Re: Yamaha QT50 Holding Back

• Author: Hankus (---.wholefoods.com)
• Verified User: hankus
• Date Posted: 05-16-08 10:02

The QT petcock is up = reserve, horizontal = off, and down = normal. You should be able to ride with no issues in either the down or up position, as the fuel draws from the same place. What it sounds like is either a partially clogged jet, a jetting issue, or a clogged air box.
Two preliminary things to check: remove the air filter and go for a short test ride. If that made it run better, consider getting a K&N style filter and 86’ing the stock air cleaner. If that didn’t make a difference, remove the carb, disassemble, and thoroughly clean everything. Be sure to remove the smaller jet behind the main jet and clean it, that sucker will cause all kinds of issues with any amount of dirt, however miniscule. (Add an in-line fuel filter if you don’t have one regardless of the test outcome!!!) If neither of these did much to change your performance, do a plug chop and see where you’re at. You probably need to upsize your jet for improved performance. Good luck! – David