Fuel Petcock - Arghhh!

I bought a "K&L rebuild kit" for the petcock on Whole Lotta Rosie.

I figured I would do the right thing, while the tank was being painted, and rebuild the petcock, so everything would be fixed, cleaned and painted, right?

No good deed goes unpunished. After I rebuilt the petcock, with the new K&L kit, I started to have fuel delivery problems. Here are the symptoms post rebuild:

The petcock, in the "ON" position will starve the carbs of gas in about 5 minutes of riding!

If I move the petcock to PRI," then the bike runs just fine. Well, it hesitates a slight bit at take off, but after that, it runs fine.

If I move it to "RES," it runs OK, but not great.

So, I am guessing that I have to take that petcock apart and see if there is any debris in that diaphram. The vac line is new and tight, so I know that vacuum is not a problem.

I will post a reply after I pull the petcock apart and see what's happening in there.

I might even take some pics if I find something interesting...

 

"ON" and "RES" are vacuum-operated; "PRI" is not. Read chacal's section on petcocks, there are a couple different styles internally and how you deal with rebuilding them is different.

Did you install an inline fuel filter while you were at it? (Has nothing to do with your problem, just a good idea.)

 

Chuck the pet chook in the bin and get an ON, OFF, RES', fuel tap from chacal. The pet chook is just another complication to go wrong. "The less the moving parts....

 

LOL, I hear ya! Yes, I did install an inline fuel filter.

That is usually the first thing I do when I start a carb cleaning!

It is amazing how much "stuff" is in the gas, and tank!

I will pull the petcock apart one more time to see if there is any debris in there, but I am more inclined to chuck it for a regular shut-off valve like Chacal sells.

I think I should just open an account with him!

 

Skippy Sounds like your diaphram may be a source in the problem. I may be wrong though, but I just rebuilt my petcock and it was pretty dirty even with the intank filter. Works like a Champ now though. I used OEM parts so im not farmiliar with the K&L kits.

 

Hey,
When i bought my bike I was having fuel delievery problems up the ass. from the petcock to the carbs.

I have cleaned out the carbs and desided to go with a non-vacuum petcock.

I changed the petcock for 2 reasons. 1) If I wanted to remove the tank the 'Off' option is awesome 2) removing the vacuum part = one less thing to go wrong.

 

A properly operating Yamaha vacuum petcock will keep the fuel from flowing in the "ON" position unless the motor is running, allowing the fuel tank to be removed as needed.

A properly operating Yamaha vacuum petcock is a wonderful thing, as it eliminates human error from the equation (forgetting to turn the gas on/off.) Malfunctioning, they can and will try to drive you crazy. For me personally, either a new Yamaha unit or one rebuilt with OEM parts is the way to go.

 

http://www.maxim-x.com/petcock.html