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Tee dee .049/.051 crankcase pressure Empty

Tee dee .049/.051 crankcase pressure

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Tee dee .049/.051 crankcase pressure Empty Tee dee .049/.051 crankcase pressure

Post  JPvelo Fri Oct 26, 2012 1:27 am

Does anyone have experience with tee dees on crankcase pressure from the factory nipple? Is a check valve necessary? Fine thread needle valve?
Thanks guys, Jim
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Tee dee .049/.051 crankcase pressure Empty Re: Tee dee .049/.051 crankcase pressure

Post  Ken Cook Fri Oct 26, 2012 4:47 am

I personally could never get this to work and that was with a check valve. Once you drill the case your committed. If any air leaks are present, the system will fail. In my opinion the instructions tell you to drill a far too big of a hole. The engine would surge violently up and down. Backplate pressure is far superior. The stock needle valve also makes setting the engine on pressure troublesome. Even with the backplate tap, the hole required for this to work properly isn't greater than the width of a pin. I was using brass pressure nipples tapped into the aluminum. I would then take a extremely fine piece of wire and place the wire into a candle to blacken it. I would solder the hole I drilled in the nipple and insert the wire. Solder won't stick to the blackened carbon on the wire. Once removed it left a very tiny hole in the nipple. The other problem you may experience is case flooding. You can't turn the engine over without it priming the venturi and this can be problematic until you find a sequence to start it. These are findings I experience so good luck. Ken

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Post  andrew Fri Oct 26, 2012 7:48 am

@Ken Cook wrote: .......Even with the backplate tap, the hole required for this to work properly isn't greater than the width of a pin. I was using brass pressure nipples tapped into the aluminum. I would then take a extremely fine piece of wire and place the wire into a candle to blacken it. I would solder the hole I drilled in the nipple and insert the wire. Solder won't stick to the blackened carbon on the wire. Once removed it left a very tiny hole in the nipple............

Here's a picture of a backplate tap to give you an idea how small the hole needs to be. This is a backplate from a NORVEL, but the idea is the same.

Tee dee .049/.051 crankcase pressure Norvel13

NORVEL Pressure Tap
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Post  fit90 Fri Oct 26, 2012 9:52 am

I have never had any luck with the crankcase pressure nipple. I have had lots of good luck with backplate pressure, though. If using any crankcase pressure do as Ken suggests and use a very small hole for the pressure feed. I like to fill my pressure nipples with J B Weld or solder and drill a hole with a #75 or smaller bit. I also like to use a check valve when figuring out the needle and starting procedure. After that is figured out needing a check valve depends on your plumbing set up, starting procedure and personal preference. I have not had any luck with the stock NVA on pressure but a fine thread NVA makes everything easy and repeatable, Also, using pressure allows for the the use of enlarged venturis. If you decide to go the pressurized route good luck and keep us posted.
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Post  SuperDave Fri Oct 26, 2012 10:37 am

This discussion has caused me to refrain from drilling a pressure port in the stock location.

Is a pressure-port on the backplate available from a vendor or is it a DIY proposition?
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Post  fit90 Fri Oct 26, 2012 12:38 pm

You can occasionally find backplate pressue fittings on ebay but they are an easy DIY project. I like to make them myself by taking a short (3/8" or shorter)piece of 1/8" or smaller fuel tube, fill about 1/8" of the tube with J B Weld or solder, drill a hole that is a few thousands smaller than the tube in the backplate then pressing the tube into the hole with the solder filled end going into the backplate and finally drilling your hole through the solder. I just use a table vise to do the pressing. If your fuel tube is too long it will probably bend during the pressing step. Good luck with it. It sounds like a great opportunity to use that cool new soldering iron. I have a butane Weller that I have had for close to 20 year and I absolutely love it.
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Post  SuperDave Fri Oct 26, 2012 12:47 pm

Just used the Weller butane torch to tighten the heat-shrink tubing on an electrical project here at home. Used the supplied heat deflector to prevent burning the heat-shrink.

Slick!
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Tee dee .049/.051 crankcase pressure Empty Pressurizing a TeeDee

Post  Paulgibeault Sun Oct 28, 2012 4:47 pm

Gentlemen,

Another way I've sucessfully used is to drill & tap the existing TeeDee backplate then
screw in a (trimmed) K&B 4-40 pressure tap (hole I.D. is .025"). I imagine if you
find your needle too sensitive to set then you might consider filling it in & going down
in size...
The fine thread needle valve although nice is not absolutely necessary. What is absolutely
necessary is making sure your NVA is sealed. With the stock unit a small piece of silicone
fuel line over the whole needle valve & spring clip can help here.

Cheers, Paul


Last edited by Paulgibeault on Sun Oct 28, 2012 4:52 pm; edited 3 times in total (Reason for editing : Editing info)
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Post  RknRusty Sun Oct 28, 2012 8:37 pm

My LHS sells pressure nipples that can be screwed into a tapped backplate. And if necessary, filled in and re-drilled to the size passage you need.

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