Build a Bultaco TSS from scratch

[PSchrauber]

I just got two little parts again for my Bultaco project, when trying out if they fit this reminded me on your task building a TSS from scratch. Now after around 14 month my rebuilding is going on, just small parts here and there are missing, (but these details makes the rebuild first complete in my eyes). ...

Anyway as it is a real sport bike too your task rebuilding a TSS from sratch came again in my mind.

How original do you want to go with the rebuild?

There is the frame, then the engine, but in my personal view also very important are the brakes.
Going fast is all about acclerating and braking so where do you want to go in terms of braking?

The original standard Bultaco brakes work as long as the chrome plating stays inside the hub.
If so they work good for trials machine as long it's dry, maybe for dirt bikes too but for a racer a no go.

Then the suspension here the fork and rear shocks, standard Betors from a Alpina or Sherpa models might be to soft, MX to long and standard road forks (...well do theses for street bikes really work ...?) (May be I'am just spoilt when it comes to suspension, but brakes this is as important as a good working motor)

Do you have any kind of porposive idea befor I start any bla bla bla?

[stainlesscycle]

Originally Posted by darmst6829

For the motor Bultaco made a 125cc that had a geared primary drive.
Dave

that's a one year only motor, primary kick and all. hard to come by afaik...

[PSchrauber]

As the OP haven't shown up my bla bla bla statement follows as already mentioned..

I'am not keen in building a TSS street racer from scratch but I believe this project will take a long time until you will find all pieces you need and then the inset of money, ...

Why not build a hybrid, using as many Bultaco parts you can get for a priceworthy amount and add newer components where you can't get these rare like hens teeth and there weight in gold worth pieces. This Butaco
will certainly make likewise much fun then a TSS I believe, (it was posted here a couple of months / years ago I believe):



There are some parts where I would take other materials like the fenders, the forks and the black rims are in my view discussable, but the remaining rest i just fantastic!

[blaine.hale]

Originally Posted by PSchrauber

I just got two little parts again for my Bultaco project, when trying out if they fit this reminded me on your task building a TSS from scratch. Now after around 14 month my rebuilding is going on, just small parts here and there are missing, (but these details makes the rebuild first complete in my eyes). ...

Anyway as it is a real sport bike too your task rebuilding a TSS from sratch came again in my mind.

How original do you want to go with the rebuild?

There is the frame, then the engine, but in my personal view also very important are the brakes.
Going fast is all about acclerating and braking so where do you want to go in terms of braking?

The original standard Bultaco brakes work as long as the chrome plating stays inside the hub.
If so they work good for trials machine as long it's dry, maybe for dirt bikes too but for a racer a no go.

Then the suspension here the fork and rear shocks, standard Betors from a Alpina or Sherpa models might be to soft, MX to long and standard road forks (...well do theses for street bikes really work ...?) (May be I'am just spoilt when it comes to suspension, but brakes this is as important as a good working motor)

Do you have any kind of porposive idea befor I start any bla bla bla?

Now we're getting to the right questions!
The frame and engine were the first points I wanted to tackle with being "original." Those will stay as they are.
I'm really up in the air as to update the other components or not. The logic in me says yes, the rest of me says "No! only period pieces!"
I honestly would like to ride it as they rode in the 60s and 70s. Really it's dependent upon what is the right price with the least amount of modification. Which, the above, leads me to the original pieces as they're all pretty ambiguous with what bikes they can fit on in the Bultaco line up, require little to know modification and I can source those bits from a local horder pretty easily.
So I guess the answer there is original parts haha. That leads me to what is the best in the category. Logic dictates that I'd want some beefier dirtbike forks...so which from their line up would be best? What also had their best drum brakes?
Clip-ons and such are negligible to me. It's all about frame, engine, brakes and suspension in keep original.

[blaine.hale]

Originally Posted by PSchrauber

As the OP haven't shown up my bla bla bla statement follows as already mentioned..

I'am not keen in building a TSS street racer from scratch but I believe this project will take a long time until you will find all pieces you need and then the inset of money, ...

Why not build a hybrid, using as many Bultaco parts you can get for a priceworthy amount and add newer components where you can't get these rare like hens teeth and there weight in gold worth pieces. This Butaco
will certainly make likewise much fun then a TSS I believe, (it was posted here a couple of months / years ago I believe):



There are some parts where I would take other materials like the fenders, the forks and the black rims are in my view discussable, but the remaining rest i just fantastic!

See, now thats got my other side of the argument thinking. I hate you, sir.

But really....keep up with these ideas.

** I sold my laptop yesterday to build another desktop so I haven't been on to keep up the research and responding heh.

[jbcaddy]

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)

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Date: 2012-02-25, 8:07PM PST
Reply to: vbrnc-2871280364@sale.craigslist.org ^{[Errors when replying to ads?]}

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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

• Location: Chico/Oroville
• it's NOT ok to contact this poster with services or other commercial

[blaine.hale]

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

[stainlesscycle]

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?

[blaine.hale]

Originally Posted by stainlesscycle

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?

Looks like I need to call him back.

[PSchrauber]

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:

[stainlesscycle]

Originally Posted by PSchrauber

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.

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..

[PSchrauber]

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.

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).

[stainlesscycle]

Originally Posted by PSchrauber

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.
.

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....

[Twin-shocker]

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?

[stainlesscycle]

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...