/pale/grey other than water ingress - the water is either getting in from riding in water with poorly sealed gearbox or getting in from the coolant circuit.

The bronze bushes are normally a light push fit in the swingarm tube

Brian I would love to see it too. You should be able to post photos on Trials Australia www.trials.com.au Alternatively you could email me photos and I will post them up David

yes its a byproduct of sugar manufacture. I have no idea how it works but it is commonly used for cleaning up rusty steel for automotive restorations. Have a look on google if you really want to know how it works.

Dunlop rears are not available as tubed type and their tubeless rears are incredibly difficult to keep on the rim of tube type rims at trials pressures. No idea about Vee Rubber tyres I ride only twinshocks with tube type rear rims and happily use IRC tube rears and fronts and Michelin fronts. All three are readily available and work fine. If Michelin made decent tube type rear tyres I would use them too. The front tyre brand does not have to match the rear tyre brand for the bike to work well, but on a twinshock the performance of the front tyre is important for the steering to work well. I reckon Pirellis MT43s are woeful compared with modern tyres for trials competition use. Of course if I was riding a trials bike on the road much it would have Pirelli or MITAS tyres as they wear out more slowly than proper competition tyres.

Important things to do if there has been water in there Remove all rust from all the steel bits - especially the whole way though the ID of the fork tubes. Pitting is not important but getting rid of any particles that might come loose in service is important. Remember that the springs can rub loose anything not part of the parent metal. I have recovered a set of severely rusted (internally) forks from a 348 Cota by cleaning all traces of oil out of the tubes and then plugging one end and filling the with molasses and leaving for a few weeks. This dissolves the rust and leaves the steel alone. Similar molasses treatment was used for the other steel parts like damper rods and springs. I haven't used molasses on any aluminium parts and suspect it may damage them. I usually use a specialised aluminium corrosion treatment for those parts. You should not need to polish anything except the outside of the sliders (for visual appeal). The sliding surfaces (ie damper piston to ID of fork tube and the anti-bottoming devices) do not need polishing. After you get the bike rideable, use it for a few hours then change the fork oil to remove the fine particles generated by the running-in process. The only remedy for pitting of the chromed surface of the tubes is to have them re (hard) chromed or to buy new tubes. This is commonly required on old bikes.

The cap pulls the tapers together. Make sure the bottom clamp is fully free, loosen the cap a bit, spray some penetrating stuff around, load the forks so there is a pull on the taper and then use some persuasion techniques (tap cap downwards/tap on OD of clamp/apply heating etc. Another way is to let all the oil out, take the spring out, leave the cap off and use the slider like a slide hammer to shock the taper free. The stuck side may have a rusty fork tube bore or maybe the fork tube is bent or maybe the slider has a dent. Maybe the fork leg is completely full of oil or water.

Thanks Manuel. I don't need photos because your description is perfect. I went out to the shed and pulled a 348 cover off and found that the 348 flywheel slot is long enough for my two-pin tool to work fine similar to having two holes. Mystery solved. David

On your bike, the gusseting at the headstock looks standard but there is a doubler/patch on your front downtube that is not standard. I have two Bultaco frames (both Alpina M115/116) that use that same arrangement for the headstock gusseting and one of them has cracks in the gussets at the bottom ends of the main gussets. To me your frame looks like it has been either repaired or strengthened at that same point on the front down tube. If no-one else has photos of a Model 125 frame, I will post photos of my M115/116 frame showing the cracking. I looked at a few of my Bultacos and they have five digits after the model number. Cracking of the frame downtube below the steering head gusseting is a common frame failure mode on dirt bikes and is usually attributed to spirited riding (repeated overloading). Frontal impact as in front wheel hitting a tree/car/wall etc with a frame design like your Sherpa T usually causes the top and front main frame tubes to deform into a curve, rather than to crack.

Hey Belldane that makes me wonder what tool I use on my 348. You've got me thinking now. I know I usually undo the nut with a rattle gun but what do I do it up with??? hmmm....

Yes it is standard practice on some bikes to have the head sealing against the sleeve without a gasket. The sleeve usually sits proud of the top of the barrell on such bikes and there is usually a recess in the head that locates on the sleeve. The head being aluminium and the sleeve being cast iron or steel makes for an effective joint.

Gearbox oil and pre-mix oil will migrate downwards through the foam over time leaving the top sections short of oil and the bottom sections sloppy. If you only use the bike the same day as oiling the foam, it probably doesn't matter if you use filter oil or premix oil in the filter because it won't have time to migrate. Before air filter oils were developed, it was common practice to oil filters with either two stroke premix oil, or 4 stroke engine oil. Another thing some people do for events where the air filter needs to be replaced more than once during each day of an event, is to wash the filter that comes out in a strong premix ie petrol and oil mixed at say 10:1. This means they only have to own two filters per bike. You wouldn't want to have any sparks nearby while you are doing the washing and drying though.

Using a strap spanner is doing it the hard way. The easy way is to use an adjustable two-pin spanner to hold the flywheel still. I haven't found a flywheel yet that doesn't have at least two holes in the face. Available at any tool shop.

If you intend to get it welded eventually, don't use plastic metal filler, epoxy or silicone sealant on the hole or your weld repair will take more labour to complete due to having to get rid of all the gunk before the welding can start.

Mike I didn't say that extending by 50mm was right. I said that other people had extended theirs by about 50mm. I've also seen someone make a TY175 swingarm up that was about 100mm longer than standard. I've been considering extending the swingarm on one of my TY175s and was thinking that I would add about 25mm but haven't decided yet. When you fitted you mono TY forks, did you use the mono TY clamps or bored-out TY twinshock clamps? If you used the mono TY clamps it will have made very little change to the wheelbase or steering geometry.

There is no "best" way but most I've seen have extended the axle plates to move the wheel about 50mm further back. Others have made a complete swingarm.

Be careful there are three different types of M49 frame. The last type (after about M49- 02800 from memory) is the one that is very similar to the M80. The earlier M49 frames are nothing like M80 - they are very similar to the M27 frame. Another thing before you buy another frame - make sure it has a legit frame number or you will be no better off

I think it might be a bit dicey to grease the taper surface. I remember that warning being drummed into me when I was an apprentice machinist. I don't remember why though!