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Old 07-23-2013, 06:08 PM   #1
beemerphile OP
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Best carbs for 77 RS big valve motor?

I am doing a ground-up restoration of my 77RS (into an S because I lack the original fairing). It will get Nikasil cylinders and new compatible rings, rods reconditioned, and the heads rebuilt and dual-plugged. It will also get a crank-mounted ignition system on an EnDuraLast alternator. It will retain the stock 308 cam with a new chain (I guess). It will get a new set of Keihin 40mm stainless pipes.

The question: What is the best carb set-up for this combination? I do not have the stock 40mm Bings. What is has is a dogged out set of Mikuni 38mm flat-slides. What SHOULD it have if it were to be the very best it could be?
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Old 07-23-2013, 06:17 PM   #2
Jon-Lars
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Cool2

Dellortos.

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Old 07-23-2013, 06:48 PM   #3
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Dellorto's . . . and a BMW 336.

I prefer the rubber mounted Dellorto's over BMW's clamp mounted units. I like them without the choke too. One less cable. I just use the pumps versus the choke. My Dell's don't have the enricher bodies on them and they have the pumps disconnected. It would be impossible to start but I have Dell's with ticklers like a /2 Bing.

One reason I like Dells is because the airbox snorkels fit them. I have late model square airbox snorkels on mine with no radiator hose and double hose clamps like in the photo above. I filed about a third of the velocity stack threads off and the late snorkels fit right on them with one hose clamp and no hose just like they do on the later stock Bing setups. Way cleaner look IMO. That and two cables versus four.
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Old 07-23-2013, 07:07 PM   #4
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Quote:
Originally Posted by supershaft View Post
Dellorto's . . . and a BMW 336.

I prefer the rubber mounted Dellorto's over BMW's clamp mounted units. I like them without the choke too. One less cable. I just use the pumps versus the choke. My Dell's don't have the enricher bodies on them and they have the pumps disconnected. It would be impossible to start but I have Dell's with ticklers like a /2 Bing.

One reason I like Dells is because the airbox snorkels fit them. I have late model square airbox snorkels on mine with no radiator hose and double hose clamps like in the photo above. I filed about a third of the velocity stack threads off and the late snorkels fit right on them with one hose clamp and no hose just like they do on the later stock Bing setups. Way cleaner look IMO. That and two cables versus four.
Not sure I follow all that. Wouldn't have a picture, would you? I was not aware there were so many options with the Dellorto's. Much to learn here.

Jon-Lars, your RS is awesome.
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Old 07-23-2013, 07:13 PM   #5
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I just put them on my 77RS, using the same intake and fittings as on my R90S:

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Old 07-23-2013, 07:23 PM   #6
Bill Harris
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Ooooh. Nice project. Coming back from the darkside, eh?

From what I've heard, the Dellortos work very well. And just look impressive on the bike. Best of luck finding a good set...

On the resto, pics please as the work progresses...

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Old 07-23-2013, 07:21 PM   #7
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Quote:
Originally Posted by beemerphile View Post
Not sure I follow all that. Wouldn't have a picture, would you? I was not aware there were so many options with the Dellorto's. Much to learn here.

Jon-Lars, your RS is awesome.
Look through a Dellorto manual. They have all the options. They are on line.
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Old 07-23-2013, 08:35 PM   #8
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Originally Posted by supershaft View Post
Look through a Dellorto manual. They have all the options. They are on line.
Links to this? I can find a page full of PHM type carbs on Dellortodirect, but nothing that explains what the differences are between the different models (such as BS/BD, CS/CD, NS/ND, etc.). Is there a US reseller that has the knowledge to kit one with starting jetting, cables, and connectors as a Sudco or Rocky Point would do with Mikunis and Keihins?
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Old 07-23-2013, 07:37 PM   #9
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Quote:
Originally Posted by beemerphile View Post
What SHOULD it have if it were to be the very best it could be?
Best at what?? If sport touring for long distances and easy maintenance, the stock 40mm Bings will do just fine, thank you. Use the stock Euro jets for that year and you are golden.

Others can do just fine, if your skill in setting up the right jets is up to the task. If tinkering through such trials and errors is something you like doing, do that.

But factory Bings is a quicker road to decades of good service with stock cables and procedures giving easy install setup.

DoktorT screwed with this post 07-23-2013 at 07:43 PM
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Old 07-23-2013, 07:47 PM   #10
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Pissed Fuel injection

Since this is open to everybody's opinion (you asked!!) I would go with fuel injection!!!

AirHead with fuel injection that's the Ticket!!

Ok - 38mm flatside - stick with the flatside carbs.

Fuel Injection Hmmm??? I planted a seed let's see if it will grow.
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Old 07-24-2013, 08:32 AM   #11
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I have a project to remove the Dels and reinstall Bings.
(to stop cable chafe when using the 43 lt Acrebis tank)

The project has been sitting on Ray Peaks bench for near two years.
Neither of us are motivated.

Has anyone ever gone back to Bings?
I don't seem to be able to find their posts telling us how excited they were with the change.
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Old 07-24-2013, 09:24 AM   #12
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Originally Posted by Rucksta View Post
I don't seem to be able to find their posts telling us how excited they were with the change.
Maybe that's telling...

- If the tops of my boots were too dry and odorless, I'd install 40mm Bings
- If I needed a constant bruise on my right mid-shin, I'd install 40mm Bings
- If I wanted to turn the gas off by kicking it, I'd install 40mm Bings
- If I wanted to twist - wait- go, I'd install 40mm Bings
- If I didn't like to use engine braking, I'd install 40mm Bings

I'm sure there are other reasons I can't pull up right now. To the benefit that they are undemanding, I would say "So is an ugly girl". The Bings are really the only thing I have ruled out. I have Mikunis on my R75/6 and they do well, but I wanted to take this build upscale from the R75 where it makes sense. Just trying to learn what is out there and what kind of trials or sucesses people are having. No bones to pick with the Bingers. I spent a few decades there.

Fuel injection! Hmmm? How to get a fuel pump into a /7 tank???
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Old 07-24-2013, 09:26 AM   #13
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I had 38mm mikunis on my 77 R100Rs and would never own another Airhead without putting them on it as well.
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Old 07-24-2013, 09:27 AM   #14
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Originally Posted by Sniper X View Post
I had 38mm mikunis on my 77 R100Rs and would never own another Airhead without putting them on it as well.
Flat or round slide?
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Old 07-24-2013, 01:02 PM   #15
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Quote:
Originally Posted by beemerphile View Post

Fuel injection! Hmmm? How to get a fuel pump into a /7 tank???
You could put a small non-submersed pump right beside the starter and feed it from the stock fuel crossover under the airbox.
A microsquirt injection can use the starter teeth on the flywheel for crankshaft positioning and two camshaft sensors to get the correct TDC info. With the BMW cable splitter under the tank you can drive the TPS and you can use a completely gutted Bing40 as an injector-holder+throttle-plate, and route the cabling to drive the injector through the intake air duct from the air filter housing.
Voila- almost invisible EFI mod for the airhead. (You would see the second set of fuel lines from the fuel pump to the "carbs".
(I did a project like this for a thumper, needed to be invisible because on my side of the pond it is almost impossible to get something like that through the hoops of bureaucrazy*)

Cheers

AlpineRAM

* bureaucrazy is not a typo- it's a definition for the crazy in the offices of the authorities.
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