R27 Cold Start Nightmare

[wa1nca]

Salis site also shows both 11&7 gram floats for R27
Item #43
https://www.bmwclassicmotorcycles.com/p ... buretor-2/
11grams for Bing 35-073
7 grams for Bing 35-072

My Bing reference for r27 shows only Bing Type 122

Now I am confused

[schrader7032]

I went by what Vech has on his old website.

[wa1nca]

Salis site also shows what weight and carburetor #'s the the 2 different float should be

13110039186 11 gram float carb # 1/26/46-52-79-83-93

13110039187 7 gram float carb # 1/26/55-68

https://www.bmwclassicmotorcycles.com/p ... buretor-2/
#43

Your carburetor 1/26/68 should have a 7 gram float

[schrader7032]

Hmmm...something seems fishy here. In all those runs of carb numbers for the R26/27, they are all 11gr except for two carb numbers in the middle of the run of numbers...they get a 7gr float. Strange.

[wa1nca]

Salis site also shows what weight and carburetor #'s the the 2 different float should be

13110039186 11 gram float carb # 1/26/46-52-79-83-93

13110039187 7 gram float carb # 1/26/55-68

https://www.bmwclassicmotorcycles.com/p ... buretor-2/
#43

Your carburetor 1/26/68 should have a 7 gram float

I called Bing USA today:
They confirmed
1/26/55-68 uses a 7 gram float

1/26/52-79-83-93 uses a 11 gram float

Salis site appears to be correct for the above listed carburetors

I asked why most were 11 grams and two where 7 grams
He said ask Bing !!

I didn't ask spec for 1/26/46 R26 carburetor

[schrader7032]

Curiouser! I checked RealOEM for the R27 carbs and it does show an 11 and 7gr float but doesn't really indicate which carbs they are to be used on.

So it seems that the /52 carb requires a 11gr float while the /55 carb requires a 7gr float. In the Bing manual, it's nice that these two listings are right next to each other so it's quite easy to compare. It turns out that all of the settings and notations for these two carbs are IDENTICAL. So how can that be? The carb Type is the same -- 122. Doesn't that mean that the carb body is identical? Why would there be different floats? Floats are all about buoyancy and their weight displaces the amount of liquid equal to their weight. I'm trying to grab onto the physics as it relates to, what appears to be, entirely identical carbs. I'm not seeing it!!

Further checking the Bing book, all of the R26 and R27 carbs have the type 122 carb. Looking deeper in their book at the 122 carb blowup, they reference their part 35-073 which in the table says is 11gr float. So it appears their book is wrong. The type 120 carbs all require the 7gr float (part 35-072). Seems that the 120 carb is generally used for the later twins.

[Worleybird89]

Update: After much tinkering with the carburetor, I can get a cold start pretty consistently in 1 to 3 kicks.
My procedure (nothing fancy):
- Turn on fuel and watch for flow through the filter
- Press and hold ticker for a 3 count (roughly 2 seconds)
- Turn on Ignition
- Kick

Unlike my R60 carbs, the idle mixture screw on this one seems to work as expected, and I think I have it slightly to the rich side of peak RPMs. I'm getting good throttle response in both directions, and a nice solid idle.

Hot restart is another ball game. After a short 10 minute test ride today she would not fire at all right after turning the ignition off, then back on. I'm replicating what might happen if she dies at a stoplight, for example. After a few dozen kicks, first without prime, then with prime, I had to have my son push me down the driveway. She fired back up after about 20 feet in 2nd gear. Another try later, with a longer wait before the restart and I was able to get her restarted right away.

Has anyone else experienced something similar with an R27 and found a solution? Still running stock 6V ignition.

[Dover Rider]

Well for what its worth, I found that if its off and still warm from a ride to the store, when I try to start it I don't turn the gas on until i kick it over and it fires. For some reason mine floods easily after it runs. I also cant tickle when I first start, I just turn on the tap and go put on my helmet and jacket, then kick it and it usually starts. Very fussy and I've been out of breath a few times trying to push start it. Everything new in the carb, new advance springs. One thought on the erratic high idle, the slide could be sticking a little, check the flange for flatness. Still not daily driver qualified. Love to hear from the guys using these for the cannonball run.
1964 R27

[schrader7032]

My R69S seems to be harder to start warm like after a gas stop. What I do is to leave the petcock off and open the throttle wide open. I then kick the lever 5-6 times to clear the combustion chamber. Finally, leaving the petcock off, and hand off the throttle, I push the key down and then kick the start lever. Bike usually rumbles to a start, I can coax the throttle to get it to run better and better. And finally, I turn the petcock on.

[Daves79x]

If it does not start in one or two kicks when hot, hold the throttle wide open - DO NOT tickle it.

Dave