Build a Bultaco TSS from scratch

Discussion in '2 smokers' started by blaine.hale, Feb 21, 2012.

  1. jbcaddy

    jbcaddy Long timer

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    probably nothing you would be interested in, but it is Bultaco parts. No, it is not mine, I just saw the ad and remembered your post. Hope i don't get banned for it. JB

    http://chico.craigslist.org/mcy/2871280364.html
    Bultaco Frontera Motor 1974 - $85 (Chico/Oroville)
    <HR>Date: 2012-02-25, 8:07PM PST
    Reply to: vbrnc-2871280364@sale.craigslist.org <SUP>[Errors when replying to ads?]</SUP>
    <HR>

    I have the bottom end to a Frontera Model Bultaco. I bought this to drop into my 1986 CR250 Frame but now I have no money for the project. Crank moves free and this has the wide ration transmission 5 Speed. Includes Primary Chain, sprockets and balancer, no side covers or cylinder or head.

    I can send pics if you are interested,

    Call 530-354-7400
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    • <!-- CLTAG GeographicArea=Chico/Oroville -->Location: Chico/Oroville
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    #21
  2. blaine.hale

    blaine.hale Long timer

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    Had someone call me with a Pursang motor but he thought it was a 175cc so I passed =\
    #22
  3. stainlesscycle

    stainlesscycle Long timer

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    it doesn't matter what cc's (125/175/200/250) on the pursangs they all have same stroke. you just need to swap the top end. was this a right shift motor?
    #23
  4. blaine.hale

    blaine.hale Long timer

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    Looks like I need to call him back.
    #24
  5. PSchrauber

    PSchrauber Been here awhile

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    In my personal view I would look up a complete engine and I would look for at least 250cc, if not even more.

    Why? In my experience 125cc engines are on-off throttel driven you always need rpm, it already starts when getting away, it's fun in the first run but always screaming out of the corner? ... the 175cc will do it slighly better but still lacks grunt.
    A more grunty engine is much more comfortable to ride, you can also use the bike for calm riding around without stressing others and your ears.
    If you want some chalenge go for a big pursang engine one with 360 or 370cc then you have a mans bike, where you can cruise or open the throttle so your adrinalin gauge will too increase rapidly.

    For the brakes, I would search for good Acront rims, if not available I would buy new Morad, they look very much the same. Hubs should be Grimeca Douplex drum brakes with air cooling, these will stopp the bike I believe, not as good as any disc brake but durable.

    Forks, as already mentioned the trails or trials forks would do the work if they would be stiffer, I would try to get a pair with fork clamps, straightend the stanchions, never swa a straight used dirt bike stanchions, let them be rechromed, then new and modern seals from Ariate which work miles better. Then I would mount progressive springs and adjustable pre-load fork caps which you get from Magical and use 10W to 12,5W fork oil this combo would give you a good fork that will take all these small road impacts but will be stiff enough not to sink during hard breaking.

    For the Shocks I would go for rockshocks or NJB shocks both are full rebuildable, springs and damping will be adjusted to your specs and they are light progressive and priceworthy too.

    Nothing else to add, without one exeption try to get the late Pursang engine with reeds, gives you some additional power and grunt:

    [​IMG]
    #25
  6. stainlesscycle

    stainlesscycle Long timer

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    what i was suggesting is that the bottom ends interchange with the tops - a 125 pursang can be made into a 250 with just cyl/piston/head. there are some cylinders that will not work with some bottom ends, but if you stay with pursang numbers, especially mod 134 or higher, it all works together. (you can't take a pursang top and stick it on a lobito bottom for example) the heads are easy to figure out, they are stamped.... finding a complete post 1974 pursang motor may be a little difficult - buying a bottom end, then doing the top end is usually easier in the us. there's tons of 250 cyls USUALLY available... finding 200 pursang cylinders is more challenging. you don't want a 125 top end (although you could sleeve a 125 top end to 250 quite easily) - the sleeve is so thick on the 125, they don't cool, and end up seizing very easily..



    let me know the numbers of the 175 motor, and i can tell you which cylinders work with it..
    #26
  7. PSchrauber

    PSchrauber Been here awhile

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    The interchangeability between the models, here I have only knowledge for the Sherpa models,
    The main cases, crank, of course cylinder, piston, cylinderhead and con-rod, but too the flywheel,
    the intake and so many bearings and seals between model 198, 198a 198b (250) and 199, 199a, 199b
    (350) are differnet. The 175cc Serpa model 221 from the same era like the 199 up shares the bottom
    of the model 190 (250cc). They might look the same but are not. Anyway the Pursangs might not have
    such a complex parts setup.

    Finding parts in good condition is sadly in Europe a task too and for the Pursang model much more difficult here then in the US. On the other hand we might have it easier to get Sherpa parts.:wink:

    Would be nice to read and see some outcome from the TO, belonging parts and decisions. (I know that collecting all the components will take some time).
    #27
  8. stainlesscycle

    stainlesscycle Long timer

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    i believe bultaco realized in 1975 or so, that they could not compete in the mx market, so engine development slowed down to almost nothing (aside from some port changes - and at model 192 head/gasket change), they put all their eggs in the competition trials market, which was probably smart, but were unable to downsize to 'just' a specialty trials bike maker... hence the rapid changes and improvements in the competition trials bikes. the trail bikes (alpina etc.) suffered a similar fate. they went from making quality mx bikes to quality trials bikes, seeing the niche market was their only hope....
    #28
  9. Twin-shocker

    Twin-shocker Long timer

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    No wonder the Bult MX motors didnt work that well............anything which uses the same crankcase volume for a 250 as a 125, wont run that well, and I guess primary compression ratio is going to be way off on some of the motors?
    #29
  10. stainlesscycle

    stainlesscycle Long timer

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    yeah, it was all designed around the 250. the 125 is just drastically sleeved down (THICK iron liner - cooling was the main issue). the 250 and 200's can run phenomenally well - but hard to get wide range power - can be very peaky - which is ok for street, and ok for some mx.. but not great for woods.... the 250 has a bit of grunt, not bad for a 40 year old motor.. but the sherpa s / pursang / astro were obviously designed for top end...


    there were some different heads - they are marked as to the ratio. but yeah, the crankcase volume is all the same. lotsa motors still do it that way though - for example the gasgas 200/250/300 have all the same crankcase volume, just different stroke on the 200 and different crank balnace weight.. but that's a reed motor...
    #30
  11. Twin-shocker

    Twin-shocker Long timer

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    Does the crankcase volume not affect the primary compression ratio then? Not sure whether or not the transfer port velocity might be affected if the ratio was overly high?
    #31
  12. stainlesscycle

    stainlesscycle Long timer

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    not sure if you're referring to it's effect on modern motors or on buls?

    on a modern motor with a powervalve, it's not so much an issue. the cranks are stuffed, so the crankcase volume changes become less an issue.. also the gg is shorter stroke...

    on the buls, no power valve or reed, i'm sure the primary compression ratio has an effect on the port velocity...
    #32
  13. PSchrauber

    PSchrauber Been here awhile

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    The later Sherpa engine have drilled holes in the piston an "deep vertical grooves" for additional flush, so the crankcase volume is importand.

    [​IMG]

    To determine where to drill, ... was wicked, (old piston left new one right), as the location of the grooves can
    vary between the cylinders the holes where made by hand to the specific cylinder. (the shown used piston is the original one with around 1600km, the new one is NOS with first excess). By the way the piston pin is not centered as the ultra short stroke in combination with 85mm bore tends to nod/wobbel to avoid this the pin axis is moved some mm.

    [​IMG]
    #33
  14. blaine.hale

    blaine.hale Long timer

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    I'm loving all of this information guys!
    I'm going to check out a guys lot this week to pick up an alpina with a friend. I'm going to ask him about a metralla frame and late pursang motor (he has a few bultacos laying around.)
    #34
  15. blaine.hale

    blaine.hale Long timer

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    Someone texted me this pic and is asking $200 for it. Looks like an early model Pursang, I'm thinking MK4? I know that's not the engine I want and I'm not pursuing it, but thought I'd share the whole process.

    <img src="http://dl.dropbox.com/u/25955029/0305121702.jpg" width="800" height="600"></img>
    #35
  16. PSchrauber

    PSchrauber Been here awhile

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    As there is missing the carb leaving the intake open the bike will have enginewise some corrosion problems.

    The bike will be in weight around 90 kg of metal = 10&#8364;/kg => 90&#8364; => 110$ would be my offer, if I would live near by. In my opinion too many issues, the thickness of the frametubes will be lowered by corrosion too and certainly there will be micro corrsion between weldings and the tube too, so I would not use this frame for a running bike.
    #36
  17. stainlesscycle

    stainlesscycle Long timer

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    i'd be all over that - wheels and front end is worth over 200... but as a project....it's some work. and it's not a big port motor.
    #37
  18. blaine.hale

    blaine.hale Long timer

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    Maybe it would be good trading material to work towards what I need..
    #38
  19. spo123

    spo123 Man About Town

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    Bultaco dirt bike and extra frame - $500 (South Hill Puyallup)

    <hr> Date: 2012-03-09, 7:39PM PST
    Reply to: v4gpn-2894147133@sale.craigslist.org <sup>[Errors when replying to ads?]</sup> <hr>
    Bultaco dirt bike. Needs to be restored. Bultaco road bike frame without engine. Asking $500 obo


    • Location: South Hill Puyallup
    • it's NOT ok to contact this poster with services or other commercial interests
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    PostingID: 2894147133:evil:eek1:lol3:deal
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  20. 996DL

    996DL Buell me

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    finally back in paradise...
    Poor seller probably isn't even out of bed yet, before his phone starts to ring off the hook !

    :photog:rofl

    996DL
    #40