Bing 64/32/325-326

[montmil]

This is an interesting bit of minutiae regarding the Bing CV carburetors, Models 64/32/325-326, most often found fitted to the 1981-1982 R65 and 1982 R65LS.

A question was posted on the Airlist http://airheads@micapeak.com asking if these were the correct carbs for the gent's 1981 R65.

Here is an interesting response from Robert "Snowbum" Fleischer. http://bmwmotorcycletech.info/
Da 'Bum's response below is posted verbatim and in it's entirety.

I found his ideas interesting, particularly the "carb runs lean" comment.

Monte


Yes, used on the 1981-1982 R65 and the 82 R65LS.

The /325 was the USA version of the left carburetor.

main jet 145; needle 2.66 (some shipped with 2.68 which worked better); 3rd clip position; 40 idle jet.
The carb runs lean and works better with a slightly richer main, say 148; and a 2.68 needle jet.

You might even try the 4th notch on the needle and a 45 idle.

Snowbum
 
  

[Mike V]

Monte,

I saw that too - and responded to Paul.  He was referring to my gruntyman66 photobucket site and my carb pictures.  If you remember a while back i posted a thread about struggling with 325-326 carbs due to the lean condition and flat spot off of transition from idle after my restoration and complete carb rebuild.  Drove me insane trying to correct it. I was ready to re-jet the carbs until I found a pile of fine tank debris in the bottom of my bowls.  Oops.  After yet another carb rebuild (o-rings only) and installation of a paper in-line filter I have the beast running very nicely and smooth with stock jetting and needle setting (3).  Mine came stock with the 2.66 needles, 145 main and the 40 idle jet.  My next move was to go to the 2.68 needles and 150 main's but clearing the carbs of crud solved my problem.  I actually tried throwing in some 150 mains with the resulting standard jetting and it did nothing for the stumble but made it run rich. Bum's advice is very interesting to me also. Tank relining is on the "to-do' list.

I pulled out my old 11/1980 edition of the BMW parts Catalogue and looked up the outdated number.  Tom was correct about the PN being discontinued.  The old PN's are: 13111336977(L) & 13111336976(R) I think, and don't show up on the current Real OEM listing.  As Tom mentioned the replacement carbs are 335 & 336 as shown on the fiche.  http://tinyurl.com/3t9tkey

And yes, these (325 &326) are the standard equipment US carb for my 81 R65, 6385070 production date: 9/1980.  No problems at all with them after I cleared them of red lead tank smoodge.

[montmil]

I moved my needle clip to the numero 4 position and  immediately cured my mid-range stumble. Did this before the 'Bum posted his most interesting Airlist reply.

Happy R65.

Monte

[Bob_Roller]

The Bing carbs are set from the factory for sea level elevation and 60 F. (15C) .

Lets face it, these bikes are operated over a wide range of conditions and sometimes they need to be adjusted to local conditions .

[montmil]

Right you are, Bob Robert [smiley=thumbup.gif]

It can be reassuring to read something from Snowbum or Tom or Matt that one's tuning ideas are not so far out in left field after all.

Monte

[Bob_Roller]

On a typical 'hot season' day here in Phoenix, the 'density altitude' is around 6500 feet (2000m) .

To put it into easier terms, Phoenix is at 1100 ft (340m) above sea level, with the decrease in air density at 110 F. (43C) is the equivelant of being at 6500 feet (2000m) above sea level .

[Cano]

If you run these carbs and have a mid-throttle flat spot, I very much suggest trying da 'Bum's recommended jetting changes.

Background -- over winter I bought a 1982 r65ls that had been sitting +20 years.  Disconnected and plugged the pulse air system.  When rebuilding the carbs, I noted it had the stock jets.  Bike has been running good, but I alwys thought the plugs looked pretty darn lean and there was a flat spot on acceleration.  This weekend went to the 148 mains and 2.68 needle jet, and what a huge difference in driveability.  Flat spot is gone, and there seems to be more power across the board.  There is even better throttle response, especially off idle (never had a hesitation or stumble per se), but it is soooo much smoother now.  Finally, in general the bike seems to run much smoother as well -- I noticed less vibration.  

I'll probably try the next larger idle jet as well sometime in the future, but at this point I did not want to have to re-synch the carbs.  Swiching out the main and needle jet was super easy -- just take the float bowl off -- no need to remove the carbs or mess with your cable adjustments.  Make sure you remove the elbow from the air cleaner so you can lift the slide and needle when installing to make sure the needle is not hanging up on the atomizer/needle jet, etc.