If you’re a rider who loves riding below are some basic motorbike troubleshooting tips to keep you riding. This is in Q and A mode in various parts to make it easier to find solution.
Motorbike Engine Troubleshooting Part 1
- Problem – Engine wont Start, but turns over with electric or kick starter.
- Cause – Lack of fuel, lack of spark,low compression.
- Check the petcock. Is it on? if there clean, fresh fuel in the tank? Is it getting to the carburetor? The first two problems have obvious solutions.
- fuel is not reaching the carburetor, work from the petcock down. If it’s a vacuum petcock, turn the lever to PRIME or RESERVE. If fuel doesn’t flow, suspect a plugged petcock.
- Make certain the fuel line is clear. fuel is reaching the carb inlet looks ok ?, but not flowing into the float bowl, tap the bowl with the handle of a screwdriver.
- If the float is sticking, the rap should free it up. If no fuel flows, the float needle may be frozen. In any event, you’ll need to remove the float bowl to determine the problem. If fuel doesn’t appear to be the problem, your next check should be for spark.
- To check for spark, remove one of the spark plugs, laying it on the head and turning the engine over. Be extremely careful to wipe up any spilled fuel before performing a spark check.
- If there is no spark or a very weak one, replace the spark plug with a known, good plug.
- If the spark seems adequate with the new plugs, replace any gas-fouled plugs, and try to start the engine.
- Fouled plugs are rare on modern street bikes, but there is always a chance that the engine was over-choked during a cold start, or that the choke was left on too long after the bike started, fouling the plugs.
- If the new plugs have no spark, troubleshoot the ignition system as required.
- Problem – Engine will not turnover with electric starter.
- Cause – Dead battery, safety switch engaged, blown main fuse, or bad starter solenoid.
- Check battery by turning on the ignition switch. If the lights work and the horn blows, chances are that the battery and main fuse are good and the problem lies elsewhere.
- Make sure that you are following the correct starting procedure: transmission in neutral, kickstand up, clutch pulled in, kill switch is on.
- If nothing comes on, check the main fuse first.
- the fuse is good, then check the battery with a voltmeter and charge or replace as required.
- If the battery tests good but engine still won’t turn over, likely suspects include a bad starter-safety interlock (not all bikes have these), bad starter relay, or even a bad starter motor.
- Make sure the interlock, if there is one, is working. Troubleshoot the starter circuit as required. Refer to your service manual here, as it’s
- likely to have a “no-start” troubleshooting tree listing the most common scenarios and their solutions.
- Problem – Engine turns over, has good spark and good fuel, but still won’t start.
- Cause – Low compression or slipped timing.
- If a compression-check reading indicates low cylinder pressure, adjust the valves and recheck.
- it’s still low, you’ll have to examine the top end. If compression checks out good, retrace troubleshooting procedure.
- Let me point out here that sudden loss of compression in one or more cylinders indicates a serious problem. On the other hand, a lo average compression reading just means the engine is getting tired.
- Slipped ignition timing is a somewhat obscure problem, but it does occur, especially on kick start-only bikes. If the wood-ruff key that locates the ignition rotor has sheared, the rotor can slip on its taper. The ignition will still have spark, it’ll just occur at the wrong time.
- This can be a tough problem to find. The easy way is to set the engine at TDC and see if the timing marks still line up.
- Fortunately, the repair is normally straightforward: replace the key, re-torque the nut, and go on your way.
- Problem – Engine starts hard, idles poorly, and runs erratically.
- Cause – This may occur after washing the bike, or after it’s sat for a long period of time. It’s often caused by water in fuel or dirty carburetors.
- Restricted fuel flow.
- Bad plugs
- Drain the carbs, and see how it runs. If big globs of water pour out you’ve found the problem.
- In severe cases you may need to remove the float bowls and blow out the jets.
- Check the fuel-tank vent, and replace fuel filters, check the lines for obstructions, and check the float needle and seat for dirt or sticking.
- Replace, with known-good plug(s). If the situation occurred
gradually a tune up is indicated. Adjust valves, replace plugs, replace
fuel and air filters, and clean and adjust carburetors.
This is the end of the part 1 of Basic Motorbike Troubleshooting.