Any New Info On Replacing or Repairing Gt550 Petcocks?

[hailwood1965]

Did the usual petcock rebuild kit on my 1973 GT550.

Initially it seemed to function okay, but right away I saw some seeping around the bowl portion of the petcock ... which got worse as the days passed.

Also, after sitting for a few days the bike started to run like crap and I suspect that the whole engine is now flooded as it didn't really leak as much fuel as I suspected was in the tank.

I have the original 1973 petcock with separate lines running to each carb. There is no "off" on it.

Pulled the tank off today. With the valve on "reserve" I pulled the lines off. Fuel sprayed/leaked everywhere out of the petcock. Popped one fuel line off and fuel sprayed right in my eyes. Total joy!

I did search the site. Wondering though ... Is there any new info on replacing the petcock with a manual unit and plugging the vacuum line?

Also, should I drain the crankcase through those front of the case valves, or?

Suggestions welcome.

[pearljam724]

I never had much luck with rebuild kits either. Buying an original, new petcock is the only way to go in my opinion. Unfortunately, new and original petcocks are very expensive for all vintage bikes. Especially, early GT models. The prices are tough to digest for me. But, once you take that leap. It should last for at least 5 years. Today's ethanol fuel reaks havoc on some plastics and some rubber. Perhaps this is your experience with the rebuild kit. A lot of plastics sold in China don't go through proper testing to verify that the product is ethanol resistant. As far as other options. Any petcock with the same mounting hole spacing, clearance inside and under tank will work on any bike. You may have to be creative and make your own with a shut off valve that doesn't need to be vacuum assisted. That would not be difficult at all if you wish to go that route. If you speculate that a descent amount of fuel has gotten to the crankcase, I would drain it immediately. You only need to drain crank oil under the center of the engine. On a 4 stroke, personally I wouldn't be too alarmed with a little gas in the crank oil. But, I wouldn't want ethanol touching the crank seals on a 2 stroke. Not for a minute. It's also important to have a tank sealed and a line filter to assist with having a dependable petcock. Rust particles can make a petcock age quicker than it should.

[tricky1962]

You could plug the "prime" passageway in the petcock to give you an "off".

I did this on my T500 and it's not inconvenient. The only trouble is that if you drain the carbs for any reason, it might take a few churns on the starter motor or kicks in my case (usually about six or seven) to get enough fuel into the floatbowl to allow it to fire.

[Alan H]

If there's fuel in the crankcases, then the carbs are passing fuel past the floatbowl needle valves as well, so these need looking at.
Yes you can remove the SRIS valves under the cases and drain the engine.
Take the plugs out and spin the engine over after draining the cases too (cloth over the RAM Air cowl or there will be petrol all over the place.)
Trouble with blanking the prime position off, is that if the bike is left for more than a day or so, or if it's summer (hot) then the carbs will always be empty when you try to start, so it hammers the battery a bit. Motobatt is the cure for that one.

Never had an issue with fuel taps.
Use a genuine set of seals for it or a new tap completely.

[jabcb]

Pingel sells new manual & vacuum petcocks. They are a pricey. They use the T500-style tank mount & require an adapter plater for the tripples.

The Pingel vacuum petcocks have 3 positions: off, on & reserve. Off is a true off position & doesn’t rely on the vacuum mechanism. But there is no prime setting, so you’ll need to use the starter or kick start to prime the carbs.

[tricky1962]

Trouble with blanking the prime position off, is that if the bike is left for more than a day or so, or if it's summer (hot) then the carbs will always be empty when you try to start, so it hammers the battery a bit. Motobatt is the cure for that one.

I admit I have never had a problem with empty carbs after a hot summers day, but if I let it stand for a couple of weeks or more, then yes the bowls empty (because I have cracks in the float bowls).
However, as a soft southerner, I can just about get it going with six or seven kicks on the kickstarter - I'm sure the GT550 has one of those! and would have thought a roughty toughty northener from oop north could have managed that?

Anyway, my main point is, despite my float bowls leaking, over the summer and within a week, my bike starts first kick, because there is still sufficient fuel in the carb. If left longer then yes I have to kick a few times. In fact, because the tap dribbles when in the ON position, if I've left it for a few weeks, I can switch it to ON and leave for 5 minutes to dribble/fill the float bowls and then it starts first kick anyway - win win

[wavehog33]

I just modified a new petcock for a 1976 GT 550. right out of the box and the vacuum diaphragm leaked. I modified this area and filled it with devcon 2 part metal epoxy, eliminating the vacuum feature of the petcock. The prime then became reserve. The reserve became the off feature. works like a champ!