Honda NSR 125 R Alcast JC20 (1990 to 1992) Specs and Info

NSR125 JC20

Used parts available from a Honda NSR 125R Alcast (JC20)…….

NSR 125 Alcast

A little bit about the Honda NSR125R Alcast………

Bike manufacturer: Honda
Bike model: NSR 125 R Alcast

Honda model code: JC20
Years (in the UK): 1990 to 1992

Frame number: Started – JC20-0—–

Dates, models and updates:

NSR125 R-K (March 1990 to March 1991) – Alloy Alcast frame lightweight sports bike. Single rear shock (monoshock). 17 Inch, 3 spoke wheels. Bean can style exhaust silencers. Full fairing with twin round headlights. Front and rear disc brake. Available in red, white and blue colour scheme.

NSR125 R-L (April 1991 to December 1991) – Same as R-K model but now has six spoke wheels (instead of 3 spoke), new front mudguard and also now has a race plate graphic on the tail piece. Available colours: red, white and blue or black, purple and green.
NSR125 R-M (January 1992 to April 1992) – No changes

NSR125 R-N (May 1992 to December 1992) – Now available in black and grey

Please Note regarding above dates and models:
There were LOADS of grey import Honda NSR125R’s many of which were registered at different times to the official UK release dates.

Frame: Honda Alcast frame. 2 Piece die cast aluminium (alloy) frame (bolted together) made by Grimeca

Engine type: 2 stroke, single cylinder (water cooled)
Engine power: 12 bhp (UK model)
Engine size: 124.8 cc
Bore x stroke: 54 x 54.5mm
Engine Cooling: Liquid/water cooled
Other engine stuff: Honda RC-Valve equipped (Revolution Control valve)

Fuel system
Fuel: Unleaded petrol
Fuel tank capacity: 13 litres
Fuel system: Carburetor (Dellorto)

Gearbox, clutch and final drive
Transmission: 6 speed
Gearbox Oil: Scooter gear oil
Clutch: Wet, multi plate clutch
Final drive: chain drive

Ignition, Electrics and Starter
Ignition: Electronic CDI
Starter: Electric and kick start
Battery: YTX5L-BS / CTX5L-BS / DTX5L-BS

Weight ‘n Measures
Dry weight: 130 kg

Wheel base: 1,350mm

Wheels and Tyres
Front wheel:
Rear wheel:
Front tyre: 100/80-17 (tubeless tyre)
Rear tyre: 130/70-17 (tubeless tyre)

Suspension and Brakes
Rear suspension: Single rear shock absorber (Honda Pro-Link mono shock)
Front brake: 2 Piston Grimeca single disc and caliper (hydraulic brake)
Rear brake: 1 Piston Grimeca single disc and caliper (hydraulic brake)

Useless stuff…….
Designed and assembled by Honda Italy (Honda Italia Industriale S.P.A).
The Honda NSR125R was a fully faired version of the Honda NSR125F naked bike.
The UK versions of the Honda NSR125-R were restricted to 12bhp but many of the grey import bikes were unrestricted.
The NSR 125-R uses a similar engine to the Honda NSR125-R JC22 (Foxeye model) and the MTX 125.
The ‘NSR’ part of the Honda NSR125R comes from Honda successful
NSR 500 GP bike.
The NSR 125 JC20 used Honda’s RC Valve (Revolution Control valve) which monitors the engines RPM and opens and closes a 2 blade exhaust valve. The RC valve was controlled by an electric servo motor.

Buying advice:
Hell, where to start! Unfortunately, as with most bikes that were made by Honda Italy, the NSR125R does have a few ‘built in’ gremlins…….
The starter motors were prone to failure due to them being mounted on the front of the engine (where they collected all the dirt from the front wheel!).
The RC valve system can be problematic, usually either due to the control box being faulty or the servo playing up (or both!).
Electrics and wiring were never great on these bikes either.
There were also subtle changes between all the NSR125’s manufactured for different countries, which can make sourcing spare parts a bit of a problem!
If your buying one, buy it cheap and have a back up bike if your planning on using it for getting to work ever day.

’90 to ’93 Honda NSR125-R JC20 Spares

Sources/Thanks to:
Wiki article about the NSR125

20 thoughts on “Honda NSR 125 R Alcast JC20 (1990 to 1992) Specs and Info”

  1. bought one myself talk about a project, spent 500quid doigher up. Great going bike flat out I’m doing 120mph not many up to date bikes can keep up with it, not bad for a 125, just need 1 thing and I’ve looked everywhere! Does anyone know where I can get a full set of decent fairings, wouldn’t mind a New set but I would consider an old set belongs they ain’t to badly damaged email me if you do thanks!

  2. i hope sum1 can help me im trying to find the spec of my bike it is an nsr 125 fn jap import but there are no specs listed b4 1990 im also told it was shipped to italy and raced but i av no idea wether thats true or not. ive also been told its 33bhp but ppl r now saying thats unlikly so how or where do i find out this info please help if any1 can

    1. If yours is a JC20 model (made between 1988 and 1994), it was designed and made by Honda Italy (Honda Italia Industriale S.P.A).
      Unfortunately, your particular bikes history (whether it was raced or not etc) is only likely to be known by the previous owners, so check any paperwork you have with the bike.
      You can also look for signs the bike was raced (drilled nuts and bolts for lock wire etc).
      I think the non UK NSR’s were around 26bhp, so unless it’s been heavily tuned it might not be 33bhp?
      The only way you’ll find out what the BHP is for sure would be to run it up on a Dyno…

      1. yeah it is the jc20 model and thanx av been told to run it on a dyno also if you know of this the lettering says its an fn on frame and logbook but when ive tried to insure it theyve never heard of one and tell me its an rk am i cracking up

        1. Are you sure it’s an NSR125 (not an NS125 F)? If your frame number starts JC20-020 the bike will be an NSR125R, if it starts with JC20-000 it will be an NSR125F and if it starts with HI-TC01- it might be an NS125?

    2. My Honda Italia 125 outed out 33bhp as they are unrestricted. And fully power valved. This is acording to a web sight I came across while checking what best plug to put in.

  3. I own a Honda NSR 125 JC20 1990, Importet from Italy used in Germany and brought it with me to the UK.
    I own this bike now 6 Years its my baby, it is more reliable than my Ford KA was …
    Since 1990 it only gets filled with Castrol Oil, Castrol Gear oil and Castrol coolant, if you look properly after these machines they will run forever !!
    I dont kow shit about mechanical stuff but i can take the whole NSR apart and assemble it back together even in pitch dark with my headlight ๐Ÿ™‚
    You will outrun any 125 ( Apr RS might keep up but thats it)on the road and easily keep up with big bikes on corners.
    And there is nothing better than the smell( and sound :P) of an oยดl 2stroke.

  4. Hi guys,
    a quick question, would any of you have the steering stem diameter ?

    It’s for a project I have with a NSR125 fork but I need to know the diameter of the stem ๐Ÿ™‚


  5. Well I’ve just fished my FM with full arrow exhaust n I say depending on the quality finish off yr bike 1700-1950 if u lucky n it looks the dogs.

    1. Look on ebay in Holand. It cost about 120 ยฃ for the bigest part left or right (from tank to the tail) i saw it 4 weeks ago. They have all fairings from front to the back.

  6. Look on ebay in Holand. I saw 4 weeks ago it cost about 200 โ‚ฌ for fairings big left or right, from tank to the tail. Of course it was new with the stickers on it.

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