Petcock repair vs. Replacement

So, yes I did rebuild my fuel petcock at the same time I cleaned and redid my carburetors. Bike ran fine for a week or 3, then decided to suddenly die on me. Problem was electrical, and Im sorting it at the moment.

Fastforward to the other day going through electrics. I notice the oil level was WAY too high. Pull the cap and take a whiff. Straight gasoline smell in my oil that had 9 miles on it. 9 miles.

Got ANOTHER rebuild kit, and rebuilt again. This time I made sure that there was absolutely NOTHING inside of the petcock at all. Squeaky clean. Put fuel in the tank and turned it upright. Gas comes pouring out of the petcock.

It seems a bit off that a lump of metal could go bad. Anyone else have this problem?

 

You'd better buy a new petcock. Yours was probably not machined with accuracy. It wasn't a problem with the original "plunger" equipped with a taper o-ring, but the o-ring in the rebuit kit is of a standard, round section which can't compensate for the way the petcock body is machined.

Not easy to figure without a drawing, I'll try to find something...

 

Here it is:



Also have a look at the other pictures in the album.

 

Shouldn't your floats shut off the fuel flow from the petcock before it got to the case?

 

Yes, in a perfect world they will. The world is not perfect, and neither are my needle seats apparently. They looked good going back in, but I guess being trashed from ethanol the first time, then bathed in more ethanol the second time around has caused them to stick and not seal.

Im going to spill some urine into the breeze here. Ive got the first diaphragm and plunger that is technically still good, and I have some valve lapping compound. Im going to try and grind the plunger seat a little and see if I can get a good seal. Worst case scenario it doesnt work and I have to buy a petcock.

 

Do you have a stock petcock?

Have you see these write ups?

http://xjbikes.com/Forums/viewtopic/t=2 ... build.html

http://www.xj4ever.com/setting%20fuel%20levels.pdf

And while the carbs are off.

http://www.xj4ever.com/hitachi%20thrott ... 0seals.pdf

Hope this helps.

 

The carbs are going to be setup by someone with extensive experience with XJ bikes this weekend.

I did catch the writeup about the petcocks. Im going in a bit further with my cleaning right now. Went out to get some 1200 grit and Im watching TV and smoothing off gasket and O-Ring surfaces right now.

 

It WORKED! Petcock works flawlessly this time around.

I guess if a rebuild kit wont work you can actually grind the seat to seal with the new O-Ring.

 

SWEET. On to them floats now. If you haven't got new throttle shaft seals and fuel supply o rings nows the time. Or the carbs will probably have to come off again. That's what we don't want to have to do again for a while.

And if you haven't "broke the rack". The carbs aren't really gonna be clean. Valves too.

 

Never broke the rack for the first cleaning. Just stripped things down and sent them to the autoclave. Came back nice and clean, and as I said worked great for about 3 weeks.

Pulling them out this time reveals that the shaft seals must be leaking because there is fuel outside the one carb that was obviously flooding.

The fuel rail seals are not actually leaking, but if you are going to break the rack you might as well replace everything.

 

As long as you're clear on the concept that your actual problem is the floats.

Any issues with the petcock were only "enabling" the floats in causing you headaches. Once your float valves are doing their job, you should be able to leave the petcock in PRI without ill effect. (Not recommended, but everything should still work that way.)

 

Oh yes. There is clearly a float issue. The leaking petcock diagnosed the leaking float for me. Im talking with chacal now about which kit I need to do the whole rack and floats. I dont want to have to take the carbs out for a VERY long time, and quite honestly I don't know how much more abuse my intake boots can take.

 

If you have the money get new ones. Or there's a way to repair them. I haven't tried this but I've heard it works.

http://xjbikes.com/Forums/viewtopic/p=3 ... tml#330799

 

That actually seems like a really easy and good idea.

Possibly clean everything very well, coat in rubber cement, and then fit the tube over. The rubber cement would make an air-tight and permanent seal, too.

I might give that a go while the carbs are off.

 

I recommend the clear cup method for wet setting the floats. Got the glass cups at Wal-Mart for like $3 a pop.