Fuel leaking at petcock bolts

I just picked up a KZ750H (is that an LTD?) that has been sitting for many years. I was trying to clean the tank out as it had a bit of varnish on the inside so I filled it with some acetone and some carb cleaner and swished it around for a couple days. I flipped it over to remove the petcock to drain the tank and found it has been leaking around one of the 2 bolts that hold the assembly to the tank. When I removed them to drain the tank I see there is just a bolt with a washer then the metal of the petcock, and then it threads into the tank. They bolt inside of the O-ring seal that goes between the petcock and the tank, and the threads penetrate into the tank. I am surprised only one of them is leaking since I really don't see anything there that seems like it would seal it from gas leaking around the threads and out. Should there be a rubber washer or an O-ring or something that goes under the bolt heads? I would guess it requires thread sealer or something but since they bolt inside of the O-ring even if the threads were sealed it could leak around the shaft and the head of the bolt.

Might want to make sure the washer wasn't warped, or a crush washer.

Those washer are supposed to be nylon, not metal. Ed

A good hardware store might have the nylon washers in the needed size.

Oh man - No wonder the fuel tank was completely empty when I got it.

Looking at it again there evidence of a leak on one side of the petcock and the bolt I'm having trouble with. Having the wrong washers would do that!

Would plain old hardware store nylon be good enough, or should they be the specific kawasaki nylon washers? Partzilla has a really reasonable price on what are allegedly the oem washers, but if hardware store ones would be just as good I see no point waiting for them in the mail. I looked up the washers before posting the question but everybody just lists them as 10mm flat washers, no mention of them being nylon instead of the metal ones I have.

Thanks for the help!

They are 6mm washers, not 10mm.

You're right, there is no mention of them being nylon, and that is a poor omission on the part of the Kawasaki guy who wrote the descriptions. However, when you look at where the washer (part # 92022-183) is used you'll find it is only used on the petcock screws but on many different KZ models.

I ordered new ones a long while back as part of a larger order, but I would think any 6mm nylon washers would work as long as they're not too thin. Ed

Sorry - I measure things in strange ways. They fit M6 bolts and are roughly 6mm ID but also roughly 10mm OD which is what I meant. Many things I say only make sense to the voices in my head

I'll hit up a couple hardware stores and car parts stores to see if I can track down some suitable nylon washers. Looking at other parts diagrams I'm going to replace the bolts with smooth-bottom flange head bolts as well since that seems to be done on some of the other models. They look to be M6-20 with 1.0 thread pitch so that should be no problem to find. A little more surface area to make the seal would help if I can't track down precisely the same washers.

I found one reference to the dimensions of these washers and they were listed as either 1.4 or 1.5mm thick. I'll make sure anything I grab is of comparable thickness.