This is the generation that catches people out. The body still looks like a GS. The headlight is now round, with a lip underneath, and the temperature gauge is digital. Under the engine covers it might be the old Rotax 123 or the newer Rotax 122. Parts for one are not parts for the other.

Two engines, one shape

The brief is specific. Italy switched to the MP and the Rotax 122 from 1995. Most of Europe and the UK stayed with the Rotax 123 until about 1997–98. A 1998 plate can be either. Registration year is not an engine identity.

On a 123, look for “Rotax 123” cast at the left rear by the engine number, a Dell’Orto VHSB 34 and SEM ignition. On a 122, look for “Rotax 122” cast on top of the left crankcase by the cylinder, and a Dell’Orto PHBH 28. From the MP model on, the plate should start ZD4, with the model code in positions 4–5 and the year letter in position 10. W is 1998 in the brief’s table. A frame number that starts GS is still a GS, even if the headlight is the later round one. The brief files “late GS” in this generation.

Open power is given as around 22 kW. MPA0 is 11 kW. MPA1 is 5 kW and is tied to an 80 km/h figure. UK bikes were often sold at 15 bhp. Those are three different statements in the sources. This site does not collapse them into one kit of parts. To verify on the bike whether you have a powervalve blade or a blanking plate, and which code is actually stamped.

1998 liveries

The 1998 Valentino Rossi replica is a documented livery. rs125.it and Decalmoto list it. An Italian-market bike of that year is likely a Rotax 122 and a PHBH 28, because Italy moved to the 122 in 1995. That is a likelihood from the market change, and the brief marks it To verify on the casting. An MP VIN should start ZD4MP and carry W in position 10. Italian spec may be the open bike, around 22 kW, which is not learner-legal at full power. A bike of that age that has not been UK-registered follows the brief’s import path: NOVA, then a V55/5 with the type-approval exemption, not an MSVA test.

A 1998 Chesterfield is not a scheme the sources list. Chesterfield is the 1994 Extrema, Biaggi Chesterfield is 1995–96, and Chesterfield returns on the 1999–2005 bee-tail. To verify whether a bike in those colours was built in another year and first registered in 1998, or whether it has been rebodied. The engine could be a GS with a Rotax 123 and a VHSB 34, or an MP with a Rotax 122. A frame number starting GS means a GS. UK bikes of this era were often sold restricted to 15 bhp. A bike already registered in the UK uses a normal MOT and V5C.

Clocks and parts

Old clocks fail, and there is no torque figure or part number here for a replacement. The 123 parts problem from the Extrema carries forward for any bike in this generation that is still a 123. A 122 is easier to feed, but only if you stop buying 123 gaskets for it.

Liveries

Biaggi Chesterfield (1995–96), Romboni (1996, one source), Racing Silver (1996–97), Harada (1998, continuing to 2000) and the Valentino Rossi replica (1998, continuing into 1999 on the next body). Replica means decals. The bike underneath is the standard code of that year.