13 BMW 1983 R80ST Rebuild, Refinish Carburetors

Introduction

This bike came without any carburetors. I found a set of used 32 mm BING carburetors (64/32/323-324) after searching through a box of used carburetor’s in one of Clem Cykowski’s storage rooms that I can use . The date stamps on them indicate the 323 was manufactured in 11/1982 and the 324 was manufactured in 10/1982.

Useable Carburetor From Clem's Used Carburetor Pile; 64/32/323-324

Useable Carburetor From Clem’s Used Carburetor Pile; 64/32/323-324

Right Side Carburetor (64/32/324)

Right Side Carburetor (64/32/324)

Right Carburetor Manufacture Date (October 1982)

Right Carburetor Manufacture Date (October 1982)

Left Side Carburetor Number (64/32/323)

Left Side Carburetor Number (64/32/323)

Left Side Carburetor Manufacture Date (November 1982)

Left Side Carburetor Manufacture Date (November 1982)

The BING manual indicates the set of used carburetors I got were used on the R80 engine. But I learned from Bud Provin that the 1978 R100/7T also used this carburetor model. The BING manual does not show the R100 used this model. Oh well, with that many changes in R80 carburetors it’s likely BING doesn’t show them all in their manual.

According to the MAX BMW parts fiche, the R80ST originally had the 64/32/351-352 model carburetors. However, MAX lists two other models that can be used with the R80ST. Parts fiche typically list what is still in stock and will work, not necessarily what was originally used. Tom Cutter at Rubber Chicken Racing Garage told me that the 351-352 carburetor model was the original carburetor used on the two year production run (1983-1984 model years) of the R80ST. He also mentioned that the first 12 R80ST used the same carburetors installed on the R80 G/S.

  • 64/32/351-352 (to 10/1984)
  • 64/32/321-322 (to 03/1985)
  • 64/32/357-358 (from 11/1984)

According the the BING carburetor manual, these are the jets used in these carburetors.

Model Slide Main Jet Need. Jet Jet Need. Atomizer Idle Jet
64/32/351-52 907-3 135 2.66 251 591 45
64/32/321-22 906-3 150 2.66 241 591 45
64/32/357-58 907-3 135 2.66 251 591 45
64/32/323-24 906-1 150 2.66 241 591 40

The BMW part numbers for the jet needles are:

BING #        BMW Part #   
251        13 11 1 337 692
241        13 11 1 255 840

The BING manual shows 7 different carburetor models used on bikes with the R80 engine. That’s a lot of changes. I learned from Bob Fleischer that BMW made a lot of carburetor changes in the 1980’s, particularly with the R80 engine. They were trying to meet emissions requirements and to correct reports of low mileage for the R80 engines. So that explains the large number of BING manual entries.

Based on input from Lloyd Provin, and the fact all the MAX identified carburetors used with the R80ST engine had “45” idle jets, and the fact BMW was trying to lean out the motors to meet emission standards, I’m going to use a “45” idle jet when I rebuild the carburetors. I’ll use the same main jet (150), needle jet (2.66) and jet needle (241) that the 323-324 carbs came with. Then as I do my shake down riding of 1,000 miles or so, I’ll adjust the carburetor jetting if required.

Bob Fleisher provides a link about two service bulletins BMW published regarding changes to the R80ST carburetors and the low fuel mileage situation.

There was a change made in August 1984 to the top of the air box so that the two snorkels are different lengths (part# 13 72 1 337 675). I’ll consider this modification if I have issues with low fuel mileage, but for now, I plan to use the original cover with equal length snorkels (part# 13 72 1 337 228).

Reuse Of 1983 R100RS Documentation

These 32 mm carburetors are very similar to the 40 mm carburetors used on my 1983 R100RS rebuild, and both are constant velocity carburetors. So I will reuse that documentation as appropriate. The  64/32/321-322 carburetors I’m using on the R80ST use the handlebar chock lever as is the case with the 94/40/114-113 used on the 1983 R100RS. So the details of the carburetors are the same with the exception that the 1983 R80ST carburetors I am using are 32 mm instead of the 40 mm ones used on the 1983 R100RS.

Resources

Here is a link to the theory of operation of the Bing Constant Velocity type of carburetor:

Bob Fleischer has a lot of information about various types of Bing carburetors on his web site:

The exploded view diagrams for these two types are the same as shown below, even though some of the parts are different on the two types.

BingAgency_MOTORCYCLE-CV-EXPLODED-VIEW

Source: The Bing Agency

Parts

I bought more parts than are required to rebuild the carburetors since parts were missing and damaged on these carburetors. Below is the carburetor rebuild parts list and the missing-damaged parts list. All were contributed by Euro Motoelectrics in support of my goal to auction the bike and donate all proceeds to the Motorcycle Relief Project.

Carburetor Rebuild Parts

Part #                    Description                                                              Qty
13 11 1 258 051  SET: GASKET SET CARBURETTOR 1
13 11 1 255 840  NOZZLE NEEDLE (to 05/83), Jet Needle 2
13 11 1 261 702  JET – 2,66, Needle Jet 2
13 11 1 254 766  FLOAT 2
13 11 1 254 768  PIN, Float 2
13 11 1 254 738  CSK.FILLISTER HEAD SREW, Throttle Plate 4
13 11 1 260 972  MAIN JET – 150 (to 05/83) 2

Missing-Damaged Carburetor Parts

Part #                    Description                                                              Qty
13 11 1 335 600  VENTURI, Main & Needle Jet Holder 1
13 11 1 254 760  NUT 4
13 11 1 254 759  WAVE WASHER 2
13 11 1 337 368  LEVER, Choke 1
13 11 1 337 369  LEVER, Choke 1
13 11 1 336 924  IDLING JET – 45 (from 05/83) 2
13 11 1 335 302  IDLING MIXTURE SCREW 2
13 11 1 254 736  SPRING, Idle Mixture 2
13 11 1 260 973  PRE-ATOMIZER 1
13 11 1 254 732  WASHER 2
13 11 1 337 359  FILLISTER-HEAD SCREW, Slide Ring 8
13 11 1 335 306  SPRING WASHER, Slide Ring, Throttle Bracket 12
13 11 1 335 606  TENSION SPRING, Throttle Return 2
13 11 1 259 869  FILLISTER HEAD SCREW, Vacuum Port 2
13 11 1 259 870  GASKET RING, Vacuum Port 2
13 11 1 337 370  TENSION SPRING, Choke Return 2
13 11 1 335 318  FLOAT NEEDLE, Rubber Seal 2
13 11 1 335 320  CLAMPING SPRING, Float Needle 2
13 11 1 335 324  SPRING (to 10/84), Slide 1
13 11 1 337 358  SUPPORTING RING, Slide 1

Video: Rebuild Bing CV Carburetors

I made a general video about rebuilding Bing Constant Velocity (CV) carburetors. The technique is applicable to 64/32 (32 mm) and 94/40 (40 mm) CV carburetors. There are some differences in certain models including the choke and throttle linkages and the spring added to the top of slides in some models. So, you will see all the specific details in this write-up.

VIDEO: Rebuild Bing 94/40, 64/32 CV Carburetors

Carburetor Disassembly

Since parts are missing on my carburetors, I didn’t have to remove all the parts. Here is how I disassembled the 1983 R100RS carburetors which is put together the same as the 1983 R80ST carburetors I am using.

Here are some pictures of the R80ST disassembled carburetor. Not all the parts are there.

Parts Before Cleaning & Polishing

Parts Before Cleaning & Polishing

Parts Before Cleaning & Polishing

Parts Before Cleaning & Polishing

These Carburetors Use The Rubber Tipped Float Needle

These Carburetors Use The Rubber Tipped Float Needle

Cleaning and Polishing

I start by soaking the carburetors in Chem Tool carburetor cleaner over night. To restore the finish on the carburetors takes a lot of elbow grease and patience, but the result is worth the time. This section from my rebuild of my 1973 R75/5 carburetors provides the details of how I do this for carburetors.

Here are some before and after pictures of the R80ST carburetors.

Carburetors Before Cleaning & Polishing

Carburetors Before Cleaning & Polishing

Carburetors Before Cleaning & Polishing

Carburetors Before Cleaning & Polishing

Using Q-tip & AutoSol Metal Polish To Clean Carburetor Crevices

Using Q-tip & AutoSol Metal Polish To Clean Carburetor Crevices

After Cleaning & Polishing

After Cleaning & Polishing

Rebuild Kit Parts

EME supplies a carburetor rebuild kit. I added new floats, float needles, float pins, main jets, needle jets and jet needles as well. Here is a description of the kit from the 1983 R100RS 40 mm carburetors which has the same types of parts as the 32 mm R80ST carburetors, but the diaphragms are different since the R100RS has 40 mm carburetors.

Assemble Carburetor

The assembly procedure for the 1983 R80ST carburetors is the same as for the 1983 R100RS carburetors.

Here are the jet sizes, needle clip position and idle mixture screw turns I am starting with.

  • Main Jet:         150
  • Needle Jet:      2.66
  • Jet Needle:      241
  • Idle Jet:            45
  • Needle Pstn:    #3
  • Idle Mixture:    0.5 Turns

Here are some pictures from the assembly of the R80ST carburetors

Idle Jet Location

Idle Jet Location

Main Jet & Needle Jet Carrier Parts Orientation

Main Jet & Needle Jet Carrier Parts Orientation

Silicon Grease For O-rings

Silicon Grease For O-rings

Silicon Grease On O-Ring

Silicon Grease On O-Ring

Main Jet, Needle Jet Carrier Location

Main Jet, Needle Jet Carrier Location

Main Jet Carrier Installed

Main Jet Carrier Installed

Idle Adjusting Screw Parts

Idle Adjusting Screw Parts

Idle Adjusting Screw Location

Idle Adjusting Screw Location

Orientation Of Right Enricher (Choke) Disk Inside Housing

Orientation Of Right Enricher (Choke) Disk Inside Housing

Orientation of Enricher (Choke) Arm With Dimple Next To Intake Tube

Orientation of Enricher (Choke) Arm With Dimple Next To Intake Tube

Enricher (Choke) Gasket

Enricher (Choke) Gasket

Enricher (Choke) Gasket

Enricher (Choke) Gasket

Enricher (Choke) Installed

Enricher (Choke) Installed

Choke Linkage Inner Arm Orientation

Choke Linkage Inner Arm Orientation

Choke Linkage Outer Arm Orientation

Choke Linkage Outer Arm Orientation

Choke Linkage Hardware Detail

Choke Linkage Hardware Detail

Choke Linkage Orientation

Choke Linkage Orientation

Choke Linkage Arms Orientation

Choke Linkage Arms Orientation

Throttle Shaft Parts

Throttle Shaft Parts

Installing Butterfly Plate In Throttle Shaft

Installing Butterfly Plate In Throttle Shaft

Butterfly Plate Installed With Blue Loctite On Screws

Butterfly Plate Installed With Blue Loctite On Screws

Throttle Linkage Hardware Detail

Throttle Linkage Hardware Detail

Left Throttle Linkage Orientation

Left Throttle Linkage Orientation

Inner Throttle Linkage Arm-Notch Is For Throttle Return Spring

Inner Throttle Linkage Arm-Notch Is For Throttle Return Spring

Inner Throttle Linkage Arm Orientation

Inner Throttle Linkage Arm Orientation

Outer Throttle Linkage Arm

Outer Throttle Linkage Arm

Throttle Linkage Arm Hardware Detail

Throttle Linkage Arm Hardware Detail

Throttle Linkage Arms Orientation

Throttle Linkage Arms Orientation

Vacuum Port Parts Detail

Vacuum Port Parts Detail

Vacuum Port Screw & Washer Installed

Vacuum Port Screw & Washer Installed

Float and Bowl Parts

Float and Bowl Parts

Rubber Tipped Float Needle With Wire Bale

Rubber Tipped Float Needle With Wire Clip

Float Needle Location

Float Needle Location

Float Needle Clip Fits On Float Tab

Float Needle Clip Fits On Float Tab

Float Hinge Pin Serration Orientation

Float Hinge Pin Serration Orientation

Float Bowl Gasket

Float Bowl Gasket

Float Bowl Gasket Installed

Float Bowl Gasket Installed

Float Bowl Bail Orientation

Float Bowl Bail Orientation

Carburetor Slide Parts

Carburetor Slide Parts

Diaphragm Installed On Top Of Slide

Diaphragm Installed On Top Of Slide

Measuring Float Needle Height For #3 Position

Measuring Float Needle Height For #3 Position

Length Of Float Needle In #3 Position (37.8 mm)

Length Of Float Needle In #3 Position (37.8 mm)

Carburetor Slide Spring Installed

Carburetor Slide Spring Installed

Carburetor Top Installed With Two Screws

Carburetor Top Installed With Two Screws

Throttle Return Spring

Throttle Return Spring

Throttle Spring Installs In Groove On Inside Throttle Arm

Throttle Spring Installs In Groove On Inside Throttle Arm

Throttle Spring Orientation-Long Arm Goes On Inside Throttle Arm

Throttle Return Spring Orientation-Long Arm Goes On Inside Throttle Arm

Throttle Return Spring Installed

Throttle Return Spring Installed

Enricher (Choke) Return Spring

Enricher (Choke) Return Spring

Enricher (Choke) Spring Installed

Enricher (Choke) Spring Installed

Repaint Carburetor Emblems

The white paint was gone on one of the carburetor emblems and was faded and missing is some spots on the other carburetor. So I repaint the emblems. I use pinstripe white paint. I make a stamp out of small piece of balsa wood. I paint one side of the balsa wood and then press the painted side on the emblem to apply paint to the raised part of the emblem. There are some nicks in the emblem and low spots. I use a round tooth pick to fill those in with the with paint. And, some small spots of paint ended up on the black emblem, so I used a razor blade to scrape them off.

When the paint had dried over night, I used some Forever Black to touch up the black areas of the emblems. If I get some on the white paint, it can be cleaned off with a clean blue shop towel before it dries.

Emblem White Paint Gone

Emblem White Paint Gone

Balsa Wood Stamp I Made

Balsa Wood Stamp I Made

Balsa Wood Stamp Cut To Fit Carburetor Emblem

Balsa Wood Stamp Cut To Fit Carburetor Emblem

White Pinstripe Paint

White Pinstripe Paint

White Paint Applied To Balsa Wood Stamp

White Paint Applied To Balsa Wood Stamp

Pressing Balsa Wood Stamp On Emblem

Pressing Balsa Wood Stamp On Emblem

Touching Up Emblem Paint With Toothpick: Note Some Spots Of Paint On Black Part Of Emblem. I Scraped Them Off With A Razor Blade

Touching Up Emblem Paint With Toothpick: Note Some Spots Of Paint On Black Part Of Emblem. I Scraped Them Off With A Razor Blade

Forever Black

Forever Black

What Done Looks Like

Here is the rebuilt and refinished carburetors.

Rebuilt & Refinished Carburetors

Rebuilt & Refinished Carburetors

Finished Carburetor Rebuild-Refinish

Finished Carburetor Rebuild-Refinish

Finished Carburetor Rebuild-Refinish

Finished Carburetor Rebuild-Refinish

Finished Carburetor Rebuild-Refinish

Finished Carburetor Rebuild-Refinish

Finished Carburetor Rebuild-Refinish

Finished Carburetor Rebuild-Refinish

Revisions

2022-10-30  Corrected info about the carburetor model used on all R80ST US bikes.
2022-11-03  Correct Missing-Damaged parts list.
2023-12-22  Added Video section on rebuilding Bing CV carburetors.

2 thoughts on “13 BMW 1983 R80ST Rebuild, Refinish Carburetors

  1. Thank you Brook for another very detailed explanation/teaching of these carburetors! Your videos of this very important project are amazing too! Again thank you for taking the time and work to show us how to work on our own beloved Airheads.

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