Flow Measurements on Ewarts Fuel Tap

Hi RobSS, Although AMC took over in 1953 they were not producing Nortons at the AMC facility untill the Norton factory closed around 63 , Once AMC took over production they started to change all sorts of things from threads to finishes .I have bikes from both factories but only really regard The Norton Birmingham produced bike as a "proper " Norton . A sort of snobbery!. I am interested in the Ewarts flow experiments as I have had an odd experience of Running out of fuel on main, turning on the reserve and finding it all gone tank dry. As the tap filter and standpipe are intact I can only assume that the fuel reserve can seep through the main tap workings at just enough rate to keep my 99 ticking along ( one was tested to over 100mpg !!). Going to fit my spare Ewarts to the Atlas to replace the modern leaky tap. Have to warn son about the non reserve reserve!.
 
texasSlick said:
Here is one that looks promising. States 1/4 Inlet; 1/4 Outlet, but is it NPT or BSPP? I am guessing the lever on the side is Reserve Function. All brass suggests good quality.
From India.
www.ebay.com

NEW FUEL PETROL GAS TANK TAP PETCOCK 1/4 X 1/4 FOR BSA, NORTON AND TRIUMPH | eBay

Product Color May Slightly Vary Due to Photographic And Lighting Effects.
www.ebay.com
Click to expand...

Did a flow test on this style.
260ML/minute same for main and reserve
The top of the tube for main is lnot much over 1/2" above tanks bottom
I'm going with a rethreaded 3 position DAPCO
My 63 slimline is a small tank test bed. I will attempt to rotate the rolling chassis between the 122SS, then 650SS, then combat spec atlas before going back to the original 20 engine commando CR pistons.
YRMV:)
 
I do not think 260 ml/min is adequate for a hopped up 650, or a stock 750, and certainly insufficient for a warmed up 750.

If you look at my data in post #1, 260 ml/ min is not enough to satisfy the flow rate that a. 0.125" needle orifice can pass.

Many users of chopped dual Monoblocs report their engines "poop out" at WOT over 5K rpm.
They are simply running out of gas! My Atlas with the monster needle and seat that I have, pulls hard right up to 6800 rpm. Looking again at my data, I am getting 354 ml/ min with a 0.200" needle orifice.

Slick
 
Can't you make a brass connector to the fuel
pipe that is bored a bigger hole like the ewarts fuel tap that I used to use on my Norton?
 
Bernhard said:
Can't you make a brass connector to the fuel
pipe that is bored a bigger hole like the ewarts fuel tap that I used to use on my Norton?
Click to expand...

Read Note (6) following the data table. A slightly larger bore is not likely to yield a significant increase in flow.

Slick
 
Triton Thrasher said:
I’m tempted to try this BSP on/off/reserve one:

Flow Measurements on Ewarts Fuel Tap

https://www.ebay.co.uk/itm/Universa...-/222346771350?_trksid=p2349624.m46890.l49292
Click to expand...
It arrived. It flows 200 cc in a minute, from a full Slimline tank. I won’t be using it on any 650 of mine.


This little devil passes 550 cc in 15 seconds. My bike may be slow, but it’s not because of a restrictive tap.

Flow Measurements on Ewarts Fuel Tap
 
Ordered two dapco off-on-res petcocks from MAP.
MAP confirmed they are from DAPCO/Dexter Mi
I may call Dapco how big a run/batch and how much $ to make BSP threads in and out.
 
extract from BDM

38. PETROL TAPS. A really silly one.In my youth when I knew even less than I do now but thought I knew it all I once had problems for a long time with a bike that would slow when holding the throttle well open for a long period of time…..even with a gale up my rear along say ‘The Mountain Mile.’ I could NOT understand till one day I wondered….. 120mph….30 miles per gallon? 4 gallons per hour = 32 pints per hour = one pint every 1 min 52 seconds……Placed the tank on two chairs put a pint pot beneath and turned the tap on……one pint in 2 minutes 20 seconds………..Q. E. D. Cause? The new petrol tap I had fitted had too small a bore and I was suffering increasing petrol starvation the longer the throttle was wide open. One of those nice big bore brass chromed ‘Enots’ gas type taps instantly solved that problem. A friend had a similar problem not long ago…we EVENTUALLY found the crap they put in petrol had resulted in the neoprene seal expanding and partly blocking off the fuel flow through the tap.. Av gas once caused the ‘rubber’ tube we had used to flexibly mount the carbs on our Atlases to swell and partly block off one inlet tract causing somewhat erratic running….so stupid a reason for the engine not working correctly we never thought to check it and only found it when someone took a look down the inlet tract with the slide fully retracted….
 
Independently I found the same thing a little after 2002. Black rubber lined petcocks would swell and cause big problems. I got them OEM from ANIL (BSA REGAL). The DAPCO are viton rubber which is OK for ethanol. On a bike tygon 4040 is fine for the hoses, however 4040 is NG for OPE where the E-10 touches the exterior of the line when inside the fuel tank.
 
flow see post 4
post 4 above


Flow Measurements on Ewarts Fuel Tap


petcocks
MAP#MAP0654
These are often ebay shown as HD application.
left=off
down= on/main
right=on/reserve as shown
They readily take rethread with BSPP die and is how I tested it on my BSA B25? tank
 
norton bob said:
Hi RobSS, Although AMC took over in 1953 they were not producing Nortons at the AMC facility untill the Norton factory closed around 63 , Once AMC took over production they started to change all sorts of things from threads to finishes .I have bikes from both factories but only really regard The Norton Birmingham produced bike as a "proper " Norton . A sort of snobbery!. I am interested in the Ewarts flow experiments as I have had an odd experience of Running out of fuel on main, turning on the reserve and finding it all gone tank dry. As the tap filter and standpipe are intact I can only assume that the fuel reserve can seep through the main tap workings at just enough rate to keep my 99 ticking along ( one was tested to over 100mpg !!). Going to fit my spare Ewarts to the Atlas to replace the modern leaky tap. Have to warn son about the non reserve reserve!.
Click to expand...
If you have anAtlas tank there is a tube on the bottom which the tap threads onto. This lowers reserve internal pipe giving less on reserve, somthing to watch out for.
 
Bernhard said:
If you have an Atlas tank there is a tube on the bottom which the tap threads onto. This lowers reserve internal pipe giving less on reserve, somthing to watch out for.
Click to expand...
Yes the slimline tanks have the threaded pipe extension to allow tap clearance from behind the frame rail. The dapco petcock stand pipe is log enough to be useful but not overly generous. If I can be successful to get a reasonable price for BSPP on both ends , I'm confident a little longer stand pipe& screen could also be negotiated.:)
 
dynodave said:
jk

Certainly would help firm up a good #
Click to expand...
If I can get out of my driveway tomorrow and get to my shop, I will make the measurement.
I have to pull a 5% grade for 400 feet, before I get to the level, then 150 feet more on the level to get to the pavement.

I will post the numbers here.

Slick
 
Received the two from MAP.
The stand pipe is 2.0" from the flat spot/base of the threads. So, with the 3/4 tank mounting pipe, 1-1/4" for reserve- minus the sealing washer thickness. 1-1/2 quarts? in a slimline tank?
I'll be running a die over it and do a fill-reserve test with kerosene.:cool:
 
MichaelB said:
A very nice set of taps that was in a box of bits on a purchase.
These are full port, ball valves. No restrictions. Flow very well.
Very well made, smooth action.
Click to expand...

Are you aware this thread is over slimline tanks that we all know have only one outlet spud?
The second issue is over the off/main/reserve both being on one petcock because again the tanks has only one outlet.
The third issue is that a restrictive low flow rate on single outlet petcocks is detrimental to engine heath at high throttle settings.
 
Back
Top