I am trying to make my first part an intake and could use a little help. I need 2 one for a 19" and another for a 21" rubber mount Dellorto
1) Steel or aluminum
2) 1" or 3/4"
3) Bending --> I bent 1" aluminum with a standard EMT bender and the radius is huge. Also, it bowed the radius in the bend I would like to keep it round. Advice on how to get tighter bends would be great
Youre best bet for fabbing one is steel tubing.
I find old cro - moly bicycle frames are good for straight pieces
and bmx handelbars have a good assortment of pre made perfect bends and mountain bike bars have a good taper,just cut the taper at the desired diameter for the carb .
Use flat stock for the flange, sand it with wet dry sandpaper on a nice flat patio block
http://www.mopedarmy.com/forums/discuss/download.php?f=7&file=1191841471_beforeafter.jpg
cut your tubing into little wedges
fail!
ITS DARK ,
can u use copper tubing?
yes but it can be tough to make a flange out of it to mount and seal and be strong enough to hold a carb at rpms
and you have to braize it no solder!
Crackstar, that looks nice! ...and that's aluminum, isn't it?
So why are most intakes aluminum instead of steel? Is it easiar to mass produce (cast, machine, and drill)?
Is it because aluminum conducts heat better, so this helps to vaporize fuel?
Any ideas?
Yesh! Aluminum from an old ski pole, it just happened to be the first thing i grabbed and it fit the 14.9 dellorto. i got patterns for flanges for puch, minarelli and AV7 saved on the puter
if you use the cut and weld method you just have to make sure you get the inside of the intake nice and even.
You need enough penetration to close all the sharp edges but not have too much weld that it closes off the passage. If you do you have to grind it smooth.
Thats why I prefer pre-bent tubing.
I clean them between each weld, that way anything that blows thru is easily reached to clean up. I prefer the cut and weld method cause its faster. and easier to make the complex bends. Its difficult to see in the pic but that intake was made for a Cimmati city bike with the intention of keeping the carb under the side covers. so it has two bends in it. one goes to the right and the other pushes it forward
i use copper tubing and heather hose, i solider all the copper parts together with my torch and plumbing solider.. works great see pic ^^
I am trying to fab up a tomos intake for a phbg myself. It wouldn't be so bad accept for the reedvalves.
heater hose is your friend!!!
how do u attach heater hose to a flat intake port that has bolts hold it on?
i had to cut the intake down to have just the flange and enough room for the hose..
heater hose dont stand up to gas for really long.
Maybe a season.
yea copper holds up great. you dont have to braze it you can just solder it with a regular propane torch. i made the flange out of mild steel and soldered the copper directly to it.
cool. its pretty, simple, ugly and functional at the same time!
btw - rattle can black spraypaint works wonders!
Large washers also make good flanges.
Brazing is easier on the metal than welding. I keep blowing thru thin metal when I weld, even with a torch.
I'm impatient. and hot.
yea if im going to weld thin stuff i usually braze/solder it or use a mig. Im no good with delicate stuff using a stick.
I used copper tubing & heater hose w/ hose clamps to make an intake. Works great. It's just no the prettiest to look at.
I vote cast aluminum, though it's not something you can pick up and do tomorrow. I used 20mm ball bearings pressed through the interior to ensure a consistent 20mm diameter.
Go to a hardcore plumbing supply shop. Ask for a spring tool to bend copper pipe of whatever diameter you like. They will hand you a spring that you stick inside the copper pipe. This tool prevents kinking. Bend at will.
copper or aluminum btw
Something occurred to me the other day that others may find useful. I was looking all over my shop for some sort of curved tubing out of which to make an intake (and even though I wound up using my old exhaust header) I realized that a segment of steel road bike handlebars would work great assuming you have the ability to both weld on a base plate as well as fabricate a carb mount.
For example, if you were to take enough out of the following bars to give you ~90° of turn, fabricate a mounting plate out of ¼ inch plate, then use some ¾ plumbers pipe turned down on a lathe to match your carb mount, it would be beautiful.
Just be sure to remove any chrome before welding, or hold your breathe!
Gah - WTB post preview or edit ability!
Didnt I say that about bike bars in the initial response to this question?
Oh my goodness, I totally missed that - sorry :)
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