GT750 Petcock gasket problem

[Willie]

I received a replacement petcock gasket yesterday that I had ordered from Paul Miller. Its the rubber one with the 4 large holes and one small hole in the center. Anyway, the one I received was the wrong diameter. The OD of mine is 1 3/16" (approximately 30.6mm) vs the 28.8mm of the one I received.
I just did another search on ebay for the petcock gasket and noticed there are 2 different part numbers listed. The one I bought came in a ziplock bag and did not have a part #, so I don't know which of the 2 part numbers I got.
All of this leads me to believe that the different part numbers correspond to different diameters. Does anyone know if this is the case and, if so, what part number corresponds to the larger diameter that I need?
I have sent messages to a seller of each of the 2 part numbers, asking them the OD. I sure hope they respond with the info I need in case I don't get an answer here.
FWIW, I am confident that the petcock is the original one that came with the bike in '74.

Thanks,
Willie

[Barry S.]

The early ones were small and later ones large, call Paul and he will probably send you a new one or just go to Suzuki dealer and order it, still available.

[old racer]

I have UK part numbers,But i connot see the US numbers being different.
The 72 J.73 K.part number is 44376-31050.
The 74L.75M.76A.77B. part number is 44376-33150.I believe superceded by 44341-33150.
The smaller one suits J.K. the larger one suits L.M.A.B.

[Willie]

Thanks guys. I emailed Paul and he responded by asking me for my mailing addy. The one I need arrived a week later.
Next issue is the 2 rubber gaskets that go between the petcock and the tank. Their sealing surfaces have flattened out over time.
I have them soaking in Automatic Transmission Stop Leak with the hope that they'll swell up to their initial "plumpness".
I figured it was worth a try before buying 2 new ones for about $25.
I'll let you know all know if my little experiment works. I'm also open to any other home remedies.
Willie

[GT750Battleship]

Hi Willie,12 years ago I used red fibrous washers on the bolts that hold the tap assembly to the fuel tank,never had a fuel leak in all that time,dry as a bone VERY cheap fix I think you will be spending the money for the rubbers though...I can't think of a cheap fix for those unfortunately Alpha Sports Suzuki selling those two rubbers for about $15 US dollars
Cheers,
Roger

[Coyote]

$4.91 each at Partzilla. Just get one and do away with the spacer block. Bolt the petcock directly to the tank. The spacer block is just another place to develop a leak, and does nothing for a living.

[Willie]

$4.91 each at Partzilla. Just get one and do away with the spacer block. Bolt the petcock directly to the tank. The spacer block is just another place to develop a leak, and does nothing for a living.

Thanks guys. The idea of eliminating the spacer block never occurred to me. Score! I wonder what its purpose was and how odd that they'd spend money on an unnecessary item. You just decreased the amount I have to spend by half.
I'll order the gasket from Partzilla this afternoon. As for the red fibrous washer idea, I had previously used black rubber washers that have long dried out. I picked up a couple of nylon washers yesterday even though I can't imagine they'll seal very well. I'll head back to the hardware store and get a couple of fibrous ones. Thanks for that idea as well. I imagine I'll have to get shorter bolts as well.
FWIW, the o-rings did not return to their original "plumpness" over night.
Willie

[GT750Battleship]

Hi,the spacer block allows more fuel to be drawn/picked up when on reserve,well that's the theory anyway
Cheers,
Roger.

[Coyote]

Hi,the spacer block allows more fuel to be drawn/picked up when on reserve,well that's the theory anyway

I'm not buying that. Not at all. I think if that were true (I don't know how it could be) the manufacturer would have changed the casting. No different than passing fuel through a hose. I believe the spacer block sole purpose was the make the control lever more convenient to reach.

[Willie]

IMHO Coyote's theory is very plausible. Affecting the reserve level would be as easy as lengthening the pick up tube. That would be a lot cheaper as well.
Making the control lever longer would probably have made it easier to reach and, again, cheaper than adding a spacer block and an additional gasket.
Anyone else want to weigh in on this one?
Willie

[Willie]

Hi Willie,12 years ago I used red fibrous washers on the bolts that hold the tap assembly to the fuel tank,never had a fuel leak in all that time,dry as a bone VERY cheap fix I think you will be spending the money for the rubbers though...I can't think of a cheap fix for those unfortunately Alpha Sports Suzuki selling those two rubbers for about $15 US dollars
Cheers,
Roger

Well guys, reinstalling the petcock didn't work out the way I'd hoped. I liked the idea of leaving out the spacer block, and did just that. I did use a new rubber o-ring gasket though between the petcock and the tank. I used rubber-backed "sealing washers" instead of red fibrous washers because I thought they'd seal even better. They didn't.
Gas leaked out around the bolt heads like there weren't any washers at all.
I'm glad I didn't put more than a pint or so of gas in the tank. It made the cleanup a little easier.
When I pulled the tank off to set on its side I noticed it had also leaked around the petcock/tank interface.

So here's my question, should I have put any sealant on that o-ring before bolting the petcock to the tank?

Also, I really torqued down on the bolts to make sure they sealed. How tight should the bolts be and should I have wrapped the threads with teflon tape?

I'm going to replace the sealing washers with red fibrous ones and try this again.
I look forward to the next round of responses.
Thanks,
Willie

[jabcb]

The stock sealing washers are like Stat-O-Seal washers. They seal the bolt threads.
The stock washers are around $2 at a local Suzuki shop.
Stat-O-Seal washers are $15 for 10 washers at McMaster-Carr.

I've never had any trouble with the stock washers.

[Coyote]

Is your tank nice and smooth where the petcock mounts? Smooth and flat? The gasket can only take up so much. It wouldn't hurt to wrap the threads on the 2 retaining bolts, but I have never found that necessary. It could be the threads are just too loose. Did you re-tap the holes for any reason? Does your gasket have a 'flap' on one end? If it does, that needs to be carefully cut out with a razor blade or an x-acto knife.It will never seal if it has a flap on there. That flap is for later petcocks and was there to hold in the 1 piece fuel strainer. Otherwise, the gaskets are identical.

[Willie]

Is your tank nice and smooth where the petcock mounts? Smooth and flat? The gasket can only take up so much. It wouldn't hurt to wrap the threads on the 2 retaining bolts, but I have never found that necessary. It could be the threads are just too loose. Did you re-tap the holes for any reason? Does your gasket have a 'flap' on one end? If it does, that needs to be carefully cut out with a razor blade or an x-acto knife.It will never seal if it has a flap on there. That flap is for later petcocks and was there to hold in the 1 piece fuel strainer. Otherwise, the gaskets are identical.

Great questions and thanks for mentioning that "flap". The tank mounting surface is smooth and flat and I didn't chase the threads. But about that "flap".... I was examining that flap just this afternoon and wondering why it was there. It does cover a recessed area in the petcock but I didn't see any reason for that area to be sealed. I also took another look at the parts drawing while ordering the sealing washers (yeah, I couldn't find them or a substitute locally) and that flap wasn't present in the drawing. When looking at the petcock from the side, with the gasket in place, I noticed how that flap is higher than the surrounding sealing surface. So thanks for mentioning it and suggesting that I carefully trim it out as that's what I had considered doing.
Thanks alot for responding to my post.
Willie

[Coyote]

Yeah. They show you one thing and you get another. I think the 'flapless' gaskets are long gone. I haven't seen any in a long time. But it is an easy 30 second fix. Ditch the flap!