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About DickyM

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    New Member

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  • Bike
    Bultaco Sherpa 198A

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  • Location
    Witney, Oxfordshire, UK

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  1. DickyM

    Sherpa Brakes

    Hi Lorenzo, thanks for your comment. I think you're right about the front hub being sleeved with a ferrous liner. It is in good nick anyway. The rear chrome is very good and as you say I will keep until it fails. Both front and rear wheels had galvanised spokes but front had alloy nipples and the rear steel.
  2. DickyM

    Sherpa Brakes

    Chrome then. Wasn't expecting that but obvious now you've all said. Leave alone and rebuild the wheel then. This bike is full of odd surprises. I'm pretty sure that drums and wheels are original fittings as in fact I think were the tyres. Date codes definitely pre 1990 anyway. So front wheel no sign of chrome plate and a magnet sticks to the liner. Rear brake chrome plate and the liner is completely non magnetic so makes me wonder what they actually put the chrome plate on to. Also front wheel had all aluminium spoke nipples whereas rear wheel all steel. Using up stock as they got towards the end I guess. Picture of front wheel hub posted for comparison. Thanks for all the replies on the subject and to Woody for the paint info.
  3. DickyM

    Sherpa Brakes

    Hi All Hoping to benefit from your collective experience. Getting on OK restoring my Sherpa 198A and am currently working on the wheels/brakes. Front wheel all sorted and rebuilt. On the back wheel though the steel brake liner pressed into the hub has a highly polished, almost mirror like finish. I thought this should be roughened up a bit with some wet and dry before reassembly. Problem is the surface is beyond glass hard and wet and dry doesn't seem to touch it. I've never personally come across this before. Any ideas on how to get under this hard glazed surface, or should I just leave it as is? The bike was a non runner when aquired so never ridden so no idea if the brake worked properly or not. Brake linings look fine and nothing obviously wrong with them. Whilst I'm asking for the benefit of everyones experience anyone got any recommendations for black paint for the motor? It was originally black so I want to refinish the same. I'm thinking mostly for the barrel and head as obviously they get the hottest. Never had a painted motor before so no experience. Any suggestions welcome. Thanks in advance
  4. Hi Ian T I'm refurbishing a later Sherpa 198A and had exactly the same decision to make a few weeks ago. I got similar costs quoted so I decided to buy new ones from InMotion. These are different to yours as mine have parallel tops. I'm pretty sure they are pattern replacements but that said I thought the quality was excellent. Everything fitted and lined up as expected and they had a quality feel about them. I haven't tested them on the bike yet as that is a long way off but I think the InMotion ones are fine. I'm glad I bought them as eventually I found a nasty crack in one of the originals right down at the bottom where the circlip holds in the damper assembly. Good luck!
  5. DickyM

    198A carb info

    Thanks for the replies. Apart from the situation with the new throttle slide that basically answers all my questions. The guys that sold the slide don't know the answer to the question about that either so I will make a new needle retaining disc to my own design. Sorted. Very little wear on the slide bore actually but the slide itself was badly worn so not that keen on originality feetup just trying to keep costs down a bit for the time being. Not sure what I'll find when I take the engine apart but I dare say there will be lots of expenditure. I was originally after a british two stroke for a project but they are very expensive and not many about that I was interested in. Always admired the Sherpa and when I found out the gear change can be arranged on either side (rhs for me) and there were plenty available at reasonable cost I went for it. Cost me £900 but I can see by the time I've finished it would have been far cheaper to have bought one already done up. But where's the fun in that? I have though been quite shocked at the cost of spares, particularly second hand junk on ebay. Cheers.
  6. DickyM

    198A carb info

    Hi All Getting on with restoring my Sherpa 198A and currently trying to sort out the carburettor. Stripped it and generally wasn't too bad except for worn throttle slide and a bashed about float chamber. Anyway jets and needle were as specified in the Owners Manual but as general detail is a bit thin I have referred to an Amal Mk2 Technical Manual available off the internet. Totally confused now so I'm hoping forum members can put me right. Attached pdf shows the needle jet, Carb Bits.pdfmain jet holder and main jet taken from my carb. Needle jet is the 2 stroke variety without the bleed hole but according to the Amal Technical Manual (extract on pdf) the main jet holder is a 4 stroke type. Picture in the Owners Manual seems to show this 4 stroke holder but it is not very clear. Is the main jet holder currently fitted the correct one or not?? Owners Manual and the Amal Mk2 Technical Manual both show a main jet 'screen' on their respective exploded views which seems to be a mesh of some sort that fits over the main jet. Is this necessary? I've never seen one before in my life. Spray tube. The one on my carb looks a bit like the one described in the Technical Manual extract as coming from a late Norton 850 with the cutaway facing the engine. Is this correct? Throttle slide was badly worn so bought a new one which appears to be teflon coated. Relationship of cutaway to needle height is identical to the old one but internals where the spring fits is different. See picture on pdf. The needle retaining disc doesn't fit properly into the new slide because of the lug. All shown in the picture. Is there a different type of needle retaining disc available or do I just bash the lug flat and reuse that? Finally I have a problem of my own making. As the float bowl on the original was badly bashed I shopped around and bought a new one at the best price I could find. Problem is in my ignorance I didn't realise there are 2 stroke and 4 stroke versions. I appear to have ended up with a 4 stroke version which comes with a fat float needle and a brass seat with a 3.1mm (.125') bore. The original float bowl has a slimmer needle , a nylon or similar seat and a bore of approximately 2.2mm as near as I can measure. Does anyone know what will happenif the bike was run with this 4 stroke set up? Would it work ok or do I need to faff about sourcing and fitting a new seat, needle etc?? I would be extremely grateful for your advice. Thanks
  7. DickyM

    Sherpa power curve

    Thanks for the replies guys. I'll do as you suggest feetupfun and cadge a ride on an earlier bike for comparison when I can. And your thought Greg about downgrading the power output on paper is a very real possibility, one I hadn't considered to be honest. An earlier version of the VW emissions scandal! I'm not at all worried about this power output thing and as I said before the bike will be rebuilt to it's original spec (or as near as I can get it) All I was querying really, admittedly being a bit of an anorak about these things, was to find out what the actual engine differences were. I dare say I'll find out more when I split the engine. Dealing with the cycle parts first. Thanks again.
  8. DickyM

    Sherpa power curve

    Thanks you both for yourPower Graphs.pdf comments and your comprehensive reply feetupfun. Could be that the 238cc unit was tested at the back wheel but that would be a big loss through transmission for a chain driven bike and it would be odd to put the 250 and 350 on the same graph, one measured at the back wheel and the other at the crank. Understood all you said feetupfun and you can pick up the torque reading at lower revs from the graphs. Clearly having useful power at lower revs is good for a trials bike. It's just that 14.1 bhp is so low and the 350 doesn't seem to have suffered in the same way. 14.1 is even lower that the 1959 BSA C15 I used to own which was rated at 15 bhp if I remember correctly. For a Bultaco 238cc made 21 years later 14.1 just didn't seem right. Interestingly, to me anyway, I also noticed that the power curve given for the Alpina 250 (again 238cc I believe) in the Workshop Service Manual is almost identical to the 198 graph included in the Owners Manual. I have attached a copy of the power curves in question so you can have a look for yourselves if you like. All the best
  9. Hi All Just joined the forum. I've made plenty of visits as a guest and found it very useful so thought I'd join as I think I'm going to need plenty of advice with my project. Bought a 198A Sherpa T 1979/1980 vintage over the Christmas holiday as a retirement project. It's a bit of a wreck with everything falling into the 3 B's category. Bodged, bent or busted. However that's fine and going well so far. But I have a question that no one seems to know the answer to. So heres hoping. Before I bought the bike I did a bit of online research. I discovered, on this forum somewhere actually, that max power output of a 250 Sherpa was around 20 bhp compared to around 21.5 bhp for the 350 version but with the 350 having much higher torque. As soon as I bought the bike I also bought myself a Workshop Service Manual from In-Motion Trials. This covers all models up to model number 200 but actually excludes the 198 and 199 series. In this manual there are power and torque curve graphs for 250 and 350 Sherpas showing max bhp as 20 and 21.5 respectively and torque as 2.72 and 3.15 M/Kg. Exactly as expected. However the bike came with an owners manual specific to the 198 and 199 model series. This is a proper printed glossy booklet printed in Barcelona in November 1978. When I got round to reading it several weeks after acquiring the bike I found there are power curve graphs shown in this book also. The 350 is much the same with max power shown as 20.8 bhp but with a lower torque of 2.76 M/Kg. The 250 however shows a maximum power of only 14.1 bhp and torque down to 2.04 M/Kg. IE Power down 30% and torque by 25%. These figures are also repeated in the general data section. What goes on? Can anyone shed any light on this? I find it hard to believe that Bultaco, faced with ever increasing competion from Japan, would take a proven bike with impressive history and track record and suddenly decide to lop power by 30% and torque by 25%. It seems that they did but what on earth did they do to the engine? I have not seen any reference to this anywhere and believe me I have dredged the internet. I am aware that the cc of the 250 ws dropped to 236 cc but surely this didn't lead to a 30% drop off in power. The outcome of this is irrelevant to my project bike as I will refurb it as it comes. I'm not chasing power but I like to get under the skin of a bike and I'd just like to know. Does anyone know what happened here and what they did to the motor to strangle the power. Thanks in advance.
  10. Thanks Rich, appreciate it. Hope the guy who has just started trialling has got good knees!
  11. Hi All New member just signed up. I've been using this site as a guest for long enough so thought I ought to sign up. When I retired a few years ago I decided I was too old for bikes so sold bike and all my odds and ends. Few years on and bored I yielded to ebay temptation and bought myself an absolute wreck of a Bultaco 250, 198A for not much money. Having great fun working on it even if by the time I've finished it wont be a cheap option! Always fancied a trials bike, lean and functional that's how I like them. Now we are all on lockdown my wife is even glad to get rid of me for most of the day in the garage. Biggest issue with the bike is undoing the handiwork of previous owners. Some people should be kept away from doing anything mechanical by law in my opinion. Anyway hope to pick the brains of the Bultaco experts on the forum soon as there are a few things I need to sort out. Take care all in these times of the Coronavirus and enjoy your biking, whatever it is.
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