section swept

As all of the spring is carried in the fork tube pressing down on the bottom of the fork slider all of the spring is unsprung weight. The fork slidertube is unsprung weight to. It’s fun working out what is and isn’t sprung and unsprung weight! I never did trust Newton’s Law preferring instead to follow the writings of Bart Simpson, his diagrams on which part of a progressive spring compresses first are a joy to the eye. The calculations as to which part of the progressive spring rebounds first are a positive cure for insomnia. Girder fork discussion anyone.....anyone???

You will know if it’s tubless as the valve will be a sealed fit to the rim. Fit a tube and the problem goes away! Or as oni nou suggests seal everything up but you can get a tyre sealant that you paint on to the tyre bead or/ and rim. This product is used by the car trade when an alloy rim and tyre bead leak air out, the tyre is deflated and the bead pushed away from the rim and the sealant is applied by brush. The tyre is then forced back onto the rim by compressed air and the sealant goes off after a few minutes sealing the bead to the rim. The main reason your tubeless tyre loses air is the pressure is too low to maintain enough force to keep the bead against the rim. When not in use pump the tyre up to 30 psi and leave overnight, re check pressure in the morning and see if it’s lost any pressure,this should all be done with cold tyres. Now you simply have to remember to let the pressure out to your favoured riding pressure. The whole reason for going tubeless apart from a marginal weight saving ( the tube) is to prevent the tube from being trapped or pinched when the tyre is pushed against the wheel rim and puncturing, tubeless prevents this but presents other issues namely one talked about above. Tubeless also allows for quicker puncture repair but that’s about it. Nasty rumour going around that 2020 bikes will have marvel of marvels....tubed tyres or even no air in the tyre at all just a type of indestructible compressible mousse.?

Go with the progressive springs, you get smoother and predictable action. In any case all suspension springs will eventually sag, collapse or break due to the life they have to lead. If the manufacturer used better quality material in the first place you would still end up with the springs becoming weakened and softening to a lesser extent. Secretly some works riders will ditch the springs after a few rounds and fit new or different rated springs. A main reason for poor handling on any bike be it road, track or whatever is the springs going off song....weakening...that’s both ends.

You may also have a cylinder head gasket leak allowing oil into the coolant. This would show up by forcing coolant out of the radiator due to leaking engine compression pressurising the cooling system. The water pump shaft is poorly supported and will eventually wear the seal oval. The seals in your pictures look to be worn, but that could just be my opinion, it’s never the same when you can see the real thing in front of you. Do away with the pump and shaft, get the shaft hole welded up and fit an electric water pump which fits in the hose, outside of the engine, problem solved.?

Looks as though you have suffered some serious corrosion ( just stating the obvious). The materials used to make the tyre plus some water getting in between the tyre and rim have all reacted when the wheel rotates and static electricity is generated. This acts on the conductive surface of the wheel rim and eats away at the aluminium. Static electricity can be generated in most of the rotating components of an engine, you even get the crankshaft journals being attacked by this phenomenon and wheels are the worst offenders....travel sickness is put down to static build up. Water as moisture never goes well with aluminium if left to its own devices and add static and you have a cocktail waiting to cause trouble. If you replace that now dubious rim I would be coating the inside of the rim with a good quality paint, what you have suffered is quite common with some rims. The paint goescsome way to stop the reaction and when dried helps to seal the tyre bead to the rim, it does make removal a bit harder though.j

There is a vast difference in the number of posts between you guys, now play nicely and keep being helpful by sharing your knowledge, experience and helping others to enjoy their pursuit. Otherwise no ?????????????????

Before you go changing things have a look at the diameters of your current AJP caliper (one L in brake caliper) pistons, now compare with the Braktec/Bricktop/Brokentop whatever you call them piston diameters. Now have a look at the brake master cylinders and compare piston diameters. If they are all the same as each other there will be no hydraulic advantage to gain only that the bores of each original item may be slightly scored and worn. Very often just giving the whole system a dam good clean with careful attention to the caliper and pistons. Clean using soapy water and a not too coarse toothbrush to scrub around the caliper and piston areas. With the hydraulics still intact gently operate the brake lever to pump the pistons out a few mm, put some packing in between the pistons so they cannot pop out. Look at the pistons and any signs of rusting or scoring could mean a caliper seal is damaged, they don’t always leak fluid out but can allow air in! Light discolouration should come off with the toothbrush action, if it’s on the very edge and away from the seal then a light use of a cleaning agent like toothpaste (yes it does work very much like gentle metal polish). Clean thoroughly all traces of polishing agent and dry, use a small paint brush and apply to the exposed piston a quantity of brake fluid....no penetrating fluids like WD etc unless you have brake grease. Gently ease the pistons back into the caliper, refit caliper to fork leg checking that the caliper sits evenly with disc in the middle of the caliper body. Now clean the brake disc thoroughly on both sides with soapy water and a scrubbing brush, while the disc has soapy mixture on it get a piece of 1200 grit wet and dry and glaze bust the brake pad area of the disc using gentle wiping pressure around the disc, I am assuming that the disc is not scored too heavily clean and dry thoroughly...a common failing here is to fit new brake pads to an old disc and expect instant perfect braking, which is not the case.....the scored lines around the disc reduces the contact area between the pad and the dis by up to 50% until the scores have cut into the pads and bedded in by which time you will be seriously teed off and start looking at other choices, like you currently are. A new disc and pad set of the correct material should provide comparable braking to when the bike was new. It’s a manufactures specification that gets you a bike with a brake that is progressive and not instantaneous stoppie power....usually meaning the rider going straight over the handlebars?. It’s this that makes it so easy for after market manufacturers to supply at great expense to the purchaser brakes that exceed the original set up! Personal taste ie what the works riders use and what’s fitted as standard are usually worlds apart from what the average Mr Trials Rider actually needs. To refer back to another comment, ask yourself WHY is this alternative brake system being offered ‘cheap’??

If you have a Dremmel try cleaning up the chewed area that the retaining nut tightens against. If you are converting to electronic ignition you will need the old flywheel....but check with your supplier as some kits contain a flywheel as well. Don’t give up on getting the flywheel off because sooner or later you will need to change those contacts or at least reface them and then of course the crank seals will need doing or even the main bearings. So get your sleeves rolled up and don’t give in....the flywheel went on so it must come off. Check very carefully that there is no bodge up pin inserted into the hub of the flywheel locking it to the crankshaft, although I would have thought that would have been overcome by the puller. Can’t see any suppliers of new flywheels but someone may know of a few. While you are looking at the flywheel the correct retention used by Yamaha is: first on a flat washer, next on is a spring washer, last is the retaining nut listed as special....TY Parts UK have these in stock. That flat washer if it’s still in the flywheel hub could be the cause of your problem, but I would have thought by now it would have at least budged a little. Go for it there’s always fleabay if it all goes pear shaped. Have you used a hot air gun or blow torch (carefully) on the inside of the flywheel hub? It’s amazing the effect a little threatening can do to an obstinate inanimate metal component???

Despite not being original with some owners colour choices you do sometimes wonder what Bultaco we’re doing with some of their colour choices. White gets you noticed but clever and subtle colours get even more noticed by the officanardos sometimes with negative remarks but it’s your bike colour it what you will. The Hammerite you bought at a really good price is probably way out of date/ use by etc but silver is too close to the bare aluminium of the forks. Hammerite Satin Black would be as close to Bultacos original blackish paint, but it doesn’t matter what you put on those forks will eventually get scratched and scuffed by all manner of Mother Nature’s products rocks, roots, tree trunks etc etc oh and other bikes sharp bits. If you use Hammerite, re- coating to build up layers can be tricky if you go for the Hammered finish, the second coat can sometimes react with the first and you end up with a pickled finish a bit like painting cellulose onto oil based paint. It’s not a good look at all. One type of paint that you might consider is Chassis Paint, this goes on with no primer usually but doesn’t seem to mind about fussy preparation either. When it’s fresh it can be scratched but tends to act like galvanised metal in that the scratch will have the paint dragged into it. At bike cleaning time wash the forks in the normal way and if the forks are showing scratches that you want to hide put a little of the chassis black onto a soft cloth and carefully rub the Chassis paint into the scrathed area....hey presto scratch covered up. You could try it on a piece of scrap alloy on just small area of the fork slider before committing. If you have a Heavy Goods company or bus and coach business near you it might be possible to blag a half litre for not very much dosh. I did a 1973 Sherpa 325 frame and swinging arm in this paint, it didn’t chip very easily, more importantly when I later sold the bike through a well known motorcycle newspaper the buyers convinced themselves that the frame was a special manufactured item, I told them it was standard but they wouldn’t agree, still paid the full asking price?. I have to say that with the frame in black and a Sammy Miller aluminium tank and seat unit in light blue the bike did look very different from the drab standard silver, really good looking.....now when you consider I painted the frame by hand with a brush the end result was very good. Unfortunately I only have one or two photographs of the 325 in its original guise but none when it was painted.

That’s a good suggestion from Mark, but shouldn’t you be talking to the selling dealer about this as it may be a warrantable issue. Bear in mind every time the engine spits coolant out that depletes the anti-freeze content/strength unless you top up with coolant mix. If the water pump impeller has broken up all the pieces need locating and removing otherwise they may cause restrictions to coolant flow. Hope resolve the problem, it may just be a kinked hose causing the problem, still I’d be asking the dealer fo advice.?

Even though your bike is relatively modern it is none the less 7 years old and springs do go weak, when considering what they are put through. Wish I could get back to weighing my 11/12 stone, trying to get under 15, so imagine any bikes springing and the punishment it’s getting. If you can afford it replace the springs just to get the ride height closer to original with fresh oil in the forks, the rear unit may be too expensive or you might get it rebuilt. There will be many riders who will tell you to just get on and ride, but you are noticing the bottoming out and can at least try to modify or improve the technique of body weight transfer, but with new springs you might be surprised at the difference in your bike and it’s response to your input. Hope you get good results?

As the vent holes are now blocked this will make the fork tube seals work harder as the internal pressure build up has to be released somewhere, so this mod may cause the seals to leak (as mentioned previously) the pressure will now be blowing out through the lips. This is probably better than a face full of fork oil! I thought Bultaco used a tiny ball bearing on top of the tiny spring in the fork cap to act as a one way valve, thus stopping oil ejection.?

Hello Ciaran, sorry to dampen your enthusiasm but as the engine has sat for eight years you may possibly find that the oil seals have hardened up. The bearings to may have corroded including the crank and big end so I would definitely be inspecting those. You may be lucky ( it’s an Irish thing) and find everything all lovely and new as previously described, fingers crossed but damp and condensation can be the devil. Hopefully the oil that was in the gearbox and clutch may have protected the internals, pull the head and barrel to check for smooth running of the main bearings and big end, check little end too! ?

When you have fitted the correct pulled into the flywheel, tighten the centre bolt until it is pushing against the crankshaft centre threaded portion. You will need to lock the flywheel to prevent it turning against your tightening the puller centre bolt, try to do this with care as you may damage components inside the flywheel space. Take a 2 pound hammer or copper faced hammer would be better and give a sharp blow to the puller centre bolt, aim to hit the bolt face square on. Now tighten the centre bolt a little more ( half to a full turn if possible) and hit the bolt again. This may sound brittle but it usually works. If you found no washer behind the crankshaft flywheel retainer nut then it’s possible that the nut has chewed the metal of the flywheel into the crankshaft, brute force may be the only way. If this is your first time at doing this it can appear to be a bit of a trial but you should succeed. Be careful if you use a puller that grips the outside edge of the flywheel as this may crack the thing. Good luck?

Front forks don’t look as though they are responding as well as they should to your input, not binding at all are they. Top marks for effort?

Yes VS do a god job, have their trials spec rear shoves on my Sherpa.

Happy spannering?

When all said and done it’s still a nice looking thing!

Very fragile design!

You may well have the correct tank, but the buck that was used to make the tank may be out, where did you get it from? Is that 10mm each side or overall? If this is the case then you only need 5mm clearance to be obtained either side. Have you contacted the supplier of the tank, they may be able to offer advice or suggest a fix as this won’t be a one off. You could try gently persuading the tank guides (for the rubber blocks) to move inwards by pressing against the area with a flat piece of plywood, a 2mm inset leaves 3mm to find. Try the tank on the frame with no rubbers and see what you have. I dare say if you could have been a fly on the factory ceiling ar Ossa, when the assemblers fitted the tank I suspect that there would have been a fair bit of pushing going on the achieve a fit. Overtime the tank would have given anyway what with the riders legs pushing up against the tank. Have you measured the old tank and have you checked to see if there is any depressions around the tank slider mounts? Have you got the correct tank rubbers? Lube the slide mounts with silicone and the rubbers and try to gently persuade the tank on, shaving a little (1-2 mm) off the heads of the rubbers may also win you a little extra clearance. I hope you find a satisfactory fix ?

You may be referring to plastic metal or chemical metal, these are a temporary repair and intended to be a permanent fix for a fuel tank. By the time you have removed a good proportion of the paint you will more than likely have a few more perforations to worry about. You say that this is just a couple of hundred pound bike, I think you’ll find that many people would love to be able to buy a Bultaco for a few hundred quid! What model exactly have got? It doesn’t matter really, they are all worth saving from binging ruined as field bikes etc. Even if you have limited funds restoring to trials riding/competition condition would be very worthwhile. It doesn’t matter what mskevor model of trials bike that you own, it will get scratched and properly so in rock strewn events. Painting over some of the chips and dings is relatively acceptable in most people’s eyes, being looked upon more as the ‘patina’ of use. Works bikes never had special paint finishes as they were work horses and just got cleaned up after an event. Keep you £200 Bultaco clean and well maintained, don’t bother about shiny finishes to the engine or wheels, just attend to that tank and prepare it as best you can, apply some correct colour for the model type and don’t worry about orange peel, “they’re all like that sir!”. Ride and enjoy. By the way there is a kit sold in the auto market place called Petseal and there must be others available that you might consider. After you wasted a few quid on buggering about trying to seal the split, some welders are quite prepared to weld a steel fuel tank, and if they have the skill, knowledge and equipment will weld aluminium fuel tanks. It’s a matter of getting rid of any residue fuel and vapour, sticking the tank filler over a running cars exhaust and filling the tank with exhaudt fumes fo a few minutes can work but you need to know what you are doing. Steaming the inside can also work, welding with 20 foot extension poles gives a modicum of protection if it all goes pear shaped...I jest. Please don’t do any welding on the fuel tank without seeking the right person for the job. A new alloy tank will cost over £300 and a plastic tank for later Bultaco’s will be anything from £ 100 upwards depending on where you buy. Have a look at Shedworks, InMotion (Bultaco UK) or just type in alloy petrol tank, e-bay or other auction websites may have a good used one but you’ll pay through the nose prices. Hope this little lot is useful to you, whatever you do, forget that your bike only cost you a little under the cost of a replacement fuel tank and look after it.??

Ossa produced a bike called the Wildfire a sort of road bike with 230cc and a four speed gearbox.Ossa made very few of these and so they are rare. They also made a trail type bike called the Pioneer, this had a four speed transmission. I don’t think Ossa used a four speed gearbox in their trials bikes, other than in pre development stages of their trials iron, but I could be wrong. You may be looking at something like a cobbled up Trials special, take care with your money on this one.??

Might be blue after you’ve rebuilt and fire it up....oil smoke.

Yeah in a pink Konigsegg

Sounds like these are just casting numbers and not matching case numbers. If line boring and other matching of cases has been carried out then I would expect to see after casting markings and not cast in markings. Complicated aint they these Cub devices!