Author Topic: petcock threads? (Read 5882 times)

solg · **on:** February 02, 2014, 11:10:03 pm

does anyone have information? I am trying to determine what threads are on a 2008 iron barrel Karcoma brand petcock. I thought they were BSPP but,They are different than the BSPP brass adapter I have.(see photo)

ace.cafe · **Reply #1 on:** February 03, 2014, 01:08:40 am

I don't know. It seems the threads are always changing on RE things. It might be metric on late models. Or not.
I usually just try different things in the hole until I find what fits. Then you know what it is.

solg · **Reply #2 on:** February 03, 2014, 01:35:18 am

i haven't found anything that fits that thread. Im wondering, could cut that stub off and drill & tap it for 1/4" NPT ?

ace.cafe · **Reply #3 on:** February 03, 2014, 01:41:46 am

I think you could just drill it and tap it.

Ballroom dancer · **Reply #4 on:** February 03, 2014, 06:04:42 am

Slow down for a moment. Why are you replacing the petcock? I have repaired three of these and they fail because of a weakness in the design. If when removing or installing the petcock it is turned even a little bit the nylon reserve tube shears off. I repair them by installing a piece of brass tube from the hobby shop in place of the nylon screen, seal, reserve part. The tube is just a touch small so I expand it by putting an arbor (number size drill bit shank) inside and very lightly tapping it while rolling it on a steel block. When it's almost a push fit I locktite the tube in place. Must use an inline filter after the modification.

I don't have the answer to what size the thread is but the nut which connects the petcock to the the tank spigot is both left and right hand threads. The pitch of both of these appears to be 1 mm. Oh, one more thing. I use a thin slice of 1/4" urethane tube for a gasket although if you have an O ring the right size that should work. I also show a Briggs and Stratton petcock from a lawnmower shop. I've used these on ultralight airplanes and they work fine if you decide to go that route. The Briggs and Stratton petcock is 1/8" pipe thread. If you want I could repair your petcock for you but you must have the nut.

ace.cafe · **Reply #5 on:** February 03, 2014, 12:15:14 pm

I think that his problem is insufficient fuel flow at higher rpms on his
Fireball, so he needed the fuel tap to flow more fuel than the previous one he had.

solg · **Reply #6 on:** February 03, 2014, 03:14:22 pm

Yes Mr Ballroom. Tom is correct. The petcock I have is actually in good shape with no leaks. This was adequate for the bike in stock form. My concern is for the performance demands of my bike in its Fireball form. Although I have not opened er up yet as it is still a pretty fresh build, I can see the stock petcock having a hard time keeping up with things. After all the Pingel fuel taps "pass more gas"

Ballroom dancer · **Reply #7 on:** February 03, 2014, 05:07:17 pm

Thanks guys. Now I know what I have to plan for someday when I modify the engines on my 06 and 08 iron barrels.

ERC · **Reply #8 on:** February 03, 2014, 07:36:40 pm

The threads on that petcock should be 1/4x19 BSPP. I just measured a couple I have and they come out to that size. ERC

solg · **Reply #9 on:** February 03, 2014, 11:07:48 pm

Thats what I am told but, as you can see by the above photo the BSPP fitting is a bit larger in dia(.51") and coarser in thread (19 TPI). The threaded stem sticking out the bottom of the tank is .45"in dia. and the threads are metric (1.0) that stem is more like 12mm X 1.0

ERC · **Reply #10 on:** February 04, 2014, 07:57:13 pm

I looked on Hitchcocks site and your shut off looks like what they describe as a Karkoma shut off and it says you need an adaptor that they sell. ERC

solg · **Reply #11 on:** February 05, 2014, 03:02:33 pm

Yea, I called Hitchkocks this morning. They say that adapter won't work in my application

ERC · **Reply #12 on:** February 05, 2014, 03:21:20 pm

Not cool you'll have to do some thread cutting. ERC

ace.cafe · **Reply #13 on:** February 05, 2014, 04:50:51 pm

I just talked to Chumma on the phone.
He says he will email you about some method that he worked out to handle this petcock issue.

solg · **Reply #14 on:** February 06, 2014, 12:07:41 am

Email received. Thanks Tom. Ive already cut off the tank stem though. Im in the process of boring it now. ill find out shortly how taping a pipe thread into it goes.

devon john · **Reply #15 on:** February 15, 2014, 05:15:15 pm

just done that , cut the male tube off drilled out and taped to 1/4 "BSP .
theres plenty of meat there and now loads of choice of taps.

john

solg · **Reply #16 on:** February 15, 2014, 07:26:19 pm

after cutting off the pipe weenie sticking out the bottom of the tank. i taped it for 1/4' pipe thread.I made a bad choice in Ebay sellers or I would have included a pic of the petcock mounted to the tank. This photo will follow.

solg · **Reply #17 on:** February 21, 2014, 02:50:44 pm

Well, the project is complete. Rod, you are right the Pingel is a bit pricey but its well made, completely rebuildable, and the action is incredibly smooth! Not to mention it looks awesome.I should have no issues with fuel flow with this thing.

aleman · **Reply #18 on:** February 22, 2014, 07:21:25 pm

Hey, hey! I'm glad you got that worked our Solg. That looks great, and a little more compact than my set-up. Yeah, it's spendy, but just a superior way to go. You'll never fuss with it again. Nice job.

solg · **Reply #19 on:** February 22, 2014, 09:00:07 pm

Thanks. I had a coupling on there at first but the outlet tube aligned better without it. Its subtle details like this that I enjoy.