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Bultaco M80


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17 hours ago, Frankness said:

 he said the best way to tell is by weight prototypes were heavier ...mine is very heavy ........ he could have been pulling my chain though 

Back in the days of the Model 80 Sammy Miller was doing his best to cut weight. From slightly earlier than your bike  I have seen published pictures of weigh bridge tickets done by Sammy Miller of a standard bike and his specially modified bike with a  weight reduction. At that time where Sammy led the factory followed.  Many books and magazines with pictures of works bikes from early 70’s show bikes covered with drilled holes to remove weight so weight was a known major issue. Your chap in the T shirt have been right as frames could have been beefed up to avoid breakage but I doubt it. I think your chain was thoroughly pulled..........was he laughing as you walked away?

We must remember that in the early 1970’s Spain was still under the control of Franco with many import restrictions limiting steel tube supply.  Don Morley in his book Spanish Trials Bikes refers to tales of works riders smuggling Reynold 531 tube into the factory to have special frames made. I guess if this is true this would have been in an effort to get both improved strength and weight reductions.

I still think your frame is a standard production frame which somebody has added lugs to at some time. I think the G as far as anything special is concerned is a red herring. But this is just my opinion.


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Well i'm quite happy to put my hands up and say i have no idea about prototype motorcycles  i'm a chippy not an engineer ... but i do know about design models for future manufacturing are fabricated in factories ...more often than not they try to use an existing design as a template as it costs thousands to re tool machinery ...so you pull a few off

the production line as templates ( and mark them hence the odd lettering on the head stock) then change what they need to change ... As for design in the factories i've worked in they used cheaper or end of line materials for the models (yes could be heavier or lighter) ....test the model then send it to the next department where it is used as a template 

So in my mind i think yes its possible ..But i no nothing about motorcycle manufacture ... And nothing about Spanish factories in the early 70s 

I'm still open minded ...... im going to sell it as its too heavy for me (i'm getting on now 59)  i wouldn't usually look into bikes but i know a guy who bought a Beamish for a few hundred quid turned out to be a works model ... he rebuilt it from the ground up and sold it for 20k ...just don't wanna be the guy who sold it to him ...lol

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True prototype bultacos carried the M100000 serial.  Before the purists tell me M100 was the 125 pursang please know factory protos always were labelled M1xxxx.   They could have been metrallas, pursang or anything bultaco wanted.  Most Sherpa T factory rider models were actually numbered model units taken from the assembly line and given to respective riders. Be it M80,92,133,159.  Bultaco did whatever they pleased it seems.  Vesty has many times corroborated this..... see his Facebook page and pics for evidence of this.   True factory Sherpas were carefully blueprinted well set up bikes for lampkin, vesty , soler, bulto etc etc 

The G on the headstock more than likely was used to identify what the particular tube on the frame was to be used for.   Bultaco frames were not assembled and welded at the factory.   They were all pre made at another factory away from the assembly line.  This assembly plant likely needed identifying marks to know where to place each tube in the jig for welding.  Hence the letter stamp.  I have a M27 that has the same letter on the headstock.  This isn’t coincidence. They probably did hundreds of frames a month if not thousands and each piece would need to be labelled to know it’s fitment.  


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On 20/07/2018 at 12:15 AM, lorenzo said:

Do you really believe if the factory made a prototype they would make it heavier than standard ?

No way - much more likely the extra lugs were added by a previous owner  for sidecar use. The early frames are very heavy anyway owing to the quality of tubing used. I've heard this referred to as "gas pipe" and the like by knockers, but it was all that was available to the factory at the time.


My M80 frame has 4mm thick gusset plates and the frame tube walls are 2 mm thickness. But it’s not gas pipe or water pipe or conduit tubing either. How do I know, because one of the previous owners must have used the bike in a rock breaking trial and flattened the bottom frame tubes, so I cut them off and made replacements using 1.5 mm seamless tube. It’s still a heavy frame though! ??

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On 07/07/2018 at 11:15 PM, Frankness said:

Yes thats a possibillity but i have a letter of authenticity from bultaco written in 94 confirming its a 1972 250 sherpa and those lower brackets were factory welds they are too uniform for after market do it yourself  ..could be a production line mistake i suppose ..or a design team prototype hence the letter G stamped on the frame ??

My M80  frame number is about 30 numbers before your’s and the reg document states 1972 so we can accept that year as true?

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From having had in my possession an ex ISDT Triumph a long time ago now, I can say that from a conversation that I had with Roy Peplow I learned this. There were 5 bikes specially built, frame number one was EXP 01 and this was the jig original. This stayed by the jig for assembly and fittings to be added or modified, the design buck in other words, it was not for use as a finished machine. EXP 02 was the build frame from which 3 more bikes were produced, EXP 03, 04 and 05. Roy was able to also inform me who had which bike, that they were all 500cc or there abouts and had Police spec exhaust cams. On the road they would all manage 100mph ( brave). He then told me he could remember all of this easily as he had all the details in a little black pocket book. At the time I was more interested in selling the bike having just put the bike through the workshop ( I took it in p/x as a non runner in bits against a new bike) as I was a bike dealer then, even the man himself Sammy Miller had a ride on said EXP 05 the bike in my possession. Having travelled a fair distance with the bike in my pick up all the way to Mr. Millers place in Hants, he confixrmed it as a factory bike but wouldn’t pay the price I was looking for so I returned to my shop and sold it the next week for £1200 (1979 prices). If only I knew where it was now? I add this factual story as an indication as to how a manufacturer might number their ‘specials’ . 

Edited by section swept
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  • 3 months later...
On 7/21/2018 at 7:50 AM, stevem75 said:

The G on the headstock more than likely was used to identify what the particular tube on the frame was to be used for.

 I've two M80 frames, one is stamped G and the other is stamped with a number 3. From my own manufacturing experience I used to think they might have been an inspectors stamp but your idea may well be more plausible Stevem75.



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