tank-mounted petcock change to manual-->possible?

[iamverb]

It's time to upgrade my sucky (er, vacuum ;D) petcock to a manual valve, and there's been a lot of discussion about how easy it is to swap them out, but has anyone had any success doing it with a tank-mounted petcock?

The petcock threads are described as "large" and "coarse", but I haven't found an accurate measurement anywhere yet .


left: tank-mounted vacuum petcock that gives me less fuel anytime I need more
right: The threads look like 3/8"npt (interchangeable with 14mm 1.5pitch). If you know already and want to save me a long walk to the hardware store with my old petcock to test on their thread gauge, I'll be super-appreciative, but until then, I'm going on the assumption I eyeballed it correctly. I will measure before I buy, though, just in case .

I have a few solutions I'm considering (listed in order of preference)
Please share your criticisms, concerns, tips or success stories.

1. The Keihin petcocks on Honda ATVs and mini-bikes look about right, and they're usually around $10 on ebay
pro: best price, easy to find parts and rebuild kits, built in fuel screen, least jerry-rigged of all my options, plug and play (maybe)
con: I have no idea whether they're the right size or not, and I haven't found any one selling one that's kind enough to post the measurements (anyone got a monkey bike or ATC trike in the garage they're willing to go measure?)

2. Universal vintage Japbike petcocks (for larger bikes) mount on male 3/8" and some have 1/4" hose barb outputs.
pro: plug and play, easy to find parts and rebuild kits, built in fuel screen
con: very pricey compared to other options (around $35-40 plus s&h) unless someone knows where to get one cheap?

3. My local plumbing supply store has yellow brass female to hose barb adaptors, then I can use a lawnmower-style cutoff.
pro: cheap! ($2 for adaptor, $10 or so for cutoff)
con: couldn't find an elbow adaptor, so the ideal fuel line run will be difficult (since the bottom of the adaptor will be so low already), also, yellow brass is propane / natural gas line safe, but gasoline?

4. A female to female 3/8" adaptor (plumbing store) will allow any pre-1974 Harley petcock to be fitted (they're 3/8" male).
pro: cheap - I know where to get old Harley petcocks really cheap ($15 and shipping on ebay)
con: pricier than #3, and I have to wait for ebay, the adaptor's still yellow brass

5. (this one gets a little wacky) 14mm / 1.5 pitch is a standard(ish) fuel injector adaptor threading for some VW, Volvo, Audi, BMW and an occasional GM (go figure), but the output is for 3/8" high-pressure fuel line.
pro: adaptor will actually be for gasoline,
con: A lot pricier than yellow brass, 3/8" fuel line from tank will mean using another adaptor between tank and shutoff


I'm open to suggestions, or if you've done it and can share a success story?

[indy50]

I went to the plumbing supply with petcock in hand, came out with a part ( I have no idea what its called ) female threads matching the ones on petcock on one end, The other end a nipple for 1/4" hose. Total cost $1.98 No more vacuum petcock problems : Priceless. BTW install a manual shutoff (can be found at any auto parts or lawn mower shop.) Did this to a Roketa MC08 50

[iamverb]

Thanks! That's exactly what I was hoping to hear!
Was the part you bought yellow brass?

[motomech]

The Honda Elite scooters used a vacuum petcock like that and they were totaly problem free.
I can't recall exactlly, but they may have used finer threads(like 1.25 m/m).

It seems to me that having to reach up under the plastic every time you ride is not very convienent.

All the Chinese versions of that petcock can't be bad. There's millions of GY6 scooters out there that have not had the V.P.'s changed out.
Why not buy a couple and try them?

[iamverb]

You're right that most VPs don't ever give any trouble, I don't recall ever having trouble ever in over 20k miles on any of my Hondas. A direct replacement would probably be fine, I just figured that for the same price or less, I could go with something that didn't completely stop my gas flow at WOT. Also, I'm not too worried about inconvenience - I've never had sidepanels on my current scoot, so there's nothing in the way.

Mostly, though, I'm just really cheap and a cutoff valve is under $10, while the VPs are 15 to 20 plus shipping.... ;D

[webo]

the way I did mine was:

a 3/8 npt (female) to a 1/4 npt (male). then I used a 1/4 npt female to a 1/4 barbed. I purchased a briggs and stratton 1/4" manual shut off valve at autozone. total price was less than $10. I searched high and low for a 3/8 npt to a 1/4 barbed but could not find it. my tank is up high and quite small, so I didn't require an elbow. I'm sure you can find a 1/4 npt elbow to 1/4" barbed. All items purchased at home depot. don't forget to use telfon tape on the fittings. and yes, I believe that brass is safe to use for fuel ( copper may not be so good).

[iamverb]

Thanks webo - I didn't even think of using a 1/4" elbow. That should make it really easy.

[thedannymullen]

So I am assuming this would convert to gravity feed only? I am thinking of attempting this on my scoot, but ahve not had the time .

[balsa1]

eagle ATV Pars have a manual one that is a direct replacment but manual valve the name and number is fuel valve (11550,A87,2 hope it helps

[nodestiny]

Anybody want to post some pics of their at tank fuel setup, just for fun?

[iamverb]

cheapchinaman - if you're not gravity feed, your pump probably isn't attached to the tank the same way a vacuum contolled petcock like mine is. If your pump is attached to the tank like that, though, and you were going to convert to an electric pump, you'd run into the same problem. Webo and indy50's solutions above (or my #s 3,4, &5) should work fine in that case, though.

balsa1 - Here's a link to the item you posted www.eagleatvparts.com/product_info.php?products_id=90011 and it does look like it might be exactly right - anybody used this yet? It's about $5 and shipping more than what I was thinking of doing, but if it's exactly right, that's hard to argue with....

nodestiny - I love pics and I'd love to see other people's set ups. Mine's posted (and I'll update it as soon as I change over to manual). Anyone else?

[indy50]

Use search feature, a couple folks posted pics of this. BTW vacuum pressure is almost 0 at wot and my stock petcock would not supply enough fuel for wot riding. (Which I do a lot of !)

[balsa1]

Yes it works I have one on my scoot even though I have to reach under the plastic I look at it as another anti joy rider deturant.

[greg]

i swithched to a manual fuel valve. in the mechanics forum i posted a link to a good heavy duty inline valve works great. yes i to have to reach under the body to turn it but thats no biggie. guess if it was a big deal i could just mount it to the inside of the underseat storage. i took the old vaccuum petcock to a local ghardware store (a big one) and i ended up with a brass piece at a 90 degree angle coming off the bottom of the tank with a male barbed end to that. i used yellow teflon tape to seal.(yellow is safe for gas).but it would still stall after a block like it was out of gas so i just turned out the lean/rich screw out 1 turn and so far so good.

[schoei1]

I don’t have any experience with the tank mounted petcock, but if you can run the fuel line to the plastic on the side, you can drill a hole and mount the shut-off valve on the plastic as I did. Even at one time, I was using both an inside shut-off and an outside shut-off valve.

[iamverb]

greg - sounds like you got the perfect adaptor. My local Ace only had straight ones, so I'm thinking of using a second 90 degree adaptor like webo suggested, but if I can find one like you got - Gold! Mind me asking which big hardware store you found one at? And thank you for the reminder about the yellow teflon tape - very important tip.

schoei1 - that's a great solution for placing the valve. I don't have sidepanels, so it doesn't work for me, but I know it's an issue for most folks!

balsa1 - man, that's tempting. If I don't find the exact right adaptor, I might end up springing the extra $10 for that. Thanks for the follow up on fit and function!

[revgeorge]

What worked on my SunL was an "inverted flare" fitting. You may have to go to a real hardware store (as opposed to a home depot/ Lowes/Home plus). I got a 90 degree elbow w/ one IF side and one NPT side. Then I tied in a ball valve, which then went to a hose barb.

I would recommend the Yellow (GAS) Teflon tape. It is designed to hold up to gasoline, kerosene, etc.

-+G

[greg]

iamverb...http://search.stores.ebay.com/RANDYS-ENGINE-REPAIR_fuel-shutoff_W0QQfciZ15QQfclZ4QQfsnZRANDYQ27SQ20ENGINEQ20REPAIRQQfsooZ1QQfsopZ1QQsaselZ65709142QQsofpZ0

think i will somehow mount it to the side also. i have the gasline going down about a foot then going back up to the carb. seems to work though i wonder if it will when the tank is low. pressure would be less to push it up to the carb?

[iamverb]

OK, I know I should let sleeping dogs lie, but I finally got around to putting the new fuel valve on (hmmm, day one of having two wheels on frankenscoot again, and what do I do but take it apart to upgrade it again... sigh) and wanted to show what I ended up doing. Thank you, everyone for all your tips! (esp. the reminder to use yellow teflon tape)



From the fuel tank: reducing coupler, 3/8" to 1/4" FPT to FPT, connected to a 90-degree 1/4" to 1/4" street elbow, connected to a 1/4" FPT to 1/4" hose barb adapter. Lots of Gas-safe yellow teflon tape at every junction.
Clear yellow 1/4" fuel line, fuel valve and filter from a riding mower. Everything past the filter is 3/16" Bando fuel line. The vacuum lines were all removed, except for one short piece connecting the two vacuum sources, to close the loop. (shoulda took a pic before I put the seat back in - sorry)

Yellow brass pipe fittings: $11
Mower valve and filter: $9
Having all the fuel I need when I'm WOT going up a long hill, and being able to replace anything that goes bad for less than a 10-spot: not quite priceless, but totally worth it.

I'll report back if this set-up is anything less than exemplary.