User guide

Fo R s&s ‘d’
ca R b u R e t o R s
GENERAL INSTRUCTIONS
ThunderTech Products - 6655-A Amberton Drive - Elkridge, MD - 21075 - PH: (410)579-2929 - Fax: (410)579-2835
A.
Tapping bowl vent for tting
EXTERNAL FLOAT BOWL VENT
ADJUSTABLE AIR BLEED
CIRCUIT
Ifyoudonothavethefacilitiestoproperly
install this fuel module, professional
installation is available from Zipper’s.
Highvolumeshopsmaywanttoinvestin
ourThunderJetinstallationxture(shown
inthephotosp/n713-910)whichsecurely
holdsthecarbbodyandoatbowlatthe
correctpositionsformachining.Usewitha
millwheninstallingThunderJetsinallS&S
modelE/G/B/Dcarbs.Readallinstructions
fullyand carefullybefore proceedingany
further.
Loosendrainplugandremoveoatbowl
andmanifold.Installtwo(2)studsincarb
manifold bosses; use these to center
carb in milling machine vise. Be careful
nottoovertightencarbinvise.Therst
two steps are recommended to further
enhance your carb’s performance along
withtheinstallationofyourThunderJet.
1.Pressureintheoatbowlisstabilized
withtheadditionofthisexternalbowlvent.
Locatethenewventholeintherearofthe
carbwall.438”abovebowlgasketsurface
and1.906”fromthemanifoldangeofthe
carb.Openholewithasmallcenterdrill
thenplungea5/16”endmilltoadepthof
.562”belowtheraisedsurface.Usea½”
countersinktochamfertheraisedsurface
tohelpstartthetappingprocess.Chamfer
only slightly not touching the lower level
surface. Tap with 1/8” NPT tap. Install
1/8”NPTstreetelbowand1/8”NPTx3/8”
hosenippleusingasuitablethreadsealer.
The hose nipple should be positioned
pointingup.
Air bleed passage drilled & tapped
for jet.
Fuel tube hole drilled/tapped, area
relieved for ThunderJet
THUNDERJET INSTALLATION
2. Earlier versions of “D” carbs are
manufactured with a xed size air bleed
passage (current “D” models are now
machined for adjustable air bleed jets).
This modication will allow the tuner to
adjustthemainjetairbleedsizeformore
control over the main jet circuit signal
NOTE: On“D”applicationsusingonly(1)
ThunderJet,theThunderJetmountsonthe
sideofthecarbfacingtherearofthebike
(9:00position).Ifusing(2)ThunderJetsfol-
low all instructions below and mount one
eachinthe9:00and3:00positions.
timing and fuel volume. Locate the xed
air bleed hole and bore with ¼” drill until
youreachthecrossdrillincarb(DO NOT
GO PAST CROSS DRILL!!)
.Spotfacethe
area with 1/2” end mill for mating surface
ofjet. Use 5/16-24 starter tapinhole and
removetousea5/16”bottomtaptonish
job.Originalairbleedsizeis.042”andthe
suggested range is .054-.072”. Use S&S
mainjetsforthis.
9:00 POSITION
3. Drillandtaphole.750”fromtheend
ofthecarbthroat,offsetslightlyabovethe
throttlebutteryshaft.Usealetter‘i’(.272”)
drill and tap 5/16”-24 thread. You will be
drilling through the middle of the original
oatbowlventpassage;thisisOK,itwillnot
affectperformanceoroperationofthecarb.
4. You then need to relieve the area
around the hole you just threaded for
air bleed spacer clearance. This is best
accomplishedonaverticalmill witha3/4”
end mill. With the cutter starting near the
bowlarea,mill towardthetop ofthecarb,
removing material at least ¼” above the
centerline of the fuel tube hole. Use care
nottobreakintotheenrichenerairpassage
locatedabovethehole.Leave.170-.185”of
carbwallfor the short threaded portion of
thefueldeliverytube.
Double-nut and tighten fuel tube
in place
Do n o T o v e R T i g h T e n b o D y
o R f u e l T u b e b R e a k a g e w i l l
R e s u l T !
ThunderJet body (nipple down),
bowl cent & air bleed jet in place.
5.Installthefueldeliverytubefromthe
insideofthecarburetorthroatout.Double
nutthedeliverytubeusing(2)¼”-28jam
nuts and carefully lock into carb throat
(DONOTOVERTIGHTEN).Removejam
nuts(notneededafterthisstep).
6.Installaircorrectionspacer,o-ring,and
ThunderJet with fuel nipple facing down
towards oat bowl. Trim small opening
side of air correction spacer, if needed,
to achieve a hand tight location 1/6 of a
turn from permanent location and nish
tightening with wrench. (.006” trim = 1/6
turn).
3:00 POSITION
(Part 2 of twin T-Jet installation)
7. Drill and tap hole .950” from the end
ofthecarbthroat,offsetslightlyabovethe
throttle buttery shaft (letter ‘i’ (.272”) drill
and5/16”-24tap).
8. Youthenneedtorelievetheareaaround
theholeyoujustthreadedforairbleedspacer
clearance.Thisisbestaccomplishedona
verticalmillwith a3/4”end mill,oncenter
ofyourthreadedhole.Becertaintoleave
.170-.185”ofcarbwallfortheshortthreaded
portionofthefueldeliverytube. (Some D
carbs are equipped with dual oat bowl vent
passages (forward and rear of carb throat);
you will be cutting through the forward vent
passage if equipped. This passage must
then be plugged, as its location will subject
the passage to positive air pressure at
speed, resulting in uctuating pressure in
the oat bowl, adversely affecting jetting.
Drill the passage past the ThunderJet
mounting area and tap it 5/16”, 3/8” deep
and plug it with a set screw. The external
vent described in step 1 must be performed
to replace this original vent.)
Hole A (9:00 position), B (3:00),
C (12:00)
13. ReaD Tuning
insTRuCTions
FOAT BOWL
PRO-STOCK OPTION
(12 O’Clock Position)
Spot faced, drilled/tapped for 3rd
T-Jet (Pro-Stock option)
fuel tube hole drilled/tapped,
area relieved for T-Jet, fuel tube
installed. Circle shows where vent
passage should be plugged
9. Follow steps 5, 6 & 7 from the 9:00
segment.
IfathirdThunderJetisdesired,drill,tap
(letter‘i’(.272”) drilland5/16”-24 tap)and
spotfaceTOPcenterofcarb1.200”fromair
cleanerbackingplatesurface,leaving.170-
.185”wallthicknessfortheshort threaded
portion of the fuel delivery tube. Follow
steps5,6&7fromthe9:00segment.Point
hose nipple towards rear of the bike and
slightlyinward.
10. Clampbowltomilltableat35degree
angle.Seephotoforbowlnipplelocation(s).
At the bottom of oat bowl, beside drain,
drilla#3holeandtap¼”-28.Spotfacethe
areaaroundtheholetogiveaatsurface
for the o-ring to seal against and reduce
thicknessenoughtoallowthenuttoattach
ontheinsideofthebowl.Installfuelnipple
ando-ringthensecureinsidebowlwithnut
provided(nowasher).Stakethreadswitha
punchtolocknutinplace(makesurethis
devicedoesnotinterferewithoatactionor
movement).Repeatformultiplebowlnipple
locations.
12. Clean all carb parts; reassemble
and install fuel line with clamps provided
(trimfuellineifneeded).Installonengine.
Installfuelline,turnfuelvalveonandcheck
forleaksbeforestartingengine!!