Transplant Or Not?

[turbohead]

Dear all,

 

I have just found an Aprilia TXR312 from ’88, used for competition for the first 5 years or so, then stored (or forgotten) for most of the 25 years until today. Is that Rotax engine an easy transplant to an early (1981) SWM 320? 

 

If so, is such a transplant OK and within the spirit of modern twinshock rules, like electronic ignition, modern fork internals and so on…? 

 

Or should this Aprilia better be stored for another couple of years, waiting for the hype of early air-cooled monoshock bikes …?

 

Please, tell me what you think of all this!

 

BTW, after draining the tank and transmission, giving it a little fresh pre-mix and transmission oil, the Aprilia started second kick. Good runner with minimal bad noise, excellent clutch, gearbox and general behavior. Couldn’t resist a quick run over the rocks behind my workshop, returning smiling like a child. 

[baldilocks]

If you do swap the engine over you won't be the first person to do so. Lots of people fit the clutch cover as well

[pschrauber]

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.

 

 

 

Edited June 13, 2016 by pschrauber

[gasgas249uk]

That looks gorgeous. Very very nice and unmolested. Enjoy

[nigel dabster]

it would be cheating to ride it as a twinshock in competition. Will the carb fit ok in an swm frame?

[pschrauber]

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.

Edited June 14, 2016 by pschrauber

[metisse]

The poster stated he was looking to use the engine only in a early SWM rolling chassis.  I imagine most of these Aprillia's are having the clutch harvested to try and make an original SWM less tiresome, and this maybe some of the reason for doing it in this case.  I will let more informed poster's and SWM followers pass comment or not... to whether this is an acceptable, in the spirit of twinshock,  mod.  I have fitted later jumbo forks to mine, but decided to leave the clutch casing alone, and persevere with the original. I too would keep it intact to ride in the appropriate class. 

 Out of interest bikes,  with engines from... 307/309 Fantic, Honda Rtl, and dare I say it Majesties or copies with Mono Ty engines accepted still in the Twinshock class in the Uk .  Here in France they are no longer able to ride if inserted in to twinshock frames and they have died a very sudden death with the aircooled mono class starting albiet slowly.

 

[nigel dabster]

mono engines are not acceptable afaik in any uk twinshock class its cheating isnt it?

[b40rt]

Oh god, here we go again.

[turbohead]

Interesting to read your comments, I very much appreciate your views. Thank you all!

 

 

However, from a personal point of view, I have decided to go the mild cheating way. One of my TLs is going to get the TXR engine, at least while I rebuild the old one (the rest of the Aprilia will be left alone, waiting for a proper mono class or something). At the same time, that TL will get repositioned footrests, HFS inserts for the front forks, Powerdynamo electronic ignition, modified exhaust system, Öhlins modified shocks, steeper head angle and so on, but no new paint or plastics to be sure to not disturb every true, no-cheating SWM rider out there. As I return to trials after decades riding enduro, I am keen to keep a low profile, just learning again to keep my feet up as good as I can...