GT750 Petcock gasket problem

[Willie]

Okay. I installed the new gasket (w/o the flap) and bolt seals last week and let everything set for a week before filling the tank. I added gas today and there wasn't a drop to be seen around the petcock UNTIL I started the engine and let it run awhile. Now the diaphragm is leaking. I don't see it being available on the Partzilla parts diagram.
Does anyone know where I can get the diaphragm without buying an entire petcock assembly or rebuild kit?
Thanks again,
Willie

[GT750Battleship]

Hi,pretty sure you'll have to buy a kit ! It won't hurt to replace everything,as other things will fail in time,especially if you disturb them..
Cheers,
Roger

[Coyote]

The only place that might include the diaphragm is at HVC Cycle. That part was never sold separately from Suzuki. I have never seen any other kits that include the diaphragm,

Now then. If your petcock was working actuated by the vacuum, the hole or crack in the diaphragm can't be very severe. Remove the back and work the diaphragm free. I use a dull pen knife for that. Hold the diaphragm up to a very strong light and look for pinholes and tiny cracks. Seal those with some fuel resistant sealer but don't glob it on. Don't forget to put the spring back in place on assembly or your fuel will never shut off. Can you tell exactly where it's leaking? Bowl gaskets and lever gaskets are readily available. I don't remember what year your bike is but the 76 and 77 use a V seal on the lever. Those are available too.

[Willie]

I LIKE the way you think, Coyote! I already have some fuel resistant adhesive left over from repairing the slide bellows on a Hawk GT I had a few yrs ago. I'll see if I'm able to repair the diaphragm. I've already replaced the round gasket under the lever along with the o-ring between the petcock and tank. The bowl gasket/seal has remained dry, at least, so far.
Thanks ALOT!
Willie
FWIW, I'd post a picture of the bike but the file size is too large. I'd shrink it if I knew how. But that's a whole different problem.

[Coyote]

Willie, email me the picture. I can shrink it with software I have and post it up for you. coyotesdoins@cox.net

[Willie]

I took the diaphragm assembly apart this afternoon, looking for leaks. I found dirt and corrosion but no leaks. I did make a discovery though that I feel is noteworthy as it relates to the spacer block between the tank and petcock that was discussed previously.
I believe the spacer block is to prevent the back side of the petcock, specifically the diaphragm assembly, from making contact with the lower edge of the tank. This edge resembles a lip, of sorts. I'm going to reinstall the spacer and see if it helps prevent the leak that I now feel had to do with this contact. I'm hoping that the old o-ring/gasket will seal.
More to follow,
Willie

[tz375]

Don't HVC sell a gasket kit that includes two of the O rings with cross bars? I know I bought a couple of sets /kits over the years. Maybe it was Parts n More.

Last GT I finished, or was it the one before that? I used a GS or GSXR fuel tap with whatever gasket/O ring it came with. They are available at a much better price than a Jen-You-wine GT750 part and looks good enough.

[Willie]

Not sure which gaskets you're referring to that have cross bars but would like to know if the GS and GSX fuel tap bolt holes line up with the GT holes. If this set up still leaks, I can see switching the hole thing over and being done with it.
Thanks!

[tz375]

This:

http://www.hvccycle.net/suzuki-gt-fuel- ... -hvc200s1/" onclick="window.open(this.href);return false;

Or

http://www.ebay.com/itm/suzuki-gt750-gt ... 38&vxp=mtr" onclick="window.open(this.href);return false;


Or try one of these
http://www.ebay.com/itm/suzuki-fuel-gas ... ce&vxp=mtr" onclick="window.open(this.href);return false;

http://www.ebay.com/itm/VACUUM-OPERATED ... 70&vxp=mtr" onclick="window.open(this.href);return false;

Check teh bolt spacing. Many Suzukis (and others) use the same spacing.

[Willie]

Thanks again. I've replaced all the gaskets/o-rings that are included in the links you posted. As for the GS petcock.... I'll measure the distance between the bolts on my GS1100E and see if its in the ballpark. Amazing how much things have gone up in price since the 70's.

[Willie]

FWIW, I put gas in the tank yesterday and let it set overnight before inspecting it this afternoon. Seeing that it was still dry, I started it up and let it run a few minutes. Still dry. Looks like I may've fixed it.
Thanks for everyone's help.
Now to dial in the jetting.
Willie

[Willie]

FWIW, I put gas in the tank yesterday and let it set overnight before inspecting it this afternoon. Seeing that it was still dry, I started it up and let it run a few minutes. Still dry. Looks like I may've fixed it.
Thanks for everyone's help.
Now to dial in the jetting.
Willie

Disregard the part about having fixed the problem It started leaking after about 10 minutes of running time this afternoon. In light of having nothing to lose with this petcock, I'll try sealing all diaphragm contact surfaces with some Permatex this evening and give it another try tomorrow. At least I have a spare GS petcock to try if this doesn't work. I sure hope the bolt holes line up if I need to use it.

I guess I'll be starting a new thread soon re: dialing in the jetting.

Willie