fueltap with reserve

hi all, I have bought 2 BAP fuel taps from Andover Norton at different times. I have asked for a tap with a reserve, and they have sent one main and one reserve, I need one with both on the same tap, I have twin carbs so must need a reserve on each tap, (don't I ?). I have one of these with both on the right side which was fitted when I bought the bike, and only replaced as the left side tap sheared off when tightening the lock nut. where can I get these please.

mudplugger said:

I have twin carbs so must need a reserve on each tap, (don't I ?).

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There would normally be a pipe connected between the two feed pipes, (or directly between the carb banjos on late models) so either the main or the reserve tap then feeds both carbs.

My 74 has a reserve on the left side. Runs fine on the one right side main tap which feeds both standard concentrics.
Cheers
Don

Matt at CNW sells 3 position taps Off-On-Reserve. They are not shown on the web site. Email him and ask. I have been using them for 3 years (10% ethanol) with no problem what so ever.

I got a set from Matt (CNW) and they work great. Simplified fittings too.
I open both to normal position, and also use both on reserve if needed.
My Premiers are connected at the bowls, so in theory only need one tap at a time.
But I think opening both taps ensures fuel flow at high RPMs.

I've been wondering if you always run on the main tap which has a little tube that draws gas from a higher level that any water precipitated out of the gas would be trapped in the bottom of the tank. Might not have been a problem in the past but with ethanol? I always run with both taps on anyway but is there a baffle between the two sides? I'm thinking I might just buy reserve taps without the pipe for both sides from here on out. I'm not riding great distances in no man's land and I always check the gas level before I start a ride.

htown16 said:

I've been wondering if you always run on the main tap which has a little tube that draws gas from a higher level that any water precipitated out of the gas would be trapped in the bottom of the tank. Might not have been a problem in the past but with ethanol? I always run with both taps on anyway but is there a baffle between the two sides? I'm thinking I might just buy reserve taps without the pipe for both sides from here on out. I'm not riding great distances in no man's land and I always check the gas level before I start a ride.

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The pre-ethanol gas would allow a bit of water to collect (condensation from repeatedly drawing in humid air as the fuel is used up) in the bottom of the tank, (water wouldn't mix with gas) eventually rusting moto tanks through, usually near the pinch weld.

With ethenol fuel, it WILL mix with and hold a small quantity of water in suspension, thereby eliminating the age old problem of the above mentioned failure.

I've discontinued the use of "Dry-Gas" in all my gasoline fired vehicles and equipment for this reason. It's redundant with ethanol fuel.

If you want quality 1/4" BSP main/reserve type taps, try Steve Goode M/Cs on 01938|850544. He stocks an Italian made tap. I have had these on my O.I.F T160 for several years with no problems whatsoever. He has them listed on ebay, item numbers 152060790176 & 152093836613.

Martyn.

Many thanks for all the input, I had a look again today and the tube joining carbs is there, I remember reading something about having both taps open which led to a big senior moment thinking I had bought the wrong taps. I will look at these others as I think it would be better with both taps having a reserve. I am off to Spain in 10 days on it and am just making sure it is right up together. cheers.

When buying a petrol tap do owners even think to ask whether the tap they are buying will allow the flow through them to supply the needs of their carbs when running at full throttle for a few miles or do they like me a zillion years ago in my full throttle everywhere death defying days of youth wonder why the motor goes slower the longer one holds the throttle fully open? Personally in my knowing nothing youth I had simply fitted larger and even larger main jets and was up to 340s before I eventually found my problem.
Go work it out as I EVENTUALLY did ...... ASSUMING flat out along The Mountain Mile....120 mph?....30 miles per gallon?.....Thus in one hour / 60 minutes thats 4 gallons / 32 pints. Now thats getting on for a pint just under every two minutes.
I took my tank...shoved it on two chairs....shoved a pint container under it and with watch in hand turned on the tap and counted 2 minutes 20 seconds before one pint flowed and instantly learnt why my Dommy ran out of breath when holding the throttle fully open for long periods.
I bought a proper fuel tap, a nice pretty brass lump still in its Beck Arnley packaging ..(arked Enots of cdourse!!) removed the 340 main jets and jetted the carbs correctly....... Another learning curve completed .........
Have just had a look on the web and found lots of fuel taps but none that gave their fuel flow rate....... but I dont suppose many think of such things just like me in my youth......

J. M. Leadbeater said:

When buying a petrol tap do owners even think to ask whether the tap they are buying will allow the flow through them to supply the needs of their carbs when running at full throttle for a few miles or do they like me a zillion years ago in my full throttle everywhere death defying days of youth wonder why the motor goes slower the longer one holds the throttle fully open? Personally in my knowing nothing youth I had simply fitted larger and even larger main jets and was up to 340s before I eventually found my problem.
Go work it out as I EVENTUALLY did ...... ASSUMING flat out along The Mountain Mile....120 mph?....30 miles per gallon?.....Thus in one hour / 60 minutes thats 4 gallons / 32 pints. Now thats getting on for a pint just under every two minutes.
I took my tank...shoved it on two chairs....shoved a pint container under it and with watch in hand turned on the tap and counted 2 minutes 20 seconds before one pint flowed and instantly learnt why my Dommy ran out of breath when holding the throttle fully open for long periods.
I bought a proper fuel tap, a nice pretty brass lump still in its Beck Arnley packaging ..(arked Enots of cdourse!!) removed the 340 main jets and jetted the carbs correctly....... Another learning curve completed .........
Have just had a look on the web and found lots of fuel taps but none that gave their fuel flow rate....... but I dont suppose many think of such things just like me in my youth......

Click to expand...

I HAVE pondered what you say JM. Especially since my Atlas came factory stock with a 0.200 inch dia. needle orifice, (not typical) and the Ewarts tube is only 1/8 inch (from memory). The typical Atlas needle orifice is 1/8 inch. I will be doing a flow test as you did.

Perhaps it was because of the results you found, that some bright chap thought extended float bowls was necessary.

Slick

Remove the float bowl drains and put a container under each. Open the taps. You need to get around 300ml per minute out of each carb. The engine only needs about half that but the 300 is with the floats bottomed out and the needles full open. Less than that amount of flow could result in the fuel level dropping in the bowl with the throttle wide open.

If the carbs are connected with the double 180 degree banjos, you need to open only one fuel tab.

http://amalcarb.co.uk/banjo-double-180- ... -pipe.html

Ralf

texasSlick said:

J. M. Leadbeater said:

When buying a petrol tap do owners even think to ask whether the tap they are buying will allow the flow through them to supply the needs of their carbs when running at full throttle for a few miles or do they like me a zillion years ago in my full throttle everywhere death defying days of youth wonder why the motor goes slower the longer one holds the throttle fully open? Personally in my knowing nothing youth I had simply fitted larger and even larger main jets and was up to 340s before I eventually found my problem.
Go work it out as I EVENTUALLY did ...... ASSUMING flat out along The Mountain Mile....120 mph?....30 miles per gallon?.....Thus in one hour / 60 minutes thats 4 gallons / 32 pints. Now thats getting on for a pint just under every two minutes.
I took my tank...shoved it on two chairs....shoved a pint container under it and with watch in hand turned on the tap and counted 2 minutes 20 seconds before one pint flowed and instantly learnt why my Dommy ran out of breath when holding the throttle fully open for long periods.
I bought a proper fuel tap, a nice pretty brass lump still in its Beck Arnley packaging ..(arked Enots of cdourse!!) removed the 340 main jets and jetted the carbs correctly....... Another learning curve completed .........
Have just had a look on the web and found lots of fuel taps but none that gave their fuel flow rate....... but I dont suppose many think of such things just like me in my youth......

Click to expand...

I HAVE pondered what you say JM. Especially since my Atlas came factory stock with a 0.200 inch dia. needle orifice, (not typical) and the Ewarts tube is only 1/8 inch (from memory). The typical Atlas needle orifice is 1/8 inch. I will be doing a flow test as you did.

Perhaps it was because of the results you found, that some bright chap thought extended float bowls was necessary.

Slick

Click to expand...

Fuel flow is an interesting topic IMHO. Extended float bowls obviously work, and 'contain' the issue for many, but they still don't 'correct' the issue that supply is not keeping up with demand. What they're doing is delaying the symptom for long enough for it not to become apparent.

I have come across many cheapo fuel taps that, for various reasons, generally impede flow. They must be responsible for many a tale of holed pistons etc.

It is surprising just how much fuel an engine can need on WOT at high revs. I'm honestly not sure if I got my maths right, but I once calculated that my 840cc Triton was doing 12 miles to the gallon at a race meeting.

In normal road use, many people seldom use WOT other than for very short periods (some never). But its certainly a topic about which I am cautious, and I am a firm believer that a little extra spent on good petrol taps is a sensible precaution.

Matchless said:

If you want quality 1/4" BSP main/reserve type taps, try Steve Goode M/Cs on 01938|850544. He stocks an Italian made tap. I have had these on my O.I.F T160 for several years with no problems whatsoever. He has them listed on ebay, item numbers 152060790176 & 152093836613.

Martyn.

Click to expand...

Martyn,
Just bought a pair on your rec. They're as good as you said.
ta
sam

Fast Eddie said:

Fuel flow is an interesting topic IMHO. Extended float bowls obviously work, and 'contain' the issue for many, but they still don't 'correct' the issue that supply is not keeping up with demand. What they're doing is delaying the symptom for long enough for it not to become apparent.

Agree!

I have come across many cheapo fuel taps that, for various reasons, generally impede flow. They must be responsible for many a tale of holed pistons etc.

It is surprising just how much fuel an engine can need on WOT at high revs. I'm honestly not sure if I got my maths right, but I once calculated that my 840cc Triton was doing 12 miles to the gallon at a race meeting.

I think your math correct. A simple example will support this. My Atlas averages 48 mpg cruising at 60. A rule of thumb is that four times the horsepower is required to double speed. Thus one can expect 4 times the fuel consumption, or about 12 mpg. if I were to go flat out WOT and make the max Atlas speed of 119.

In normal road use, many people seldom use WOT other than for very short periods (some never). But its certainly a topic about which I am cautious, and I am a firm believer that a little extra spent on good petrol taps is a sensible precaution.

Not to mention no leaks!

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Continuing the analysis, 12 mpg at 120 mph is 10 gal per hour fuel consumption rate, or 1 1/4 US pints per minute. This agrees with what JM Ledbeater found above, as I am sure he was using Imperial pints.

Slick

0.5 lb of fuel per hour per hp, so the boatowners' websites say!

50 hp at full throttle and high rpm.

So 25 lb of fuel per hour when you're trying for your top speed.

An Imperial gallon weighs 7.39 lb

So, 3.4 imp. gallons per hour, or 27 pints.

0.45 imp. pints per minute. That's 266 cc per minute.

Then you want a margin of safety. Maybe you reckon you've got more than 50 hp. Maybe it's running a bit rich. Maybe old bikes are a bit inefficient.

Back on fuel taps, I have one side with a standpipe and the other drains to the bottom of the tank. Considering the division between the two sides made by the center tube tunnel, a quart or so in the side of the tap with the standpipe can't be accessed. I think I may remove the standpipe. What good is it?

Triton Thrasher said:

0.5 lb of fuel per hour per hp, so the boatowners' websites say!

50 hp at full throttle and high rpm.

So 25 lb of fuel per hour when you're trying for your top speed.

An Imperial gallon weighs 7.39 lb

So, 3.4 imp. gallons per hour, or 27 pints.

0.45 imp. pints per minute. That's 266 cc per minute.

Then you want a margin of safety. Maybe you reckon you've got more than 50 hp. Maybe it's running a bit rich. Maybe old bikes are a bit inefficient.

Click to expand...

Triton Thrasher: I find no flaw in your computations. 0.5 lb fuel per hp is a reasonable number for an air cooled engine. After adjusting for 60 hp (the advertised hp of my Atlas), and for US gallons, I get 33.8 US pints per hr, or 0.56 US pints per minute, or 265 ml per min. This assumes an engine thermal efficiency of 30%.

Your analysis is more rigorous than my simple "rule of thumb" but I would have expected closer agreement. My Atlas delivers 48 mpg, having measured the fuel economy many, many times. I have never ran it flat out long enough to get a rate of fuel consumption at 120 mph! Nevertheless, the rule of thumb for hp going up as the square of the speed is well accepted. So, as yet, I cannot explain the wide variance in results. I'll continue to think about it, but for now, I will accept the more rigorous computations.

I have started measurements of my Atlas' fuel delivery. I have first measured "reserve only", having filled the tank to just below the "normal" running inlet. My Atlas has a 0.200 inch dia. needle orifice with an alcohol rated needle (this is factory stock, but not typical!). I removed the float cover on the Monobloc, turn the tap to reserve and let the fuel spill out of the bowl into a funnel. Results: 230 ml per minute! Will continue these measurements on main tap, and with both main and reserve on simultaneously. Results say don't go racing with only reserve fuel level!!

I have a 0.125 orifice needle and seat. If time permits, I will duplicate the measurements using the smaller orifice, and post results here.

Slick

All sounds pretty close to the 300 ml/minute out of each float drain I quoted earlier. I got that number from Pete R on the Triumph forum. He was an old hand who really knew his stuff, unfortunately he recently passed away. Not sure how he came up with number but you could generally accept anything he posted as hard won fact.