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Bultaco Alpina design changes


jimg
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On 18/7/2017 at 6:08 PM, jimg said:

I need to know any (if any) basic design changes of the Bultaco 350 Alpina years 1974 to 1975, 1975 to 1976 and 1976 to 1977.  I do know in 1975, the brake and shifter was moved to the right and left, respectively.  Primarily, I need to know design changes regarding these items: Suspension (travel length) on front and rear, rear suspension mounting points, frame changes (including any engine mounting point changes) and swingarm changes. 

I may need to buy Haynes manuals for each year to get detailed specifics (part numbers), but any help from you will greatly be appreciated.  Thanks. 

  

Out of curiosity, can I ask why you need such a large amount of information? Are you restoring multiple Alpinas or writing a thesis on Bultaco Alpina frame geometry ?

Edited by model80
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4 hours ago, model80 said:

Out of curiosity, can I ask why you need such a large amount of information? Are you restoring multiple Alpinas or writing a thesis on Bultaco Alpina frame geometry ?

Yeh, I wondered something like that too.

For what it's worth, I've had a go at summarizing the changes that I've gleaned over the years:

Alpina changes

M85 – near identical to M80 Sherpa, but with Matador gear ratios, longer seat & larger tank. One-piece tank/seat unit. Airbox under seat a la Sherpa. Full width 125mm dia front hub , mud-catcher alloy rims, round barrel & head, bolt-on footpegs, 2-piece header & midbox, triangular rear muffler. Single gusset at steering head (on centreline of tubes). Tapered fork-tubes (at top triple clamp). Alloy top triple, steel bottom, with built-in angular offset (a la Sherpa). Some had high-mounted front guard (early?), some low-mounted (late?). Late ones had recessed swingarm pivot (like early M91/2 Sherpa) & weld-on footpegs & the swingarm was slightly diff to match the recessed pivot. Not sure if they used the longer Pursang footpegs or shorter Sherpa pegs.

M99 – 325 version with square barrel & head, 60mm stroke.

M115/116 – extra frame tubes above swingarm pivot (like late M91/92 Sherpa). Frame seemed lighter, perhaps thinner gauge but still mild steel. Top shock mount moved rear-ward (on bracket behind the rear frame tube). New tank-seat unit. Airbox on right side (somewhat like M107 SD Matador) under removable cover. Angled/offset inlet manifold. Conical 140mm front brake, chrome-lined. Stepped gusset at swingarm pivot a la late M91/2 Sherpa. Pursang alloy triples & non-tapered fork-tubes to suit. No angular offset in triples (which is why these & later Alpina’s steer so differently to Sherpa’s) with 20mm less overall offset. Shorter wheelbase. Shoulder-less alloy rims. Dual gusset (folded over) at steering head. New longer seat; slightly new colour scheme. On these models the rear central-downtube was recessed for the swingarm pivot (like the equivalent model Sherpa) which I believe enabled the engine to be mounted about 15mm further back. I’m lead to believe the fork-tubes are longer than Sherpa ones too but not sure when this occurred. 350 engine had 64mm stroke, bigger crank (wider and larger dia), different crankcases to suit & diff stud spacing from earlier 325 engine (if I recall correctly).

M137/138 – much lighter Cro-mo frame, said to be 8 lbs lighter; very thin gauge which fractured everywhere, despite extra gussets/tubes under the airbox. Left side shifter, right side brake, Mk8 pursing rear hub (chrome-lined), one-piece header/mid-box, boomerang/clubfoot rear silencer, sidestand attached to swingarm (instead of frame), new swingarm (20mm longer?) with what appears to be lugs for passenger pegs. Longer wheelbase, more ground clearance. New clutch cover. My 137 engine has square barrel & head & duplex primary drive.

Later models (165/6, 187/8 & 212/3) had completely different frames, swingarms, tanks, shocks etc to the earlier Alpina’s, with rear engine mount bracket hung from swingarm pivot. These are similar frames to the 158/9 Sherpa’s and very different bikes to the early Alpina’s. Forks, triples & wheels look to be about the only things in common with earlier Alpina’s. They were said to have gone back closer to the Sherpa, but maintained the Pursang triples & Matador/Frontera gear ratios. M165 & 187 250 models appear to have the shorter 158 style Sherpa frame, with wheelbase specified as 50”, whereas 166, 188, & 212/213 models have the longer 159 style frame, with wheelbase specified as 51.6”.

 

Bultaco brains trust, feel free to correct it where required

Edited by jc2
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Further to JC2,

Fuel tank cap for 115/116 is push-in while 137/138 is screw-in cap

137/138 frame has different headstock gusseting to 115/116. 137/138 has very thin gussets without folds

Some 137/138 have same rear hub as 115/116

Some 137/138 have left side rear brake pedal

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Great information jc2.  No thesis...My need to identify design changes from the 115/116 Alpina and later models are because I'm going to race an Alpina big bore in vintage harescrambles.  The rules to qualify as a vintage bike is the bike need to be a 1974 or older bike.   But, "Like Design" bikes are allowed into the vintage class if one can provide evidence that a post 1974 manufactured bike is "Like Designed" as related to that specific bike model.  A Like Design bike is a bike where the suspension travel, suspension mounting points, engine mounting points, frame material, and frame and swing arm are of "Like Design" and there is no performance advantage.  "Problem" with Bultaco, and I assume other bike manufacturers of this era, is the bikes model number may extend through several years and may also have design changes within the same model number.  So, why don't I just get an Alpina that is 1974 or older?....well....They are hard to find here in the States and I'm trying to open up my options of available bikes.  So, lets say I find a model 188, good shape, good price, etc., I would need to provide "evidence" that the model 188 is a "Like Design" bike to a model 138 (which according to several sources, the model 137/138 was an available bike in 1974 (September).   From all the great reply's on this topic, is looking like any model after the 137/138 would not qualify :-(

  

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  • 2 years later...

Hi have 85 and 213  definally different , . I personally like 213 , it cost more to restore . Harder to find parts , I just found a short block . After a few years ,

I blown original ,, worn engine , it’s on my list ,, 85  was a deal to purchase engine little worn ,, rod loose , found another no problem , , frames are different in weight and balance 

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