Yamaha 1986 qt50

General discussion forum for repairing and riding mopeds

Moderators: ItsLookingUp, pehuskey, Tab, mountainmoped, JD, John

Yamaha 1986 qt50

Postby yamahopper86 » Mon Jun 18, 2012 10:53 am

I have a 1986 yamaha qt50. It starts and runs well but blows white smoke out of the muffler and the exhaust pipe gets extremely hot after a few minutes of running. I disconnected the oil pump and mixed the gas at 30:1. I also cleaned the air filter, muffler and carb. Any advice would be greatly appreciated.
yamahopper86
Net Rider
 
Posts: 2
Joined: Sat Jun 16, 2012 9:04 pm
Location: United States

re: Yamaha 1986 qt50

Postby JD » Mon Jun 18, 2012 3:16 pm

If the exhaust (and engine) are getting abnormally hot, that's an indication that you might be running lean, e.g., too much air and/or not enough gas. That's not a good place to be. The bike will seem mighty peppy, but if the piston expands too much from the heat, it will start rubbing against the cylinder walls causing potential damage or, in the worst case, a seizure.

Have you done anything to open up the air box beyond normal specs? Is the exhaust a performance unit? Anything you do to increase the airflow through the engine could result in leaning up the mixture, which means you need to compensate by increasing the fuel flow, generally done by installing a larger jet in the carb.

jd
...Operating with impunity in the legal gray area between bicycles and motorcycles....
User avatar
JD
Master Regional Rider
 
Posts: 1696
Joined: Wed Dec 03, 2003 5:42 pm
Location: Huntington Woods, Michigan

re: Yamaha 1986 qt50

Postby John » Mon Jun 18, 2012 4:06 pm

Also decrease the oil 40:1 is adequate. Without a kit 50:1 works also. Please use synthetic oil for the mix.
John

"Plan your life like you will live forever, and live your life like you will die the next day!"
User avatar
John
Master Regional Rider
 
Posts: 4445
Joined: Tue Nov 18, 2003 9:52 pm
Location: Caledonia, Ontario, Canada

re: Yamaha 1986 qt50

Postby yamahopper86 » Mon Jun 18, 2012 10:23 pm

I added more gas to change the oil ratio to 40:1. It has a standard exhaust pipe and the air box is the way it came. Are there adjustments i can make to the carburator without replacing the fuel jet. Would removing the fuel filter help. i am willing to try anything. thanks
yamahopper86
Net Rider
 
Posts: 2
Joined: Sat Jun 16, 2012 9:04 pm
Location: United States

re: Yamaha 1986 qt50

Postby John » Tue Jun 19, 2012 6:21 am

You may have a partially plugged pipe with coking of the carbon/oil and that might be what is burning off. Needs to be cleaned maybe.
John

"Plan your life like you will live forever, and live your life like you will die the next day!"
User avatar
John
Master Regional Rider
 
Posts: 4445
Joined: Tue Nov 18, 2003 9:52 pm
Location: Caledonia, Ontario, Canada


Return to Moped Riders

Who is online

Users browsing this forum: No registered users and 10 guests

cron