Tech Tip Tuesday: Motorcycle Won’t Start
You go outside and kick the starter on your dirt bike or crank over your cruiser and it’s a no go. If it worked recently, it shouldn’t be too hard too figure out which of the three main elements it’s missing (fuel, spark, and compression). Today’s tech tip tuesday will help you figure out what might be the culprit that’s keeping your bike from starting up.
First things first, check that you have fuel in the tank and if it’s low turn your petcock to reserve (if you have one). Sounds silly, but many people start tearing into their carb and electrical only to realize that they’ve simply run out of gas. If you’re good on gas, verify that fuel is going to the carburetor(s) by pulling off the line to the carb and then turning the fuel petcock on. Gas should flow freely through the tube. If it doesn’t you may have a clogged petcock or inline fuel filter. If that is the case, you’ll need to remove the tank and petcock and clean out any debris that may be clogging the strainer in the tank or screen inside the petcock.
If you’re getting good flow to the carburetor, there’s a chance that your carburetor is clogged and blocking fuel. Review our post on cleaning a carburetor and make sure your jets and float valve are all clean and clear.
Once you checked that the bike is getting fuel, the next easiest thing to check for is spark. Do this by removing the spark plug and inspecting it for damage, discoloration, or debris blocking the electrode. If your engine is indeed getting gas you should smell or even see some gas on the the plug. Thoroughly clean the plug or replace it with a new spark plug. Now take the clean spark plug and connect it to the boot/wire and touch the metal tip (arm that sits over electrode) to the engine block or a good ground bolt. Now kick the bike over a few times or hit the electric starter (make sure to set it in neutral and have the kill switch set to run) and you should see a blue spark going from the electrode to the metal arm even in broad daylight. If there is no spark, check the wires and connections to and from the coil or ignition system. Check for corrosion, cuts, tears or loose connections. If everything looks good and you still have no spark, you might be in need of a new part such as a stator, coil, cdi, or plug wires, but we’ll have to save troubleshooting those for another post.
If you checked your plug and you do have spark and it still isn’t starting, the next thing to check is compression. In order to do this you’ll need a compression gauge if you have a 2 stroke or electric start motorcycle. If you have a kick start 4 stroke, it may be difficult to test compression with a compression gauge due to automatic compression releases, so you will need a leak down tester. Both of those tools accomplish the same purpose by testing how well the cylinder hold air which will tell you if the rings or valves are leaking. Follow the directions for each tester (usually attaching it to the spark plug port) and match the readings to where they should be according to your repair manual. If compression is low, you’ll need to remove your carburetor and exhaust to try and find out if your exhaust or intake valves are leaking. If the rings are leaking you will most likely hear air coming from the crankcase breather hose.
By now you should have been able to deduce what might be ailing your bike and hopefully have it back on the road. If not, you may have a more serious internal problem with your engine and may need to do further troubleshooting or take it to your local mechanic.
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