Discussion in 'Motorcycle Related Discussions' started by Fast Eddie, Apr 13, 2019.
The builder of this seems to think they’re ok...
Not quite sure what I’m looking at ....
As single Amal feeding a 1000cc+ JAP powered drag bike.
Admittedly, the Amal is assisted a tad by the large blower...
That is strange to behold. I take it the forks are never turned to the right, or are my eyes telling me another fib?
Being that the fuel line is about the size of a garden hose, you have to think that the mains aren't 220's or 260's, unless you count drilling out 220 mains with a 1/4" bit as stock parts....
Why have a steering damper when you can't turn the handlebars anyway ?
Or does the carb just bend to one side.
Turn? TURN??? We don't need to stinking TURN!
Possibly the wheel is already turned to the right as far as the steering stops allow?
Gentlemen, gentlemen, calm yourselves, the wheel is not quite as close to the carb as it looks in the pic (it’s still close, just not quite as close).
Profuse apologies for my poor photography!
I'm not upset...just somewhat befuddled. Not the first time either, and certainly won't be the last guaranteed.
After all these years, I now find I have been mounting my Amal's backwards!
On a serious note, it is not fuel flow that I question, but air flow. A blower augmenting the appetite of a 1000 cc engine, must surely push sonic limits within the carburetor.
On second thought, I do question fuel flow. What is he using for a needle and seat? Even an alcohol rated needle and seat will not pass much more than a pint per minute.
I predict this blower - carb arrangement will be an epic failure.
Yes, ‘‘twas air flow I was referring to Slick, hence I also mentioned the blower would assist matters a tad.
I would have thought the blower would simply ‘force’ enough air through the carb. I’d also imagine that would play havoc with jetting by upsetting ‘normal’ Venturi principles? But if it’s on methonal or similar, I think this is a less precise art than petrol.
It is, after all ‘only’ a 1000cc (ish) twin, so the carb is ‘only’ providing 500cc of charge at any one time.
There was a monstrous 2litre plus job next to this with a Harley look-alike lump in it, that had an intake that you could quite literally lose your arm in !
The ergonomics of Seat, pegs, bars together with the weird bikini fairing would indicate a drag bike. The hosepipe for fuel and slightly larger air intake suggest it also. Now if the two silver cylinders on the frame are NO2 canisters...
Thx for this important thread FE...now I can put aside my plans to deploy twin Amals and just keep riding my single ;-)
The blower is not forcing air, but drawing it thru the carb ...... the carb will choke the blower!! Blowers, after all, are intended to boost the mass flow over that of natural aspiration. The blower cannot do that if its' own air supply is limited by the carb!
I can imagine the frustration this guy will have chasing the "right" jetting, when his poor performance problem will be due to limited airflow.
You can get tablets for that!
The amount of mixture forced into the motor is a function of the flow, the pressure and the time. With that single carb there would be little resonance, it would work continuously. On a conventionally aspirated motor, there are pressure pulses in the inlet tract and the cylinder filling is more dependent on the valve timing. With a blower, it is more normal not to use race cams., especially on the exhaust. Here in Australia, we have one blown Vincent speedway sidecar. It's noise level is horrendous because of the cams. My brother has ridden it a few times.
In that photo, it looks as though the rear of the front wheel can move sideways about 3 inches both ways - more than enough for a drag bike. Most road racers would only have that much lock.
I see two different things happening here, one, forced/ram air induction which will hit the carburation at sweet 60 (MPH) and two, the blower which will come in as soon as the engine has enough revs. It may be almost impossible to get the carburation right with this set up.
My guess is:
40MM 1000 series MK1 ?
1900 main jet( or less) ?
Not sure why he did not use an amal 40mm MK2 like I have for my drouin, to go on my 920 commando.
I looked at the 1000 series for a project. The largest I could come up with was 38mm.
I used 2 Dellorto 41 mm pumpers instead.