Petcock overhaul

Hi all,

In prepping my "new" '82 Seca 400 for the road, I discovered the crancase full of gasoline.

The automatic petcock is dripping when in the "Run" position, so I suppose
it needs the guts replaced.

I see a part in the parts manual called a "fuel cock valve set", which I assume is what I need.

I'm sure some of you out there have overhauled a petcock -- anything I should be aware of before untertaking this little job?

Thanks,
HH

 

Is your petcock vacuum operated? When mine is in "normal", I turn it to the ON position, and it opens with vacuum. When in prime, it flows whether there is vacuum or not.

I would also be worried about why it is coming out the carburetors into the intake. It sounds like that is what is happening.

If that is the case, you might need to do a carburetor rebuild to get the floats "unstuck". That is what is causing the overflow. It could be due to the bike sitting for a long time, and gasoline varnish building up in the carburetor. Or the valve could just be worn out.

But before you do that, tap the bottom of the float bowl. That might unstick it enough that it won't do it again. That is what happened to mine after I did a rebuild. Only had to do it once, and it solved the problem. I guess it was first time jitters!

 

To piggyback on Richard03's post, if you decide to do a carburetor rebuild, be sure to replace the o-rings under the float needle seats (if so equipped). They were the culprit for my crankcase filling with fuel, no matter how well my floats were functioning.

He's right, though. The floats in these bikes have a tendency to stick after the bowls get empty.

 

Richard & Maverick:

Thanks for the tips.

Yes, my petcock is the vacuum type. When in the "Run" position, it's only supposed to flow if the engine's running, but mine drips all the time.

I was wondering if the floats were phase two of my problem, since I thought they should keep gas out of the cylinders even with the bad petcock.

I've seen float valves on other small engines get stuck closed, so that the bowls never filled, but this my first experience with them sticking open. I guess either the float itself could be hung, or the seat where the valve closes is bad or has trash in it.

I keep reading about SeaFoam fuel system cleaner elsewhere in the forum. I assume that you mix it with a tank load of gas? Do you think that would do any good in this situation?

Thanks again,
HH

 

Maybe it would help... maybe.

Apparently there is a really really good carb cleaner made by Yamaha. The short version of the story is that they shipped a bunch of bikes to the states with gas in them, sat on the floor, gummed up. Their chemists made this formula that is carb part safe so they could really quickly clean the carbs without taking them apart... I've never seen it in person but from what I can tell it looked in the picture to be a black bottle about 2 litres.

Anyhow - the floats tend to stick in their resting position. In our bikes the bowls are full all the time unless you drain them. It's not uncommon for them to stick open.

The 250 board has a REALLY good carb cleaning faq for the bandit 400. It is also a four cylander bike so it's really quite simular to the 650. Same cleaning process...

http://faq.ninja250.org/index.php/How_d ... filters%3F
http://faq.ninja250.org/index.php/Cleaning_the_carbs_1
http://faq.ninja250.org/index.php/Cleaning_the_carbs_2

 

Thanks Woot.

The bike seems to be running well, so I think first I'll try the tap-tap approach on the fuel bowls.

If that doesn't work, I'll drop the bowls and check the float and valve operation.

Hopefully I won't have to get into a full cleaning/rebuild just yet.

Thanks again, everybody!
HH

 

Your fuel cock needs to shut off when the bike is not running even if your floats are working properly. Oldbikebarn.com has rebuild kits with new diaphragm and o-rings. Easy to replace i did mine.

 

Monster:

Yes, I'm still planning on overhauling the petcock. I've got a rebuild kit on order from a Yamaha dealer.

Glad to hear yours is working. Any cautions or tips from your rebuild experience? I've seen a couple of postings from guys who rebuilt their petcocks but couldn't get them to operate properly, and ended up buying new ones.

Thanks for your post-
HH

 

mhhpartner: Make sure your surfaces are smooth and clean. Mine had peices of the old o-ring stuck to it. If your kit is like mine you will have to reuse the plastic block the diaphragm is on. To remove the diaphragm push it through the center hole. It took me awhile to figure that out.

 

Monster:

Thanks for the tip. I'm picking up the petcock kit today. Not sure when I'll actually install it, but I appreciate the heads-up about the diaphragm.

I'll follow up after I'm done (hopefully) or with more questions!

HH