Dual Motorcycle carburetors project

[styroman]

I have posted as a separate topic, information about my VW Trike rebuild project. The engine on the trike is built using a 1600 dual relief case, 1300 cylinders, and 1200 heads; and it was done for fuel economy, so the original builder could economically tour the United States as part of his bucket list.

Since I have it all apart anyway, and because I already know what the cold weather does to my dune buggy here in the Pacific Northwest, I decided to go with dual carbs on the trike.

Looking around, it seems no one has manifolds for a dual carb installation on 1200 flatheads. I found one company in Europe that has them, but they are expensive, and are made for 34mm carbs. I'd have a Grand into that kind of conversion, and 34mm carbs are just too big for the flathead ports.

So, for a few weeks I chewed on the matter, researching all the time, and have come up with what I hope will be an awesome dual carb setup for my trike, and would also work with later single ports, by using larger motorcycle carbs.

Here is an image of my project trike, in case you have not seen it in the volksrod/other/trike index. I will post gallery photos of my carburetor project below.

[styroman]

I thought this would be interesting enough to have its own topic; as I have seen many requests on The Samba for information about putting dual carbs on 36hp engines.

The first two photos show the carbs mounted on reducing ell hoses. I plan to sacrifice this manifold by cutting the flanges off, leaving an inch of tube on each flange so the hoses can be clamped onto them.

I plan to use stock motorcycle throttle cables on the carburetors, and have chosen this one becaus it has an additional inline housing length adjuster:

I purchased two pair of carbs. One pair are straightforward slide carburetors, and are purely cable operated. The second pair have a butterfly valve and vacuum diaphragm operated slide and metering jet, which should make them more economical going down the road. Both pair of carbs are 24mm, essentially the same ID as the VW manifold flanges.

I am also going to plate off the stock fuel pump, and am installing a 1.5-2 psi electric fuel pump. In this photo is also shown the throttle cable splitter I am going to use to operate the two carburetor throttle cables, using a single Harley style handgrip cable.

[styroman]

I will cut the hoses down to a minimum usable size; and, if necessary, put a support strut under the carburetors, attached to the shroud bolts directly below.

[[email protected]]

I like where this is headed.

[toiga]

Hi, what kind of carburetors are you using? This is a interesting conversion!

Keep up the good work

[jaxdream]

Styroman please be aware you are giving up your heated from exhaust intake . These VW engines like a heated intake or else icing Might occur. This a problem especially with T4 engines when carb (s) are used . If you make them short enough , you might luck out. Your project , good luck with it. Letting the head heat them might work out , just be aware of the non-heating issues . Research the elimination of heated intakes , might find a solution .

Jack

[styroman]

[modok]

Above 40f you don't need any heat. Just adequate velocity. Below 40 F some heat is needed, but not very much.
Do not exceed intake 1.25 MCSA, save for a few inches straight out of the carb.
If you follow that, it will work, GREAT

If you don't, well, you can apply heat, to whatever degree

[styroman]

[sgmalt46]

love what you are doing. but i would run 1300 heads and run weber icts. simple . short manifolds . no need for heat. dependable. good mileage.no tuning issues. like i said i love the idea. but may be a bitch to tune?and a lot of work. just thinking out loud.
_________________
55 deluxe 23 window bus
64 crew cab
55 rag top beetle
66 beetle
71 square back (sold) ! good luck with it Henry!
46 beetle 552nd royal army service corps CCG

[styroman]

[styroman]

[styroman]

While I am planning on cutting up a sacrificial intake manifold to make this dual carb setup, I am also cogitatin' on casting or welding up a pair of aluminum manifolds instead. I can do either in my home shop.

[styroman]

[styroman]

[styroman]

So, while I was assessing the use of these new components for the dual motorcycle carburetor conversion, which I think will work nicely, my concern is still about the carbs pointing towards the tires, and prohibiting the use of a stinger exhaust. I cannot modify these manifold to turn them aft, because it will not allow enough height and reach for the carbs to fit over the cooling tins.

A little more poking around the internet and I found some mandrel bent elbows of 1.25" OD 6061-t6 aluminum tube, 1.125 ID. I could cut the legs on these to a precise length, then make a flange/foot of aluminum plate that would have all the function of the stock foot, and could be MAP welded to the tube. This would allow the carbs to both point aft.

So, I think this, plan C, will be my first plan of attack; and if they do not work out I will go back to plan B, using the short cast aluminum motorcycle manifolds above. I have pretty much scrapped plan A, utilizing silicon hose as a manifold.
_________________
My Trike Project: http://www.thesamba.com/vw/forum/viewtopic.php?t=666742

[alanhall]

As far as I know all dual carb conversion manifolds include provisions for a balance tube running across the engine interconnecting the two manifolds. You might need to modify these to allow use of a balance tube.

[styroman]

[styroman]

[styroman]