Broken Cota frame

[keychange]

Thanks Joe - called one and they said they didn't want to do it if it is chrome molly - they said use tig . I'll try Cameron Scott - he has a 247 and he should know.

[FM350]

No production Spanish TS frame was made using crom-moly tube. To check this for sure then see if yours was originally TIG or bronze welded, and if it was then repairs will need to be carried out the same way.

I would guess your frame has broken due to a combination of "cold" MIG welds, which have not penetrated the engine mount plates fully, and very possibly slight cracking which has been caused by loose motor mount bolts?

To repair you will need to find someone who is good with a MIG set (anyone who says your frame is chrom-moly, either doesnt know what they are doing or doesnt want the work!), and after the tubes have been brought back into the right position, welded together ensuring a proper full penetration weld. Other than cleaning off the paint there is no real need to prep the tube, as its thin enough to easily be welded with a 200A set without this.

The 100% correct way to do this job, is to put the frame into a jig, remove the broken down tube entirely and replace it with one made from similar tube (I would guess heavy gauge ERW). Cost of doing that unless you can do it yourself though is probably not going to be far from getting another bike for spares and using the frame from that.

[keychange]

Spoke to Cameron Scott last night, Cameron and his wife Erica host the CamCota trial near Coffs Harbour and they operate Camesco Fabrications. Thankfully Cameron owns an old Cota and is very familiar with them and I can also testify from past experience that he is a wiz with a welder so I am really confident I am in safe hands. I will remove the powder coat, rig up a turnbuckle/s and chain jig to pull it together and then trot it down the mountain for surgery.

I will post a completed pic when all done - thanks for input.

[sherpa]

Sherpa T's came with Chrome-moly frames from about 1972/73 onwards [midway through the model 91/92 run]
These frames are much lighter than the earlier frames and have much thinner tubing.
Cheers Greg

[keychange]

Yes and I think the 1974 Cota comes with a "lighter frame" so not sure if the CrMo but it could be

[sherpa]

Yes I am not as sure about cotas but I think the Ulf Karlson 247, black frame and upgraded cases was the first of the chrome moly 'lighter' frames. I can recall many 348's and early 349's cracking frames, mainly in the headstock area

[FM350]

Sherpa T's came with Chrome-moly frames from about 1972/73 onwards [midway through the model 91/92 run]
These frames are much lighter than the earlier frames and have much thinner tubing.
Cheers Greg

I have an M158 frame, but it seems to made out of roughly MIG welded ERW tube. I would guess that in actual fact the later Spanish frames were made out of thinner (and cheaper) ERW tube rather than heavy gas pipe used on the early ones, which reduced the weight a little but also increased the chances of problems like the OP has, that also effected the very last 340 Bults made in the early 80s. If a frame is TIG or bronze welded then it may be CM or CM/ERW (Miller frames), but if its MIG welded its certainly not CM, as this welding process will mean that the chances of cracking are increased maybe 200%.

[Bully fanatic]

The M158 Bultaco frames were an abomination. The 158`s were made really cheaply and had really thin low quality steel frames. All of the 158`s I have seen have all been turning into choppers as the headstock bends outwards. They did this in the seventies and they still do it now if they are used. Graham.

[FM350]

Personally I have yet to see any Spanish frame that is that great! Poor design using cheap materials never tends to work that well, but in terms of function the earlier Spanish frames made out of heavy gauge gas pipe, seemed a lot less prone to breakages? With better basic design though there is no good reason why cheap materials shouldnt work fine for trials use, and frame breakages on bikes like Fantic, Honda, Yamaha are very rare, even though these bikes are also made using cheap ERW tubes.

[brownie]

Definitely no internal ERW seam in my M183 chromoly frame
Bultaco can still proudly stand by their reputation as being the best trials bikes made in their time