Norton 19S - Page 29

The throttle valve needle may be removed or
adjusted for position by removal of the spring
clip at the top of the slide.
I
2
3
4
5
6
7
Fig. 18
Diagrammatic section through Mixing Clzamber
I-Mixing Chamber Top
2-Mixing Chamber Cap
3-Carburctter Body
4-Jet Needle Clip
s-Tbrottle Valve
6-Jet Needle
7-Pilot Outlet
I-Pilot by-pass
9-Pilot Jet
10-Petrol feed to pilot jet
tr-Pilot Jet Cover Nut
12-Main Jet Cover
13-Main Jet
14-Jet Holder
15-}lleedle Jet
16-Jct Block
17-Air Valve
18-M.ixin,1 Chamber Cap
Sprmg
19-Cable Adiwter (Air)
2o-Cable Adjwter (Throttle)
21-Ticlcler.
23-Banjo.
29-Pilot Air Adjustina; Screw.
30-Throttle Adjustina; Screw.
Remove the float chamber cover by remov-
ing the three screws securing it, and withdraw
the hinged float, this will enable the nylon
needle which controls the flow of fuel to be
withdrawn and cleaned.
Removal of the nut at the base of mjxing
chamber gives access to the main jet which
may be unscrewed from the jet holder which
also carries the needle jet, accessible by re-
moval of jet holder. Removal of these parts
enables the jet block to be pushed or tapped
out through the large end of the mjxing cham-
ber
body when the jet block locating screw has
been removed. This screw lies to the left of
and slightly
below the pilot air adjuster which
is the horizontal milled headed screw equip-
ped with restricting spring.
29
79. RE-ASSEMBLY OF CARBURETl'ER.
Re-assembly should present no difficulty
but the following points should be watched.
The washer fitted to the stub of the jet block
should be in good condition, also the one fitted
to the needle jct holder. When fitting throttle
valve ensure that taper nccdle really enters the
centre hole in the jet block, and that throttle
works freely when mixing chamber top cap
be fitted and secured. Fit float with narrow
side of hinge uppermost and ensure that side
cover washer and body arc clean and undam-
aged to obtain a petrol tight joint
80. CARBUll1TER TUNING.
There
are four distinct phases of tuning
and each must be handled separately to obtain
best results for any particular set of conditions.
Pig. 19
General viem of Carburetter
For all
these positions the air valve should be
fully open, the engine should be at its normal
working temperature, and the machine should
be driven on a slight up gradient to ensure
engine pulling whole time.
1st MAIN JET.
This jct controls the fuel ~upply when the
throttle is more than ¾ open. With the throttle
fully open and the engine pulling hard,