Dual Carbs?? Maybe??

[dentat2]

I've got an '80 XS11 Special and I'm also working on a '75 CB750 Honda Chopper. I found a carb kit for my honda that replaces the 4 stock carbs with 2 big mikuni's. I'm wondering if anyone has tried something like that with the XS, or if anyone would be interested in that at all. Here's the link to the kit, its from a place called Cycle X http://www.cyclexchange.net/Carb%20S...omp%20Page.htm

[Geezer]

For it to work correctly it would have to be a 1-4 2-3 system like the old spaghetti exhaust system. The 1-2 and 2-3 design will have 2 cylinders that have overlapping intake cycles that will starve one cylinder or the other.

Geezer

[crazy steve]

For it to work correctly it would have to be a 1-4 2-3 system like the old spaghetti exhaust system. The 1-2 and 2-3 design will have 2 cylinders that have overlapping intake cycles that will starve one cylinder or the other.

Geezer

Uhhh... if the carbs are sized right, why wouldn't it work? As long as the carb can deliver enough fuel during overlap, you should be fine.

This has been done before; look under the hood of a lot of older sports cars. Three side-draft SUs feeding six cylinders...

I'd be more curious about what it would do to fuel economy.

'78E original owner

[Rstyduck]

Why not just one Rochester Q-Jet 650cfm 4bbl on a custom intake?

[dentat2]

Now since the kit from cycle x uses the 1,2 and 3,4 system does that mean the CB750 does not have an overlapping system?? I'd really like to find out if i can use on of these on my special.

[crazy steve]

I can see at least one reason why this particular setup won't work on a XS11, and can think of several more; first, the port size at the heads is much smaller than the XS, so you'll have a terrible port match. The angle of the ports in the head are different, so where will the carbs end up? Is the port spacing (center to center) the same? Right there is enough to kill any chances this kit would fit a XS11. Plus these carbs would be too small for the larger motor; this kit is for a 750, and the 1100 represents nearly a 50% increase in displacement.

I'm not saying the concept wouldn't work, just that this kit won't work for a XS11. With the right intake manifolds and properly sized carbs, I can't see why something like their kit couldn't be done.

'78E original owner

[dentat2]

I knew the CB kit wouldnt work, just wondering if it would be worth trying to build one for the xs.

Also, doesnt the intake boots have to be the same size?

[crazy steve]

I knew the CB kit wouldnt work, just wondering if it would be worth trying to build one for the xs.

Hmmm, define 'worth'. Fabricating the manifolds would be a major undertaking if you're trying to maintain/increase flow. They're claiming a 15% gain in power, but spent some dyno time to arrive at that; notice the mini-plenum their intakes have. These aren't something you could whomp up with a welder and some tubing.

I suspect that anything a shade-tree mechanic could come up with would at best maybe be equal to OEM, and would likely perform worse. While I applaud the idea, it's not something I'd try on my budget...

'78E original owner

[dentat2]

Thats what I was afraid of. Im going to be picking one up for my CB but it sure would be pretty cool on my XS too. So thanx for the thoughts anyway.

[b.walker5]

I've often thought about this idea myself, and wondered out loud more than once if a couple of side draught webers or delortos would work okay. I'll probably never do it, and it would need a custom manifold of some sort but I think, for the bobber or rat bike builder it would be pretty cool.

[dentat2]

The main reason im getting it for my CB (and i know im about to get torched for this) is cause it looks super cool. 2 big ole carbs stickin out each side of that amen frame is gonna be bad a$$. And if it performs better than stock well thats great too. Just thought my XS would look pretty hot with the same sort of set up.

[DGXSER]

I hope no one would TORCH you over it. There are many on here who follow the concept of "form follows function", as opposed to your reversing that, but hey, its your bike and your "fun" getting it to work and stay working.

Me, I consider myself to be just about a founding father of the KISS principle. (Keep It Simple, Stupid!!) And in my opinion, having been in more than a few carbs, I have not seen any to date that are simpler than the ones on an XS, even my '51 Eveinrude 3.3 outboard carb was at least as complex.

I understand the desire for more horses when the thing runs out of gittyup when your looking for more. Thus the reason I drive an '84 Cutlass with a 502 Ramjet in it. I just never found myself in that position on an XS11.

[Rstyduck]

But with all that said, If its not really going to cost you much to sit in the garage with a beer and tinker on an intake over the winter to install these two carbs then go for it.
Ive dumped hundreds into crap that dont work. Ya gotta try or youll sit there pissed off wondering if it could have worked.

Like a drunk chick in the bar, ya dont know till youve spent the time and money just to have her pass out and go home with her friends instead of you.

[freak_leg]

I understand the desire for more horses when the thing runs out of gittyup when your looking for more. Thus the reason I drive an '84 Cutlass with a 502 Ramjet in it.

I like your style!! I want to see picutes of this ^^

As for running 2 carbs, If anyone gets this to work well and atleast be as good as stock I'll be all over it like white on rice! Theory would dictate that getting 2 carbs to sync would me much easier than 4. As I come from the EFI generation trying to get one carb to work correctly is a PITA but getting 4 working well and working with each other has had me chasing my tail with the XS for about a year now.

[Rstyduck]

I like your style!! I want to see picutes of this ^^

As for running 2 carbs, If anyone gets this to work well and atleast be as good as stock I'll be all over it like white on rice! Theory would dictate that getting 2 carbs to sync would me much easier than 4. As I come from the EFI generation trying to get one carb to work correctly is a PITA but getting 4 working well and working with each other has had me chasing my tail with the XS for about a year now.

Do you get dizzy running around in circles?