Doing Basic Carburettor Checks if your Bike Doesn’t Start


Having an engine that just refuses to start can be one of the most annoying things of them all. It seems so simple as you only need fuel and spark, but it can be a little more complicated. Luckily, the other checks are easy and once they’re all sorted, it can only be the carb giving you the issues.

In the guide below, we run through a few common issues you’ll find on a motorbike carb that could give you a headache when it comes to starting. Having the right mixture is important as it determines how well the bike runs.

Start with Timing and Spark

To get the fuel to burn in the engine, you need to have a strong enough spark and that spark has to ignite at the exact right time. Therefore, before you do anything to the carb, check that the timing is right by lining up the crank mark with the cam gear.

Once that’s confirmed to be in good order and all covered up again, remove the spark plug wire, put a screwdriver up the plug and let it lay somewhere close to metal (about quarter of an inch away). Do not touch the screwdriver while testing as it will give you a shock. With the screwdriver in place, turn over the engine while looking at the gap between the screwdriver and metal part and you should see a spark running between them.

If you don’t see the spark, you might have a faulty CDI, coil or even spark plug wire, which might just be your problem. First, replace the items mentioned and ensure you get spark before moving on. If you get a spark that you didn’t get before, put the bike back together and try start it first.

Checking the Carb

If you have spark but the engine won’t turn, move on to check the carb. Start with the float by using the carb is actually getting petrol. Towards the bottom of the carb, you’ll find a nozzle and a screw. Attached a clear pipe to the nozzle and turn the screw, which should start to fill the pipe with petrol. Allow it to run through just a little to ensure the carb is getting enough fuel and that it’s clean.

Before you detach the pipe, hold the bike in an upright position and hold the tip of the pipe upwards next to the carb to see the level of the float. The petrol should reach about the high of where the float bowl and carb meet.

Clean the Carb

If the float is around the right level, you’ll need to remove the carb, open it up and use a decent carb cleaner to clear the jets. Be sure to make marking of your air mixture and idle screws and count how many times they turn out as this will make reinstalling a lot easier.

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