I am getting ready to rebuild a set of PD50B carbs also. Rebuild kits are hard to find in stock anywhere.
I have tracked down the following info for parts interchange. Floats, Float bowl gasket, Needle valve, Mixture screw, and Float bowl drain screw will all interchange with 77-78 CB750A, and 77-78 CB750K carbs. This means that the cheaper more available kits for the 750A, or 750K carbs can be used. with one exception.
The 750A, and 750K carbs do not use a metal cross over tube for the accelerator pump, and fuel delivery curcuit, and do not contain the o-rings in the kit. All other o-rings, and brass pieces are included in the full keyster kits.
NOTE: The jets contained in these kits
will most likely not be the correct jets.
Edit:Updated info on the o-rings cgswss10 wrote:Oh by the way, those o-rings can be replaced by standard "dash" sizes. The fuel rail are "-010" and the acel pump rail take "-007" o-rings. Of course you have to use "fuel proof" o-rings which would normally mean "Nitrile" AKA "Buna-N" o-rings NOT regular neoprene rubber.
viewtopic.php?f=4&t=6013&start=15Parts available from Sirius Consolidated INC.HONDA CB650 KEYSTER CARB KIT 1979 KH-1204HONDA CB750A CB750 AUTOMATIC KEYSTER CARB KIT 1976 - 78 KH-1260HONDA CROSS OVER TUBE O-RINGS (1.5 x 6.6 & 1.8 x 3.7)NOTE: I have not positively confirmed that theses are the correct cross over tube o-rings
CB650 CB750 LTD 1979 AIR CUT OFF VALVEHONDA FLOAT BOWL GASKET (Single)CB750 CARB FLOAT BOWL GASKETS (Set of 4) 1977 - 1978HONDA FLOAT BOWL DRAIN SCREW (Single)HONDA CX500 CB650 CB750 CB900 FLOAT BOWL DRAIN SCREWS (Set of 4)HONDA CX500 CB750 AIR SCREW NEEDLE O-RINGS PACK of 25HONDA CB550 CB750 XL80 XL185 CARB SLOW JETS (KHS-49A035)HONDA CB450 SC CM450 CB750A CB750 ACCEL PUMPNOTE: The pump rod may have to be trimmed to length on these. The pump diaphram is correct.
NOTE: The fuel pump rod for the CB750A is the correct length, and will directly interchange with the PD50 carbs.
Choke Shaft SealsThe felt seals can be obtained through
OldSchoolCarbs.
Part interchange info:Float Bowl interchange for gaskets16010-393-305 GASKET SET
CB750A (76-78)
CB750K (77-78)
Carbs #116015-KFC-910 CHAMBER SET, FLOAT
CB125S (78-79)
CB550K (77-78)
CB650 (79-80)
CB750A (76-78)
CB750F (77-78)
CB750K (77-78)
CM185T (78-79)
XL100 (77-78)
XL125 (76-78)
#2 Carb w/Accellerator pump16015-428-771 CHAMBER SET, FLOAT
CB650 A (79-80)
CB650C A (80)
NX250 A (88-90)
XL250R A (82-83)
XL250R AC (83)
XL250S A (80-82)
XL500S A (79-81)
XR250L A (91-96)
XR250L AC (91-96)
16023-393-004 CHAMBER SET B, FLOAT
CB750A A (76-78)
CB750K A (77-78)
Note: These float bowls are identical to the above, but include the accel pump.
#3 & #4 Carb16015-KN4-A10 CHAMBER SET, FLOAT
CB550K A (77-78)
CB650 A (79-80)
CB650C A (80)
CB750A A (76-78)
CB750F A (77-78)
CB750K A (77-78)
CRF100F A (04-12)
NSF100 A (06)
XL100S A (79-85)
XL350 A (77-78)
XR100 A (81-03)
Float bowl vent "T" joint16036-438-671 JOINT SET, THREE-WAY
CB650 A (79-80)
CB650C A (80)
CB900F A (81-82)
Float16013-405-004 FLOAT SET
CB125S A (80-82)
CB550K A (77-78)
CB650 A (79-80)
CB650C A (80)
CB750A A (77-78)
CB750K A (77)
CM200T A (80-82)
XL100 A (77-78)
XL100S A (79-85)
XL100S AC (85)
XL125S A (79-85)
XL125S AC (84-85)
XL185S A (79-82)
XR100 A (81-84)
XR100R A (85)
XR185 A (79)
XR200 A (80-84)
XR200R A (81-83)
XR250R A (81-82)
Float Needle valve16011-382-004 VALVE SET, FLOAT
CB125S A (78-82)
CB400A A (78)
CB400TI A (78-79)
CB400TII A (78-79)
CB550K A (77-78)
CB650 A (79-80)
CB650C A (80)
CB750A A (76-78)
CB750F A (77-79)
CB750K A (77-79)
CB750L A (79)
CM185T A (78-79)
CM200T A (80-82)
CM400A A (79)
CM400T A (79)
CX500 A (78-79)
CX500C A (79)
CX500D A (79)
XL100 A (77-78)
XL100S A (79-85)
XL100S AC (85)
XL125 A (76-78)
XL125S A (79-85)
XL125S AC (84-85)
XL185S A (79-82)
XL250R A (84-87)
XL250R AC (84-87)
XL250S A (78-81)
XL350 A (77-78)
XL350R A (84-85)
XL350R AC (84-85)
XL500S A (79-81)
XL600R A (83-87)
XL600R AC (84-87)
XR100 A (81-84)
The latest part that replaces this item is:
16011-KCK-910 VALVE SET, FLOAT
16011-KCK-910 VALVE SET, FLOAT (Float needle)
CRF150F A (03-07)
CRF230F A (03-07)
XL125S A (85)
XL125S AC (85)
Pilot Needle Screw16016-KC2-970 SCREW SET A
CB1000C A (83)
CB1100F A (83)
CB125S A (80-82)
CB125S A (84-85)
CB125S AC (84-85)
CB400T A (80-81)
CB450SC A (82-83)
CB450SC A (85-86)
CB450SC AC (85-86)
CB450T A (82)
CB650 A (80-82)
CB650C A (80-81)
CB650SC A (82)
CB750C A (80-82)
CB750F A (80-82)
CB750K A (80-82)
CB750SC A (82-83)
CB900C A (80-82)
CB900F A (81-82)
CBX A (80-82)
CM200T A (80-82)
CM250C A (82-83)
CM250C AC (83)
CM400A A (80-81)
CM400C A (81)
CM400E A (80-81)
CM400T A (80-81)
CM450A A (82-83)
CM450C A (82)
CM450E A (82-83)
CX500C A (80-82)
CX500D A (80-81)
CX650C A (83)
FT500 A (82-83)
GL1100 A (80-83)
GL1100A A (82-83)
GL1100I A (80-83)
GL500 A (81-82)
GL500I A (81-82)
GL650 A (83)
GL650I A (83)
NX125 A (88-90)
NX125 AC (88-90)
NX250 A (89-90)
NX250 AC (90)
XL100S A (80-84)
Edit: Added carb specs. Thanx for the info usbear.PD50 Carb Specs CB650 79-80, CB650C 80PD50A JET, MAIN (#90) SLOW (#35) slide is 56 B (small air cut out) needle - 59 A (high clip position)
PD50B JET, MAIN (#90) SLOW (#35) slide is 81 B (larger air cut out) needle - 35 B ( lower clip position)
PD50D JET, MAIN (#95) SLOW (#35) slide ?? needle ??
Hopefully this helps.
edit: 6/17/12 corrected misinformation on #2  float chambers
edit: 7/25/13 added carb specs.
edit: 11/02/13 added choke shaft seal info.
Ghost