I can't wait for the fancy welded manifold so I'm making one from PVC

[chuck c]

I spent an hour plus at Lowe's getting some funny looks. Well, I was carrying around a Solex carb and Goldwing airbox in the electrical and plumbing departments, that might have had something to do with it.

It hit me that the make conduit parts out of easy to work and glue PCV and that includes things like junction boxes. So after an hour or so I found a set of parts that just might make a functional manifold. The flange is a standard aluminum spacer which I will epoxy to the PVC fitting. This kit has one advantage: I can rotate the carb if needed for clearance and glue it down once I find the right spot.

The only thing I really dislike is the fact that the carb is so far off center. If I decide that won't fit or makes the cylinders unbalanced I can plug that hole and drill one in the center. I might do that anyway.

It's all 1-1/4" conduit parts. The corner junction, 2 offset fittings, 3 straight fittings (one is for the carb) and a chunk of conduit. Total of about $26 for plastic and the flange was $13. It's narrower than the original air box and about the same height. I'll try putting it together tomorrow and let you know how it goes. I will take pics. If the kluge works I'll post drawings and a part list.

 

[dan filipi]

Looking forward to this build.

 

[slabghost]

That will work if sealed but I'm pretty sure you'll find two cylinders running leaner than the other two.

 

[chuck c]

Yeah, that's likely but I think I can compensate for it with a baffle inside the box. That off-center position also puts the carb smack in the middle of the open space in the frame, which is another plus.

 

[joedrum]

this will be neat build ..... opcorn:

 

[chuck c]

Here are the parts used.

To reduce the height I cut off the socket on the back and sanded the threads down a bit on the fitting to get it in. I'll cut the back one off the box later and fill the hole. I glued the aluminum flange on with a fine line Gorilla Glue. I could have glued it onto the socket on the box but this will allow me to turn the carb if I need to to hook up to cable, fuel, etc. and clear linkage. Once I know what angle works and clears everything I'll make any in the future by gluing the flange directly to the box, it's less work.

 

[chuck c]

The fitting protruded too far into the box for my liking so I cut about 1/4" off. I stuck them on a piece of pipe and used a spacer as shown. It worked nicely with full control and no fingers near the saw blade.

 

[roncar]

Usually when I go into a DIY store, I have to run off the sales people with a "I'm thinking outside of the box" statement. They just wouldn't understand. :builder:

 

[dan filipi]

Interesting build.

 

[chuck c]

If you want to make your own there are 3 important numbers:
97, 36, and 7.
97mm is the distance between the runners, 36mm is the offset between the right and left sides, and 7* is the downward angle the runners need from the plenum to the carbs.

I marked the positions of the holes and drilled a small starter hole using my 100 year-old drill press then used a hole saw to open them for the fittings. A note about drilling or using a hole saw in PVC. The hole saw will get hot enough to melt plastic in a few seconds. To get a clean hole with minimal grief, use a lubricant and only saw for 2 or 3 seconds at a time, pulling it out to cool down for a few. I used WD40 but kerosene works. The very best stuff I've used to hole saw plastic is soapy water. See the slug on the left is very clean and on the right has lots of melted bits. It got a little to hot on the right one. Save the slugs! They might be handy later.

One reason I love this old drill press is if the drill or saw gets stuck, the belt pops off.

 

[chuck c]

The runners seem to line up well using the OEM air plenum for reference.
The carb fits!

 

[chuck c]

It looks good so far....

 

[chuck c]

Sweet! I want to see how it fits with an air cleaner. I could use one of those offset connectors for the carb to get it the inlet closer to center of the box. It also looks like I could move back 1/2" and still clear the frame. I have to get my air cleaner before I go any further.
I think I've got something here. More later but now I'm going for a ride.

 

[dan filipi]

Looking good!

 

[Ansimp]

+1 :good:

 

[Omega Man]

Great build so far. opcorn:

Our members really do think outside the box. Supported by other members without bloated editorials on how this can't work from those with an agenda or self indulgent bloviation from the likes of CM85 and his ilk.

 

[slabghost]

oh2: Dang! I knew somethin' was missing! :smilie_happy: :smilie_happy:

 

[joedrum]

nice work .... great pics and wright up ... that is old drill press ..... k:

 

[canuckxxxx]

Very interesting idea to use electrical PVC fittings. opcorn:

Could you turn the carb around so float bowl faces front...to centre the carb? How close a fit is the 1 1/4 PVC into the OE manifolds?

To get the 7 degree down slope you could heat the runners with a heat gun and bend them down.

Brian

 

[chuck c]

The ID of the 1-1/4" is pretty dang close. I'll measure it tonight. The OD is identical. I intend to play with the carb position when I fit the air cleaner and the throttle cable. The box is a bit narrower than the OEM air plenum. You're about the 3rd person to suggest the heat gun bend. I have nothing to loose trying it, I have plenty of material to play with. But before I do that I'm going to hit the store again. They sell 45 and 90 pre-bent elbows made from the conduit so they are the same OD and ID. I may see if one of those can be cut to work.