My "stock" NSR
And here it is, a 1990 JC20 model, sold as brand new in 1991 and now mine with some 7800 Km.
It is rated at 12 PS and I get it up to about 140 Km/h.
It drives ok but there are some things I don't like:
- The original colors are pale from the years and the sun.
- The bike collapsed once from the stand and the left side of the fairing has a big break.
- The motor performance is poor (due to regulatory restrictions).
- The fork is too easy and dives too much.
First of all I made an inventory of all parts actually in use:
- Ignition CI-598B
- Exhaust Valve Control TV-78
- Carburettor Dell'Orto PHBH-28, jetted 132/70/52
- Chain and gears looks pretty used
- Fork seals are drown
- Brake Pads have some 2 mm last
- Reeds are original glass-fiber
- Restricted exhaust
- No restriction plate in the inlet
And this is the result after the inventory...
The 12 PS restriction is done mainly by the combination of CDI and exhaust.
Looking around in the Internet (Thank you Geneva-Racing) I found that the ideal Ignition would be the CI-572 usually built into UK bikes.
The TV-78 is already ok as it fully opens the exhaust valves.
The 28 round-slide carburettor could still be used and would give a strong midrange power but it will lack of top power.
A 32 or 34 flat-slide would be better.
- The difference between round and flat-slides carburettors it that the flat-slide creates less air turbulences as it has flat walls.
The round-slide has curved walls (for the slide piston) disturbing the flow and at half-open throttle turbulences are created
by the air flowing under the flat bottom of the round piston.
Most of the flat-slide carburettors have an oval shaped bore and are therefore taller then round-slides
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