Beulzabob

My Feedback: (1)

I've read a few links here concerning how to make a venturi gasket out of medium fuel tubing. I don't really understand how to cut the tubing. Do you just remove material from the i.d. and slip it over the joint? If anyone could post some pictures of how it's done or the completed gasket, I would really appreciate it!

Thanks again,

Robert

Tim Wiltse-RCU

Robert,

Just cut a very small piece of tubing and push it over the end of the air tube.It will be a tight fit though. I think I use the small size tubing. I'll post a picture later.

Later,
Tim

Tim Wiltse-RCU

Robert,

Here is a picture of a slice of tubing. Not the neatest one but you get the idea!

Later,
Tim

Tim Wiltse-RCU

Here it is on the tank. This one is a little thick but is shows how to do it.... sorry for the bad picture. Hope this helps.

Later,
Tim

Beulzabob

My Feedback: (1)

Thanks Tim!

Now it's perfectly clear. I'll give it a go tomorrow. I hope that improves my idling.

Take care,

Robert

Tim Wiltse-RCU

Robert,

Don't forget another bad spot for an air leak is the needle itself. A little Plumbers tape(teflon tape) will solve that problem.

Later,
Tim

Beulzabob

My Feedback: (1)

Seems to be working pretty well

I have one other question though, when I bench run the engine I can get about 3-1/2 minutes of run time on 25% nitro, but the engine leans out about a 1/4 turn worth of needle adjustment. That is to say I have to richen the mixture by 1/4 turn to keep it running. It's basically a black widow with an unmodified Golden Bee tank. I'd prefer the long run time because it's going on a glider. Seems to have plenty of power until it starts to lean out. Does this sound fairly normal. I think it is because there's no pressurized tanks on these engines. What are your thoughts??

Robert

P.S. it's set at about 2-1/4 turns out at the end of these runs.

Tim Wiltse-RCU

Robert,

At what point does it start to go lean on you? If it's at the end of the tank then that for the most part is normal as the engine starts to suck air into the line. Three and a half minutes is pretty good. If you opened the air tube/venturi up some is would give you more power at the cost of run time, 2 1/2 minutes or so. Even this would give you plenty of time to get your glider nice and high!

Later,
Tim

Beulzabob

My Feedback: (1)

If I start the engine run at about 2 turns out from closed it starts going lean around 1-1/2 minutes into the run. I think it will run about 2 minutes total at this setting. I want to get it set right because real runs tend to be different than bench runs. If I want to open up the venturi a little more, where can I find those drill bits. Should I search under a specific type of bit? Haven't seen anything like them listed at Lowes or Home Depot. Would an auto parts store sell them?

Thanks again for all the help,

Robert

Tim Wiltse-RCU

Robert,

It sort of sounds like you are leaning on it alittle hard to start with and it's getting hot. What kind of mounting do you have it on? Is it getting plenty of air moving around it. Try another gasket under the head or try a different plug sometimes thats all it takes to make a happy engine! As long as you are using it on a R/C glider make sure of course that the fuel line is at the bottom of the tank and not to the side like for C/L. I got my drill set from Lowes or Home Depot. You should have no problem finding the right size.

3/32"=.0938
5/64"=.0781

Later,
Tim

Beulzabob

My Feedback: (1)

Hi Tim,

I have it mounted to the end of a 2x4. I'll try it richer at the start, but I've noticed that it doesn't seem to like that. Adding shims? Is that to reduce compression or change the timing?

LOL, didn't realize those were standard size bits.

Thanks again,

Robert

Beulzabob

My Feedback: (1)

Oh, I'm pretty sure that tubing is at the bottom. I'm able to get to the end of the tank capacity with it(3-/1/2 min.).

Robert

Tim Wiltse-RCU

Adding the head gaskets is to lower the compression. Little Cox engines are funny, sometimes a given engine just won't like a certain cylinder or piston or head. Their weird most times a little change will yield big rewards in the way a engine runs.
Just a couple of weeks ago I had a engine that I have spent alot of time on doing mods to and it was a real sweet runner. I made a 800 mile trip to show a friend and the darn thing would run for 30 sec. and then stop. After taking it apart a hundred times thinking I had a air leak or some dirt somewhere I changed heads and it was back to normal! Go figure.. the old head looked fine to boot.

Later,
Tim

Beulzabob

My Feedback: (1)

You rock man! I added 2 shims(3 total) and got a 3:20 run! It slowed down quite a bit the last 30 or 40 seconds, but that's still a massive improvement. I'll try it tomorrow with 2 shims to see if it gets any better.

I wonder if the problem you had with the engine you mentioned was due to a change in barometric pressure at the new location? Will it run okay at home again on your old setup?

Take care,

Robert

Beulzabob

My Feedback: (1)

I ported the venturi and the backplate to .078 and will give that a try. The backplate had a really small opening and I'm wondering if that was originally from a queen bee tank or from something else. I'm going to order a tach this weekend so I can really see what I'm pulling. Any suggestions on a tach?

Robert

Zeetah

How do you cut the fuel tubing so that it is so flat ? When I use an xacto (new blade), I get a slight lip.

Tim Wiltse-RCU

Robert,

I use a GlowBee Tach myself. Seems to work real good. When enlarging the venturi just make sure you don't drill the hole in the backplate bigger than the hole in the tank tube.

Zeetah,

When cutting the little o-rings just do the best you can. When you bolt everything back together it will squash flat.


Later,
Tim

Beulzabob

My Feedback: (1)

Hi Tim,

I held the tank and backplate together and drilled them out at the same time. Funny, I had to change to a different head to get it to run right and after enlarging, it wants to have 3-1/3 turns out compared to the previous 2-1/2 with the smaller venturi. That needle setting seems more inline with what everyone else seems to do. I got about a 2:10 run draining a full tank. Should be about right for powering the 2M glider. I also enlarged the fuel pickup tube to 1/16". I also sealed the back of the backplate where the screws enter with goop and put teflon on the needle valve threads. It's not starting as easy as before, so I think I'm back to experimenting with shims. If I want to do the mod where I align the cylinder opening front to back, should I sand material off the crankcase? It didn't look like I could sand the cylinder because it screws inside of the crankcase.

Later,

Robert