Leaky Petcock question.

Hi Everyone,

I think I have confirmed my "flooding" question in a previous post. Supposing the tank was full, I then turned the petcock to RES and let the bike sit over night, would I have a puddle of fuel under the bike the next day? Now, we are assuming that the petcock is good.
The puddle was directly under the airbox, coming from a hose at the bottom of it. I cleaned the puddle of fuel off of the floor and moved the lever to FUEL and no puddle. Is this normal with a full tank or have I confirmed a leaky petcock that must be rebuilt?

I took the bike out for a toot around the block tonight, which was very exciting, I can't wait for spring!!!
Anyway, I noticed that as I slowed down, clutch in, that the engine was bogging down, almost wanting to stall. Could this be another sign of the engine getting too much fuel as a result of a possible leaky petcock?

Thanks in advance for any and all help.

Chuck

 

The petcock should not pass any fuel at RES or ON unless the engine is running.

You have a two-fold problem:

Leaky petcock (easy fix with a rebuild kit)
Leaky float valves (float height adjustment or float valve cleaning may be necessary).

Neither is a big deal to fix, but could turn ugly if left untouched.

You should be able to leave the petcock in any position, and never see a drop of gas on the floor.

On top of that, you need to change your oil, as the gas might have seeped into the crank.

 

Thanks for the quick response stereomind,

Would Seafoam do the trick or do I need to remove the carbs and do a rebuild of them as well?

Thanks,
Chuck

 

With the motorcycle off put the fuel valve on "ON" (FUEL?) and disconnect the hose to the carb. Does fuel run? Try it on "RES". If you put it on "PRI" it should flow.

If fuel flows on "RES" but not "ON" or vice versa, you don't need a whole rebuild kit. There is a seal behind the fuel valve selector that wears out. About $8 at your Yamaha dealer. It's the disc with 5 holes in it.

Even if it flows in both positions I would try the $8 seal first as it seems that most people don't have much success with the full rebuild. According to the parts guys at my local Yamaha store that sealing disc is the most common problem. It was definitely my issue.

The other part of your problem is one or more float needles leaking. Could be a bad float level, but most likely the rubber tips on the needles are shot. I believe Chacal will be along momentarily to quote you a replacement set of needles and seats.

 

you may not need a full rebuild, but you will have to pull the carbs to get to the bowl screws.

Before you take the carbs off, check the fuel level in the bowls. Search the forums for float height, it's been covered a few times. Basically, you can attach a piece of clear tubing to the drain hole on the bowl, hold it up vertically, and open the drain screw (start the bike for a few seconds first), See where fuel level ends up. It should be about 2-3 mm below the very top of the bowl. Now do that 3 more times for the other bowls :-D

That should give you an idea which carbs need to be adjusted.

 

Leaky needle and seat will let the bowl overfill. Do what stereo said (fuel valve on PRI). If you have one or more that slowly rise to the level of the carb throat you have a bad needle/seat.