woody

Not quite, as all wine tastes like gnats p*** - at least there are some good trials bikes... As stated in above and previous posts, a 200 is your best bet and that really means a Beta as the best option. It's ridiculous to buy a 290/300 whatever and then try and tune it down, it's a waste of effort, trying to get it to run right with whatever changes you make is trial and error and it is still a big engine after all that. The 200 has the correct power characteristics as standard. Trials is not all about power until you are on much bigger expert level sections. A 200 will happily pull a 17 stone rider up anything at novice/inter level. A big engine and too much power will just give you a miserable time in the sections.

You have the needle at its richest setting so that won't help matters at the throttle openings you are having problems with. I'd guess that the problems you're having are just due to having to reset the carb jetting from autolube to premix - assuming the bike was running fine before. These are the settings from the manual for a 4GG bike, carb is the same as yours, a TK, although not the autolube version. Main jet - 165 Air jet - 2.5 Needle - 5C77 Needle clip position - 3 Needle jet - S85 Slide - 2.0 Air screw - 1 to 1.5 turns out Starter jet - 0.7 Float height - 21 - 23mm The mix of 50:1 Castrol TTS is fine as that is what I ran mine on with no problems although you can go to 80:1 if you wanted which is the recommendation from Yamaha for TTS.

No good for the Yam though as the springs are really small diameter

If I remember rightly when the autolube was removed from the old twinshock models, the carbs needed jetting changes (maybe just the main jet) as going to pre-mix alters the petrol/air mix, as per reason 3 above. If I can find my TYZ manual I'll look up the jetting and you can compare to your carb

Is this the mount for Robregordo then Jim 250 springs are no longer available from Yamaha, or at least that's what my local dealer was told when he tried to order some for me last year. You could try JK Hirst, see what they have. No-one in the UK does replacement springs as far as I know but B&J Racing in the US does uprated replacements. For damper rod mods speak to Craig Mawlam at Yamaha-Majesty.com as he got the info from Shirty when he bought the Majesty stuff as to what they did to works bikes forks. I'm sure he'd do the mod to yours if you needed it. He'll be at Wrighty's show so you could ask him there.

80lbs springs is a very high rate for a trials bike. I'm about the same size/weight as you and I used 90lbs springs on a Pursang when I raced one a few years ago. Angled shocks usually require a stronger spring rate than upright but I used 60lbs springs on my Majesty (Falcons) which are angled and they worked fine. I think the recommended rate for the Gripper for Falcons is 60lbs. Try dropping to those, 80lbs may be giving too much rebound and not allowing the rear to sink down and bite in. I'm assuming it is mud/wet grassy banks your struggling for grip in. If you're running with a tubed rear still there is only one choice really and that is an IRC, the Michelin tubed is useless in mud as it is no longer an X11, that was discontinued. Pirelli is a waste of money, it is way off a modern tyre for grip level. The IRC is brilliant in mud, but, some have really soft sidewalls and they roll all over the place at our weight at under 5psi. Increase the pressure to stop the roll and they don't grip. If you aren't using one and think of getting one, if you can actually see it before you buy it (ie; from a dealer rather than on line shopping) you can see if it has a really soft sidewall by flexing it with your hand. The 'duff' ones bend all over the place whilst a 'normal' one has limited flex, say, like the Michelin. Ideal pressure if it is only mud and roots in the trial is 4psi, if there are rocks go to 5 as the IRC can puncture easily. It will lessen the chances of compression punctures. If you're using tubelss tyres on the original tubed rim, the Michelin X11 should grip fine but an IRC is better. I'd go for the IRC again, the tubeless version shouldn't have the same sidewall issues as the tubed version and is the best mud tyre. Also, the 350 Gripper can be really sharpe off the throttle which can induce wheelspin. If yours is, think about a 3mm head gasket if it only has the 1mm or 0.5mm fitted and retarding the ignition to soften it off.

Not as bad as they are made out to be. I rode one about 5 years ago and another 3 weeks ago. Both standard examples and I've also owned a standard Yam framed Majesty. Brief impressions of the TY were; Engine flat as a pancake, same on the 250 Majesty I had, but I would think most of that is down to the flywheel weight. The pickup off idle is really slow so if you need a quick burst of acceleration from nothing to get up a step, bank or whatever, it isn't there. It takes time for the power to come in so you're holding onto the throttle longer. This can in turn mean you're still accelerating when you're past the ideal point to shut off and roll over the crest of whatever it is you're going up. The inertia of the heavy flywheel can also have a negative affect at this point and keep the bike moving instead of it deccelerating quickly enough when you shut off. OK, this is generally on harder sections so isn't much of an issue in most classic events but something to be aware of if you're considering throwing it at harder stuff. The slow response also makes it difficult to pick the front up in flick turns. I took the flywheel weight off my 250 Majesty and it livened up considerably, along with running the timing at 3mm BTDC. Engine was much more responsive and changed it from being a 1st gear only bike to being able to use 2nd as well as it would pull 2nd off idle. It wouldn't with the weight on. If 2nd was in use and you shut off, no way would it pick up again up a climb, the engine would die. You can of course 320 them but they are a real bugger to get right, especially to make them rev right out. Loads of grunt though and pull any gear. There are 270 kits available using 72mm pistons and this actually makes about 264cc - same size as maximum oversize so not really sure what the difference is and why it's called a 270 kit. Craig at Yamaha-Majesty UK does this conversion but also does some porting work with it for more torque. Chassis is nicely balanced, it steers well and with the engine livened up feels lightish and flickable, although the engine is actually a heavy lump. Front forks are too soft and are under sprung and under damped, ok if you are light I guess but no good for me as they were standard forks on my Majesty. I could never get them to work 'normally' like my Ossa forks, they bottomed and topped or locked up with too much oil, could never get the happy medium - nightmare. Modifying the damper rods sorts the damping if you know how to do it, I didn't and it wasn't for the lack of trying.... better damping and stronger springs give a better action, I've tried a bike with this mod and they worked very well (one of Craig's Majesties) Decent rear shocks on the back are probably all that is needed. Angling them like a Majesty may improve things, I don't know, there was a whole lot more done to a Majesty back end than just angling the shocks. Clutches are ok, you shouldn't need to use it much but with the flywheel weight off it pays to cover it just in case it stalls too easily when trying to plonk it. Brakes are no better or worse than other bikes from the same era as they are now 30 plus years old, some will have worn better than others. So, my feeling was, only a couple of negative points which could be overcome and turn the bike into a reasonably competitive twinshock. Not a Fantic beater obviously but more than able to hold it's own with other bikes from the same era and easily capable of tackling the sections in the Miller and Normandale series. A genuine twinshock and much better bet than the converted mono route. They really are a nothing bike with no real point to them and would you be happy riding it when you know that everyone else in the queue at the section is thinking just that.

lol - it's not the mods to the bikes, I don't care what they do to them. What I think is the farce is the hypocrisy around component eligibility in the Pre65 Scottish. Certain riders are allowed to use blatantly ineligible parts that others can't - eg; Yam mono forks, Fantic yokes. They're used year after year despite all the announcements about how 'the rules will be enforced this year'. I have nothing against the riders using them, just allow everyone the same benfit. Anyway, back to twinshocks as it is a twinshock thread. I won't be at S. Shrops as it is the first round of the Normandale series this Sunday. You definitely would not be allowed to use a converted mono in that series, or the Sammy Miller. How individual clubs would handle it I've no idea, maybe move the rider into the aircooled mono class (Normandale only) or maybe just say sorry, you're not riding as the bike is inelligible (rules are specific in that must be t/s of original manufacture) At modern club events no-one polices what people enter on so riders can get away with entering on whatever, you just run the risk of incurring other riders' scorn if there is a t/s class and you beat them on their genuine twinshocks

Commercial Fleet Services on Wainright Street, Aston, B6 5TJ - they are a truck servicing and MOT depot but MOT bikes too as the MOT gaffer is a biker. Not into trials but has a BMW GS which has been used offroad whilst travelling from North to South America. It's been a couple of years or so since I used them though Dave The Frame, Unit 8, Farrow Rd Ind Est, Shady Lane, Birmingham, West Midlands B44 9ER - Custom bike builder, isn't into offroad but understands trials bikes and what they are used for. I've had trials bikes done at both places, both understand the perculiarities of trials bikes and are sympathetic to certain requirements. Always helps if you take it in a van/whatever so it is not ridden straight from the premises onto the public highway with a newly issued certificate. You have to book in advance at both, not just turn up like the good old days.

They are an odd size so not held by any of the usual bearing stockists. You can get them from Pyramid Parts, about

As long as it is in good order it will be fine for that commute. My mate bought one new and used to trial it at weekends and ride to work on it in the week. His journey was about 5 or 6 miles each way in Birmingham with 30 or 40mph speed limits so speed wasn't an issue.

There is a 198a frame, which is the same, for sale on ebay UK which you can look at. The picture isn't the best but you can still see the headstock area. http://cgi.ebay.co.uk/BULTACO-1970S-TRIALS...=item2eaa7fee14 Also a 199 frame which you can see the headstock on more clearly http://cgi.ebay.co.uk/1978-sherpa-350cc-pr...=item33598f16cd Wheelbase would be between 52 and 53". It's unusual they have shortened it for a sidecar, usually they are lengthened on the swingarm.

Sounds like you have a Cota 350, last version of the 349. They were called Cota 349/4, silver/grey frame grey guuards, red tank. Then they were called Cota 350, same bike but with red guards and forks. This is also the bike that was rebranded as the MH349 so there are 3 versions of the same model, just different colours. This is the 350 model :- http://www.ataq.qc.ca/galerie/showimg.php?...1983cota350.jpg The big giveaway of this model over the earlier 349 is the kicked up end to the swingarm and the exhaust that comes out round the frame . Timing is personal preference really but 2.5mm BTDC is fine. Oil quantities I'm not sure of for this bike but someone will have them. Good bike, hell of a strong motor.

You could try the following Bultaco UK John Collins at Port Talbot (as in John Collins, ACU Official who posts on here) Wakefield Offroad Also, make sure they know the right swingarm for the model 159 (John and Bultaco UK will, not sure about Wakefield) as the earlier ones won't fit. Earlier bikes have a solid tube from side to side for the pivot where the spindle runs through. 159 onwards has the rear engine mount in the middle of the swingarm so they are two short tubes 3 or 4" long either side with the rear engine mount bracket sitting inbetween them, the spindle passes through the bracket as well. A swingarm from the 77 and 78 bikes (up to model 199) would also do the job. I don't have any of these models so I have nothing to measure. You could also try ebay.com as there is always Bultaco stuff on there from the US but nothing that you want at the moment. I'll be surprised if there is nothing at Telford show.

I can't post pictures but the Puma bikes look standard in terms of components but have everything polished, chromed or anodised with a unique white stripe down the centre of the fuel tank which is Puma's trademeark. Go onto Todotrial Classic website, look at any of their trials reports and you'll see pictures of Puma Bultacos. Or search the Bultaco, Classic or Twinshock forums for Puma Bultaco and you should find previously posted pictures. I don't know what mods he does specifically, but the entire bike is worked on in order that everything works perfectly and in a lot of cases, better than when it left the factory. Very clever man. PS - Don't bid on the Bultaco swingarm that has just come onto ebay as it is from an Ossa MAR.... Also, the airbox is from the later Sherpa with the different sidepanels and won't suit your bike.

They're a very good twinshock, don't seem to fetch much even in good condition, parts can be a bit hard to source but in time you'll get most stuff. If you're restoring to ride and keep then it would be worth it, to restore and sell probably not as the cost would outweigh the sale value

Selector forks thickness were changed, mainshaft size changed, so did the mainshaft bearing clutch side, clutch hubs changed a couple of times, clutch spring tensioning went from nuts to pins back to nuts, cranks changed, crank seal carriers changed, shape of the clutch side crank weight changed to match the casing shape. Maybe more. On the 325, the cylinder design was changed and from 159 I think, the liner was thicker so these can be bored right out to 340, early 325 can't as liner too thin. Most of the gearbox/clutch changes above were around 1973, other changes came later. Becuase of the changes it sn't possible to interchange all parts from model to model. They may look the same at a glance but they aren't, not everything will swap/fit.

I know the bike you've bought and it is a 1976 model 159 (which would have been available late '75, hence the registration date) This link will show you the 250 version which is similar and will give you an idea of what it should look like. http://www.ataq.qc.ca/galerie/showimg.php?...6_sherpa250.jpg You can buy a book from Bultaco UK giving the history of the Sherpa, also a repro owners manual for your 159.

No, sorry Mick, don't know of any straight swap replacements, never tried the KX pegs. I never used to have any problem with the originals but need lower footrests these days, particularly with modern bars, so whenever I chop off the old mounts I just use modern replacements.

The work required for the extra 20-odd cc really isn't worth it as the gain is barely noticeable. You'd be better off finding another ignition flywheel and skimming some weight off it which will quicken the throttle response (use a spare so that you have the original to go back to if need be)

Unless the Amal is worn out stick with it, they work fine. I had a Cota 350 when they were new and there was nothing wrong with the way it ran with the Amal carb. If the carb is worn you could try a 26mm or 28mm OKO as they work pretty well out of the box with minimal changes on a MH349. Mikunis are a real pain to jet as there are many variants and they use different needle jet/needle combinations and the range of these combinations is huge, there are different slides for the different bodies, so unless you know what you have (if you get a used one) it is difficult to know exactly what to order for parts. As someone else has mentioned there are other issues, different fuel pipe sizes, different inlet spigot sizes on different carbs, adjusting screws on the wrong side etc. If you're Amal is worn out and you are buying a used carb, Dellorto, Mikuni or whatever, it could be in the same state. A new OKO is about

Honda dispensed with 2-strokes of their own accord, initially in motocross, long before the FIM tried to dictate the WTC must be 4-stroke only. All the other manufacurers that had 2-strokes continued to run them alongside 4-strokes. When the FIM said that to compete in WTC you have to do it on a 4-stroke, I suspect that if the other trials manufacturers had told the FIM to stuff their WTC the outcome may have been different. The FIM have no say in what a factory produces and if they realised that the WTC would only consist of 2 Honda Montesa riders they may have capitulated and perhaps the other trials factories wouldn't have bothered manufacturing 4-stroke trials bikes and saved themselves a lot of money - who knows? Certainly not us, only the factory heads. As in enduro, the swing that initially went towards 4-strokes has now swung back to 2-strokes. Today's 2-stroke trials bikes are easier to ride than the Mont/Scorpa/Beta/Sherco watercoolers. They are cheaper to buy, cheaper and easier to maintain and cost much less to rebuild if things go wrong.

The link just goes to the main forum but managed to find a couple of your pictures of the bike you'd posted. I'd heard of the TYZ Scottish but never seen one. I'd no idea they were like that.

Thanks for the explanation - remarkable results from what you've done. Be interesting to see some before and after pictures if you can get them up. The leaving to dry in the sun for two weeks step is going to be difficult in the UK....