woody

Thanks for the suggestion but tried both of those as well, no luck

I need the chrome front pipe for a Bultaco Sherpa 49 - the original horizontal type not the kit version as fitted to type 80 for the downward pointing silencer. There are none available in the UK at the moment, I've tried the US with Hugh's, Hogans and a couple of others but no luck. I've found a website in Spain for Romeromoto and they have them but I can't speak Spanish and his English is not too good - communications have failed after a couple of e-mails.... He has them but I just can't order one... Does anyone know of anywhere that has these exhaust pipes for sale? Mr Greeves - do you know of anywhere in Spain that I can get one from? They must be available somewhere as they are fitted on restored bikes Maybe if you know anyone coming from Spain to the Classic Offroad show in February, they could bring one with them and I could pay them there - or send the money to them first.

Why not ask Nigel Birkett who knows Yamahas like the back of his hand, is the Scorpa importer too and has stocks of spares for both. He is an honest bloke and won't rip you off.

Craig Mawlam who bought the Majesty stock from Shirty has one of Mick's original 360 big-finned motors and was using it in the Classic series a few years ago. Those bikes in the pictures are from Mick's initial spell with Yamaha, one is the cantilever, the other when he reverted to twinshock. Craig also has a 6 speed small finned 250 motor fitted in a mini-majesty frame to make a very nice Yamaha Majesty - is this the motor you mean Sam? Were there two different types, the early big finned 360 and a later small finned 250? I know you have probably forgotten more about Majesties than I'll ever know but I think the bike that Salty rode had the same type of 6 speed engine that Craig is now using but they are 250 (according to Salty) The one Salty rode had the special frame, forks, hubs - completely different from the normal Yam Majesty (similar to the forks/hub on the twinshock picture) I was told there were only 3 of those made. There is a picture of one in John Hulme's twinshock book with Shirt Snr riding it (in SSDT?) in the early 80s. It was pretty much a prototype Yam mono with twin shocks wasn't it? Nice bike anyway, I remember him riding it for a few seasons in the ACU Classic series and both he and the bike well. Anyway, back to the bikes in the pictures, Mick showed me one of the 'fuel injection' throttle bodies they used on those bikes once, made from magnesium it weighed nothing. He also had a magnesium carb and when you held it in one hand with a conventional carb in the other, the difference in weight was amazing. He also showed me some hand prepped factory gears that were very much lightened. That's how the weight was shed I guess, exotic materials and all excess metal dispensed with.

Yes, they did include a twinshock class for a few years but the trial was too hard for twinshocks by then and there were hardly any entries, those that did struggled and the class was dropped. It was hard enough on a modern bike back then, never mind a twinshock...

It already exixts. it's just called the Pre65 Scottish.... Yes it would be fantastic to have such an event but I can't ever see it happening. Twinshocks in the UK are the poor relations by far when it comes to 'prestigious' events. The Isle of Man classic is heavily weighted towards Pre65 with only 40 twinshock places, there is a Pre65 Inter-centre trial but not for twinshocks, several Pre65 championships and several high profile Pre65 events throughout the year. There are many Classic clubs catering for twinshocks but no twinshock specific events. A twinshock Scottish would be a dream come true for me as I'd love to ride my Ossa round the course. I remember on my first entry to the Pre65 Scottish there was a question asking for suggestions about the event etc. I put something along the lines of how it would be nice to be able to ride twinshocks and would there be any chance of a future event catering for them. Perhaps that is why that entry was rejected along with the following 6 until I finally got in in 2006......

I suspect that if they did, there wouldn't be enough entries to make the trial viable.....

Well done OTF - don't worry too much as it won't be anywhere near as bad as you think. The sections aren't killers by any stretch, just tricky enough to steal marks. Best get up to Bracken for a bit of rock practise. I got the rejection letter so won't be seeing you up there. More or less expected it after 'going in the note book' last year, though whether that actually had anything to do with it I've no idea - but I'd guess so. At least now I haven't got to worry about how to put fiddle front forks and yokes on that are acceptable but competitive which would have cost ridiculous money, instead that money can go towards a trip to Robregordo hopefully. Disappointed at not getting an entry but every cloud has a silver lining...

Harpower reed conversions are no longer available on the Ossa - or more accurately the person that did them doesn't do them anymore. Bikes with the conversion come up for sale every now and then and sometimes converted barrells appear at autojumbles but probably not in your neck of the woods.... I don't know who did the Romat conversions but it's in the back of my mind it may have been something to do with Mick Andrews following his return to Ossa from Yamaha. The Harpower conversions were already in existence by then. As far as fitting a reed valve is concerned it is pretty basic for a competent engineer (beyond me unfortunately as I'm not even an incompetent one) The fins are machined off the back of the barrell leaving a flat surface to mate the reed block to - either right accross the barrell or just in the area where the reed block will sit like a TY250 twinshock. Obviously the angle and height at which the reed block will sit needs to be considered here in order that the carb still sits in line with the airbox. The cylinder fins get thicker towards the centre of the barrell so where they have been machined off they can be drilled and tapped to enable the reed block to be bolted on. The inlet port is opened up to a larger diameter. On the cylinders I've seen this doesn't appear to be too scientific and the hole is rarely symmetrical.... No idea what the optimum size is. Sometimes vertical flutes are machined into the liner top and bottom of the inlet port but not always. When I had mine done it didn't have flutes and performed very well. The back of the piston is modified to allow more fuel in, either by cutting a big arch into the bottom of the skirt or by cutting a window into the skirt. The former means there is less bearing surface on the piston so it could wear out quicker, the latter retains the bearing surface as the bottom of the skirt is untouched. As far as getting a reed block to use, you could use a TY250 assembly or one off a modern bike. Some people here have used GasGas reed blocks for recent conversions. Nothing else I can think of at the moment, if there is I'll post it. Hope this is some use to you. It applies to any MAR cylinder by the way, not just MK1.

Yes, the centre crankcase castings are exactly the same on the Gripper/MAR so the Gripper engine will go straight into the MAR frame. I think you're right about the crank being different on the Gripper, it's the same assembly but the woodruff key position may be in a different place. The positioning of the cylinder studs is different too. The 250 MAR models (I'm including the green models in this) are all the same. On the 310/350 (whatever you want to call it) MAR they are spaced wider apart (sideways only) than the 250 so a 250 cylinder won't go onto a 350 crankcase and vice-versa (unless you elongate the holes - messy). I think that all the Grippers have the studs spaced the same as the 310 MAR, so to fit a MAR head to 350 Gripper you'd need the 310 MAR head - which you'd need anyway to match the 350 Gripper bore size of 77mm. You may need to check the compression ratio too as the 250 MAR heads differ, some have a deeper recess than others where they join to the top of the barrell, so you can get a higher compression ratio with some than others. Not sure whether there are differences with the 350 MAR heads but you'd need to check it is the same as the Gripper. You can achieve a lower ratio if needed with thicker head spacers but if you need a higher ratio and the MAR head has a deeper recess than the Gripper you may need to skim away some of the head casting around the combustion chamber, otherwise if you fit the thinner spacer the casting hits the barrell before the mating surface of the head touches the top of the liner and it won't seal. A conventional exhaust should work ok as I was forgetting that one of the other mods that was one at the time was to fit a Phantom motocross barrell to the MAR with a reed valve fitted. This worked ok with a MAR exhaust so there is no reason the Gripper engine shouldn't. MAR side cases will fit the Gripper engine no problem - do you want to sell the Gripper cases? (if they are the ones with the cloverleaf on them) Gripper engine in a MAR is a mod I've seen done a few times by the Spanish - seen them on photos and videos from their classic trials. Maybe Mr Greeves knows one or two tips for the conversion.

Where's over here? Surely fitting a Gripper engine and laying down the rear shocks puts it out of the Pre76 class? Pre76 Ossa is MK1 or MK2 250 MAR or the first 310 MAR. Gripper engine was 1980 and laid down shocks were MK3 MAR from '76 on. (I'm not bothered what you do as it's none of my business but modding a Pre76 Ossa with Post 76 parts to ride in a Pre76 class seems a bit of a contradiction - you may as well enter on a Gripper...) If you fit a Gripper engine what will you do for an exhaust, Gripper exhaust is expansion chamber which won't fit a MAR frame, will it work properly with MAR type exhaust? I have a '75 310 MAR and apart from lowered footrests, a skimmed head and Mikuni carb it is standard. Being perfectly honest, if I was to use it in a Pre76 class there is nothing else I would do to it. In standard form any MAR is as good as anything else Pre76. It's a nice handling bike, quick steering (in its era) good suspension at the front and with a good set of shocks plenty of feel at the back. Weight isn't an issue, or at least doesn't bother me anyway. If you want the engine to pick up a little quicker, 250 or 310, you could skim the flywheel. These weigh about 7.5 - 8 pounds. I've tried an enduro flywheel on a bike some time ago, these weigh about 6 pounds. I found it a bit light and although the engine would pick up quicker it would also stall a lot easier than with the standard flywheel. Skimming the original flywheel to somewhere inbetween the two should improve engine pick-up without sacrificing the low speed plonk which the Ossa is so good at. If your carb and ignition are good they are almost impossible to stall. A reed valve also improves torque and engine pick-up on the 250 (never tried one on the 310) and I think they should be ok for Pre76 as Ossa UK were using Harpower reed valves on their bikes then (Roger Holden could confirm this as he has just started posting on here) A TY250 reed block could also be used as this was another conversion done at the time by Romat.

Friend of mine has had TLR swingarms chromed, they are easy as all the surfaces are accessible. No idea on cost as it was a 'back door' job. Looks good with the red finish on the rest of the bike.

I don't think you've any chance of getting a frame chromed for

My 320 has a slotted backplate and welded up crank pin - Shirty mods ?? A mate who looked at the barrell said that it had been ported but I wouldn't know/can't tell. Maybe an ex-team bike

Oh dear OTF - I think that Greeves has just ensured that you and I may well be relieved of some serious amounts of cash. You'll pee yourself when you look at that site It's a bit of a random guess navigating your way around it but there is some nice stuff on there

Yes they are but you really would be better off spending your money on something else. They aren't competitive and are poor quality

So let's turn this around then and offer opinion as to what should be checked before an event to ensure that a bike is acceptable from a safety aspect - and there lies the first problem. How to arrive at a sensible checklist as opinion is going to differ greatly. Take an existing checkpoint - chainguard. Most older bikes were fitted with neat alloy chainguards. Most modern bikes have neat small plastic chainguards. Neither will offer any protection to a hand, arm, leg or whatever else finds its way towards that area during a crash in which the bike could be singing away on full throttle and the rear wheel is spinning like a strimmer. The rider or anyone else could suffer a nasty injury but the bike was deemed safe as it was fitted with a chainguard - but it hasn't prevented injury. The result, an inquest into ways of preventing it from happening again, new legislation which demands enclosed chains, solid wheels etc. etc. Extreme - probably. Unlikely - maybe not in this day and age. My point - what is safe and what isn't? Who decides? What is the outcome if a piece of signed paper decrees that a bike is safe at the start of an event but a component that was ticked off on the checklist subsequently fails and causes injury? Where do you draw the line? - Checking brake, clutch and throttle cables both ends for fraying. Frayed throttle cable can stick and causes injury - brake fluid reservoir levels. Too low and brake failure causes injury - worn chain/sprockets - Rider is allowed to start with these in a worn state and the chain jumps off near the top of a big step/climb. Bike instantly goes into reverse causing a nasty fall. Should he have been allowed to start. - Knackered rear tyre which splits around the knobble on a track or the road causing instant deflation and a crash - should it have been spotted or should there be a maximum wear markers on the tyres etc. etc. Personally I think it is a can of worms just waiting to be opened. I remember trials from years ago where scrutineering involved a quick check of the spokes brakes, tax and a horn. That was it and it only happened on road trials. That was 20-odd years ago and we weren't litigation mad then anyway. But the points I've mentioned previously are just as likely as these to be areas of negelct and just as likely to cause an incident as defective brakes or loose spokes could. So again the question is - what is a realistic checklist of things to tick off as 'passed scrutineering'. Answer - can of worms. With ultimately, some poor sod with his/her signature on a bit of paper held responsible for an incorrect decision that caused injury. And once this checklist has been established how long is it going to take one person to thoroughly check each and every bike before the event, where there are 80 - 100 bikes. If it is a 2 day event are they checked again on day 2. Are they checked on all 6 days of the SSDT. Personally I think that the rider alone should be responsible for the condition of the bike and that the regs should state this. Any problems/incidents and they alone are accountable. There is already enough red tape and paper work for club officials, this would only add to it in my view

Oh what have you done.... Getting a used barrell or barrell/piston as a pair is going to be a bit of a lottery to find one in good condition. If you buy one without seeing it get them to confirm that the exhaust threads are good. They can appear good and the ring can/will tighten up quite nicely on its own without the exhaust, giving the impression that the threads are ok. When it is on the bike with the exhaust fitted, the load on worn threads of trying to hold the exhaust in will prove too much if the threads aren't good and it will pull out, or just won't tighten when you try and fit it. Then there's the possibility that the piston may be worn and as far as I know there are no pistons in the UK at the moment. You need to buy from the States. If your barrell is ok apart from the fin I'd look to get the fin repaired with weld. Once you have to start forking out for thread repairs and pistons it's going to cost quite a bit. This isn't to say you won't find a good item but just watch out for the above. Keep an eye on ebay as they come up from time to time, Ellastone Offroad, A&B Autos, The Twinshock Shop are all possible sources. I've also been told that the later green bikes had different porting from the MAR. These are the barrells with the cut-outs in the fins (on the 250 that is - the 310 had cut-outs on all models, I'm assuming its a 250 you have) The MAR 250 had straight fins with no cut-outs, so again, something to watch if you want original look. Personally don't know about the porting being different. There is a WES rear silencer but it doesn't bolt straight on, I think you have to modify the outlet of the middlebox or something - whether this means an original silencer won't go back on I don't know. The original type bullet shape silencer is available as a repro from Spain and Dave Renham has had some in the past I think, or see the advert on th Mats Nyberg Ossa site. Forks appear on ebay but are being bought up for the Pre65 fiddle bikes as with anything else. They come up often in the States on ebay. You could buy a set from one of the trail bikes if it is only the stanchions you need as they will be the same - just depends if you can get them for less than a rechrome on your own Dished sprocket no longer available although there must be a few still lying around on dealers shelves. Bikes restored in Spain seem to be fitted with them but trying to find a retailer and then getting one will prove difficult. Steve Sell (think he trades as Marlimar on ebay) makes a new sprocket carrier which bolts to the hub and allows you to fit a modern GasGas type sprocket. He's also starting to manufacture other stuff too. Or you can just use the flat sprocket/spacer conversion that has been around for years from Sammy Miller. Gearing is personal choice, I run low gearing 10/42 but 11/42 is more common. Availability of a new Amal depends on which barrell you have and also which you replace it with. MK1 barrells had bolt on fitting, you can still buy bolt on MK1 Amal new. Some of these barrells also appeared on MK2 bikes, probably using up old stock. MK2 bikes used a push fit MK1 Amal. You can no longer buy these new. Mk2 Amal fits and was used on the later green bikes and Grippers. 350 green bikes used a Bing. Jets for MK1 or MK2 Amal are usually 25 pilot, 106 needle, 160 main, no. 3 slide, needle on middle clip. There is only one needle taper on the Amals (for 2-stroke) Anyway, a splendid choice of bike - you can look at the picture of the MAR on the Classic forum that Mr Greeves is about to buy for inspiration....

Am I the only one then, who fitted a Mitani front pipe and couldn't tell a scrap of difference in performance? - it was exactly the same as the original pipe. Fact is I never expected any difference from 2mm increase in diameter, it wasn't bought for performance so I wasn't dissapointed. I bought it purely because I hated the tuppeny ha'penny look of the original front pipe on a

Other than what has been suggested, you're limited to what else you can do really. My old 325 type 92 which my mate now owns, has a completely standard set up apart from the Venhill light cable. It doesn't have any spring adjustment as it has the springs held on by the pins, not nuts so tension can't be altered finitely on those anyway, other than washers under the springs. However, it is set up properly and is easily pulled in using one finger. No slip, no drag, no mods. Levers make a difference, I think it has domino fitted. Cheapo levers may not give a smooth action. What you really need to do is throw the clutch lever away and practise riding without the clutch and use a slow action throttle. The Bult will slug down to nothing on the inertia of the crank weights alone and is very hard to stall. Make yourself do it and sacrifice a few rides by practising it in sections. It will improve your riding no end. You can turn full lock circles in 3rd gear without the clutch on a Bult when you get the hang of it but I doubt you'd need to get it out of 1st on most sections anyway. Clutching unecessarily gets you into more trouble than it gets you out of.

Just to qualify - I didn't mean point it up the nearest hillclimb and wind it onto full throttle. My 4RT could be put into gear and ridden straight away, gently, to get the oil circulating properly, just the same as letting it idle would. The Scorpa 4T I tried (250F) wouldn't do that, they would just die, needed to be warmed up in the manner you stated - way too long in my opinion. No 4 stroke MX/Enduro bike I've had has ever needed so much time to warm up, they could all be ridden away a few seconds after starting them, as can my C15 trials bike, so it's nothing to do with carb vs. FI.

Which bike...??? 4RT no, you can ride them virtually straight off a cold start up. Scorpa 4T takes some warming up for whatever reason (I've tried 2 and both the same) Don't know why as the YZ250F I was using in enduros warmed up very quickly

From what he's described, it sounds like (note sounds like - I'm not saying is) the problem I had. If the head of the bolt has sheared off or worse, the bolt has ripped out of its housing (like mine), then the kickstart stop plate is no longer held in place. It is L shaped so if you imagine it as a leg and a foot, where the ankle would be is where the locating bolt goes and where the toes are is a locating peg that a hole in the stopper fits over. So if the bolt is no longer in place, the stop plate floats free, which could be why the kickstart has gone too far forward. The kickstart mechanism will still work but if the only damage is the head of the bolt shearing off, there is the risk of further damage by continuing to use it. The kickstart ratchet will just use the crankcase as a stop and that is when things can get expensive as it will gradually smash it away. Best get that clutch cover off quick and have a look

Nice fiery little thread this has turned out to be - seemed like a perfectly reasonable question to me..... No, I'm not Woody Hole - not telling you what my hole is made of

The head of the bolt that holds the kickstart return stop plate could shear off, as it was too soft, this is what the recall was on the original bikes, to replace it with a high tensile bolt. Also, on a number of bikes, the crankcase where this bolt locates (inside the clutch cover) has broken away eventually resulting in the bolt being torn out of its housing and taking a small part of the crankcase with it. This needs a strip down to repair the crankcase by a very competent welder, or a new crankcase half. This is obviously not commonplace but it has happened more than once - one of the reasons it is always a good idea to kickstart the bikes in the proper manner as kickbacks on the kickstart can be one of the causes