Black widow/babe bee Venturi question

Lukemiester Wed Oct 27, 2021 2:57 pm

So as I was looking through my bin of cox stuff for a tank for my jerobee, I acquired a suitable tank on a late black widow case. Plastic backplate, g-clip retainer. I took it off because I want to try my jerobee without the external tank; it’s got serious fuel delivery issues... anyways I pulled it apart to check the condition if the internals and was a little puzzled at what I saw. The Venturi looked like it was almost the diameter that I had drilled out my existing Venturi to the specs of the mouse race program. It didn’t look like it was drilled out. This got me curious and I grabbed another black widow tank with the cap style retainer, and it was smaller. Was something changed in production? Also i think I heard of the venom having a larger Venturi, is that related?

roddie Wed Oct 27, 2021 7:41 pm

Hi there young Lukemiester! Can you tell us more about the "fuel-delivery issues" associated with the external fuel tank for your Jerobee? The Cox Black Widow's had (I believe..) an enlarged venturi; to the tune of .082" dia. as compared to the standard .0625" dia. venturi of the Babe Bee and "early" Golden Bee .049 engines. The earlier engines had pot-metal (Mazac/Zamac?) backplates.. and their integral 5cc/8cc tanks used the circlip style reed-holder.

You may have success running a Black Widow tank (8cc integral to the engine).. but I would recommend what Jerobee used for the set-up. IIRC.. their external tank was plumbed to an 8cc tank-bowl which was modified (holes drilled) for an external fuel-feed.. and having the standard .0625" dia. venturi.. which draws fuel from an external tank quite well.

some photos.. (courtesy of CEF member "Overlord")

Black widow/babe bee Venturi question Imgp6110

Black widow/babe bee Venturi question Imgp7510

Black widow/babe bee Venturi question Imgp7511

Note in above photos; that there's an 8cc "non-vented" tank-bowl in place. That bowl can be found on the Cox "Silver Bee" engine.

Black widow/babe bee Venturi question Cox_si10

.. not that you'd want to alter a rare Cox tank-bowl variant.. because "any" Cox .049 Bee-variant (integral-tanked) bowl could be used. You may have to source an 8cc bowl.. but they're plentiful.

"Do" try to avoid the plastic backplates. I don't like them. The ones that I've seen, have no "barb" on the fuel-line nipple............................. Huh...

That's just stupid.

You'd do well to source an early (60's/70's) Cox Golden Bee/parts-engine.. for its' "back-end" parts.

Lukemiester Wed Oct 27, 2021 7:56 pm

thanks for the reply! the tank on mine is just in front of the right rear tire and raised farther than jerobee had their external tank. the engine tank i have was drilled by a previous owner to run an external tank, so i used it, but i think the line is just so long that it can't draw very well especially when starting and accelerating/decelerating, making the fuel flow go all over the place. this made me want to try the stock setup, because i know from running stock babe bees that it shouldnt be this hard lol. just not sure about run time but we'll see. not all jerobees had the external tank, iirc those were later than my car and came with the fancier cars, i.e. racing

Lukemiester Wed Oct 27, 2021 7:58 pm

Here’s some pictures of my setup

Black widow/babe bee Venturi question 1b2e9810

Black widow/babe bee Venturi question Image0

Lukemiester Wed Oct 27, 2021 8:02 pm

you know what im just gonna go out and mess with it right now lol
i've been putting off running it for too long tongue

KariFS Thu Oct 28, 2021 3:35 am

Have you tried it without the fuel filter? The filter, especially when located in the highest point of the fuel system, can cause trouble in fuel flow.

Also the o-ring between the venturi and the backplate is critical in an application like this one.

Good luck Smile

OVERLORD Thu Oct 28, 2021 4:54 am

Lukemiester wrote: the engine tank i have was drilled by a previous owner to run an external tank, so i used it, but i think the line is just so long that it can't draw very well especially when starting and accelerating/decelerating, making the fuel flow go all over the place.

Do you still have the clunk inside the tank and if so, is it well on the bottom of the tank? I know that the silicon tube inside the tank between the clunk weight and the rubber plug is quite short. When the silicon tubing is too thick, the clunk weight is not heavy enough to remain on the bottom and stays half way up in the middle of the tank.

Lukemiester Thu Oct 28, 2021 10:26 am

The clunk is on the bottom of the tank, I have tried it without the filter, and I did replace the o-ring with a new one but I’ll check it when I take off the tank, didn’t get to it last night

roddie Thu Oct 28, 2021 6:51 pm

Lukemiester wrote:thanks for the reply! the tank on mine is just in front of the right rear tire and raised farther than jerobee had their external tank. the engine tank i have was drilled by a previous owner to run an external tank, so i used it, but i think the line is just so long that it can't draw very well especially when starting and accelerating/decelerating, making the fuel flow go all over the place. this made me want to try the stock setup, because i know from running stock babe bees that it shouldnt be this hard lol. just not sure about run time but we'll see. not all jerobees had the external tank, iirc those were later than my car and came with the fancier cars, i.e. racing

I agree with "KariFS" regarding the fuel filter. I personally wouldn't use it. It's always best to keep your fuel-line connections to a minimum.. and use NEW fuel-line every running-season. If your engine has decent compression; it will pull fuel from that external tank when cold-cranking/attempting to start it. You'll want to use that external tank Luke. I'm guessing that it's a 1oz. capacity.. which will provide a LOT MORE run-time. You can put that fuel-filter on what you use to fuel-up. If you use a pump; then install it "in-line" with the pump's line. It is of course; very important to keep your fuel and fuel-systems CLEAN.. especially when running reed-valve induction. Does the backplate have the little mesh-screen installed at the air-intake? If not.. and any "grit" finds it's way into the venturi.. it can and will foul the reed/seat.. which ends all fun.

Lukemiester Thu Oct 28, 2021 8:52 pm

Okay thanks. I typically don’t get dirt in the tank, but I wanted the extra precaution. I use a syringe, so if i put it on, there really wouldn’t be any effect...
I guess I could squirt some back in before I fill though...
Anyways I’ve been thinking of trying to plug the other vent(s) and running the external tank to the engine’s tank so it ultimately is vented from the external tank, and draws from the #2 tank. I first want to run it on the #1 tank and see how it does.

davidll1984 Thu Oct 28, 2021 10:11 pm

Let me give you a trick first, it is not a plane but a car for the tank the best is to tilt backwards à litle with the fuel intake at the lowest fixed without using a tube or clunk inside fuel tank just a bent coper tube which points to the bottom which touch him a little The tube must go lower than the jet of the engine Intake Then go up higher Which helps to even out the fuel flow It’s simple when Accelerate the fuel is pushed to the rear which increases the flow slightly it help Not To turn lean full trotle For the fuel tank of the engine it doesn't matter It's really better to use the right back plate for the right cylinder type if use a single bypas or twin use wit the larger one Always use a screen to protect from possible dirt entering the engine a texaco tank fit à single bypas cylinder flow just Perfect wit a babe bee back plate the black widow setup wil fit à twin bypas mutch bether try use a g clip Reed valve its bether if set correct Continue to drive your little car, me today I was driving my gtp My favorite thing is that it's inexpensive on fuel Smoking

i like cox engine Small Cox Logo

Lukemiester Thu Oct 28, 2021 11:51 pm

Thank you David, the fact that the clunk is so far up bothered me, but I think I have a solution now. What I did was put a pressure fitting in the hole where the fuel line went to with a fiber washer to seal it against the tank. I then put a new pickup line in tank #1 and made sure it was pretty sealed up. Then I connected the #2 tank’s draw line to the pressure fitting and filled up tank #1. I took that line and connected it to the tank vent on the other side of the needle so that it the only place to draw from would be tank 2 and then filled up #2. Primed and ran the engine for a few minutes inside, then the exhaust got way too thick so I stopped. It started easier due to the fuel being so close and it appeared to draw fuel from tank 2...

IRL test coming after this rain stops...
Also if you didn’t catch it I ended up using the old tank and backing plate.
Thanks for the help and advice guys Very Happy

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