1979 Honda XL125S
Honda XL125S Specs…..
The Honda XL125S was a road legal off road motorcycle manufactured between 1979 and 1985.
The XL125 S had a reliable 4 stroke, 124cc, single cylinder, air cooled engine. The XL125S had a few improvements over the earlier XL125 models including electronic CDI, 6 speed gearbox and rubber mounted indicators, making them less likely to stop working in the event of a fall.
A little bit about the Honda XL125 S…..
Basic model info… |
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Manufacturer: | Honda |
Model: | XL125S |
CC: | 124cc |
BHP: | 12.5 |
Engine type: | Single cylinder, air cooled (4 stroke) |
Years in production: | 1979 to 1985 |
Style of bike: | Off road (road legal) |
Insurance: | Get a discount on your insurance at Confused.com |
Engine and gearbox specs….. |
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Displacement: | 124 cc (7.57 cubic inches) |
Engine type: | Single cylinder |
Stroke: | 4 stroke |
Bore×Stroke: | 56.5 x 49.5 mm (2.2 x 1.9 inches) |
No. of cylinders: | 1 |
Cam shaft configuration: | OHC (overhead cam) |
Compression ratio: | 9.4:1 |
Cylinder compression pressure: | 11 to 14 bar (160 to 203 psi) |
Valves: | 2 valve (2 per cylinder) |
Spark plug: | NGK DR8ES-L (x1) |
Spark plug gap: | 0.6 to 0.7mm |
Firing order: | Erm….It’s a SINGLE cylinder! 😀 |
Engine oil: | 10w40 API SE or higher |
Engine oil drain bolt location: | Bottom/left side of the engine casing |
Oil filter type: | Screen / mesh |
Cooling system: | Air cooled |
Clutch: | Wet (oil immersed) multiplate clutch |
Clutch operation: | Cable |
Clutch cable operation: | Lever (on handle bar) |
Clutch lever free play: | 10mm |
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Gearbox: | 6 Speed manual (1st gear down, 2nd to 6th gears up, neutral between 1st and 2nd gears) |
BHP: | 12.5 bhp |
Top speed (claimed): | 62 mph….Ish! (100.0 km/h) |
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Piston ring to cylinder bore clearance: | New: 0.010 to 0.040mm / Max 0.100mm |
Valve clearance (inlet): | 0.05mm (when cold) |
Valve clearance (exhaust): | 0.05mm (when cold) |
Idle speed: | 1,300rpm (+/- 100) |
Front/side view of a 1979 Honda XL125S in black
Final drive stuff….. |
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Final drive: | Chain |
Front sprocket: | 14 teeth |
Rear sprocket: | 47 teeth |
Chain pitch/length: | 428 pitch / 120 links |
Chain free play: | 30 to 40mm |
Chain stretch limit: | 518mm over 40 links |
Rear/side view of a 1979 Honda XL125S in black
Carb, fuel and oil stuff….. |
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Fuel system: | Carburetor |
Fuel tank capacity: | 6.8 litres |
Fuel type: | Unleaded petrol (91 octane grade – aka standard, unleaded petrol from your local garage) |
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Carb make: | Keihin (1x) |
Carb type: | PD21A/C |
Pilot screw opening: | 2.5 turns |
Engine oil: | 10w40 API SE or higher |
Engine oil drain bolt location: | Bottom/left side of the engine casing |
Oil filter type: | Screen / mesh |
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Clocks and switches on a Honda XL125 S
Electric stuff….. |
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Ignition type: | Electronic CDI |
Starter: | Kick start |
Electrical system voltage: | 6 volts |
Electrical system capacity: | 4 amps/hour |
Alternator output (max): | 4.5 amps (@ 8000 rpm) |
Spark plug: | NGK DR8ES-L (x1) |
Spark plug gap: | 0.6 to 0.7mm |
Spark plug ignition: | 1 x coil |
Coil primary resistance: | 0.2 to 0.8 ohms |
Coil secondary resistance: | 8000 to 15000 ohms |
Pick up coil resistance: | 20 to 60 ohms |
Battery: | 6N4-2A-4
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6 Volt battery for a Honda XL125 S (6N4-2A-4).
Shocks, brakes and wheel specs….. |
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Front wheel type: | 21 inch spoked wheel |
Front tyre size: | 275-21 (same as 2.75-21) |
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Front innertube size: | 250/275/300-21 |
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Front tyre pressure: | 21psi (1.5 bar) |
Front wheel spindle torque: | 45nm |
Rear wheel type: | 18 inch spoked wheel |
Rear tyre size: | 410-18 (same as 4.10-18) |
Rear innertube size: | 325/350/410-18 |
Rear tyre pressure: | Solo: 21psi (1.5 bar) / With pillion: 25psi (1.75 bar) |
Rear wheel spindle torque: | 70nm |
Front brake: | Drum (130mm) |
Front brake pad: | EBC H304 (1x) |
Rear brake: | Drum (120mm) |
Rear brake pad: | EBC H304 (1x) |
Front suspension: | Telescopic forks |
Front fork stanchion diameter: | 31mm |
Recommended fork oil: | 10w fork oil |
Fork oil volume: | 160 cm3 (per fork) |
Rear Suspension: | Twin shock |
Right/back view of an XL125 s in black
Weights, measures ‘n stuff….. |
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Seat height: | 818mm (32.2 inches) |
Kerb weight (with oils, fluids etc): | 106 kg (234 lbs) |
Fuel tank capacity: | 6.8 litres |
Left side view of an XL125S
Useful torque settings….. |
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Front wheel spindle: | 45nm |
Rear wheel spindle: | 70nm |
Cylinder head: | 18 to 20nm |
Magneto / flywheel: | 40 to 60nm |
Camshaft sprocket: | 8 to 12nm |
Clutch hub: | 40 to 50nm |
Right side view of an XL125S (note the homemade side panel, right side panels for these bikes are rare as hens teeth for some reason!)
Service stuff….. |
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Servicing your bike? You’ll need an XL125 workshop manual… | |
Engine oil | |
Engine oil change frequency: | Every 6,000km (approx 3,728 miles) or 12 months |
Engine oil: | 10w40 API SE or higher |
Engine oil capacity: | 900ml |
Engine oil drain bolt location: | Bottom/left side of the engine casing |
Oil filter type: | Screen / mesh |
Chain drive | |
Final drive chain frequency: | Now repeat after me… ‘I MUST LUBE MY CHAIN LITTLE AND OFTEN!!’ |
Chain and sprocket size: | 120 link / 428 Pitch chain 14 Tooth front sprocket 47 Tooth rear sprocket |
Fork oil | |
Recommended fork oil: | 10w fork oil |
Fork oil volume: | 160 cm3 (per fork) |
Frame number location…..
The frame number is usually stamped onto the right side of the headstock (the front part of the frame just below the handle bars).
Useless stuff…..
Although not a patch on modern standards and speeds, the XL125S was a good, reliable bike in it’s day and it’s fairly common to see them used as ‘field bikes’ now.
The XL125 S used the newer, slightly larger (124cc) cc engine and benefitted from a CDI ignition.
The bike also had a 6 speed gearbox which made the narrow powerband (7,000 to 10,000rpm) much more useable.
The model remained basically the same during it’s life (1979 to 1985) with changes to colours and graphics.
Buying advice…..
The XL125S isn’t a bad little bike for playing around off road, although it is a plodder so your unlikely to be competing in the Paris Dakkar rally on one!
There are a few about so there’s tons of ‘barn find’ and ‘field bike’ type bikes around. Unless you know what your doing or just looking for a pure off road (i.e. not road legal) hack it’s best to stay away from them as without the paperwork there likely to either have been nicked at some point in there history or no longer on the DVLA vehicle records.
The engines are fairly bullet proof and basic spare parts are available, but exhausts tend to rot and exhaust spares are rare (and expensive when they do come up!). However, the exhaust system is fairly simple so it wouldn’t be too difficult for a reasonably competent fabricator/welder to knock something up cheap.
The other odd thing about these bikes is right side panels, which are rare as the proverbial rocking horse poop for some reason?
The only other thing to consider when buying one is the age. The youngest of these beasties will be over 30 years old now, so if your buying one give it a good check over, especially rear shocks, fork stanchion condition (helps if the forks have had fork gaitors fitted), handle bar switches, ignition, battery etc.
Happy biking 🙂
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