woody

85mm is the standard size for the 340 Sherpa so there are oversizes on top of that which means you have a few more rebores left in your liner yet. Contact Bultaco UK/In Motion for a piston

Solway - the parts you've listed, you're not really going to be able to get those from any specific source. More likely you're going to have to scour ebay and hope they come up from someone breaking a bike. There's no-one in particular specialising in breaking Ossas The cush drive nut isn't a normal nut, it's a top hat shape with an allen bolt head - just in case you didn't know and it's actually there in the parts you have without you realising. The brake pedal assembly is common to all MAR models, which offers a bit more hope when you see bikes being broken. The front exhaust could prove difficult. Try Wakefield Offroad as they have broken a few Ossas over the years. Steve Sell, as mentioned above runs his own engineering business, the Ossa stuff is a hobby/sideline. He's helpful and enthusiastic about Ossas but we have to understand it's not his main businees. He will be at Telford. As far as I know though, he doesn't buy up and break Ossas, so not sure what used parts he has.

You'll probably find it just strangles the motor and makes it run roughly - which bike are you trying to use it on? You'll also find it's probably noisier than a clubfoot as well, as there isn't the volume. I have a newly repacked original banana on my '72 325 and I altered its inlet and the outlet of the middle box to the same as the later bikes and, on the banana exit, cut off the end of the 'spout' which is tapered so that it wasn't restricted. It's now about 25mm instead of around 20mm (or less) Makes a decent pop pop noise at low speed but even though it's all repacked, it still isn't as quiet as a repacked clubfoot.

Weren't they made for the older bikes on which the inlet and outlets on the rear silencer and the outlet on the middle silencer were smaller than the later bikes, so you may not get it to even mate properly with the middle box if you're fitting it to a later bike. Were they to replace the clubfoot? I thought they were an alloy replacement for the banana silencer of the '73/74 bikes before the clubfoot was introduced

The book is a decent read but doesn't offer much to trials versions specifically I think to make the WD box fit you have to machine the inner casing on the distributor side to take different size bushes as the shafts are different diameters. There may be more to it than that though, I don't know. I don't know of anyone who has done it, so can't point you to anyone.

Yes, reduce it on primary to whatever it should be (I can't remember) and then fine tune with gearbox/rear sprocket combo. Again, can't remember but someone will have what the 'standard' set up is I ran mine on a normal road box and had no issues with the gearing / ratios for sections. I managed to get a proper trials box for mine eventually but I'm not sure it made a huge difference and I'm sure it felt slower on the road.

You don't mention whether it was bought as a runner or whether it has been laid up for some time. Does the carb flood as it should if you hold the tickler down? Essential for cold starting as that is effectively the choke and even after it fires you need to flood it a couple of times whilst running until it warms and runs on its own. From what you're describing, yes the pilot jet or pilot circuit itself could be blocked, especially if the bike has been lying unused for some time. Remove the jet and check if blocked. Even if it is, also remove the air screw and use aerosol brake/carb cleaner to flush through the pilot circuit, spraying it into the air screw housing, pilot jet housing and pilot intake in the rear of the carb. Once you're happy the circuit and jet are free from blockage, try the bike again.

My old C15 was on 250cc (I didn't notice any difference when the bigger Triumph piston was in to be honest) It was on standard road cam, head and valves, followers, low compression piston (ie: flat top piston for standard trials CR that is about 6.5:1) PVL ignition with a Rex Caunt CDI unit with a softer pick up - this was one I asked him to do for me before they came on the market a few years ago, not a current one. I think the one change I made that gave the biggest difference to pick up from idle, was spacing the carb back using two of the tufnel inlet spacers (forget how thick they are - 3/4"?) This made pick up off idle very smooth and predictable and virtually eliminated coughing/spitting back in all but the harshest of throttle opening. I used to run it with no tickover so that when I shut off it would come to a virtual stand-still with no clutch and it would pick up again off the throttle cleanly and with no hesitation. Carb was a 22mm Amal I'm not sure you can put a WD gearbox in a distributor engine as a straight fit as I think the shaft sizes differ.

Spud, you're missing the main point. There are trials that suit these bikes, country wide. The fact that they are a decreasing sight is because fewer people want to ride them, or feel safe to do so, no matter how easy the section. One cough stall and 350lbs of old iron is going to fall onto the rider who no longer has the strength to hold it up or speed and reflexes to get off it quick enough - it has little to do with the available classes, as people who just want to ride their bikes do so in a suitable event. See the Talmag. There are rigids in the Miller and PJ1 series - in the latter they have their own class. No-one modifies tele-rigids (the big 4-stroke variety) so I'm guessing they are pretty well period. Have a guess how many there are. I can't offer anything other than a logistical viewpoint on the problems of running classes for these bikes - as mentioned in my previous comment. I've no interest in riding one except for maybe a one-off bit of fun as I'm game to ride virtually anything on that basis. On a regular basis, no chance. My mate has an original '63 AJS and neither of us wants to ride it week in week out - him not at all after his one and only outing a few years ago. Locally, we have the BMCA who have been running Pre65 events for 30 years. The same riders are still turning out, some have fallen by the wayside, some no longer with us. A few new faces but not many. There were a good few on bigger bikes up until a few years ago. 30 years on, they can no longer handle them except for the odd one-off ride as most are in their late 60s minimum. Nothing to do with the sections, just the riders are 30 years older and they want to enjoy themselves without broken bones. Their focus is now lightweight Bantams, James, Cubs, C15 etc. Enjoyment on a more manageable scale. They aren't yet at the point where they want a section that is virtually a green lane so that they can ride the big 'un. Personally I don't think the support is there. Riders who would have enjpyed (!?) these bikes back in their day are now in the main too old. The number of 'new' riders that would be attracted to them is probably miniscule.

Spud, if you ride your AJS regularly, you must realise that there is no one governing body that presides over Pre65 events A national championship such as the Miler series has it's rules set by the ACU. The PJ1 championship, I'm not sure who governs that. The Normandale championship has a Pre75 class, again rules set by the ACU. I daresay the VMCC set their own rules for their events. One off events such as the Talmag, Manx Classic, Scottish or individual club trials for Pre65 are run by the individual clubs responsible - they can set any criteria they like for the rules, routes, classes. Their event, their rules. Are you talking about trials in your area or a national championship. Both the Miller and PJ1 championships have routes that accommodate a pretty standard Pre65 bike. Then there's your next problem. What do you class as original or standard. You only have to look at DW's pictures to see how modified bikes were back then, using components that were available to improve them. So does original mean use of period components or as it left the factory? I think you'll have a really tough job finding someone with the knowledge to differentiate and regulate that. They'd have to be in their 90s.... Now consider the small band of people devoted to putting on these larger trials. On the day of the event, a few of them will be out checking the route/sections etc. One to take the entries, one to start competitors off, one or two to sort observers. Where's the extra resource coming from to find someone to look at the bike in detail to decide whether they are correctly adorned or in the right class. Imagine the time this would take. And what do you do if Miller tunrs up on GOV132 - Pre65 but hardly standard... I think you're chasing eutopia and you're not going to find it. Surely it's about riding your bike for the enjoyment of it. You find an event that has suitable sections for you and your bike. I imagine you know who is on a more standard bike and who is on a trick version, so you can still compare scores like for like when the results are out. Or is it about having an award for a standard spec machine? Straight away, riders will look for an advantage - human nature. Can't help wondering from your posts if you're serious about this or having a bit of fun...

Yes Sparks, indeed they have. Every one I've had has split on that part of the seam and other places. They seem to just split from vibration, no matter how much cushioning I put under them. Also, where your legs rub at the rear of the tank it can gently file away at the seam and it splits there too.

Looks a nice tank but it isn't the same shape as the 198/199b alloy tank, which is what the original poster was asking about. They were unique to the UK bikes and a squarer, flatter shape

ok, I'm happy to be corrected on that if that's the case but I really didn't think they were accepted. There are definitely stranger rules in force just south of the border, yes.... I know what the rules say about Ossa etc forks but this is where the reasoning is flawed (seeing as they look just like MP etc) The rules actually say nothing about billet parts, they just say forks/yokes must be of Pre65 design. But as we know, new billet yokes are allowed. They aren't Pre65 design. Montesa Cota yokes look identical but you can't use them. Ossa yokes/forks are of a design almost identical to MP, but you can't use them Same logic applies just south of the border where the rules are actually a lot more explicit than the Scottish rules, stating that replica parts are allowed as long as they resemble the original (see last paragraph) which makes them even more of a contradiction of purpose, as the purpose is supposed to be to keep period appearance. Ultimately the clubs are entitled to run whatever rules they like but for me, taking a purely pragmatic view, the rules are flawed and fail in what they are supposed to achieve, hence my opinion that it's all contradiction and bollocks...

The problem with making the comparison with those two frames is that the 198a/199a frames were quite different from the earlier frames. Your '100' frame, from what I can see in the pictures, doesn't have the bend in the front tube that a '76 - '78 250 has, neither does it have the 250 swingarm pivot position, which was lower than the 350, hence my guess at a 350 frame from '76 - '78. You can't really compare dimensions with the 'A' frame. The model 199 had a new frame which differed from the '76 - '78 frames, the engine was moved back, swingarm pivot moved. The 'A' models then had another new frame with the engine moved higher. So laying an older frame over later doesn't really give you the overall dimension of the bike once the forks, swingarm and wheels are fitted. Put forks and swingarm in and you'll probably find the wheelbase is around the 52.5" mark. Difference in weight is a mystery, although I've no idea of the weight differences in frames from '73 onwards, as that is when they changed to using lighter tubing.

The problem being is that on the custGP site it shows a large washer in between the top felt seal and large washer. Not sure I follow this bit. You have all the parts you need as you've listed them in the sentence before that one. Starting with the bottom yoke. The large washer with a felt ring is the dust seal. Fit that first. On top of that fit the shim / spacer (what you've called the small washer) Then the bearing. Slide that into the headstock, then fit the top bearing, spacer, then dust seal with felt ring. Now fit the retaining nut to hold the yokes in and adjust the bearings for tightness. I think this may be where you're getting confused with another washer. Some parts diagrams show what looks like a large washer but what's probably a knurled circular nut instead of a conventional hexagonal nut. On the diagram it probably looks like a big washer. I've never actually seen one of these, all the bikes I've ever had used hexagonal nuts. You'll probably find your bike has a hexagonal nut, not the knurled type, so you should have two hexagonal nuts. Your your parts diagram only shows one - positioned above the top yoke? The thicker, tapered nut holds the top yoke. The thinner flatter one holds the bottom yoke and adjusts bearing tightness. Fit the top yoke and secure with the nut and pinch bolt.

From what I can see it looks like a standard 325 frame from a model 159/182/191. The numbers don't look right, the two number 1 digits look like they were done with different stamps, the 7 doesn't look genuine Bultaco and the zeros look suspect too. The only bike that had a number that began with a 10 was the original 4 speed Sherpa model 10, so to me it looks like the frame has been re-stamped. Compare them to the numbers on your other frames and the way they are stamped. Edit:- as I've just seen Bult's post. Where did you get the info about the prototypes being stamped 100? The only prototype I've heard of was the early 325 that was numbered 133. Never heard of anything else being numbered 10 apart from the model 10

I wonder sometimes, if frames advertised as being 531 may only have had a small section of 531 in them... maybe the part where the sticker was... Can't advise you on the type of metal but if it's any help, I mig welded my Armstrong frame when repositioning the footrests with no problems at all. On the modified Armstrong on the other thread, all the frame alterations were tig welded. As an aside, my mate who is a coded welder, reckons that all this stuff about you can only braze this or tig that is not always correct. He seems to be able to tig just about anything. He's done frames that are supposedly 531.

I couldn't say specifically that it wasn't, but I'd be surprised as the 175cc model 221 is just a renumbered 250cc model 190 with the capacity reduced to 175cc by sleeving down the bore size. The stroke is still 60mm. Originally produced for the rental market as in some countries rental bikes were restricted to 175cc. Difficult to see Bultaco producing a one-off crank when they could just resleeve the cylinder, given their financial problems as well at that time.

Can't help with that as I've never had a 199 engine apart so I don't know how the sleeve differs / locates on that engine

I don't know. Not sure if the crank is suitable for 2 bearings so I can't give you a definitive answer. However, I can't see any obvious reason why a later holder without the deeper insert couldn't be used. But I could be missing the obvious... By the way, you only use a gasket or an O ring, depending on which holder you have. Not both together.

The 175 used a 250 frame, it's basically a 250 bike sleeved down to 175. Easy to convert back to 250 with an overbore. Yes the wheelbase is correct because the 250 frames between '76 and '78 differed from the 325. They had a bend in the front tube just under the headstock and had shorter forks. They handle well and turn a bit quicker than the 325. From '78, they went back to using the same frame for the 250 as the 325. 199b - If you use an alloy tank from the model 198 you will also need the corresponding seat. That shape tank had a different slope at the rear from the plastic tank, so the front of the seat has to match. But they won't look right on the 340 at all. They only came with the plastic tank or a one-off UK alloy tank which was a squarer, different shape which is not the same shape as the plastic tank (or therefore, the alloy tank that is currently made in Spain) Shedworks do a fibreglass ethanol proof tank the same shape as the plastic tank but about 1" slimmer. Either in blue gelcoat finish or plain for painting, both options allow the use of decals (you're right, decals won't stick to the plastic tank) The exhaust looks standard. The weld you've pictured is normal. The 199b airbox is unique to the b model and works fine. The 199 and 199a used a different airbox which was considered restrictive and the factory riders used to replace it with the older type. Someone seems to have done the same to your bike for some reason. If ultimate performance isn't needed, a pair of steel bodied Betor shocks should do the job as they work reasonably well and are a reasonable price. If the bike runs fine I wouldn't waste money on a new carb, especially if you're not using it in serious competition. If you do want to fit one, a 28mm OKO (not the powerjet version) works well. I have one on my 340 and it only needed a slight decrease on the pilot jet to a 39 from stock settings. They're about £60 off ebay. I only mentioned not a powerjet version as mine is the normal carb, so I don't have jetting for a powerjet as they are different I think.

Sounds like you have spent time on sorting the bike and have most/all of areas I mentioned covered already. The way you described the engine response initially is how they are as standard, pretty flat. It takes a while to get the flywheel mass turning and then just as you want to power off it gets going. So the next thing to try is run it without the weight altogether.It will run fine without the weight fitted and you won't lose any tractability without it, but it should improve pick up again. Try advancing the ignition a little. I can't remember what the static setting is for the TY but you can advance it to 3 or 3.5mm BTDC which,along with removing the weight should help it pick up quicker. Something to note though, is that if you fit electronic ignition, they have a built in power curve which runs the ignition slightly retarded for the initial response, advancing as revs increase to give a more controlled and progressive throttle response which will keep the pick up on the lazier side. Not really needed on the TY250 as they aren't a sharp engine. More useful on snappier engines. It will probably pick up quicker on points, with it advanced as suggested. If you still want to try the 320 route after all else has failed, If I was doing it I'd look for a complete engine to convert. Once you've opened up the crankcases for the larger sleeve, I'm not sure how well it will work as a 250 again if you refitted the 250 top end if it turned out you didn't like the 320. There would be space around the bottom of the liner due to the smaller ID of the original. This may affect crankcase compression or transfer of fuel up through the transfer ports. I'm guessing, you'd need to check this out from someone with better knowledge on that than mine. Loads of TYs have been broken, getting hold of an engine shouldn't be too hard I wouldn't have thought. The Yam is a relatively short bike anyway and they are a bit light on the front on climbs, the 320 exaggerates this even more with its increased torque. The fact that the steering was steepened when they did the Majesty copy would account for the even shorter wheelbase you measured. Majesties didn't have their steering altered (generally, some did) Also, what did they do with the footrest position. If this was moved, it may also exaggerate the light front end. If you fit the mono forks, you will move the front wheel forward as they're leading axle and this will increase wheelbase further, now that you have fitted extensions to the swingarm. You may want to try a standard swingarm again when you have fitted them. The extensions will help stop the bike lifting on climbs but the addition of mono forks may not help the steering. It's all trial and error once you start modifying frames and footrest positions etc.

Sorry, forgot - the allen bolt that holds the fork leg on sounds as though it still has the original washers, as they were fitted with a flat washer as a seal and a locking washer. I just clean and inspect the mating surface of the leg to ensure it hasn't scored or whatever and fit a new fibre or copper sealing washer. Tighten with an air ratchet if you have one, using either of the methods in earlier post to hold the damper rod.

Your springs are the correct length - 17" I've used an impact driver on drain plugs, it's worked without me using too much force. The screws in the bottom of the caps are some kind of valve to prevent fork pump up due to air pressure. You should see a small hole in the top of the fork cap somewhere which I believe was to let air out and prevent pressurising. I've never understood how these are supposed to work and on Bultacos in particular have only ever served the purpose of squirting oil in my face when the forks compressed. I've always sealed up the hole and never noticed any problem of pressurising in the forks.

If you've tried the usual sources, you've probably overlooked John Collins at JC Motorcycles, Port Talbot. He has used Bultaco parts. You could also try Wakefield Offroad as they have broken lots of trials bikes over the years.