Carburetor Rebuild: photographic tour.

[Cinciride]

Thank you for all of the advice from this forum.  I received the parts from Max  [smiley=bmw_smiley.gif] on Friday (great service) and rebuilt the carbs over the weekend.  

I removed the top two screws to remove the diaphragm cover and I found two things.  
1.  There are no slide return springs in my carbs (normal for my model).

2.  The picture will speak for itself (hint: That is a picture of the slide removed from the carb with the diaphragm still attached.  You should not be able to see through the diaphragm).  I actually found this out just after I ordered my rebuild kit and had to modify my order.  Max BMW could not have been more helpful.  I highly recommend them for their service on internet orders.  

[Cinciride]

Here is the top of the slide showing the four screws that need to be removed for disassembly and removal of the diaphragm.  The top needs to be gently pried from the bottom.  There is a notch in the bottom half of the slide that will help align the new diaphragm.  Unfortunately I did not get a picture of it, but be sure you align that notch.  It not only has to sit in there for proper assembly, but will help be sure that the slide sits in the carb body appropriately when you are done with assembly.  

Removing the needle from the slide was a little tricky.  You need to pull and turn the needle.  Remember to count the number of notches that the needle is sitting on.  Mine was sitting in three notches.  

The second picture is what you see looking down from the top once the slide is removed.  That is the needle jet and with a worn needle, ruptured diaphragm, and some dirty old floats (photos to come), is the likely source of my problems.  

[Cinciride]

Here are the floats prior to rebuild with that nice yellow/brown "patina".  It turns out not all patinas are functional.  The gasket was in better shape when I first took the bowl off.  It is wrinkled because it has dried out.  On this rebuild I replaced the floats, the needle jet, and the idle jet alone with all of the o rings.  The second picture is of the pin you need to remove to remove the floats.  A couple of taps with a small screwdriver against the non-knurled end loosened it and it removed easily.  Very little force is needed to remove the pin.  The last picture is of the fresh floats.  

[Cinciride]

One last pic of the float needle and the small wire that retains the float needle on the float.  I probably should have replaced the float needles as one of them appeared a little worn (round impression on the top), but I can go back and do that later.  

[Cinciride]

Beginning to remove the main jet.  An 8 mm screw and washer.  

Next picture is the main jet itself (10 mm) in position and then out of the carb.  This was a bear to remove.  You can see the debris around the jet threads.  You can also see the debris in the channel where the Main jet screws in.  The brass is the needle jet and the atomizer distal to the debris.  That debris was hard, then crumbled into a fine powder.  It was difficult to remove, even when dipping the carb.  It took a combination of a fine needle to scrape it out of the threads, carb dip, spray carb cleaner, WD 40, and a soft cotton rag that was twisted into the channel.  It was clean when I was through.  

[Cinciride]

Here is a photo of the main jet/needle jet atomizer assembly.  The small screw that you first need to remove is off to the left of the photo and hidden by the large flat washer.  The o ring on the main jet was replaced after carb dipping the parts.  The needle jet was replaced with a new needle jet.  

The second picture is the idle jet and the air mixture screw.  Even though I have read the idle jets do not wear, I replaced it with a new idle jet and new o-ring.  The Air mixture screw was removed and dipper.

First turn the screw in and count the number of turns.  Mine was 1 and 1/4.  Then remove.  There is a strong spring over the air mixture screw.  Both parts were dipped and reused.  

[Cinciride]

Choke body removal was pretty straight forward.  Remove the four screws.  You can see in the first photo, one of the screw removed and the amount of crud that was built up on the carb body.  

In the second photo you can see what it looks like once the body is removed.  Unfortunately I did not get a photo of the gasket that fits under the choke body.  I replaced the gasket.  

I also included a picture of the varnish around the throttle body.  Once I had the carb disassembled, all of the parts went into the carb dip.

[Cinciride]

I did not photograph the reassembly.

Getting the needles back into the slides was the most difficult part.  They are slipper and hurt if you push on the end.  

These pics show the clean carb, the clean throttle, and a side by side comparison of before and after carb.  All told the kit cost around $200 including shipping for the o ring and gasket set, diaphragms, needle jets, idle jets, floats and float pins.  I had the carbs disassembled and assembled within a leisurely day.  Next is to mount them and me sure all is running well.  

[Adrian]

Thank you very much for this - I shall add it to my ever growing collection of very helpful resto work from this site. I shall be doing exactly this process in the near future as I progress thru my bike's resto. It looks excellent ..............
Now all I have to do is transfer it to a savable document of some kind  
Adrian ........................

[Adrian]

P.S. mate - what did you use as a "carb dip"? Managed to print the whole page including pictures so that will do nicely.
Adrian ......................

[Cinciride]

I looked for Berrymans carb cleaning solution because it had good reviews on other sites, but it was not stocked at my local auto parts store.  Instead I bought a can of Gunk or some similar name.  It is basically a can carb cleaning solution with a basket in the can, and the parts can be soaked in the solution to dissolve and loosen the material.  And old tooth brush, some dissecting probes from college, a can of spray on carb cleaner, liberal amounts of water, and a final blast with wd40 and they were cleaned up.  I only had to soak the parts for 20 to 30 minutes.  

[Barry]

Next picture is the main jet itself (10 mm) in position and then out of the carb.This was a bear to remove.You can see the debris around the jet threads.You can also see the debris in the channel where the Main jet screws in.The brass is the needle jet and the atomizer distal to the debris.That debris was hard, then crumbled into a fine powder.It was difficult to remove, even when dipping the carb.It took a combination of a fine needle to scrape it out of the threads, carb dip, spray carb cleaner, WD 40, and a soft cotton rag that was twisted into the channel.It was clean when I was through.

Excellent pictures.  

Removing that crude from around the needle jet emulsion tube is going to make a big difference to your carbs. That crud will have blocked off the pre-mix air supply to the needle jet and caused a significant increase in fuel consumption. It's not unusual to find that area at least partially blocked due to the carbs ingesting a mix of oil and moisture from the engine breather. You did well to get the main jet holder out in the circumstances. Mine was seized and it took me a week to shift it. I remove the main jet holder once a year now to check the area is clean and to prevent future seizure.

[Adrian]

Thank you gain Cinciride - much appreciate the help and info - now to hunt it down.
Adrian ..................

[Bill Conquest]

Excellent pics & description, thanks..how does it ride now?
Bill

[Cinciride]

Excellent pics & description, thanks..how does it ride now?
Bill

It is killing me to write this, but I have been on call all week and have not had the opportunity to reinstall them and fire it up.  Last call day is Thursday, so this weekend i will find out. I am very excited to put it back together.   As I mentioned on one of my earlier bike lust posts, every winter I get wandering eyes.  Tearing into this project has not only cured my wandering eyes, but also reignited my affinity for my bike.  Can't wait for the weekend (for more than one reason).
Colby