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340 Bultaco


modernistutopia
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Hi all, I have a 340 Bultaco, I bought it off Roy "Ago" Wilson some years back, although I have ridden it a few times it is a bit rough in places and I'm currently considering a general direction for a refurb ( i.e. do up as is or continue the development)for another go at riding it. At the time of purchase it was already in a fairly modified state i.e. having been vesty-ised to some extent at the rear end, according to Roy this could have been carried out by Chris Milner.

I managed to speak to Chris at a trial a few years ago and he could not confirm if it was his work or not, I have also spoken to Dave Renham who confirmed that it was supplied new to Dave Thorpe, I have also spoken to Dave as well but he cannot really remember it either, though he thinks it might have been registered later as KGD 111Y.

My questions are twofold,

Firstly, does anyone have any further knowledge of this bike that might change my mind about developing it further (I have already modified the steering head angle a couple of years ago) e.g. if it has any interesting history I might just leave as is and develop something else.

Secondly, what is the current thinking on 340 development especially regarding, engine, exhaust, carburation/air box etc. while I don't expect anyone to give away to many secrets it would be nice to be pointed in the right direction as I have read so much about the Puma bikes etc.

Edited by Modernistutopia
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Mmmh ... sounds to me like you have been around quite a lot and did talk about your bike with a lot of people.

As I understand, (English is not my mothertongue), you wnat to rebuild your bike but you are not sure to do so.

Maybe you post some photos, that would be nice a pic tells more than thousend words IMHO.

Than you could tell us which kind of improvements

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Mmmh ... sounds to me like you have been around quite a lot and did talk about your bike with a lot of people.

As I understand, (English is not my mothertongue), you wnat to rebuild your bike but you are not sure to do so.

Maybe you post some photos, that would be nice a pic tells more than thousend words IMHO.

Than you could tell us which kind of improvements

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Thanks for your comments and your English is also much better than my German BTW!

Yes I'll get a couple of shots of it on here ASAP.

Yes I have had a bit of a chat with its previous owners Roy. Chris and Dave though this was just bits of snatched conversation really while riding in the same trials as them at lease 6/7 years ago and I don

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Thanks for your comments and your English is also much better than my German BTW!

Yes I'll get a couple of shots of it on here ASAP.

Yes I have had a bit of a chat with its previous owners Roy. Chris and Dave though this was just bits of snatched conversation really while riding in the same trials as them at lease 6/7 years ago and I don

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The standard clutch can work well by lengthening the arm a bit (don't have an exact measurment but say about 10 - 15mm as a starter) I use Barnett plates and have backed off the tension on the springs as the Barnett friction material has more bite (according to their website) To do this you have to reduce the length of the nuts that tension the springs because if you don't they will hit the inside of the casing if they are more than about 5 turns out from fully compressed. How many turns out you have them is trial and error to find the point where the clutch doesn't slip. Fit a low friction cable.

With a bit of time it's possible to get a one finger clutch. This can also be achieved with the standard plates (which are used by Puma and Vasquez) They also drill the fingers on the basket to let oil flow from the plates easier (personally I have no idea if this is necessary or makes any improvment)

I've no idea what the airbox improvments sre. There is nothing wrong with the standard 340 airbox. Mine has a ported barrel (Vasquez but I've no idea what's been done) and the bike will rev like hell using the standard airbox, there is no problem with air supply. Carb is a Dellorto, 28mm I think.

Rear silencer can have the baffles removed and replaced by continuing the perforated tube at the inlet end of the silencer right through to the outlet and having a single pipe outlet, like the old banana silencer from around 1974 bikes. Repack both middle and rear silencers.

Mine has the steering angle pulled in but standard swingarm. You can only pull the wheel in so far on the Sherpa as the front mudguard will hit the frame so the wheelbase isn't an issue or too short. Grip is not a problem with the standard swingarm and steeper steering. Best solution for grip is well set up rear shocks and a good tyre. I really wouldn't bother with the swingarm, unless you've found a way of really steepening the steering and ended up with a 50" wheelbase.

I have Magical rear shocks, very pleased with them. Front susepnsion has the Magical spring kit with standard damping. It's transformed it.

On the clutch you can fit the weight from the 250 and also the ignition flywheel from the 250 which will save some kg but the engine will stall very easy at low revs so you need to use the clutch more. The engine will also respond much quicker, maybe too quick.

EDIT - 250 ignition flywheel if you have Femsa. I forgot some 340 Sherpas had Motoplat.

Edited by Woody
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@Woody:

Just my 0,02 Pence:

Sometimes You have to make a change to the airbox sometimes not, depending to other modifications that are done.

We came to a different solution, because we wanted to do a refinement and in our opinion better design of the tubes inside

the airbox which work as Helmholtz resonators, (like the tubes inside the rear silencer), this is done now on paper, my job is no to transfer it in practice. Can post the result later if someone is interested.

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@Woody:

Just my 0,02 Pence:

Sometimes You have to make a change to the airbox sometimes not, depending to other modifications that are done.

We came to a different solution, because we wanted to do a refinement and in our opinion better design of the tubes inside

the airbox which work as Helmholtz resonators, (like the tubes inside the rear silencer), this is done now on paper, my job is no to transfer it in practice. Can post the result later if someone is interested.

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@Woody:

Just my 0,02 Pence:

Sometimes You have to make a change to the airbox sometimes not, depending to other modifications that are done.

We came to a different solution, because we wanted to do a refinement and in our opinion better design of the tubes inside

the airbox which work as Helmholtz resonators, (like the tubes inside the rear silencer), this is done now on paper, my job is no to transfer it in practice. Can post the result later if someone is interested.

I didn't mean there was no need to do what you have done. I hadn't actually seen your post when I wrote mine.

It is just that I have read before that the Bultaco airbox is inefficient, whereas in actual use I have found them ok.

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Woody? Dave by any chance? this is Simon from down south mate if its you, trialed with you France about ten years ago on the Bultaco I'm talking about here You will also know me form riding sidecar outfits for the last ten years or so, we are also connected on Linkedin?

Hi Simon, I remember the bike well then, yes, as I had a ride on it in France and remember it being like no other 340 I had ridden. I remember the steering was done but the suspension worked well too, better than as is usual and the motor was very smooth carburation and torquey. I'm sure I tried to prise it off you at some stage.

When I read your original post I did wonder if it was that bike. If I remember it well enough, it doesn't need much doing in terms of improvement.

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Hi Simon, I remember the bike well then, yes, as I had a ride on it in France and remember it being like no other 340 I had ridden. I remember the steering was done but the suspension worked well too, better than as is usual and the motor was very smooth carburation and torquey. I'm sure I tried to prise it off you at some stage.

When I read your original post I did wonder if it was that bike. If I remember it well enough, it doesn't need much doing in terms of improvement.

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