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The springs cushions the stop during rebound of the forks.
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May be some older motorcycles have a brake cam issue and the brake cams are not working properly any more due to wear.
As one side of the pads is always leading the other trailing in connection with the direction of rotation of the front wheel.
The term "leading/trailing" ("auflaufend/ablaufend" in German) is used for drum brakes.
One brake shoe is "leading", which means moving with the direction of rotation of the drum and thus exhibiting a self-applying, or self-servo effect, which means being dragged into the friction surface of the drum and therfore producing a greater braking force.
The other shoe is "trailing", moving against the direction of rotation, being thrown off the friction surface of the drum and not retarding the drum quite so effectively.
If the brake came is bend or the shaft / cam bearing worn or the bearing surfaces worn out the brake will have less breaking power too. You can test this by mounting the brake cam 180° turned around.
You can too force the breaking power of the leading shoe by grinding off a little bit of the brake cam side that is actuating the brake shoe that is trailing while the wheel is moving forward. Then more breaking power will be transferd to the leading shoe and produce a greater braking power. But then you will loose a lot of breaking power while going backwards.
(I will not recommend this because this is not road legal, (this is often discussed by German MZ riders)).
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Mmmh ... It is possible to lock the rear and front wheel while riding on the road, but I need a lot of power to do so.
I have new pads mounted, the pad linings are centred and the chrome surface inside the hubs are in a good shape?
The brakes have long steel brake arms mounted, on the rear and front brakes, they were mounted by Bultaco, (Bultaco design but made out of steel, not alloy! Probably because of road registration):
(Even back then the brakes must had the possibility to lock the wheel as a part of practical testing the suitability of vehicle registration here in Germany).
Then I use new cables on the rear and front brake with oversized innercable to avoid any streching under load of the cable, (made by O. Colander).
Rearbrake foot lever is the original for the 199b made out of aluminium, a little bit thicker and shorter as the one for the former 199a.
Frontbreak hand lever is standard.
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A deep clean and roughten surfaces of the pads will help. Using new and soft pad material will help again.
BUT ... it's a drum brake and will be a drum brake in future.
Any drum brake is in comparison to todays disk brakes not efficient.
You might look up test from the past were these bikes where brand new, there where no complaints about the brakes back then, (I keep this in mind too).
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That sounds too interesting, please try to get them (the photos) here, so the audience has something to look at.
You might have to load them up to a picture stack like picasa, (it's free).
- load up the pictures,
- let one show up in your browser,
- then click on the shown picture with the right button, a small window appear, go to properties,
- when the properties window appear:
- look up the URL of the picture,
- copy the complete URL, (has to end with .jpg)
Then when you use the posting editor in TC past
the URL information in to the second frame that shows up
when you push the picture button while posting.
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Mmmh, looked up the post from 2008
When I look at the pic's from this posting:
I see a drum brake with pads that are not friction linings, instead sliding linings. These pads have a glazed surface by the left over/debris of brake pad material. So no wonder that they don't work properly.
Maybe this is forgotten wisdom as drum brakes on trials bikes where less and less fitted with the mid eighties ...
Drum brakes has to be maintainced regulary here:
- the hollow space,
- the pads and
- the mechanism
should be cleaned regulary from the remains of the brake pad's and other debris
as this will clogg the surfaces of the pads.
The pads of a drum brake has so much surface if you compare them to the pads of a disc brake you can't produce the same amount of pressure, (also due to the mechanical operation) and therby you have not the self cleaning effects on drum brakes as with modern disc brakes.
When you clean up the brake pads with a wire brush by hand or with a coarse abrasive cloth (again by hand) you will get a much better brake effency.
I hope this wasn't too instructive but it has to be said, regular maintaince and cleaning and you will discover a much better brake effency, even with a Bultaco.
I have ridden my SWM which has likewise drum brakes in design and performance in the Alpes and there where some really steep "downhill" sections and it worked (Not as good as with disc brakes, next time I will use a modern bike for sure ...).
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I think it has mostly to do with the material of the brake pads the material has to be as soft as possible. As newer the pads and as more softer the material combination is as better the breaking power.
The softest brake pad material is organic the filling for organic brake pads is btw temperatur-resistant resin which will harden with the time, as harder the pad as less braking power you get. I think this is the main reason especially in combination with the chromed lining a soft brake pad workes much better then a hard one.
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As already mentioned by the previous posters, to remove all paint, dirt, ... from the bearing sets is very important,
not only the side walls even the inner edges inside the stering tube.
Then I would first mount the lower bearing, and here first the lower half that comes to the triple clamp / yokes,
then the halv that has to be mounted to the steering head / tube.
Then mount the lower half of the upper bearing to the upper steering head / tube.
Now you can place the rollers with grease inside the lower bearing half of the steering head / tube.
Then again you can mount the triple clamp inside the steering tube.
After this procedure you can place the roller in the upper bearing half on top of the steering head.
Then you can place the upper half of the bearing shell.
This way you hopefully get the bearing mounted without loosing any rollers by assembling.
I use waterproof grease too, works perfect.
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As the bike runs good if the engine is warmed up, I would look up the position of the float, might be not correct.
And then you might also look for a bigger choke jet, when it's cold the two stroke engine in general like a little bit fatter air gas mix for starting in my experience.
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I would also check the ignition if the timing is still adjusted right.
Did the engine run well befor the issue occured, not too fat or too lean?
If lean you might check the crank seals too, it's an old bike and these seals
can get leaky after some years.
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You can use the YZ 125cc clutch cover from the 1975 model. They do show up on E-Bay USA.
These fit spot on, like here seen.
For the others, - in own experience, as I accidently bought first the wrong one-, you would have
to modify the engine inerta, here the pin that holds the kickstarter spring and maybe the spring too?
Luckily I have got another - the right - clutch case as I did not want to change anything to
the kickstart mechanism.
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That is exactly one reason why they invited this Aspen fuel, (the other reason is more to the health and enviroment related as this acylate fuel is not so toxic, doesn't smoke and when accidently poured to the ground will be decomposed from mother nature easier).
The backdraw is the price.
And I would not recommend to use the premix that is made for chain saws because it only has around 91 octane,
there are specail gasoline available with more octane, for further information klick here: http://www.aspen.se/Aspen_(eng)/Consumer
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The Bing Company, (still in business !!!), recommend this dealer for parts,
which I can recommend too, (but in Germany located):
Bernhard Greiner
Oldtimer Motorradhandel
Am Bangraben 16
72336 Balingen
Web: www.greiner-oldtimerteile.de
E-Mail: info@greiner-oldtimerteile.de
Here the offical list of other dealers in the UK:
http://www.bingpower.net/english/service/haendler.html
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Mmmh, maybe it's so much worth for a collector of cinema stuff ...
I personal would not spend so much for this bike, if I would win in the lottery ... this would be a 4RT to consider about,
for spending "needless" money (It got "cheaper" too "only 14K€ ) :
http://www.futuretrial.com/moto/moto-nuove/future-world-race/
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No idea what this is ... I recommend to consume the fuel and to drain the plastic tanks every time after riding for providing bubbles.
If you have a metal tanks I recommend to fill him up to the top, using fuel that can be stored for years like aspen racing,
workes perfect, I do this especially for bikes and all other engines I had after 5 years of experience in Finland
where we have really low (-30°C) and also temperatures up to +30°C, no problems so far.
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No idea which grease, for long time storing I use Ballistol oil for bare metal parts.
Works good and it leaves a pretty slick coating. The oil is designed for weapons and doesn't harm plastic or rubber.
It does even smell good and is not toxic.
Here to get in the UK: http://www.ballistoluk.co.uk/acatalog/Authorised_Ballistol_Dealers.html or try flea-bay.
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FranceTrialClassic these guys have some nice parts, are well sorted and deliver very fast, but their price pricing* does hurt sometimes.
* I hope that is the right expression
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+10
and use gasoline / petrol with as least ethanol as possible *,
in any case to drain the gastank is the best way to prevent discoloring and bubbles.
At the end of the season I use Aspen racing gas this have the benefit that it can be stored over the winter without desintegrate in something weird,
(also this "stuff" should not be stored in the gas tank of the bike).
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Most sealers work, the main point is to do the right preparation and here is the crux. The gastank was filled with oil-gas mix for years, but you need a completly oil free inner surface, otherwise the paint will not get a good connection with the fiberglas. I have therefor used small stones you take for tumbling to roughn the inner surface then some washing with acetone to really get rid of the oil.
Last prep was to use the acid that came with my gas tank sealant kit.
After this the known procedure.
Gas-tank sealant was Kreem from Germany, there is a gas-tank sealant available that shares the same name but comes from the U.S. this is not so good,
the German inventor and producer has given our a warning to use this product.
Anyway if someone is interested, Caswell will certainly do the job as well: http://www.tanksiegel.de/
Here the warning about the false product, easy to find out as the text written on the sealant cans is in English and suppose to be in German,
there should be an extra English manual on paper, ...: http://www.tanksiegel.de/usa-kreem/
I believe you better take Caswell as it is easier to get for you, the main task is anyway getting rid of the oil inside.
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No I did not mention any production run or series but I like to be correct. The frame was modified with #4902426 and as 4706 units where made from the model 49 from 1968 to 1971 the bike of the TO (with #4902625 / #4902626) should be build between 1969-1970 which is just in the "middle" of the complete production run ...
But maybe you can please tell the audience why Bultaco introduced this in 1969:
And then I highly recommend for further information:
- Francois Stauffacher: "Historia de la Sherpa T", (also in English available "Sherpa T the History"),
- Francisco Herreros Alfaro: "Bultaco - La Pasión pour el Deporte", (also in English available: "Bultaco a Passion for Sport")
Both namend autors do also state that the Kit was available in the end of the sixties / 1969 and btw. both variants where later available and do show up here and there (not often) for sale at least on the continent. There was later with the model 80 even a "Kit Excursiòn" with 10l gas tank and heavier flywheel for "motoalpinismo" (riding in the alpes) f.e. available.
The benefits of the Kit Campéon were: 1,3kg lighter, narrorer and lower gas tank while having the same amount of fuel "on board" and a better weight distribution.
I personal -as already stated- would leave the bike as it is, beside the foot pegs IF they show up somwhere for sale and of course the fenders.
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I think so, the original was painted in two colors, this is irritating me, maybe your sidepanels where just painted wrong?
Here a pic of the 250cc M49, early version: http://www.motosclasicas.org/bultaco/images/sherpa/sherpa_t_250_m49.jpg
The contact data was already given for the UK, see postings above?
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Hi Chris,
back then when the older Bultacos did not have these swing arm protection rubbers feature we used a piece of a garden hose.
We cut the tube lengthwise and fastened to it with a hose clamp on the swing arm. I used a yellow one looks nicly to the blue
of the swing arm and works perfect.
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Nice a photo, yours is an older M49 without the Kit, but I would not bother this is perfect.
I would upgrade to the metal fenders and search for the right sidecover-airbox unit, keep it otherwise as it is.
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The M49 was made between October 1968 to April 1971, the early models had a metal gas tank, an airbox with integrated side panels and grillcover for the mid exhaust.
The M49 was a great success and in the end of 1969 the M49 was upgraded and these upgrades where available as a Kit for the older M49 models too, it included:
- a combined single piece fuel tank seat with attached side panels,
- a different, (smaller seat),
- an extra airbox,
- a different exhaust system.
The later M49 models from 69/70 on were already fitted with these modifications from the factory.
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