Conversion of a BMW R27 to a Mikuni Carburetor
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- čas přidán 6. 09. 2021
- Conversion of a BMW R27 from a Bing 1/26/83 carburetor to a Mikuni VM 26-665.
With special thanks to my friend Markus and his magic lath and my indefatigable friends from cms.bmw-einzylinder.de/.
September 2021: present set-up - probably not finalized - is:
Main jet: 145, pilot jet 25, needle 3rd position.
My key criteria are cold start and smooth idle. I can't check for maximum speed, because we have a legal limit of 80 km/h and severe fines for getting caught with more than that ;^) - Auta a dopravní prostředky
Good video - even my wife likes it. My R27 had never ending fuel leak from the Bing like what is shown. The Mikuni seems the best choice. In 1 in a million - last year I found a Bing 53 in a neighbors junk pile. Cost = free! One challenge is attaching the cable but all well now. Bing KS helped with jets, needle, float, & sleeve. But doesn't leak fuel and is 'snappy'. Friend though 53 might have been via a Penton but DKW/Sachs/Maico aka 1970's dirt bikes possible also. The 53 fits fine, starts well, and helps 1964 R27 run again! Plus, ZERO fuel leaks.
Thanks for stopping by and good luck with your new carb!
Very nice upgrade sir! Cheers !
Obrigado!
Inspiring me to get my R27 back on the road. Just got a gas tank sealer kit in the mail and a few other parts. Won't be long now!
Have fun!
Very nice, Dappsull!! I need to begin my R25/3 project....
thank you and good luck with your R25!
Using Mikuni is a good idea, Bing carburetors are usualy worn out and is very difficult to put them in order to perform well.
I could’ve done with this a few years ago.
Two mechanics, supposed experts on classic bikes here in Portugal, couldn’t fix the constant leak of the bing carb on my R26. I sent it twice to Germany for another expert to have ago. I only got it to work properly after I found a classic Beemer mechanic in the north of Portugal. I’ve learnt that you need to learn what to do or find an ‘old gentleman mechanic’ who really knows what he’s doing. These guys are, unfortunately, increasingly hard to find.
Yes it's getting more and more difficult nowadays. Thanks for stopping by!
Excellent video. Can you please explain what the 'brake-fluid test' was for?
Thank you. This tests, whether the gasket between carb and cylinderhead is tight: if the revs don't change when sprayed upon it's ok.
Wieder mal ein super Video. Also bist du zufrieden mit dem Bing ?
Danke! Ich bin noch nicht ganz zufrieden mit dem Mikuni - vielleicht brauche ich eine groessere Leerlaufduese.
Bonjour, aujourd'hui vous confirmez que le fonctionnement du mikuni vm6--665 est correct avec quelles références ?
( gicleur 125 ? aiguille position 3 ? vis d'air 1.5 tours ? ) merci bien
Je suis en vacances d'hiver en ce moment. Mais j'ai eu des problèmes à moyen régime. Le ralenti et le plein gaz fonctionnent bien. Ce n'est pas encore parfait.
Someone in the States has the same carb. with these settings: main jet 120, pilot jet 30, needle in clip 4, air screw 1,5/8. Maybe it helps. Good luck!
Thank you - I will try this.....in spring ;^)
Very interesting.. it sounds great! think its a Mikunii Vm25 , what seize of main jet has? And pilot jet 20 or 25 ?
Thanks! I used a 145 main jet and a 25 pilot.
Excellent video thanks for posting, I have an R25 with the original Bing carburetor, unfortunately it is well worn , I would like to put it to one side and fit a Mikuni like you have. Please could you tell me which model carburetor and the jets you ended up using. Thanks once again.
Thank you! I am still struggling with getting the proper set-up and went down to a 20 pilot jet. Anyway: the R27 uses a 26mm carb. As far as I know the R25 has a 24mm carb, so you might try the Mikuni VM 24-4851?
@@dappsull Many thanks for your advice, I will look into this.
@@grahamkirk5974 Cheers!
thanks for sharing, what jets did you end up using?
It works fine with the 145/25 combination, maybe I will do some experiments later on (let's say next year). I will update the description then.
I understand there were 2 types of Bing for the R27. With accelerator pump, and without accelerator pump. Bing on my R27 did not have accelerator pump. It works very well and never had a problem. I have not seen an R27 Bing with accelerator pump.
Yes, there are at least 2 types. I tried both and didn't notice any difference. Here's one with pump (note brass tube at bottom of carb)
www.flickr.com/photos/dapsul/5238823204/
@@dappsull Thank you! I also had R26 and with the same carb, its engine was quicker and will jump ahead of R27 in a throttle roll-on. This is very evident in stop-and-go traffic where my R27 has a hard time keeping up with R26. I think that is the reason for the accelerator pump. R27 has more HP but needed rpm to get it. I gave up trying to make my R27 more responsive, the better method is to use same cam timing as R26. Unfortunately R26 cam has different shaft front end. This is Torque vs Horsepower, very similar to R50 and R50S. In stop and go traffic, the R50S cannot keep up with R50. By the time the R50S will pass R50, its time to slow down for next stoplight!
@@Juancheros Probaly it depends on the actual status of the engine. Actually the R27 should have more torque over the full range of revs, I think.
@@dappsull When an engine is tuned for horsepower, it looses low end torque. This is a basic compromise that can only be overcome by variable cam timing like used in modern engines. The compromise is very evident in R26/R27 and R50/R50S. The R27 and R50S both have "hot cams". Btw, I am talking from experience owning these bikes. If you understand this, then I think you will enjoy your R27 more as-is with the original Bings. The R27's greatest feature is the engine rubber mounting. There is nothing like it in motorcycling history.
@@Juancheros Thanks for your input! I am not an expert on engine design, so I have no idea of the theory. I was referring to a graphic published by BMW themselves, maybe just an advertising mock-up, but it shows, that the R27 has more horsepower and torque over the whole range:
www.flickr.com/photos/dapsul/53085960164/
How are you recording sound?
Either with the built-in microphone or - when driving - with a second microphone in a bag on the luggage carrier.
That’s a sweet bike. Did you notice any difference in performance with the new Mikuni carburettor? Do you mind if I ask how much genuine Mikuni carburettors are in Germany? I see a lot of Chinese copies on eBay, but I’m not sure we have a genuine Mikuni distributor here in UK.
I’m currently designing a BMW F650 Dakar engine based lightweight adventure bike, using a modified CCM 604 frame. My plan is to replace the perfectly acceptable EFI system with possibly a Mikuni carburettor. This will eliminate all the emissions legislation compliance complications, any one of which can cause the engine to refuse to start when they go faulty. I want a basic, reliable bike that I can fix at the roadside - as bikes used to be.
The alternative to the Mikuni is a very modern SmartCarb from the USA, which is more expensive.
Thank you for sharing your modifications.
Peace
Thank you very much! Some answers:
a) I payed 123 Euros for the carb plus some jets. I think the company is the official distributor for Mikuni.
b) Mikuni was ok as long as the temperature was warm. As soon as it dropped below about 10degC starting became a headache, so a severe difference to the Bing.
c) now comes a twist...I could get my hands on a working Bing, so I swapped back to the original set-up. Main reason was primarily the optics.
Cheers and peace!
D.
Hello Sir
I won an R 27, and I would like to have the same upgrade(Mikuni). Can you tell me where to buy it?
Thanks
I bought at mikuni-topham.de/ENGLISHSITE/ENGLISH/Frame_English.html
@@dappsull Thanks
@dappsull Please let me know if the bike runs properly with the Mikuni carburettor. Also, please tell me about your experience with Mikuni over time(pros and cons).
Many thanks
@@ETCRO80 It ran properly, but I found a working Bing and reconverted to this one because I didn't like the look of the Mikuni.
@@dappsull Thank you very much 👍