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T: Fuel Tank Fuel Tank Petcocks

Texas John

Well Known and Active Website User
Non-VOC Member
Anyone recognize these Petcocks? The Petcocks on my mid-1948 Rapide are clearly not T28 "Push-Pull" style (Ewarts?) taps, and I don't know what the T28/1 Lever style look like. Unless these are them (with a lever on the front and a small spring on the back)? I imagine these are something installed by a prior (pre-1973) owner when the old taps were hopelessly leaky, but confirmation would be nice before I replace them. Thank you.
Vincent Rapide Petcock.jpg
 

timetraveller

Well Known and Active Website User
VOC Member
Can't be sure but they look kike the ones often fitted by the go faster boys as they had a 1/4" diameter hole through them. Brass housing with tapered brass on/off through the centre which had to be lapped in to prevent fuel leaks.
 

vibrac

Well Known and Active Website User
VOC Member
Thats the very thing for racing perusal of old racing bike photos may confirm and still up to the job in these Ethanol infected days.
I certainly loved them until those ball valve O ring gas pipe taps came along certainly a lot better that those hexagON leakey ewarts things
 

davidd

Well Known and Active Website User
VOC Member
John,

They are in the style of Lightning/Grey Flash taps. There seem to be two models. One has a large bore of 1/4" and one has a much smaller bore. It is the size of the bore that determines if it is a racing tap. It is shown in Obscure Components.

Racing Tap.PNG
I would not bother cleaning it unless you already have some "EZ Turn." It is a fuel-proof grease that you would use as a lubricant for the taper. If you try and turn it without good lubrication the handle will snap.


David
 

vin998

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I had some similar fitted to my series A and the modern fuel with ethanol in it caused them to seize as the ethanol appears to strip all the lubricating properties out of the petrol. I could dismantle them and lap the tapers back in with metal polish but after 100 miles they would seize again. Fitted ethanol proof push-pull taps and problem solved.
I agree with vibrac the gas/oil ball valves work great and I have them on the rest of my bikes but series A are 1/8 BSP thread in the tank and so the gas ball valves don't fit.
 

Texas John

Well Known and Active Website User
Non-VOC Member
David,
That picture is what mine look like from the back side with the little spring and split pin. I read that entire book once, and don't remember half as much as I should. I do not have the EZ Fuel Lube so there is one more thing I need to buy. I now know not to try and turn them until I have disassembled and cleaned them and have the lube. Thank you, once again.
 

Texas John

Well Known and Active Website User
Non-VOC Member
I managed to get the petcocks out this weekend. One was fairly tight, the other I thought would round the flats before it would come loose. I heated the tank with a heat gun, sprayed duster fluid with can inverted to freeze the valve, and managed to get it to break loose. I will have to work on the threads a bit before re-installing. Anyway, soaked them in lacquer thinner for an hour, still did not want to turn. Tapped the spring side of the valve a couple of times with a plastic mallet and each one came loose and now they turn fairly nicely. I will disassemble and thoroughly clean them after the magic EZ Turn Fuel Lube arrives. I could have used that stuff when rebuilding the fuel valve on my Model A Ford! Seems the stuff is popular with the antique car people, too. David - Thanks for telling me about it.
 
Last edited:

Rob H

Well Known and Active Website User
VOC Member
I had a modern equivalent set fitted, work great initially but then as noted they start to stick due to the ethanol. Took them to bits to clean but never worked properly again.

Have just refitted the original Ewarts but with the new ethanol proof plungers from the Spares Co. Seem to be working good for now, no problems as yet
 

oexing

Well Known and Active Website User
VOC Member
Nothing to do with ethanol or modern fuel that seemed to be the root of the troubles with these taper fit fuel petcocks. Really the combination of brass body with brass taper is non-working for extended time, you get seizures and galling with like materials, just like tightening an alu nut on an alu bolt - or same with all stainless steel - seizures guaranteed. You can get the taper hardchromed and lap it in the body with super fine paste. Or do a stainless steel taper mod and no trouble ever after as I did with numerous petcocks on my bikes. Look at your brass tapers that were stuck with a magnifier, lots of seizure traces so no more sealing.

Vic
 

medat727

Active Website User
VOC Member
Vic,

How are you doing the stainless taper mod, are you turning it up on a lathe or purchasing a stainless taper pin and starting from there, I’ve looked at stainless taper pins on McMaster Carr but the tapers seem too shallow?

David
 

oexing

Well Known and Active Website User
VOC Member
Hi David,
the taper on these taps is anything of a taper, not a standardised type I guess. So you´d clamp the brass item in the lathe somehow and set the lathe up for this angle with an indicator on the taper running along the taper. So you should be close enough for a try with the petcock body and some minimal corrections possibly on the lathe when you fabricate a stainless steel copy. Some lapping with grinding paste will be essential for a seal but it is worthwhile, no more troubles with any fuel that attacks most material except Viton or teflon.

Vic
 

Cyborg

Well Known and Active Website User
VOC Member
Might be an idea to make a male lap to clean it up the bore before you lap in the new stainless taper? Or someone must sell a reamer that would work? I inherited this about 4 years ago and just yesterday took it out of the box to figure out what it is. Now I have a use for it. The other doodad is for turning very small stock.

55456FBD-DE45-4B03-844B-F07B091F5109.jpeg
 

oexing

Well Known and Active Website User
VOC Member
I just looked for 1/4 " fuel taps at Aliexpress, all brass , yes. But before trying to get a taper reamer, unlikely to get cheap with this taper, you might better have one fnew rom Ali with good body and either have the taper nickeled or chromed (hard) or copy it in SS. There are lots of other types with same thread if you accept them on the Vincent. Most are suitable for disassembling. So in case they don´t like leadfree fuel you could do a seal in cork. Fiddly job but works quite well, unlike rubberlike seals in taps. Fuel has no lubricating properties so rubber types tend to stick.

Vic
taper fuel tap
fuel tap female
fuel tap
fuel tap left or right
 

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