Tee Dee 020 Problem

Or file a bit off the bottom of the venturi.

Am I understanding this right? You converted a Pee Wee into a Tee Dee?

The tap is easily sourced which makes fixing it simple as I would run the tap and completely break out the bottom if the threads aren't all the way through. The main thing is that you not blocking the peripheral groove above the threads on the venturi due to it not seating all the way. Even a o-ring under the needle valve body or if needed above to take up clearance would also work and offer a better seal.

Thanks for the ideas. I don't think it is the threads that are the problem. I can't push the Venturi down tight into the Needle Valve Body. It is like the Venturi OD is too big to fit.

The cylinder and piston are from the Pee Wee. The rest of the parts are from Cox International and Ex Motors.

It really can only be a couple things. It’s either as everyone says and the threads aren’t cut deep enough or something is physically wrong with the parts. You also mentioned pushing, it’s a threaded part, it screws together. Maybe that’s what you meant.

Looking at your photo closely it appears that the venturi is at an angle to the carb body. It should follow a straight line which lends itself to being cross threaded. It could be just the picture.

Worst case, contact Cox International or ExModel and have them send you a replacement part(s). They have really good customer service and would be more than willing to help.

Ron

So, the venturi does not slip into the hole in the needle valve assembly? Is this correct?
Try to see if it is a good slip fit? If it is not, you need to use a piece of brass tubing with some 600 grit sand paper wrapped on it to remove some of the anodized coating. The brass tubing should be smaller than the needle valve assembly hole and enough sand paper to make a good tight fit (maybe wrapped on the brass tubing a couple of times?).
Once you have sanded enough of the anodizing off, your venturi should be a good slip fit to the shoulder of the venturi.

Now check the venturi thread depth.
Thread the venturi into the venturi body. Measure the  distance from the bottom of the venturi to the top of the body venturi (on the engine). Now check the thickness of the needle valve assemble.
If your measurement of the needle valve assembly is say 1/4" but your measurement of the venturi and body venturi is say 3/8", then you'll have to sand/shave off 1/8 of an inch from the bottom of the venturi.

I modified your photo to maybe get a better idea what your problem is?
 

Sosam117, that is it exactly. If I  remove the Needle Valve Assembly,  the Venturi screws in more than far  enough. The Venturi is just to large to fit as far as I think it should thru the Needle Valve Assembly. I will probably take some material off the Venturi to make it fit.

Thanks everyone for the thoughts.

Eric

What a brain tease. Good snag Sosam117. I used to be able to think like that.
Lots to do with perspective and seeing the problem from different angles. My
hat's off to you brother.
Hang out Eric, tons of info here.
Bob

The light turned on in my head when I carefully read Eric's problem.
I had that happen number of times when I was making up Tee Dee 049's, Tee Dee .051 and Tee Dee .09 with the Kustom Kraftsmanship venturi needle valve assemblies.

When you anodize the aluminum, you are also adding onto the surface. So your inside diameter hole will decrease.
Working at Caterpillar Fuel Systems, when we would coat our plungers/pistons, the nitride coating would add 1 to 2 microns on the outside diameter. and when you have a matched clearance of 5 microns, that 1 or 2 microns can make a difference between a working plunger/piston or a seized up plunger/piston.

It like chroming you piston to get a better fit, or using honing compound to make it looser fit.

Another example is when you drill a hole in a bike frame, then you send it out to be powered coated.
You try the bolt that fit o.k. before the power coating, but after the power coating it won't fit into the hole.
Same thing will happen with anodizing.

It is most likely the carb. body I remember getting some of these that were very tight to put together , I think it was Cox International . If your going to run that P/C from a PeeWee on the TD i would at least use a TD Hi compression head on it , I really don't think your going to get much better performance than a PW !?! When you get it fixed please report back with the RPMs Run I would like to know !

Get back,

It has a Kamtechnik turbo head. My son has a pee wee 020, so we were interested in seeing the differences. Besides I have an 010, 049, and 051 Tee Dee. So it helps fill out the set.

Any idea if either the Venturi or the NVA are reproduced? I think I would rather modify something that is still being made incase I mess it up.

https://coxengines.ca/cox-020/cox--020-venturi.html https://coxengines.ca/cox-020/cox-tee-dee--020-needle-valve-body.html form here .. https://coxengines.ca/ No P/C sets //

Well, he has 88 more Venturi's in stock. Might just order another one and see. Of course I will have to buy several other things to make the shipping worthwhile. 🤪

getback wrote:It is most likely the carb. body I remember getting some of these that were very tight to put together , I think it was Cox International . If your going to run that P/C from a PeeWee on the TD i would at least use a TD Hi compression head on it , I really don't think your going to get much better performance than a PW !?! When you get it fixed please report back with the RPMs Run I would like to know !

I believe the Tee Dee P/C on the .020 are machined the same internally as the PW. I dinnae think Cox went through the trouble of doing a taper bore on the TD and not on the PW.

You are correct. Head is identical between the two as well even if it is knurled. The performance difference is due to the front rotary induction.

Lacking a lathe, I would try gently chucking the threaded end of the venturi up in a drill
then hold a small file against the venturi as it spins to file a bit off until it fits into the nv body.
Maybe wrap a bit of tape around the threads first.
I've also chucked parts up on my drill press and used the mill vice to hold cutting tool.
I'm a redneck shade tree machinist.

Just to follow up on this. I ordered another Venturi, and it solved my problems. I need to put a mic on them and see what the difference is yet.

Glad you got that straightened out , have you test ran it ?

1Bad67 wrote:Sosam117, that is it exactly. If I  remove the Needle Valve Assembly,  the Venturi screws in more than far  enough. The Venturi is just to large to fit as far as I think it should thru the Needle Valve Assembly. I will probably take some material off the Venturi to make it fit.

Thanks everyone for the thoughts.

Eric

I have had the same problem assembling these parts. It turns out that I once asked for three units, two fit perfectly and one of them did not fit, this is because the measurement is not correct.
So, I took the piece and turned it in a drill with just a few taps of file to remove the material, it's just a little bit, and then it fit perfectly.
Remember that this must be perfectly embedded since the air and suction line, together make an exact position for the proper functioning of air and fuel suction, generating the spray necessary for the operation of the engine.
The solution is to adjust the venturi minimally so that it fits correctly.

I just measured them. The good one is .168 diameter, the bad one is .174 diameter.
Now I just have to find the time to run it. Probably next week when my son is back so we can compare it to his Pee Wee 020.

Eric