I just rode the National in Colorado in the Vintage Twinshock class on a 1976 Cota 348. The old Michilen was splitting cross wise on the knobs about 1/3 of the tire. So about 12 really bad cracks. I cleaned 28 of 36 sections. New tires are over rated.
= super skills and a twinshock Bou? Sorry for winding up but it was so obvious.
It really depends to the underground and yes in classic trials it doesn't matters so much, the radial tires came first in the beginning 80's and were firstly only available for works riders. With the TY mono the new Michelin radial tire was available for the public in W and S version, these tires changed the riding style completly in trials.
W = winter = temp. under 17°C
S = summer = temp. over 17°C
Anyway the benefits between a very good or a decent trials tire when new are also obvious on a twin shock bike the way the carcasse is build (diagonal or radial inforcement makes a huge difference) and what rubber mixture is used really makes a difference.
Still 75% is up to the rider and with a tire that sticks more to ground even on slippery and wet surfaces gives you more confidence.
I haven't tried out to ride with too little air pressure in doubt I use a tad more a puncture is something I really don't need as I' am very bad in working with tires take them off and on again...
Nevertheless I believe it is possible to ride which less air in a tubeless tire then in a tube tire. There is less risk the rip of the valve. But there is to both type of tires the rust the tire will leave the rim bead more then it's harmless.
Depens to so many factors where you have ridden, have you done some road riding with the bike, age.
I recently changed the tires for the SWM they where mounted in 2012. The edges were pretty well rounded and there were too some deep cuts too. Then the knobbies of the tire had some wear in highness too due to some road riding. But mostly the tire got stiffer compared to a new one I had mounted to another bike and in fact the newer tire did stick better on nearly every ground. Interesting on grass there was no difference as you mentioned. But sand, stones and logs were significant better to travel with the new tires. To mount them "in other direction" I did not test as the in rear stiffnes was my personal reason to change.
I was uncertain the 11teeth is so small compared to the original mounted 13teeth I believe it is that impression and the fact that the swing arm axle is mounted high so the upper part of the chain climbs a bit up rests on the the chain guide and then travels down to the sprocket.
When you have mounted a 13 front and 42 at the rear it does not happen.
I can only refer to classic Trials, to the fees for entrys:
The fee is around 15 - 25 € per event, it's in first hand for the insurance and second first-aid/rescue team with ambulance truck. Both is mandantory for trials events.
For nationals you need additional too a licence which is between 10 - 50€ depending age and membership to motorsport associations.
For non clubmembers for riding on our trials- trail- and training area there is a fee which is 10 € per day, additional you have to sign a liability waiver to the Club too to wear safty equipment and follow the environmental rules.
A press release at the local press is what my club do, it does attract people to come by and look at the trials not many that never had been in touch with trials but a few and these that came once do come then frequently or sign up too. We also did an article from the trials, now the local press send a reporter too.
When reading your posted numbers the engine should be from a model 199A this model should not have rails under the engine just the bash plate. The frame as you mentioned has rails so the question is what you have for a frame.
As the bike was used with a sidecar it can be possible that the rails or tubes were welded additional to the frame to reinforce it.
The frame number should be located at the steering stem of the frame towards more to the right in driving direction. You might look there, with thick additional paint applied the numbers might be covered. You can use paint stripper to the steering stem tube to take off the layers of paint for getting probably a view to the number.
As the previous poster mentioned some photos from the former sidecar frame would be great, too from the other frame and you engine this which might clarify doubts.
I personal would still try to get matching engine and frame assembled together if they are truly the same and if the salvage isn't too expensive. Straightening the frame does need some time and skills.
Dell'Orto as all my other bikes are using them (SWM, KTM, Beta and Aprilia), best available collection of jets and needles, floats and valves also easy to mount. The Bing is nice but the bikes are using far more gasoline with this carb the Bing is also not so easy tune to the engine needs.
The frame is very different to twinshock bikes the wheelbase for example is very short. The bike has too a lot of steering angle I would compare it ridewise to the Beta TR 34 in geometrics.
The seat position is high and a bit old school in this matter Betas, Fantics and even Montesas of that era where lower. The engine is the same as in the SWM 320 model even equipped with a heavy rotor, but no extra weight on the left side so more lively. The carb is the Mikuni clone from Dell'Orto with a idle nozzle jet and an air screw instead a mixture screw. Beside this the clutch mechanism is enhanced a lot. Last but not least the exhaust is different offering a much lower noise and the rear muffler allows easier airflow. The behavior is still Rotax in every aspect but much quicker throttle response.
We have an air cooled mono bike class so it can be ridden there. With the old fashion seat high, the low noise and the large capacity of the petrol tank you can too use it (in my opinion) very well for Motoalpinismo. Which will be the main purpose of use in future.
It's a nice bike, the color design is unique like Italian blueberry and strawberry ice cream. I know getting parts have become difficult, and it's an one off batch, just build in 1988, the former TX 311 is different and the later Climber too. But they are smooth to ride, it's very quiet, the suspension is very good too. I just did a spin again today with my new aquistion after getting some things sorted not all.
Standard Domino grips sold and mounted on trialsbikes for decades are the best in my experience and I tried out a lot. In my experience:
Fancy colors get dirty,
Groove structures feels uncomfortable,
Too fine structures are attracting dirt thus difficult to clean, they are too not very grippy.
Super soft grips are not my fashion as super hard ones. As softer the grip as easier they will come off while super hard ones are not so comfortable.
All in all to the stated pros and cons my personal conclusion and choose are the standard Dominos they do last very long have the right grip are still soft but hard in once. They are even easy to install a bit of WD40 or brake cleaner inside the grip hole and on the bar end then a quick push while turning and that's it. You have to wait a day until all the cleaner fluid has evaporated.
Another thing to consider they are price worthy too.
You might get a donor engine case in any case a new disc.
I wouldn't try using knead metal JB-weld or similar stuff as through vibration a part of the repaired spots can get loose and the output would be similar to what you have now.
Engines do show up here and there ask the community here look at LeBonCoin in France, Kiiji and Subito in Italy. (Had a likewise problem with my TR so needed too the basement which I found for good price in Italy).
Well... while the sticker tells me the car / engine combination was build in Germany, the music tells me that this car was made in former east Germany.
Anyway these radial engine need much space (beside for an air plane).
The Finnish Navy uses speed boats with radial engines.
I personal like these Lanz Bulldog 20liter one cylinder tractors a lot never thought an engine can run so slowly and still being so strong without having any hp to mention about.
You might again take a very close look to the bottom screw that holds the bowl and the main jet.
The hollow inside the bolt or screw is wider then the thread hole for the main jet the bottom to of the hollow is the deepest spot of the carb inside there can have been collected a bit of crud with the time that can be collected by the gas flow and provide a clogged jet.
I would too unscrew the mixture screw and give the inside a good clean flush with carb cleaner and compressed air. The small O-ring might be insufficient too.
Any other channel of the carb and the bowl (there is one too) I would give too a good flush with cleaner and compressed air.
It's often just small thingies that can change the behavior a lot ...
but the appearance ... well ... there is room for improvement 
Bultaco198A "help"
in Bultaco
Posted · Edited by pschrauber
Sounds to me you did all things right.
There is one thing I would like to be checked as it is an old bike.
How is fuel supply. I never had a used bike where the petcock wasn't somehow clogged. It would too explain the "uneven" running.