spray tube height in amal Mk 2

I have just removed the Amal Mk 2 carbys from my VR880 to clean them in an ultrasonic cleaner and I noticed that the height of the spray tube was different. One is 5.3 mm above the base of the venturi and the other is 4.2 mm in height. Does anyone know if this difference would have an appreciable effect on the tuning? I've been having problems with erratic idling since I bought it but I suspect this may be due either to sediment from when the tank was full of rust (now cleaned and recoated) or possibly the choke not working properly as the linkage seems uneven.

the jet holder holds the Spray Tube place.
Check That Out.

Oh yes I have and so has Amal to find the spray tubes miss matched heights don't mess with running mixture but I found their height does affect off idle throttle snap response. Spray tube top hat rims vary in thickness as does the thickness of their pot bore seat thickness both which affect final seated height into the bore. Height of tube determines how easy-soon full fuel flow can be sucked out them but not how much is sucked out them, the jet and needle and slide cut out do that. They are a slight friction fit, no need to put in hot water to expand the pot metal to move them almost too easy. Notching, sloping or a V in the back side of tube and shortening them help the off idle response, semi accelerator pump effect. Playing with my Amals tubes to get them about even I also cut down height some for more off idle tire spin to fish tail a bit into a new direction as less effort and more secure on grass and Gravel slowish speeds.

The spray tube height might affect the running at openings less than 1/4 throttle, should not affect the idle. The important thing is that the shoulders on the needles meter at exactly the same height in the needle jets at 3/4 throttle. Also you should check that the tips of the needles cannot come free (out of the needle jet) at full throttle. If one gets loose, it can hang the throttle open when you are on full noise.
On the two strokes we run on speedway, it is tempting to use short needles so that metering does not occur at full throttle, and the main jet is the only one affecting the mixture . We recess the needle jet, so that the tip of the needle is always captured. (On methanol the main jet is the same size as the needle jet in a 750 triple Kawasaki.)

Amal lore galore in here

http://velobanjogent.blogspot.com/2011/ ... paper.html

An interesting read. I note that Mk2 amals have needles with the grooves closer together to give finer tuning. I don't use Amal needles. Mikuni needles are ground with three tapers , and I run them as lean as possible right down the needle. I always use methanol fuel, and it is as critical as petrol to get right . A lot of guys run it too rich. It will still give good power, but the motor will never be as fast as it is when the carburation is leaned off to the max. When I bought my Mk2 amals, I ordered the alcohol kit. I made my own needle jets, and threw away the amal needles , they were ridiculous. I don't understand w hy 'pumper' carbs are popular, I don't think that much fuel is necessary unless the carb size is too big. My carbs are 34mm, and the ports taper back to 32mm within 25mm of the mounting face. The motor is set up to pull, not try to achieve good power at above blow-up revs.

Appreciate your summary Alan and relations to methanol. Peel's main limit is heat and its pretty simple to switch out Lake slide needle so may have to pick your brain someday for special events. I have not yet read through the article so have some catching up to do.

Btw, a really thristy engine can out draw the fuel feed past the float needle restriction so there a way to cut a slot out below the needle end that feeds direct into the bowl. BSA had a bulletin on this showing measure and drawing.