Author Topic: CB 500/550 Single Weber? (Read 5991 times)

Lostboy Steve · « **on:** November 10, 2014, 01:57:44 PM »

I know that the 750's have been seen with twin webers. Was wondering if anyone has ever tried a single weber on a 500/550.

BPellerine · « **Reply #1 on:** November 10, 2014, 05:15:54 PM »

only time I have seen a single weber is on twins,hd,triumph,or 450,dont know if they even made a manifold for the 550s,you would have to make your own.bill

754 · « **Reply #2 on:** November 10, 2014, 08:32:56 PM »

It would be worth it..

Lostboy Steve · « **Reply #3 on:** November 11, 2014, 05:17:52 AM »

Quote from: 754 on November 10, 2014, 08:32:56 PM

It would be worth it..

I know... It would be cool. Looking at those 450 500 twins, it seems like the weber is "a lot of carb" for those engines. What are you thinking 754? Make a 4 into 2 manifold and start playing with jets?

Lostboy Steve · « **Reply #4 on:** November 11, 2014, 05:28:11 AM »

Looks like I need to learn how to sandcast parts. Check this out. Cylinder Balanced.

CBGhia · « **Reply #5 on:** November 11, 2014, 08:45:29 AM »

Here ya go:

Edit: Even better stuff here: https://www.youtube.com/channel/UCNC9gjgYrzLfyMQmp31DnjA

754 · « **Reply #6 on:** November 11, 2014, 09:52:55 AM »

I would just fab a manifold, way easier than building say a header.. No sync problems, easy to get at jetting (usually)
Incredible throttle response, plus an increase in mileage that may probably even pay for it all.
They did make a single Weber kit for 750, MPD made it, I would have mp at the chance to try one for touring..

TwoTired · « **Reply #7 on:** November 11, 2014, 10:56:16 AM »

I've never used a Weber, but know they are in high regard. These use a butterfly valve for the throttle, right?

How well do the butterfly pivot shafts hold up to the strong induction pulses? Is there a replaceable bushing there? Just curious.

I can see how they might help power at red line operation. But, it would seem like operation below mid range and the low air velocities, would make the engine less responsive on the street.

Putting big carb throats on small engine is a common mistake for a happy street machine, resulting in poor low speed atomization. Works well for drag racing, high speed runs, though.

754 · « **Reply #8 on:** November 11, 2014, 11:01:37 AM »

Actually one of the few carbs using Ball bearing throttle shafts.!
Venturis change in minutes, you could have 2 28mm feeding both cylinders, or maybe smaller.
Around 6 changeable jetting element vs around 3 in some carbs..

My choice of them is reinforced by the strong low and midrange response.

Lostboy Steve · « **Reply #9 on:** November 11, 2014, 11:09:18 AM »

I had a single Weber sidedraft on a 1989 Rx-7 which had highly modified ports. It was surprisingly street-able and reliable. I also had a single down draft on an otherwise stock 1972 Superbeetle. It too performed very well. They are great carbs. I see your point about lower rpms. Its questionable. I guess theres really only one way to find out.

So figure I should start shopping for a 40 dcoe?

Greggo · « **Reply #10 on:** November 11, 2014, 12:18:36 PM »

I have a leftover ATP intake manifold for my 500/550 I've thought about using for a single carb set up...What is appropriate for the street?

Lostboy Steve · « **Reply #11 on:** November 11, 2014, 01:09:09 PM »

no idea but a 38mm is nearly impossible to find without breaking the bank...

BPellerine · « **Reply #12 on:** November 11, 2014, 05:03:44 PM »

I have 38s on my stock 750 with 28mm chokes and there is no downside low or high rpm,if you really want to nitpik they take a little more finesse to start when cold but if I had to choose only one thing for my bike the webers would be it,did they really make a single weber kit for the 750 Frank?would be cool!

scottly · « **Reply #13 on:** November 11, 2014, 08:45:15 PM »

Quote from: TwoTired on November 11, 2014, 10:56:16 AM

I've never used a Weber, but know they are in high regard. These use a butterfly valve for the throttle, right?

How well do the butterfly pivot shafts hold up to the strong induction pulses? Is there a replaceable bushing there? Just curious.

I can see how they might help power at red line operation. But, it would seem like operation below mid range and the low air velocities, would make the engine less responsive on the street.

Putting big carb throats on small engine is a common mistake for a happy street machine, resulting in poor low speed atomization. Works well for drag racing, high speed runs, though.

One of the main attributes of the Weber is that it will atomize the fuel at lower pressure differentials than most carbs, allowing a greater charge in the cylinder; this is why they are often referred to as "the next best thing to fuel injection". Cruising at 65-75 MPH is still in the low-speed jet range, and will produce 50+ MPG on my bike, while cruising at 55-60 MPH has produced in excess of 60 MPG. With the accelerator pumps, which have at least 4 different adjustments, there is no lack of low speed response. Putting a brace of DCOE 40's on a 750 is not the same thing as slapping an 850 Holley on a 283 Chevy.

BPellerine · « **Reply #14 on:** November 12, 2014, 01:10:52 PM »

you have put it very well scottly!everyone that sees them here say that I must have too much carb including an instructor from the local trade school who has solex carbs on vintage Datsun two seater,so I took the bike down and let him see ,he did not know what to say!ill

754 · « **Reply #15 on:** November 12, 2014, 02:15:03 PM »

According to the baseline jetting from Magnussen..an off the shelf 750 carb, ie one of the pair..is jetted the same as the one supplied for a 1200 cc Harley..!

754 · « **Reply #16 on:** November 13, 2014, 07:22:00 PM »

I bet I could get 65 mpg to a US gallon with a single Weber on a 750..if not 70..
But then again I hit around 60 mpg. To a US gallon with stock K3 carbs wit original K+N. Filters on it. (rubber end).

.

BPellerine · « **Reply #17 on:** November 13, 2014, 07:25:21 PM »

I think we all know what happens when you start playing around town!!haha bill

754 · « **Reply #18 on:** November 13, 2014, 07:36:07 PM »

Yeah, I know it goes form 58 mpg to about 25!!!!

Lostboy Steve · « **Reply #19 on:** November 15, 2014, 06:37:24 PM »

Well I still say this would be a really cool adaptation. I just need to get my hands on one.

BPellerine · « **Reply #20 on:** November 16, 2014, 10:36:04 AM »

yes very cool adaptation and not seen ,the 40 should not be hard to get,the manifold would require some thought.bill

Lostboy Steve · « **Reply #21 on:** November 16, 2014, 06:03:27 PM »

Well, the project is moving slower than expected as other things have become more important financially. Once I get the roller back together, I will purchase a carb. I have the engine on a work bench and so now might be a good time to start fabbing up a manifold.

754 · « **Reply #22 on:** November 23, 2014, 07:07:49 PM »

Check out the inspiration wanted thread, by Scott S in sohc bikes.
Pic of a pattern for 4-1 intake that could easily modded for Weber

Lostboy Steve · « **Reply #23 on:** November 29, 2014, 11:24:12 AM »

Quote from: 754 on November 23, 2014, 07:07:49 PM

Check out the inspiration wanted thread, by Scott S in sohc bikes.
Pic of a pattern for 4-1 intake that could easily modded for Weber

Thanks Brother, Will do!

Lostboy Steve · « **Reply #24 on:** November 30, 2014, 12:37:59 PM »

So the question is, who will cast a part if I make a wooden model of it?

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Author Topic: CB 500/550 Single Weber? (Read 5991 times)