Standard Petcock Alternative

[dbeardslee]

Pretty sure the Specials are 34mm on center ...

I think you're right. Part N More is showing 34mm, 44mm, and 46mm adapter plates, as well as the petcocks.

[Brak]

Would an adapter plate like this work on a special tank?

I seem to remember something is different with them, like the mounting surface is angled, or something like that.

[dbeardslee]

Would an adapter plate like this work on a special tank?

I seem to remember something is different with them, like the mounting surface is angled, or something like that.

The only difference I know of is that the tower on these petcocks is round, and slightly too big for the slot in the tank. You put the plate on the tank, mark the location of the center hole with a sharpie, and then dremel it out. It's a very small amount of material that needs to be removed, but it does need to be removed.

Mack posted a pic that shows what the modified slot looks like -

[motoman]

Yes the plates come with 32, 42 and 46mm on center. I think the special was 32mmoc, but you should check before ordering.

Definitely looks to be a good option choice Mack! Fortunately, my original Venturer Standard petcocks still working fine.

[TopCatGr58]

Hey Mack,

I'm preparing to do this mod for my XJ tank. My special petcocks fit the XJ tank. I tried to measure them with my calipers, but the tank is still in place, thought I found 35 mm, but could be 34..same as the size adapter plate PNM offers.

A member gave me a Standard adapter plate and petcock years ago, never used it, so now I'm going to put it on with another new one I found on eBay for only $18.00. Even with the price of the $8.00 adapter plate, it will still be cheaper than the rebuild kit for the OEM unit. AND I'll have NEW parts with hopefully better designed valve??

A few questions. The adapter plate seems to be chrome steel. Since the mounting holes are at 44 mm for a standard, I should have room for drilling new holes with the 34 center to center spacing in the plate. The other holes shouldn't cause a problem with sealing since they will just be over part of the tank that is sealed. I saw that the plate comes with a gasket. Would you concur with my rationale above?

My other question is with what sealant do you use for the petcock to adapter plate NPT threading? I researched online, found that the Permatex AVIATION form a gasket sealant brush on stuff in a small tub is what it suggested, being very fuel resistant.

My other question is that I could probably make an adapter plate out of some 1/2" thick 6061-T6 aluminum plate. Do you think that it would be okay vs. steel plate? Do you forsee a problem with mixing metals, the steel threads of the petcock and the aluminum plate.....even since I'll be using sealant?

And instead of using just the thin flat gasket, I could also make an oring channel similar to the one on the OEM petcock...I think I like the O-ring better than the flat gasket??

T.C.

[HalfCentury]

34mm

My XJ tank is off for intake boot replacement, carb rebuild, petcock rebuild, etc, etc.

The actual measured CTC reading is between 33mm and 34mm. Being that my HF caliper is a budget digital instrument, the absolute accuracy of the caliper is highly suspect. My day job involves calibrated measurements of electrical phenomena.

Here is another observation. My XJ tank appears to be OEM stock maroon paint. The paint under the petcock mount is disintegrated and is gooey where the dissolved paint is sticking into the tank.

If your XJ tank is unmolested stock, you probably have this happening underneath your petcock mount. I suggest addressing the loose goo.

Also, there is dissolved paint stuck to the petcock O-ring and stuck to the underside of the petcock mount. All of this should be cleaned up for a leak-free re-mount.

Just my 2-cents worth.

Cheers

[natemoen]

TC, how old you actually mount the plate on the tank? The stock setup has nuts welded into the tank for the screws to thread into.

[TopCatGr58]

Hey Nate,

The adapter plate is bolted to the tank using the OEM threaded holes. The 3/8" NPT threaded petcock is threaded into the adapter plate, and that's why it needs a good sealant between the adapter plate and petcock. The Adapter plate will seal against the tank in a similar fashion to the OEM petcock, but the plates from MikesXS just have flat gaskets to seal them with.
I like the use of the O-ring, and would probably ALSO add some of that fancy Aviation Sealant as well.

50Century, my tank is far from OEM paint, been stripped, repainted, and will be stripped/repainted again soon for this 2nd REBUILD! Thanks for confirming the bolt spacing.

T.C.

[mack]

Tc

I didn't have to use any sealant on the threads at all where it mounted to the plate. Very good fit but if you need to, "seal all" works perfectly with gas.
The adapter plate came with a fuel resistant rubber gasket that fits between the plate and the tank so metal compatibility wasn't an issue but you still need to clean the paint off and prep the surface to ensure a nice flat tight fit. If your over sizing the adapter plate and covering the existing mounting holes I don't see how you would attach it to the tank. You need something to thread into right. I'm sure an adapter is available at the XJ spacing. You really don't want to have a gas leak while riding. These motors get pretty hot and you don't want to be a tracer going down the road. I tested mine for a week before I would even mount it on the bike. But my tank had a lot of pin holes that I needed to repair before I red coated the interior and pressure tested it. Before painting it. But still I filled it and watched for leaks for a week anyway.

[Brak]

I can now confirm the special tank usese a 34mm adapter plate.





So glad to be rid of the stock petcocks.

[Brak]

well. 4 months later i noticed the adapter plates are leaking.
dripping down from the allen head bolt, not from around the base...

so in this case; if it's leaking between the adapter and the tank, and dripping out through the bolt hole, seal all should work, but if it's actually working it's way down the threads, i'm not sure what to use

guess i'm tearing back apart this weekend.

[dbeardslee]

If it's leaking around the bolt heads it's probably because the little fiber washers weren't up to the task. Get yourself an aluminum can and grade school type paper hole punch. Punch a hole in the aluminum, and carefully trim around the outside to match the dimensions of the bolt hole. Make several for each bolt - they make excellent crush washers.

I have a cheap set of punches that I use to make 'em near perfect. I punch out the OD first, and then punch out the ID as close to the center as I can get. They work great. Also good for stopping leaks around the bolts that hold your cam chain tensioner. JAT

[bikerphil]

Teflon tape (yellow type for fuel) would also work on the threads.

[skids]

I once tried replacing the regular screw bolts with allen head cap bolts and metal washers with fiber washers. They leaked down the threads. I found some flanged head bolts and used fiber washers without the metal washers. It worked. It looks like your bolts are counter sunk?

[Geezer]

I think it would be pretty easy to make those adapters out of plate aluminum on a drill press. I'll have to give it a go when I get my bikes out of storage.

Tony