Possible TD Air Leak

bakergw Sat Mar 20, 2021 3:35 pm

Hi All,

I have four TD 049 engines. Note: I have built these up myself from parts so they are not representative of the engines you would purchase from Matt or Bernie . All are setup us follows. Kamtechnic head with 3 glow gaskets, and Turbo plug, Kamtechnic rear rotary plate, Cox drum muffler with pressure take off to fuel tank (yes, I understand the SPI concenrns), standard OEM carb body, collet, and OEM NVB with black needle and spring clip. All of them actually run very well and start fairly well for brand new engines.

The problem I have is that once running, I could effectively richen the needle all the way until just before it falls out and the motor continues to rev flat out. This makes me think I have got an air leak somewhere in the engine assembly. I have tightened everything up on all of the motors as far as I believe is reasonable. placed silicon fuel tube over the needle valves. I am thinking of applying sealant to one part at a time, whatever I do, I will do one thing at a time. I do not like silicon in motors at all!. I have used yamabond in the past which was/is a fantastic sealant that can be used with or without gaskets to seal race motors made from "hiroshima wonder metal" Smile

but I doubt I can readily source it anymore (today anyway), I have also used permatex in the past and found it sealed well and I can still get things apart without having to resort to stupid measures.

I have checked the turbo plug with fuel on it whilst running to look for bubbles and seems ok. I could replace the radial screw in mount with a standard backplate to see if that is leaking, I have the OEM NVB mounted backwards to work with my muffler and have used a copper 1/4" glow plug gasket with it to try and seal the gap. Also have used the standard spacers you can buy for this.

Any thoughts appreciated! especially on sealants that are good temporary sealants without binding the motor together for life.

Thanks.

Cheers,
Gary

aspeed Sat Mar 20, 2021 3:52 pm

If the carbs have previously been opened up to run on pressure then they could do that. Do the usual things like check for cracks in the plastic near the carb, The fancy new aluminum ones may leak a bit because they don't crush when the collar is tightened like the old plastic type does.

bakergw Sat Mar 20, 2021 3:57 pm

Thanks aspeed, I have some new plastic carb bodies, I will use one engine and replace and seal parts one at a time. The carb body looks ok, but I will wash it in metho and then have a real good look. The venturi/carbs are stock OEM.

Thanks.

Cheers,
Gary

aspeed Sat Mar 20, 2021 5:50 pm

Oh, maybe one of the three holes in the venturi could be blocked that happens too.

coxaddict Sat Mar 20, 2021 6:56 pm

Could be running lean because of poor fuel suction, which is common for TDs.

davidll1984 Sat Mar 20, 2021 7:41 pm

I already have the problem myself wit tee dee without spi or very smal spi setup wit tee dee red fuel tank engine mount I couldn't find the problem I put aside No time to check What is wrong But this engine is particularly efficient for For bunch of new parts put Assemble together

**Cribbs74** Sat Mar 20, 2021 9:02 pm

Make sure the crankcase hasn’t been drilled for pressure.

bakergw Sat Mar 20, 2021 11:34 pm

Thanks everyone,

I bought all the parts as brand new parts so I would hope the crankcase/carb body hasnt been drilled for pressure. But I will check. The weird thing is it happens with four engines all made from new parts. But I have added Kamtechnic head and Kamtachnic rotary mount, added standard cox muffler using as pressure and turned the OEM NVB backwards.

I will eliminate one thing at a time by blowing through the pressure line to make sure it is working. The tank, pressure line, and fuel line are common.They may have had gremmlins inserted by the evil little laughing bastards that live in my garden. I cant ever see them but I hear them laughing and chattering.

Next swap the head for a standard Cox head, next remove NCB check carby holes and NVB hole and make sure I can blow through them. Next swap out the Radial mount for the standard back plate. Next remove muffler and take off of pressure and raise fuel tank a little above the NVB so as that I know fuel should flow.

Given that this happens to all four you would assume (HAHAHA) the problem is common. Yeh, like Gary Fu...d with perfectly good engines. Failing all of this I will try me super home made NVB/Carby and needle. Ive already
y fixed the lawn mower this morning. The missus was complaining she cant get it to turn off, so I wrapped a bare piece of copper around the plug that now sticks out the front and gave her a very special stick which can push the bare wire against the mower chassis and it turns of. HaHaHa. You would think she would have said thank you. Lol. But Nope, said Jesus your a prick Gary HaHaHA.

See how it sorts out.

Thanks All, Old Bugger

Cheers,
Gary

bakergw Sun Mar 21, 2021 3:36 am

Ok, sorted it out. Removed the Kamtechnics radial engine mount. I found as I flicked the engine it would loosen on the mount, so put a normal crankcase backplate on and did it up tight and then changed over to standard bearer type test mount.

I removed the Kamtechnics head, cleaned it, cleaned the washers that go under it and cleaned the turbo plug and re-assembled with the turbo plug done up very very tightly. My pressure line between the muffler and the tank originally had an 049 spray bar inserted into it, to try and limit the volume as I had read lots of comments as to how the volume of pressurised air/exhaust needs to be kept very very low by having incredibly small pressure takes-offs. I removed the spray bar from the pressure line and let the full volume of pressure air/exhaust flow to the tank. Filled the tank, opened Nv 4 turns, primed carby and the motor quickly started and responded beautifully to the needle as I would expect.

I will sort out the pressure line to limit the volume and get the right amount such that fuel is not spewing everywhere out the front of the crankcase :-) Going to have to have a think about the radial mounts, but not too fussed as one of the things I like about the TD is the engine bearers as opposed to the other mounting methods. But I want to work out how I can make them work. The Kamtechnic head is an awesome head in my view, and once I cleaned everything up meticulously and re-assembled very very tight it was ok. Might have to look at sacrificing a turbo plug to use to lap in the top seal on the kamtechnics head.

So combination of problems:

kamtechnics head and gaskets needed thorough cleaning and re-assembly and very tight

Kamtechnics radial mount was leaking as the motor kept moving on it as I flicked it

The pressure line was very constricted and needed to be opened right up

Piece of P..S Laughing

Easy as, now my TD 049 runs really well. Old Bugger

Cheers,
Gary

aspeed Sun Mar 21, 2021 7:48 am

Glad you fingered it out in spite of us. Now you have to make 4 planes.

gkamysz Sun Mar 21, 2021 9:47 am

I was going to bring up the fact that I have run into several cases which didn't seal with new covers. There could be a variety of reasons for this; dings and dents in cases to poor manufacturing. Sealing of the case covers must be checked.

davidll1984 Sun Mar 21, 2021 12:05 pm

On one of m'y new crankcase its back cap Bad thred that It was impossible to screw the cap completely I had to persuade him a little wit forces Lucky I didn't anodize it before I found this problem

bakergw Sun Mar 21, 2021 4:21 pm

Thanks all,

every suggestion made helped me find the source of the problem. I always appreciate different thoughts as the reason I ask is because Im not exactly sure what the problem is, and lots of different ideas mean you can put a test plan together and work the plan step by step till you find the problem. At work when a problem that is tricky comes up and I do know the answer, I often get the grads to come into a meeting room and work the problem, so as that they can learn to work a problem, and the first thing is that they dont know everything! Lol. I know very well I dont know everything and sometimes forget stuff, hence asking all of you is a great help. Every suggestion and thought adds to the solution. If someone suggests X and I test for it and it is not X then I consider the suggestion as a very positive suggestion and test result as it has ruled out X. Ruling things out has more value than is often recognised, hence the suggestions carry more vale that is often recognized. I Love This Forum!

Now I just need to sort out the Radial mount coming loose. Im thinking I need to put a bolt through the mount from the back that is just under or over one of the bearers in the direction the thing loosens in, look at lapping it in somehow maybe? use filthy sealing stuff that says it doesnt go hard and lock but always does for me. (its my super power) Lol.

Thanks to all who contributed to the solution. And I certainly do have plenty of wings and profiles to mount them in HaHAHa Maybe a lot less complete ones after I take them out. HaHaHa. I fly like I stole them, but Im not very good lol!

Cheers,
Gary

balogh Sun Mar 21, 2021 5:01 pm

Gary,

Apply a short, plumber's silicon tape on the threads of the radial mount and span it tight. Then use a TD starter spring instead of flipping the prop.

https://coxengines.ca/cox-.049-snap-starter-spring-tee-dee.html

That won't generate an external torque in the direction of the backplate removal. Also, when the Right Hand prop is already spinning, the engine reaction torque will span rather than losen the backplate.

Just my 10 cents.

bakergw Sun Mar 21, 2021 10:04 pm

Hi Balogh,

Im out of thanks , so I cant mark you up thanks si I will simple say Thanks Heaps Thumbs Up

The plumbers tape is a fantastic idea!!! See what I like about the real engineering process where people just put up ideas!. Now I read it, it is so obvious, but I would never ever ever have thought of it!! This Site Rocks!

I have tried springs on my 049 TD engines and they make starting easier, but I have found once the engine is run in properly I can finger start them reasonably well, though not as well as a spring. The thing is, I absolutely have to use a muffler where I fly, and the NVB has to be turned around with a spacer and I cannot for the life of me stop the springs getting eaten with great regularity. I have taken the muffler off, put the NVB around the normal way, used normal driveplate and Cox 6x3 prop and have bought heaps of springs from Bernie but they all get eaten real quickly. So I have unfortunately given up on springs on my TD's. I use springs on my surestarts and frictionless springs on other reed valve 049 engines and never had a spring problem, but the Tee Dee 049, I have six, All eat springs faster than Nitro. lol!

So I am learning to set them up real well for starting easily and repeatably with my finger.

The plumbers tape is such a great Idea!! Thankyou. Once tested I will let yourself and others know how it worked out. cheers

Cheers,
Gary

balogh Mon Mar 22, 2021 1:13 am

Gary, how are the TD springs eaten? Do they interfere with the prop? Or simply lose their elasticity after several starts by simple elongation? I have rarely used those springs but other than they cannot turn more than a full circle before get butted on the crankcase, they seem to have no other issue.

bakergw Mon Mar 22, 2021 1:33 am

Hi Balogh,

The prop gets them. These are brand new springs. The most I would ever get out of a spring would be six starts / runs before the prop gets the spring and wraps the spring around the prop and the crankcase whilst running, which obviously stops it. The springs, props etc. are from Bernie and two of the TD's are brand new NIB Tee Dee 049's and they also do it. I do not wind the spring beyond about 3/4 of a turn as they are quite tight and definitely no good for more than a turn.

I havent asked Bernie if their is a trick to making them work, which I probably should. But I have read everything I could about it, including using the spacer if you have a muffler and the NVB backwards, but still doesnt work. With or without the muffler and the NVB standard position still have the problem. I tried smoothing the nose cone and carb body with my dremel to make it easier for the spring to retract but still have the problem. So I just figured either the springs arent right or I am not putting them on properly but cant really see much different of a way to put them on.

thanks.

Cheers,
Gary

davidll1984 Mon Mar 22, 2021 10:11 am

This is how it look like wit normal setup spring wil seat near its ventury

balogh Mon Mar 22, 2021 11:25 am

bakergw wrote:Hi Balogh,

The prop gets them. These are brand new springs. The most I would ever get out of a spring would be six starts / runs before the prop gets the spring and wraps the spring around the prop and the crankcase whilst running, which obviously stops it. The springs, props etc. are from Bernie and two of the TD's are brand new NIB Tee Dee 049's and they also do it. I do not wind the spring beyond about 3/4 of a turn as they are quite tight and definitely no good for more than a turn.

I havent asked Bernie if their is a trick to making them work, which I probably should. But I have read everything I could about it, including using the spacer if you have a muffler and the NVB backwards, but still doesnt work. With or without the muffler and the NVB standard position still have the problem. I tried smoothing the nose cone and carb body with my dremel to make it easier for the spring to retract but still have the problem. So I just figured either the springs arent right or I am not putting them on properly but cant really see much different of a way to put them on.

thanks.

Cheers,
Gary

Gary, if you bend the hooked end of the spring a bit backwards the get it out of the path of the blades, then even if vibrating, the hook may avoid catching the prop?

bakergw Mon Mar 22, 2021 2:08 pm

Hi Balogh,

I have tried bending it back a bit, but the spring seems to want to move forwards. I think if I did it without the muffler and bent the spring back a bit as you suggest it may well work. When I put the springs on without a muffler they look like David has shown in his picture. I definitely have to use a muffler where I fly. Maybe I need to modify the muffler with my dremel so as that the NVB is in normal position and then the spring should go right back into the normal position as shown by David and then if I put a bend on the front of the spring might solve he problem. Thing is, it/they have eaten springs in totally normal config. I will try as you suggest, the worst that can happen is another spring gets eaten. lol!

Thanks Balogh and David!

Cheers,
Gary

bakergw Mon Mar 22, 2021 2:39 pm

When I get home from work tonight Im going to try changing the plastic carb body for an aluminium one and a brand new collet and drive plate, still turn the NVB around and use the muffler but see what happens with a new spring also with a bend on the front. Had a quick go this morning and the plastic carb body doesnt want to come off readily. Looks like I will need to mount the engine solid in the test bed to get purchase to turn the carb body and remove it. the collet came off easily. Ive never needed to take a carb body off before :-) Now is as good a time as any to learn Thumbs Up

I think this is all telling me to start the engine by hand really. lol!

As it is, I have read in some threads somewhere on CEF that the aluminium carb bodies need some sealant as they can leak air a bit at times. Oh well, keeps me busy. Smile

Cheers,
Gary

balogh Mon Mar 22, 2021 2:54 pm

Gary

Unless you have the latest aluminum NVB with the fake pressure nipple on it, your starter spring will have nothing to hook on. Older aluminum bodies do not have that nipple on which the spring is anchored.

bakergw Tue Mar 23, 2021 2:02 pm

yep, got the latest cheers

Cheers,
Gary

bakergw Thu Mar 25, 2021 2:19 pm

Hi All,

Sorted out the leak with the seal between the radial mounts and the crankcase, tested and found a very easy and simple solution. I put on a standard 049 reedie crankcase gasket from either of https://coxengines.ca/cox-.049-crankcase-gasket-3.html or http://www.exmodelengines.com/product.php?productid=17598&cat=268&page=2. I carefully put the gasket on over the threads of the kamtechnik https://kamtechnik.com/ radial backplate after cleaning and drying all surfaces and did it up nice and tight. Remounted and tested the engine. Ran perfect! unmounted the engine from my test bed and re mounted the engine on my test bed and ran perfect again! No leaks, no slipping of the plate! Perfect.

I very much like the heads and radial mounts made by Greg at Kamtechnik and have bought over several purchases 10 heads and six radial mounts. Each of my engines has a Kamtechnik head on it and I put killer Bee type cranks in my reedies just to toughen them up a bit, maybe dont need to, but its easier to be sure. I lalso like being able to put radial mounts on my Tee Dees at times, especially when I think I might have built something a bit big or heavy for my readie and the Tee Dee sorts it out.

Cheers,
Gary

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