Overflowing float bowl repair for 80/81 carbs

Most of you will already know this but for those who don't this sure made a big difference. I've carefully cleaned the float needles and seats many times but still have a strong gas smell in the garage and once in a while a little drip of gas into the airbox from the carbs overflowing.

I finally realized that my needles and seats were sealing perfectly but the seat was leaking in the carb body. I don't know if you can get that small o-ring individually from Yamaha or if you need the whole kit but I found a set of 6 o-rings at PepBoys (airconditioning hose rings) that were nearly a perfect fit (a little tight but worked well) and cost under $2 for the set. I can leave my petcocks (manual petcocks) turned on with a full tank of gas now and don't get any drips or gas smell in the garage.

The float and float needle act as a fuel valve. On the '80 carb, you pull off the floats and the needle. There is a phillips head screw in a clamp holding the brass seat into the carb body. Remove this screw and clamp and lift out the seat. There is an o-ring around it on the '80 and I would bet on the '81 as well. I just checked and the picture in the service manual is of a '78 and that seat is threaded and has a washer/gasket so this o-ring stuff wouldn't apply to those carbs ('79 probably same as '78).

Last modified: Feb 24, 1999

After some good insight from Sid (thanks Sid), I thought to look at the float seat again. In good light I noticed the seat had some rough edges which prevented a good seal. I took my drill and put in a 5/32 bit and drilled ever so lightly and for just a few seconds in reverse. Leak solved.