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-   -   Best carbs for 77 RS big valve motor? (http://www.advrider.com/forums/showthread.php?t=906054)

beemerphile 07-23-2013 05:08 PM

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?

Jon-Lars 07-23-2013 05:17 PM

Dellortos.

http://i44.photobucket.com/albums/f13/R90S/img234.jpg

supershaft 07-23-2013 05:48 PM

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.

beemerphile 07-23-2013 06:07 PM

Quote:

Originally Posted by supershaft (Post 21937348)
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.

Jon-Lars 07-23-2013 06:13 PM

I just put them on my 77RS, using the same intake and fittings as on my R90S:

http://i44.photobucket.com/albums/f13/R90S/aar90s.jpg

supershaft 07-23-2013 06:21 PM

Quote:

Originally Posted by beemerphile (Post 21937500)
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.

Bill Harris 07-23-2013 06:23 PM

Ooooh. Nice project. Coming back from the darkside, eh? :D

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... :deal

--Bill

DoktorT 07-23-2013 06:37 PM

Quote:

Originally Posted by beemerphile (Post 21937023)
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.

Biebs 07-23-2013 06:47 PM

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

AirHead with fuel injection:freaky that's the Ticket!!

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

Fuel Injection Hmmm???:deal I planted a seed let's see if it will grow.

beemerphile 07-23-2013 06:54 PM

Quote:

Originally Posted by Bill Harris (Post 21937647)
Ooooh. Nice project. Coming back from the darkside, eh? :D

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... :deal

--Bill

No Bill, I am keeping the darkside and just two-timing it a bit. I bought back a 1977 RS that I bought new and sold to a friend in 1991. It has been melting into his barn floor for the last decade and I thought enough was enough.

As far as the goals for the build - a strong performing S bike. I don't mind fiddling but I'm not into mechanical masturbation. I'd like something with a starting set-up that would run with some tweaking to optimize it. I don't want to have to "discover" the entire set-up.

beemerphile 07-23-2013 07:35 PM

Quote:

Originally Posted by supershaft (Post 21937626)
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?

Bill Harris 07-23-2013 08:08 PM

Quote:

Originally Posted by Beemerphile
I bought back a 1977 RS that I bought new and sold to a friend in 1991. It has been melting into his barn floor for the last decade and I thought enough was enough.

Ah, then this IS going to be a good project to follow. A resto of an old bike is one thing, but one with your history attached is entirely on another plane.

--Bill

mnsty 07-23-2013 08:08 PM

Bings

beemerphile 07-24-2013 04:18 AM

Quote:

Originally Posted by Bill Harris (Post 21938513)
Ah, then this IS going to be a good project to follow. A resto of an old bike is one thing, but one with your history attached is entirely on another plane.

--Bill

I met my wife of 31 years on this bike. I had it running for a few moments before I began the teardown. When my wife heard it she said it was a flood of memories. It was my first BMW and cost me $4,755 back when a rather nice car did not cost that much. So, history, yes.

rheritage 07-24-2013 04:30 AM

I have a 78 Euro 100RS with stock 40mm Bings, plan is to install Mikunis, already have them on my R75/5 and love'em.


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