6 carbs???

[kmack]

Here's an interesting thing for you mechanical types to ponder. I had this idea running through my head last night right before I went to bed. The quiet and stillness of the night helps me think up some pretty weird sh*t!!:stupid:

I got to thinking about carb setups

dual SU's

dual Webers

triple Webers

etc.

Now the intake ports on the L series heads are apprx. 40 mm in diameter. (This was measured on an N42 head off an L28)

I have a small stash of motorcycle carbs laying around ranging in size from 30mm to 38 mm in throat size. I know for a fact that you can get individual carbs up to 45mm. (Anybody see where I'm going with this yet?)

All of a sudden I had this wonderful picture of six individual carbs lined up in a row along side my L-series motor in my 240Z! What a sight that would be!! Now, the intake manifold would have to be custom built, but I don't see that being all that difficult. It would be nothing more than 6 straight little pipes welded to a flange. Pretty easy. Fuel lines would be easy enough, also. Individual pod filters would help sort out the dust particles. The only kicker would be how to run a throttle linkage. (I'm still thinking about this one... )

Now if triple Webers sound great while on the throttle, can you imagine what 6 carbs would sound like at about 5k rpm? Pure HEAVEN!! Imagine the tuning possibilities!!!

So am I the only wierdo to think of this? Anybody have any ideas for a throttle linkage setup? Cables would be easiest, but how to tie all 6 together is the difficult part. Food for the thought processes....:cross-eye

[St.stephen]

throttle linkage shouldn't be that hard to come up with. you could probably copy something off of an 1100 street bike.

the jetting possibilities would be scary on a 6 pack of bike carbs. I'm thinking though of fuel delivery since the bike carbs are gravity fed their fuel...

[Fun_in_my_z]

Thats sounds hard,but at the same time it sounds like it could be fun.:devious:

You just better have em all tuned right :tapemouth

[kmack]

Originally posted by St.stephen

the jetting possibilities would be scary on a 6 pack of bike carbs. I'm thinking though of fuel delivery since the bike carbs are gravity fed their fuel...

Jetting wouldn't be any worse than the old Honda CBX 6 cylinder bikes. And if you stick with Mikuni carbs, you can get jets and needles at any old motorcycle shop. Synchronizing would be straight forward also. I've done sets of 4 all the time. Takes less than an hour.

Fuel delivery would be no less than a typical SU setup. Low pressure fuel into a standard type float bowl w/ needle seat.

Now that I think about it, my old KZ650 had a great throttle setup. All four carbs were linked together by a rod that pulled on the throttle slides. A single cable was run to actuate the throttle rod. A modified version could be made of the same setup. Man, my brain is working overtime on this one.

Thanks for the idea, St.Stephen.

[HS30-H]

kmack,

Take a look at this thread:sextuplet carb thread............. :classic:

Cheers,

Alan T.

[Victor Laury]

A PHH Mikuni, DCOE Weber, Delo's, and others are just a pair of single throat carbs that share a float bowl.

[240znz]

I'm doubting it would sound any different? Why would it? As Victor points out, DCOE's are single trottle bodies that share a common float bowl.

Apart from looking wicked, are there any benefits to going with such a setup?

Great pic Alan!!!!:classic:

[speedyblue]

How about taking the butterflys out of all the carbs and making a slide throttle between the carbs and manifolds, like on the old racing porsches. Not the most reliable for a daily driver. (Grit tends to jam up the sliding plates) But still something different, and bound to get a second look anywhere.:sleepy:

[kmack]

Originally posted by 240znz

Apart from looking wicked, are there any benefits to going with such a setup?

Biggest benefit I can see is that you could perfectly tune each individual cylinder for peak performance. No sharing of carbs per cylinder. I know some would be leary of the tuning aspects, but I've tuned everything from single cyl, two cyl, to 4 cylinder bikes. All with engine modifications. The toughest part has always been access to the carbs. On an L-series engine, access would be nothing.

Another question popped into my head last night. MY common sense tells me to use carbs with same size throat diameters as the intake ports. But when you stop and think about the throat size of the SU's, do you really need to have the same size throat diameter or would it be better to use one of a slightly smaller diameter? As long as the carb could flow the required CFM's of air & fuel to the intakes.

Any more thoughts?

Alan, what size throat diameters were the FCR kits?

[St.stephen]

See I was thinking the same thing...you can perfectly tune each cylindar jetting wise and bike carbs aren;t that hard to sync once you get the hang of it. The carbs are cake to work on and access to them is nice and easy. In all honesty, the SU's have always resembled bike carbs to me.

How does the choke setup work on a multiple carb'd bike? My experience has always been two stroke dirt bikes and they've always had a pull up choke knob.

the intake doesn;t seem that tough to make and you can easily adapt the motorcycle intake boots as well.

Which slide carbs you thinking of using..D or round slide? either way the linkage wouldn't hard to use the existing Z style linkage that will connect to a rod that will move all six slides at once.

[kmack]

Originally posted by St.stephen

Which slide carbs you thinking of using..D or round slide? either way the linkage wouldn't hard to use the existing Z style linkage that will connect to a rod that will move all six slides at once.

Initially, I was thinking round-slide carbs, like the old-style Mikunis from the early-mid 70's. Down side is most of those are a cable-type pull on the slide itself. I think it could be modified to work, but I'd have to see.

The other side is you could use the CV carbs (Keihns, I believe) like the ones shown in the other thread Alan posted about. I know the idea about how those carbs work, but I've never had the opportunity to really work on those types much.

I do know that you can pin the throttle open at low rpm's and the CV carbs will let the engine rev up at it's own pace, similar to how SU's work. The old cable-pull style Mikunis force you to have a bit of throttle control. Because if you whack open the throttle, you essentially bog the engine slightly. It basically forces you to be smooth with your throttle control. And that is very beneficial with old two-stroke bikes.

On the choke issue, I grew up around the same thing. Pull knob on the carb activates the choke. But there are a couple ways around this. My old Yamaha RD had a simple setup. One pull knob activated the choke on both carbs. The two carbs were linked by a common rubber hose connected to the choke ports. A similar setup could be adapted.

Or, you could go with no chokes at all. I know my 240 is a little cold-blooded at first start-up, but it can be started without the use of the chokes. And I also no plenty of guys that run without the chokes connected at all. Just takes a little longer to start, that's all.

[St.stephen]

I always remember the Keihn D slide carbs being differant on most of the CR's I owned. However all of the KX and RM's that found their way to my house all had the round mikuni;s and thats what I am most familiar working with.

This would really be a great idea to try out thats for sure. Attaching the pull cables from the carbs to some sort of rod where you could attach to a bellcrank to the existing throttle linkage would be a good start.

see now this has me foaming to hop on my bike!! Stage three ported, turbo crank, shaved head Cam 2 fuel powered KX 125.

Its a real scalded ape thats for sure.