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How long is a piece of string? With a flat tyre it all depends on the going that the tyre and wheel have to deal with. When totally flat the rim will push down into the tyre walls causing marking and then eventually cut marks, if the rim is a bit notched from hard previous contacts this to will cause additional injury to the tyre wall. Run flat tyres are designed to do just that and it also relies upon the rim which with a run flat has no well, this stops the tyre from literally remounting itself off of the rim. All you can really do is take the tyre off the wheel rim and visually inspect the inside of the tyre wall for damage. There is a considerable difference between 4 psi and completely deflated, but unless you rode over any ruts or potholes then you may and have a tyre that can still be used. It’s not like you are asking the tyre to deliver rip snorting power and speeds in excess of 50 mph. So at trials bike speeds and use you might be lucky, but just like that piece of string you never can tell, no one has yet invented the self healing tyre??‍♂️??

The Sherco workshop manuals are all available on line just google them. Why dont people use this facility. Your bike should use a good quality 10w 40 engine oil.

There are some erm unusual mods like the snapped cylinder head fin and the crushed exhaust tailpipe end. The exhaust front pipe has a fairly torcherous bend/ weld at the exhaust port. However it does have character and plenty of ground clearance....I like it ??

There are one or two things you could check such as the radiator for mud and leaves clogging up the air flow through the matrix. The coolant sensor fan switch needs to be checked, as does the fan. Bridge the connectors from the sensor wire this should make the fan run, you’ll need the engine running for this. Make sure the cooling fan is free to spin and not being trapped by the surround. The coolant should contain the correct mix ratio of anti freeze to water....use distilled water as opposed to tap water, less contamination...use good quality anti freeze as this not only prevents freezing but the anti freeze also raises the boiling point of the coolant. As you have checked the cylinder head seals and replaced with new there is not much else to check. Fill the coolant slowly so that you do not create an air lock. Keep the bike upright and allow the coolant to settle, start and run the engine for a few minutes and leave the pressure cap off, be prepared for some overflow of coolant if the engin3 decides to push out some coolant, have a tray underneath the bike. Get the coolant hot and turn off engine, leave to stand for about 5 mins and then top up the coolant if needed. Fit the pressure cap back on and start engine, ride it or run it to get it hot, make sure the cooling fan cuts in. You can test the sensor by removing it and attaching a multi meter set to continuity, hold the sensor in hot water just off boiling, you should see the meter either bleep or register continuity... if not the sensor may be faulty. Not worked on an 80 but I suspect it has the same system as the 125 and 250 etc.

When the contacts open the current ceases to flow, the condenser (acts as a damper) prevents excess sparking and arcing at the contact faces and helps with the back emf. As the current to the coil has been stopped by the now open contacts the magnetic field generated in the HT coil collapses and creates the HT spark at the plug via the HT lead. The Buzz box is just the same as using a multi meter set to continuity...the bleep or buzz...indicating current flow or a complete circuit, the bleep cease when the contacts just start to open indicating an open circuit..no current flow. Of course the contact base is earthed but the moving contact is insulated, thus when contacts are closed a circuit is made, when open the circuit is broken. Testing the resistance through the points (across the contacts faces) indicates the condition of the points, high resistance to current flow = poor contact condition therefore a low resistance would be indicated on a new or refaced set of contacts. By your reasoning with the contacts always earthed they could not act as an on/off switch which is what their function is. This would mean the HT coil would never be able to create a high tension spark at the plug because it is always in the charge condition. You need to break the circuit to enable the magnetic field generated to collapse!

ATF will lube the primary chain and more importantly the sprocket and clutch hub teeth very well. The ATF in auto transmissions have bearings and thrust bearings that need lubrication to, not just the clutch packs so ATF has been formulated to deal with this requirement and to deal with very high temperatures as well. The only down side is that the clutch and primary chain may sound a little noisier than if lubed by a straight SAE 30 oil which would tend to have a quietening effect.

First off have a look where the cooling fan cowl rubs on the rad. You may need to use some thin rubber hose slit length ways to space the cowl just away from the radiator tubes. I would have thought a competent person with soldering skills could cover seal the chaffed holes. JB Weld is good stuff but may ruin any chance of a correct repair. You might consider taking your radiator to a professional auto radiator repair company, they may even be able to fit a new core.

Apologies, not that it matters it’s still a good looking Bultaco.

Doesn’t the vehicle identification number usually include the frame number?

DMW Mk 15 IAN there’s a nice big photo of your bike or rather what it should look like with good view of the exhaust. Go to google type in DMW Mk15 Trials and hey presto on images and there she is, tried to lift it to TC but no go. Hope that gives you all you need for replacements. I think the footrest position may be altered, what do you think???There you go...did it!?

Guess your not up to typing much! Hello anyway Ossa4fun, looks like the frame is in pretty good condition. Should be a really nice bike when it’s finished??

Ensure that all of the bearings inner and outer tracks are out of the headstock (frame). Measure accurately so that you have the following dimensions: Top headstock inner diameter inside of O Outer diameter of fork steering shaft Ditto for the lower bearing It is usual for the top bearing to be smaller than the bottom as it is the lower that takes most of the load. Now give Simply Bearings (google for address etc) a call and they will be able to help, or you can use their guide to select what you need. It is obviously essential that what ever you use must be correct. You can also select seals for these bearings. As suzuki250 says the originals may have been ball bearings with cup and cone tracks. You might also try other bearing suppliers as not all do the slim type of taper roller bearings needed for the headstock. Sometimes you can strike it lucky and a car rear wheel hub bearing kit can fit. Ask greeves has identified that you might have taper roller bearing outer tracks still in the frame. These can be drifted out and you may find the bearing information that you need stamped into the track outer face, once you have that your part way to sorting it. As for the exhaust you will need to research. From what I gather your Mk15 would have originally been a 200 (197) Villiers engined bike of about 1957ish year or there about. You will probably end up having to get an exhaust made or use parts from various suppliers, most of the then Trials bikes all used similar systems. Villiers Services might be able to shed more light on this for you?Pictures would be good too!?Oops you posted while I was typing...looks as though you still have an outer track in the headstock! By the look of the paint it could be a nice bike you have got yourself? Oh and welcome ?

The frame joins were not brazed, this would be far too weak. The preferred joining method would be bronze welded as used by most frame builders, some refer to it as Sif-Bronze welded but the Sif part was a welding component manufacturer. Don’t think any of Mr. Millers frames had the rear loop removed at manufacture, the Red tank Bultaco frame rear top closed lugs look to be a professional job done when the frame was built....that’s from my opinion....which might be different if I was actually looking at the frame in person. John Lee at Higham Ferrers dabbled in frames, Eric Cheney also made a few as did quite a few others. Wasp were also producing frame kits and Geoff Chandler campaigned a Bultaco engined RT4.These all looked similar but none had the rear loop deletion. Either way the Red Tank Bultaco looks great no matter who made the frame? The Blue one is very nice too!?

Don’t forget the female riders?

Ah, we all do it. ?

Why just ‘modern’ bikes, some of the ‘old’ bikes are worth far more? If owners can’t be bothered to record (write down) or ?photograph the bike and it’s identification features then your idea falls at the first hurdle. Full marks for suggesting the idea though?. Maybe members on this site, who are quite happy to list their bikes in their avatar, might like to think about who else is checking what they have to steal. I’m removing my list asap?

The video is worth watching even if you don’t have the same carb, very interesting and informative.

He’s talking about the throttle cable, but your suggestion about a longer arm on the clutch is well proven.

This might seem to be a mad question but you are wired to the ignition generator coil and not the lighting coil....madness over. You should be able to put a PP9 battery wired to the contacts to either show a break in the circuit when the contacts open using a torch bulb or a multi meter set to either continuity as you have already done or set to 20v to show on/off when contacts open. With the correct wiring connected as soon as the contacts begin to open you should see the multi meter show no continuity. When you get the sort of results you have it usually means the generator ignition coil is faulty. You should have one wire from the contact breaker insulated side going to the HT (high tension) coil and the condenser connected in series with this wire. The other wire from the LT (low tension) should be earthed. I’m sure Montesa use a black wire for the live, although not so sure about the earth so I would find a wiring diagram to confirm the pink wire is correct. Keep us posted.

I suspect that hoping off a 17....which might be well used and loose....and onto an 18 that is probably nice and just supple, you would notice a difference...especially as the engine et al will be less worn! ?

That’s exactly it, the bolts have probably been welded onto the site of the original lock stops. Some owners remove the lock stops to give increased steering but also have to address tank fouling. The correct lock stops should have nylon caps fitted, these are an interference fit. Order up some replacements £2-3.00 approx and size the lock stop bar accordingly.

By that rule then if a competitor locks either the front or rear wheel they have officially by the rules ...stopped...even though the machine is still moving. ????‍♂️

The TY 250 is a little heavier than you might be used to, the 175 is lighter as the whole engine unit is smaller and therefore lighter. The 250 A was quite a wide engine and the cases were aluminium, later engines had Magnesium cases, susceptible to corroding. The steering head angle is not that steep and so the steering can be a bit slow, frames can be cut and welded to alter both head angle and move the engine up and forward to gain extra ground clearance and better weight distribution, Majesty’s were heavily modified TY’s that gave the TY better handling, steering and traction. The later model mono shock forks are better, some use IT enduro brake plates that give you twin leading brake shoe at the front. Standard TY’s were made to be both road and trial orientated, so a compromise bike in many ways. Spares are readily available from Yambits, InMotion, TY off road and Trial and Trail. There are probably plenty more suppliers out there. Footrest position is a personal preference just make sure any welding has been done properly. The air filters can disintegrate if not looked after, the seat base can rust out and they can also crack across the middle and then crush the top of the air box. Rear sprockets can still be had in dished format or as already stated a spacer block allows a flat sprocket to be used. The gearbox sprocket cover can allow mud to collect and cause issues, many have been cut away to prevent this happening. There’s a bit of a list for you to go at, in standard form the frame was really quite well made and strong, so you shouldn’t fine any cracks, but check just in case. Yamaha didn’t undercoat their frames rather they just flashed silver paint onto bare metal so rusting can also be a bit of a problem. Good luck with your quest.?

Fuel gumming up the carb interior and jets. Modern fuel goes stale very quickly, unless of course you drained the tank before leaving the bike standing. Carb strip and carefully clean out jets.

mickwren, Having read your last post with interest, it appears that you have identified the reason for my initial comment. Now that the situation has been better explained about the intended rule change, it is less of a threat to young riders that want to progress at their rate. ?