QT50 help please

First, let me thank those that participate in this forum. I have found it to be an valuable resource.

My problem: I have a 1981 Yamaha QT50. I has only 1200 miles on the odometer, but has sat unused for the last ten years. In getting it operational, I have cleaned the carb (twice), added a fuel filter between the tank and the carb, replaced the spark plug and air cleaner element, drained and replaced the gas and oil.

It now starts and idles OK. However, when running at speed, say at 15 mph, it wll hold that speed for 15-20 seconds then start to buck, miss and backfire, often dying. Sometimes on restarting, a big backfire will occur. I must add that before I found this site and Fred's tutorial, I was "playing around" trying to get it going and may have changed some setting. Any suggestions?

A second minor problem is that the brake light does not work, despite a new bulb.


Re: QT50 help please

Ron Brown /


Your running problem sounds like you are not getting enough gas. Using a magnifier, make sure the jets and other passages in the carb do not have any crud left in them. Also check that you have no air leaks between the carb and the engine. You can spray carb cleaner with the engine running to see if any gets sucked in.

The brake light requires a switch closure or sometimes opening, usually on the brake levers. Make sure these switches are working then follow the wires to look for bad connections.


Re: QT50 help please

Hi! This can also be a faulty wire to the spark plug.Sometimes,depending on vibration or moisture in the air,they're really bad to do that.Happened to me on an ANKUR with only 20 miles on it.BYE!

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account