QT50 electrical

My turn signals, tail light, brake light and horn do not work. Any idea how to fix them?

If all these components do not work then your battery is probably dead. Chances are your headlight is blown as well. You either need to recharge it or install a new battery. These components (except the headlight) all run off the battery. After you recharge or replace the battery, you’ll want to keep an eye on it to make sure that your charging system is recharging the battery. Check and make sure that the fluid level is correct in the battery as well. It’s a good idea to buy a trickle charger and charge the battery during times when you store the bike or don’t ride it.

Some Yamahoppers with a three position key switch (off, start and run) may have electrical issues at the key switch and the horn, turn signals, tail light will not work. I’ve had luck getting those components to work (if the battery is fine) by slowly turning the key from “run” towards “start”. Somewhere between those two settings, the lights will come back on.

My headlight is burned out on my QT50. What’s the best replacement?

Buy a Honda C70 headlight. It fits perfectly inside the chrome ring of your stock headlight. Just drill a couple holes and attach the C70 headlight to the chrome ring. From there, pop it into your headlight housing. The C70 has a replaceable bulb that you can get for under $1.00. So if you burn it out or blow it, a cheap fix can be had. Also, on your stock headlight connector, you will see a code for each wire (ground, hi and lo beams). You will have to connect up different colored wires from the headlight to your QT50. The green wire on the C70 is the ground, so, for example, you would go green to black (black is ground on the QT50).

My qt50 is stumbling or hesitating under acceleration. What’s the problem?

You go to accelerate your Yamahopper and it stumbles or seems to hesitate. It’s almost as if it isn’t getting gas on a steady, consistent basis. Sometimes it may even fart through the exhaust (I mistakenly call this a backfire). A number of things could be causing this. It may be exactly that – it’s not getting enough gas. You would need to check several parts of the fuel system in this case. Start at the gas tank and proceed to petcock, fuel line, fuel filter and carburetor. Verify at each point that you have a good gas flow. The qt50’s metal gas tank is often the culprit here. Fine pieces of rust or big chunks of the stuff may be preventing fuel from leaving the gas tank. The petcock may be clogged with the stuff and so too may the fuel filter. Or your carburetor may just need a thorough cleaning. If you do clean the carburetor make sure to take a wire, guitar string or small drill bit (0.35mm) and clean out the idle jet.

Another culprit could be an air leak in the system. Too much air is almost the same as too little fuel. Check your cylinder head nuts for proper torque (84 inch/lbs). Check your head gasket as well. Check all the engine seams by spraying carb cleaner on them and seeing if the engine surges. If so, you have an air leak. Popular spots are where carb meets intake; cylinder head; cylinder jug base and where exhaust mounts to cylinder jug.

Check the wiring; especially, the wiring coming out of the magneto and leading up through the main down tube on the bike. I had a qt50 that would stumble while accelerating and hesitate over bumps in the road. Turns out the wires were missing some insulation and grounding out when they hit the frame as you went over bumps on the road.