Buying a used carburettor bike: what to check

What you need

• A torch, a clean rag, and a friend or mechanic who knows bikes
• Your licence and helmet for the test ride

Steps

1. Ask for the papers before you even look at the bike: the BRTA registration certificate (smart card, or the older blue book), the tax token, the insurance paper and the seller's NID. Motorcycles do not need a fitness certificate, so that is not one to look for.
2. Match the name on the registration to the seller's NID. If the bike is in someone else's name, the registered owner must sign the ownership transfer with you. Without that signature BRTA will not move the bike into your name.
3. Read the chassis number (stamped on the frame, usually near the steering head) and the engine number (on the engine case). Both must match the registration exactly. Filed, re-stamped, painted-over or uneven digits are a reason to walk away.
4. The number plate should be the BRTA-issued digital (retro-reflective) plate with the same number as the papers. A hand-made or mismatched plate needs a clear explanation.
5. Check the tax token's expiry date. If it has lapsed, the arrears and fines usually land on whoever owns the bike next, so agree who pays before any money changes hands.
6. Ask whether the bike has pending traffic cases or e-fines, and check yourself on the official online service before paying (our e-fines guide shows how). Unpaid cases follow the bike.
7. Write a sale receipt with both NID numbers, the date, the price and the chassis and engine numbers, signed by both of you. Then do the ownership transfer at BRTA soon. Until it is done, the bike legally stays in the seller's name.
8. Ask the seller not to start or ride the bike before you arrive, and touch the engine when you get there. It should be cold. A warm engine hides hard starting, smoke and noises.
9. Start it and watch the exhaust, then rev it a few times. Thin white vapour on a cool morning that clears in a minute is normal. Blue or grey smoke means it is burning oil (worn rings or valve seals). Black smoke means it is running too rich.
10. Listen at idle and as it warms. A light, even ticking is normal. Loud tapping from the top, knocking from the bottom, a rattle for the first seconds after start-up, or grinding are not. Look for oil seeping around the cylinder head and the base of the cylinder.
11. Hard starting together with weak pulling and blue smoke points to a tired top end (low compression). A mechanic can measure compression with a gauge in a few minutes.
12. Cold start with the choke: a healthy carb bike starts within a few tries on choke when cold, and idles steadily once you push the choke off after a minute or two. If it only runs with the choke on, or dies as soon as you close the throttle, the carb is dirty or badly tuned.
13. Once warm, blip the throttle. The revs should rise cleanly and fall back to a steady idle. Coughing, popping, a flat spot when you open it, or revs that hang high are carb or air-leak problems.
14. Look at the carburettor itself: petrol stains or wetness under the float bowl, a strong petrol smell, chewed screw heads or broken paint marks on the adjusting screws (it has been tuned a lot), and a cracked or loose rubber joint between carb and engine. Ask when it was last cleaned, and why.
15. Ask your mechanic to pull the spark plug. A light brown tip is healthy. Black and sooty means it runs rich (dirty air filter, wrong tuning or a sticking choke). Wet and oily points to burning oil.
16. The TVS Apache RTR 160 4V is carbureted but oil-cooled: also check its oil cooler, lines and oil level as in the oil-cooled guide. Old two-strokes like the Yamaha RX100 always smoke a little; the smoke test above is for four-strokes.
17. Clutch slip test: in a high gear at low speed, open the throttle quickly. If the revs jump but the bike barely speeds up, the clutch plates are worn. It should also find neutral easily, and the lever should have a little free play.
18. Chain and sprockets: try to pull the chain backwards off the rear sprocket. If it lifts away and shows a big gap, the chain is stretched. Hooked or pointed teeth mean the chain and both sprockets are due.
19. Accident signs: scraped bar ends, levers, footpegs, mirrors or engine cover; dents in the tank; new panels that do not match the rest; welding or fresh paint on the frame. Stand in front and behind: both wheels should line up, and the handlebar should be straight when the front wheel is.
20. Forks and steering: look at the shiny fork tubes for oil, rust or pitting. Push down on the front a few times; it should rebound smoothly, without clunks. Turn the bar from lock to lock; it should move smoothly, not notchy or loose.
21. Flood damage, common after the monsoon: dried mud or silt where washing does not reach (under the seat, in the air box, around wiring plugs, behind the headlight), green or white crust on connectors, rust on bolts low on the bike, fog or a water line inside the headlight or meter, a musty smell, and milky engine oil.
22. Odometer: do not trust the number alone. Both mechanical and digital meters can be wound back. Compare it with the service book stamps and with wear on the grips, footpeg rubbers, gear lever, brake pedal, seat, tyres and chain. Very low kilometres with worn rubber and a stretched chain do not add up.
23. Test ride with your licence and a helmet on a quiet road. Use every gear up and down, brake firmly once from moderate speed, ride straight with a light grip to feel any pull to one side, and check the horn, lights, indicators, self-start and kick start if fitted.
24. Before paying, have a mechanic you trust look it over, not one the seller brings. If anything above worried you, use it to lower the price or walk away.

Common mistakes

• Jumping at a price far below the usual used price for that model and year. The common reasons are a stolen bike, flood or accident damage, or papers that are missing or cannot be transferred. Be extra careful, or walk away.
• Paying an advance to 'hold' the bike before you have seen the original papers and matched the numbers yourself.
• Buying on 'the papers will come later', or with only a photocopy of the registration.
• Inspecting at night, in the rain or right after a wash. Water hides leaks, and darkness hides dents and smoke.
• Letting the seller 'just tune it a little' with a screwdriver while you wait. A quick tune can mask a worn carb or an air leak for the length of a test ride.
• Accepting 'mileage is low, it just needs tuning'. Poor mileage can also come from a worn engine; check the smoke and the plug first.

When to go to a mechanic

• Always, before you pay. A short inspection costs far less than buying the wrong bike.
• Blue smoke, knocking, clutch slip or a bike that pulls to one side: get a compression test or frame check and price the repair before you agree.
• It will not hold an idle without the choke, even after a carb clean: worn carb parts or an air leak.

More guides

• Buying a used air-cooled fuel-injected bike: what to check
• Buying a used oil-cooled fuel-injected bike: what to check
• Buying a used liquid-cooled bike: what to check
• Checking your spark plug
• Air filter: the cheap fix for weak pickup
• Monsoon riding and bike care