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Autor Thema: Bing 1/24/42 instead of 1/22/28 on R25  (Gelesen 505 mal)

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krhoff

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Bing 1/24/42 instead of 1/22/28 on R25
« am: 27 Mai 2020, 09:28:53 »

Hi experts,

My R25 has a Bing 1/24/42 instead of the original Bing 1/22/28. One of the previous owners apparently made this change, maybe using a replacement carburetor from an R25/3.

What sizes do you recommend for the "Hauptdüse" and "Leerlaufdüse"? Should I stick with the values for the 1/22/28 (Hauptdüse 100, Leerlaufdüse 45) or use the values for the 1/24/42 (Hauptdüse 145, Leerlaufdüse 35)?

Here are the carburetor specs from Tillmanns:
https://www.faak-tillmanns.com/shop/u/TVI/BMW_R_25_1-22-28.pdf
https://www.faak-tillmanns.com/shop/u/TVI/BMW_R_25_3_1-24-42.pdf

Thank you.  :)
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Bing 1/24/42 instead of 1/22/28 on R25
« am: 27 Mai 2020, 09:28:53 »

strichzwojan

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Re: Bing 1/24/42 instead of 1/22/28 on R25
« Antwort #1 am: 27 Mai 2020, 10:29:36 »

Hi,

I have a 1/24/42 on my R25/2 with the cylinderhead of the slashthree model. But as long as you have a 34mm inletvalve, the R25 head should be fine.
Congrats! The 24mm Bing is a good choice for the R25. But be aware: the air-filter should be mounted directly to the carb, (the Knechtfilter of the R25 model fits pefectly), main jet should be 110 oder 105 (!), the rest of it should be like the R25/3 settings with Bing carb.
Vmax does not increase very much, but the acceleration is fantastic. Comsumption of fuel is 3,6 litres per 100 km.

I reamed my my main jet to approx. 108 size, and that is fine for the alps around Innsbruck.

Edit: I see you live in Denmark, then take the Hauptdüse 110!

Jan
« Letzte Änderung: 27 Mai 2020, 10:32:59 von strichzwojan »
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krhoff

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Re: Bing 1/24/42 instead of 1/22/28 on R25
« Antwort #2 am: 27 Mai 2020, 10:53:20 »

Hi Jan,

Thank you. Do you mean a 24 mm inletvalve? I assume that "22" and "24" in the Bing model numbers are the inlet diameters? I have two "stifte pro Ventildeckel" so it must be a R25 head and therefore 24 mm.

Yes, the airfilter is installed directly on the carb.

I did a carb clean two years ago (I do not ride the bike that often) and changed the main jet from 100 to 110. The motivation was to see if it could a bit more power out of the small engine. I think it helped a little bit  - and it matches your advice. :)

The leerlaufdüse is currently 45, so I have to change it to a 35. The Nadeldüse is 1208, but that is the same for both carbs.

I have been riding the bike for a few years, but did not notice that the wrong carb was installed before recently. In fact, the "Schlauchschwenkanschl" and the "Deckelplatte" seems similar to those on a 1/22/28, so it is not easy to see that the carb is not a 1/22/28.
« Letzte Änderung: 27 Mai 2020, 11:29:53 von krhoff »
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strichzwojan

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Re: Bing 1/24/42 instead of 1/22/28 on R25
« Antwort #3 am: 27 Mai 2020, 14:12:27 »

R25: 1/22/28
R25/2: 1/22/44
R25/3: 1/24/42 or 1/24/41
Do not mix parts. Besides the main jets…

I mentioned the valves, because there was a R25 type that has inlet- and outletvalves BOTH with 32mm.
R25/2 and R25/3 have intlet 34mm, outlet 32mm.
The diameter of your carb Bing 1/24/42 ist 24mm.

Jan
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krhoff

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Re: Bing 1/24/42 instead of 1/22/28 on R25
« Antwort #4 am: 27 Mai 2020, 15:08:22 »

Sorry for the misunderstanding. I thought you meant carb. diameter. I am pretty sure that the inlet valve diameter is 34 mm on my R25 head.

I will have a closer look at all the parts the next time I clean the carb.

Thank you, Jan.  :)
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