Topic: Does anyone make a low-profile petcock?

[754]

 I cannot see Moving over the hole pattern and the oval o-ring sealing unless it is on a clean flat surface.

 Cutting the oval o-ring seat is a bit tricky.
 

[srook]

I am not sure how long the plate inside the tank is.  Either way with the rubber oring you don't have to go ape on the petcock screws to get it to seal.  I would still use the viton/steel sealing washers to seal the petcock screws otherwise the petcock when off will leak into the carbs and can cause the bowls to leak out of the overflow tubes or into the airbox.  I don't know how permanent a fix permatex would be.  It should seal but I would want some type of rubber gasket.  Maybe cut one out of an old inner tube. 

Any cnc machine could cut a groove for the oring into a piece of plate really easily.  It would just cost some $$ for the setup.  I think you could even seal it using a flat plate with no groove but gasket cement the o-ring into position and let it dry, then screw it into the tank.  The groove just holds the o-ring into position.  It will still seal without it. 

You can definitely drill new holes for the petcock and it will seal.  Carpy sells the same tank without the holes.  It's up to the purchaser to drill and tap the holes.  I did this on my Carpy tank and it didn't leak at all. 
Scott

[754]

The only reasonable scenario I cam imagine for the O-ring groove, is to either do a rectangle on a mill or make a wood template for a router.
 Oring without groove, I doubt it would work, use a flat gasket, it may/should work.

 Seems like a piece of 1? inch by 1/2 inch alum bar, sealed where it meets tank, mounted to existing screwholes, with small diameter head fasteners, then a hole drilled for a NPT, or Brit petcock thread .. would have to work..

 If the Dunstall tank was intended to use the stock petcock, perhaps it was intended for KO cablepull carbs ?.. I mean at one point, the tank must have fit at LEAST ONE Honda 4.. I am thinking..

[srook]

" If the Dunstall tank was intended to use the stock petcock, perhaps it was intended for KO cablepull carbs ?.. I mean at one point, the tank must have fit at LEAST ONE Honda 4.. I am thinking.."

The fiberglass tank like Kevin has came out in 1971 or 1972.  It was not made exclusively for the K0.  The variable here is the tank mount ears that are not Dunstall.  It looks like someone made them later.  I am assuming that they mount the tank too far back and this is causing the petcock fitment issues.  The tanks came from Dunstall pre-drilled for petcocks so unless this was a mistake tank that was never sent back for warranty, the issue comes from the mounting ears putting the tank in a position that Dunstall never intended.

Here are the mounting instructions from Dunstall.  This should clear up any confusion about the Dunstall tank.

http://www.buffaloschools.org/webpages/srook/files/Dunstall-Tank-Info.pdf

Scott

[754]

NEXT time someone has this problem.. be way easier had they posted a pic at the beginning of the thread...

[ksmith0034]

NEXT time someone has this problem.. be way easier had they posted a pic at the beginning of the thread...

You know 754, perhaps your 10,000+ posts has taken all the fun out of this for you these days.  But I am trying to figure out a problem here, and the fine folks like srook and others are trying to help.  I'm sorry I didn't post the exact picture you were looking for in my first post.  I promise to try harder next time.
Thanks to everyone for posting suggestions and ideas.  I will indeed try to move the petcock forward on the right side of the tank in order to clear the carbs.  I will then attempt to cover the original holes using a flat metal plate and a rubber washer of some kind.

[wildcatmahone]

If you dont want to drill more holes in your tank try repositioning those tank mounts.

[ksmith0034]

I can't really reposition the front brakets because it would throw off the whole tank/seat/quick-disconnect telemetry thing I have going on (i have some pics in my build thread).  Otherwise I would do that in a second - way easier than re-drilling my tank for sure.

[Alan F.]

Instead of cutting an oval o-ring groove in the blank-off plate, would it be simple and effective to just make a gasket from a sheet of appripriate material?

Like buna-n  http://www.smallparts.com/buna-n-sheet-60-durometer-black/dp/B003SLEZQS/ref=sr_1_2?sr=1-2&qid=1293669062

Or viton http://www.smallparts.com/small-parts-viton-sheet-black/dp/B003SLEZUY/ref=sr_1_1?sr=1-1&qid=1293669030

[scottly]

On my Seeley tank, the center hole was close to the size for a 1/8" pipe tap. I modified a brass pipe nipple to act as a barbed hose fitting. My carbs have larger fuel lines, BTW.
I also turned down the heads of the Allen screws that plug the original mounting holes for clearance.

[754]

Ksmith, dont worry about the fun being out of it for me, far from that..
 But got to ask, is the bolt pattern for sure the same as Honda, is there tapped holes into tank, on the same centers??
 And does the Pingel appear to fit if there was an adaptor between it and the tank??

 FWIW.. out of 3000 members on here most have never seen a Rickman tank, maybe 6 or less know what the bottom looks like, and only one of them appears to have found this thread.. Nobody except maybe one, guessed you moved the mounts.. 

 So that is what we had to work with the first 30 posts..

 Now as Scottly sort of confimed, as I had mentioned, the Brit petcock thread (probably BSP)is close to NPT.. So at this point, some of us still dont know what is actually in your tank, for all we know the 2 bolts may have held the plate while putting together the tank..  is there threads in the center hole going into the tank?

[scottly]

To clarify, my Seeley tank was fit with a Honda petcock. I tapped the center hole to 1/8" pipe: it was not tapped as supplied by Seeley. Of course, my main motivation at the time was that the nipple was lighter than the clunky petcock. Who needs a petcock, when you have quality carbs? 

[srook]

754
The Dunstall tank was made for the CB750 and CB500.  It was made to re-use the oem petcock.  The 3 holes were drilled in the tank to accept the Honda petcock.  The center hole has to be a bit larger than the 2 mount holes becuase the brass tube on the petcock is at an angle.  2 sets of holes were drilled so the tank could fit a CB750 or CB500 and a blank off plate came with the tank to close off the holes you didn't use.  The petcock mount holes in the tank are 6mm thread.  The center hole is not tapped.  British petcocks were not used.  The tanks and all of Dunstall's stuff was direct bolt on with little to no modification.  I have no idea if an adapter for a pingel would fit but if the adapter had the same spacing as the Honda petcock then it would bolt right up.  As someone who is into the Dunstall stuff I would just move the mounts and leave the holes as they are.  I understand KSmith's side also.  He isn't building a Dunstall bike and wants the tank and seat where he wants it.  That will involve moving the petcock, which isn't a big deal once you get a plate to seal off the unused holes.  This shouldn't be something to argue about guys.  Now what was a better bike the Triumph Trident or the CB750?  That's something to argue about 

Scott

[ksmith0034]

I drilled a couple new holes and moved the petcock forward on the right side.  It fits!!!   
There is not any aluminum except where the original mounting points were, so the one new screw hole just goes through the fiberglass then I tapped it.  I reused the original front screw hole for the rear.  Now how do I keep gas from eating through the fiberglass where the new center hole and front screw hole are?

[bgfootball67]

Man getting this cafe finished has been a pain for you Kevin.  I had good luck with the 2 part epoxy, JB Weld on my carbon fiber tank that had problem with delamination.  Also fixed a small hole on a 750 F tank that was punctured.  Either way good luck!  HAppy New Year!!!