APRILIA RS 125 : Aprilia RS 125 BASIC ROUTINE SERVICE MAINTENANCE RS

Aprilia RS125: Essential Basic Maintenance Guide

The RS125 is a race-bred machine that requires frequent, small interventions to prevent major mechanical "debt." This guide covers the core owner-level tasks:

The Transmission Oil: Unlike 4-strokes, the engine oil is separate from the gearbox. Change the 75W-90 (or 10W-40 Gear Oil) every 2,500 miles. Gray or "milky" oil indicates a failing water pump seal.
The Spark Plug (The Window to the Engine): Inspect the NGK BR10EG regularly. A "biscuit brown" tip is perfect; black/oily means you are running too rich, while white/pitted means you are dangerously lean and at risk of seizure.
Chain Tension & Lube: Maintain 25–30mm of play. A dry or overtightened chain on an RS125 puts immense stress on the gearbox output shaft bearing—a costly engine-split repair.
Two-Stroke Oil System: Never let the oil tank run dry. Ensure the "low oil" dashboard light works. Only use High-Quality Fully Synthetic oil (e.g., Castrol Power 1 or Motul 710) to prevent power valve sticking.
Coolant Levels: Check the expansion tank under the fuel tank. These bikes run hot; ensure the 50/50 antifreeze mix is topped up to prevent the "nylon" balance gears from melting.

APRILIA RS 125

SEE also the basic maintenance specifications post for measurements

and recommended oils etc.

The RS provides the high potential for circuit use. Lack of the basic

maintenance, however, will result largely degraded performance.

Servicing should be regularly performed and parts be periodically

replaced, if needed.

Aprilia RS125

Periodic replacement parts see your manual

Item Intervals Criteria

Plug cap Every (cleaning for each maintenance)

Cylinder Wear or damage

Piston Damaged skirt or wear

Piston ring Partial loss of identification point, wear

Piston pin Burning, damage, stepped wear

Piston pin clip (Every time clip is removed)

Connecting rod small end bearing Burning, wear, damage

Crank shaft formation, damage

Clutch outer Wear, damage

Spark plug Wear

Ignition coil Wear, damage

Reed valve Loose, damage

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other items needing regular attention

Front/rear suspension

Cables (throttle or clutch)

Brake master cylinder

Steering stem

Suspension link

Wheel bearings

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Checking other fasteners

Check the brake system, front section, or rear axle section for loose fasteners.

Piston

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Piston contact

Piston contact should not usually be removed. Severe contact with the cylinder is attributed to some other reasons. Pistons have special profile (out of round), which is designed to produce heat emission, providing proper contact when pistons and cylinders are subject to deformation.
Accordingly, careless piston modifications in profile will degrade the ideal profile, resulting in more contact with other portions.

Ring sticking

With the increase of service engine speeds year after year, even if keystone rings are used, sticking may result.
If rings and pistons are new, ring groove modifications are not required against sticking. However, if stuck rings are found at the time of maintenance, the modifications must be done. Stuck rings may cause engine troubles as well as a significant power drop.
Stuck rings can be identified by signs of a failure exhibited at the engine start, such as unwillingness to start engines or abnormal engine noise emitted from the silencer.

Aprilia RS 125 BASIC ROUTINE SERVICE MAINTENANCE RS

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Extreme care should be exercised during handling cylinders or cylinder heads.
In particular, flawed mating faces may deteriorate adherence, causing blow by.
If there are projections caused by flaw or dent, they should be removed using abrasive paper to make the surface flat.

However, if flaws are present across O-rings or flaws are present in the O-ring grooves, appropriate cylinders or cylinder heads should not be used since O-rings cause blow by.

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Clutch outer section

The clutch outer section should be periodically serviced and replaced if necessary. If excessive plays or cracks are found during servicing, defective parts should be replaced as soon as possible.

Carburetor

When cleaning carburetors, do not apply high pressure air to carburetors with floats installed. High pressure air would cause oil level in carburetors to get out of order, resulting in significantly wrong settings.

Carburetor float

Carburetor float section is a very delicate part. Extreme care should be exercised during disassembly.
If oil level should go wrong, see owners' manual for proper adjustment. Wrong oil level would cause rich or lean mixture, or hesitation. Also, check that floats are smoothly going up and down.
If floats do not move smoothly, rich feeling or hesitation may result when beginning to open the throttle. Also, unstable fuel mixture would cause frequent detonation.

Making reed valves thinner allows easy opening, and installation of supports secures functioning of valves when wide-open.

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wiring connector blocks are prone to corrosion and cause many electrical problems so clean these out regular also .

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basic Aprilia rs125 maintenance

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drive chain and sprockets

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chain stretch , maintain regular lack of maintenance will

damage your sprocket more quickly.

check for play via WSM .

oil the chain whilst warm after being ridden .

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brake pads for sale on Ebay UK here

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check pads visually for friction material wear , replace when low

but long before they may damage disc .

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battery

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check fluid levels (upper-lower levels)

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air filter

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clean frequently AFTER cleaning reoil the filter element

without oil you filter is useless .

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spark plug

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inspect for wear , wire brush clean , re gap or even better replace

they are cheaper than chips .

makes sure you fit exact spark plug .

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Fuel system

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inspect fuel tap and pipes , clean filter on the tank and at the carb and any in between.

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clean filters in tank and carb if you suspect fuel starvation ,if not used for long intervals

turn off fuel but expect to clean carb out before reusing bike

i have known this to occur after only a few weeks

Aprilia 34mm carb strip down video

28mm carb strip down video

Cables

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make sure all cable are in good order no fraying or other damage make sure all are adjust correctly

especially the oil pump setting < visually check oil is being delivered

i do this everyday maybe more often .

idle speed

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make sure this is set correct after adjusting cables .

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check coolant level , check for leaks ,check fins of radiator for blockage clean if ness ,

signs of water in the oil then seals could be gone on the water pump , rust coloured ? flush system and clean , check anti

freeze levels after , you can test thermostat in hot water if you want to also

but not really basic maintenance .

Rave valve

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aprilia rs125 rave valve removal video watch here

regular maintenance of this is important as deposits on blade with cause bad running and wear solenoid faster ,

remove valve from cylinder and clean thoroughly .

fit as per WSM and adjust cable and PV gaps correctly !!

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clean these out at regular intervals ( not cat models just silencer) replace gaskets on refit .

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obviously 2t should be checked daily , it seems to happen a lot where people run out of 2t

this is stupid these bike will last about 3 or 4 miles if you lucky with 2 stoke oil this should be a daily check or even after every journey , also check that your pump is delivering the 2t correct and check for air locks and bleed oil pump through some times water can accumulate in bottle and this seems to block line , i always bleed oil pump until good clean oil is coming out .

check the sight level glass on engine for oil levels regular , top up where necessary and replace regular .

as per WSM .

check brake system over

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check levers and pedals for correct operation , any looseness , out of shape or any damage whatsoever replace , make sure all mounts

and brackets banjo bolts etc are tight and not leaking , check pads for wear see earlier , and top up fluid levels ,check all hoses for

twists damage etc , if brakes are spongy then bleed brakes , i change the fluid on all new bikes i get completely i flush new fluid by bleeding until

clean fresh oil comes out , check brake lights and switch function correctly , inspect the discs for any damage scratches out of true , wear etc ,

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check tyre condition and tread depth , check wheels for balance , and check bearings for excessive play .

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very important to keep regular checks on your suspension .

check for binding during forks operation , inspect forks for signs of wear , corrosion and pitting , check the oil seals for signs of weepage

replace where any problems are found .

inspect rear shock for wear and any signs of leakage ,

there should be no binding in operation or any side to side movement of swing arm , tighten nuts if any movement is found ,

pull wheel upwards there should be no play , if this is felt its possible wear of bearings / or linkages , or mountings replace where needed .

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check for play and replace where necessary (see WSM) .

lighting system

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check all lights and indicators for correct operation and adjustment

check the contacts or bulbs and replace where necessary .

problems can occur due to corrosion within the connector blocks

these must be cleaned regular .

stand and oiling

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should be lubricated regular as these are exposed to elements , along with other exposed

items such are levers , foot rests , brake levers , chain cables , check operation of the stand switch .

oil pump test

oil pump

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check that throttle operate pump smoothly , and that all adjustments are correct

ensure scribe mark on pump are aligned perfectly .

check all pipes from and to the pump are safely connected

any leakage must be corrected as this causes oil starvation to

engine . at high mileage or after seizure clean out the oil filter or

replace pump altogether .always bleed pump after fitting or hose removal ,

bleed until good oil is seen leaving the pump ,see above video on how to test pump any testing or bleeding should be done with premix oil in tank to avoid engine damage .

CHECK oil tank level and CHECK oil pump operation daily or even prior to every journey!!.

compression test

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see the post named after this process in the blog

archives or click here , this is an important test and should be

done weekly , if you dont do this and your engine siezes

then you only ave yourself to blame.

low compression signals piston/piston ring wear

and these must be changed as soon as the compression

becomes too low .

piston change

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easy to do see the dedicated posts to these in archives or click here

ill be updating and making better videos, and posts

and pictures as i go .

front forks oil / seals change

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Aprilia rs125 fork oil amount 430ml

Aprilia rs125 fork oil type SAE 10~20

forks exploded diagram Aprilia rs125

again very easy to do hardest part is removing from the bike

but ill do a video on this soon !! .

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APRILIA RS125 CLUTCH MAINTENANCE

HERES AN RS125 CLUTCH STRIP DOWN VIDEO

SEE ALL THE CLUTCH PROBLEMS POST FOR MORE ADVICE

Repairing an End Can silencer

Here is an alternate way of repairing an end can if the carbon-kevlar tube is not totally junked and replacing is not mandatory.

The part of the damaged tube must be removed. I would still be comfortable if the rest of it is 20cm in length at least. Use a piece of thick sandpaper to mark your cutting line. Any metal saw will do the rest of the job.

The same length should be removed from the perforated pipe.

And then welded back in again if necessary.

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Piston to barrel clearance

something everyone should have in his toolbox. Piston fit fillers are cheap and very useful. You will need 0.002, 0.0025 & 0.003 inch feeler gauges as these will cover most of your needs.

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