My 049 tee dee is a turd

Andrew, you may find it hard to remove the cylinder. For some reason Cox did not think it through for those cylinders and ones with screen tack-welded to the exhaust. The wrenches just won't fit to remove the cylinder so they finally cut the top fin to accept a wrench.

One way to remove the cylinder without damage is to drill a hole in a block of wood the diameter of the cylinder fins, then saw through the hole so you can fit the wood around the cylinder. The wood removed by the saw should ensure a tight fit around the cylinder fins so you can use the wood to clamp the cylinder.

Good luck.

George

Bernie to my knowledge doesn't offer a true Tee Dee cylinder, they're modified production Sure Starts. What nitro were you using?  The fact that you put a drilled and tapped glow head on there tells me that when you finally got the engine to run it may have been due to lowering the compression. How many shims did you have under the glow plug? I would start with 3 using the high comp head and work backwards removing them to increase rpm's. Prior to installing the plug, deck the plug's mating face by placing a piece of 400 grit paper on a piece of glass and just a bit of oil and sand to flatten and true the surface. Clean the plug with some alcohol and reinstall.

In addition, did you check to see that the small holes were totally clear by sticking a small wire in them in the venturi? With the venturi out, make certain that the plastic housing isn't cracked. This is extremely important and this could be the cause of needle valve issues.  You didn't mention what prop you were using and the TD doesn't like a 6" prop. A black 5x3 works well

        In addition, remove the stock needle and place a piece of fuel tubing over the threads. Make certain that where the tubing butts into the spraybar body is totally square. I place tubing on a dowel and chuck it into a drill press and while it's spinning cut it with a X-acto. Another thing that may need to be checked is to make certain no one drilled out the venturi and it's stock. Ken

Ken just reminded me of something. Make sure the crankcase isn't drilled through at the little nipple on the side of the carb body. If it is just clean up the crankcase and plug the hole with a little JB.

Hi Andrew.
Following up on what Ken said about making sure the venturi has not been bored; if the butt end of a 1/8" drill bit will not pass through the aluminum venturi, then it is stock. If the bit passes through the venturi, then someone has bored it wider for use with pressurized fuel feed. This will cause low vacuum at the spraybar resulting in very poor fuel draw.
Rusty

Thanks for all your replies!

I should have been more specific in my original post. Prior to testing it, I did completely dismantle the engine and soak every metal component in thinners to remove all the old castor oil gunk, with particular attention paid to the nva and venturi, so blockages definitely weren't an issue. No air leaks around the NVA thread either, I have fuel line slipped over the NVA and the nva body, as the black metal clicker piece is broken & this is how I hold the NVA in position. I also reset the piston/rod ball socket. Engine turns freely with good compression and very little crankshaft end play and no side play.

I was running a top flyte 6x3 prop, as suggested this could be a bit of an issue so I will try a 5x3. Fuel was 20% nitro with 20% castor, mixed about 2 weeks ago by a reputable hobby store. Unfortunately we don't have the luxury of buying premixed fuels here in Australia. I am confident in the fuel, as I have tested about 8-10 of my reed engines and its been fine in all of them showing excellent performance.

I checked to see if the venturi has been drilled with a 1/8 bit and it has not. The crankcase is not tapped for pressure feed either, and the plastic venturi block is not cracked, its the later reinforced type and in good condition.

The only other thing this leaves is compression. I do not have spare shims on hand to play with without dismantling other engines so I will get some and try some cox low compression heads. I suspect this will yield good results, exactly as Cribbs74 said, it should still be able to run fine with this combo, just not as good as an unmolested tee dee.

Thanks for all your input guys, Ill let you all know how I get on with it once I get a chance to play with it again!

This may sound a little crazy but the idea just popped into my head. Any chance it has a LH crankshaft fitted? The way you've described its running, I've had front intake engines run like that in reverse, so maybe that's it seeing everything else checks out.

Rod.

Very clean engines sometimes don't restart nicely. After a dozen or so runs it should settle in. Basically after a piston reset the engine should be given a break in process again. The same is true for deep cleaning. However a Cox engine needs little break in. Usually 3 or 4 short runs is all it takes.

If the intake is bored out then hot restart will suffer if not running on bladder. If the intake is bored out larger than it should be then it will be even worse. I received an engine that has a very large intake that became very easy to operate after replacing the intake with a stock one. It runs significantly better on pressure bladder still.

Reputable fuel is a must, so is clean fueling equipment. The sprinkler holes are so small that barely visible debris can plug them up tight. The easiest way to clean them is to simply force fuel through the fuel nipple with the NVA open a couple extra turns - pay attention so you can reset the nva when done. I prefer a plastic syringe over a rubber bulb for cleanliness and ease of metering. The syringe can be cleaned much easier.

Phil

andrew_v wrote:Hi to all and just wanted to say what a great forum this is.

My name is Andrew and I am a cox fanatic from Australia.

I recently acquired an 049 tee dee from ebay, and I was disappointed when it arrived to see that it does not have the correct piston and cylinder. It has been fitted with a thick wall dual transfer port cylinder with no bypass ports at all. It has no SPI, it has the two slit style exhaust and the weird thing is it had no flat spots on the top of it to unscrew it from the crankcase.

Long story short, I could not get it to run with this P+C combo and the high compression tee dee glow head. I did manage to get it to start (very hard to do) with a home made cox standard plug drilled and tapped with an o.s A3 plug. It was barely responsive to needle valve settings, and the nva was just not very sensitive at all to large movements. Once it stopped, it was very hard to get it started again. Overall, it was a turd of an engine, no better than any of my reed 049's.

My question is, should I persevere with this piston and cylinder combo, or just replace it with a new tee dee unit from Bernie?

I have several other cox engines including a few other tee dees, but this is the first tee dee I have ever played with.

Hi Andrew, welcome to CEF, this is another Andrew from a different continent, but with a similar addiction to TD-s, and similar experience with cheating ebayers claiming genuine TD components sold on the engine , and seeing e.g. No 2 cylinder (instead of No 4 or 5 peculiar to TD-s) when examining the engine after it has been shipped.....

My experience with normal glow plugs and adaptor heads is, that the 049 size engine just does not even approach the normal output you could expect with stock COX head. These engines are too small for glow plug application, and this is not just the compression ratio change in comparison to stock heads, that you could remedy by adding/emoving shims. (This is a different topic related to the thermal efficiency of the Carnot cycle, and I do not go into its details, suffice to say the performance loss symptoms with regular glow plugs put on 049-s are fully verified by the principles of thermodynamics...heat input to the cycle within the shortest possible time and at the highest possible pressure in order to maximize the thermal efficiency...).

My recipe for you to test would be, that

1. Use a stock COX head, high or regular compression, and avoid using the conversion heads with regular glow plug (these are designed for much larger model engines) in it
2. check if the engine overheats.This maybe remedied by either adding more shims under the head i.e. reducing compression and hence premature ignition, and/or by making the fuel mixture richer (simly open the NV a bit).
3. Check if the crankshaft really fits inside the crank...I met abused TD-s (previous owner used unbalanced prop on it) where excessive air leaked through the excessive gap between the shaft and crankcase, making the engine start almost impossible, then run on the lean side due to leakage...and causing engine overheat. You say the side-play is not there, but try blowing into the crankcase form the prop washer side and check if there is excessive leakage.

4. Check if there is any air leakage into the carb along the threads of the Needle Valve stem..this will also lead to lean mixture/overheating/weak run. You may want then to pull a sylicone tube on the NV stem and overlap it with the threaded NV nipple on the carb, to prevent the leakage.

5. Check if the black plastic carb body has cracks, especially near the  threaded area wherethe venturi screws in. A typical point of air ingress leading the poor start-up and running conditions, on old TD-s..your vendor may not have sold you his best NV body, if he already cheated on the P/C combo...

Hope to have helped a bit.

After a deep cleaning, it may take some running to restore a beneficial coating of castor varnish on the cylinder walls to seal off the blow-by and improve its performance. If that is the case, it's probably good that you use all castor fuel.

Over here in the USA, most of us use half castor/half synthetic, which is slower to build up varnish, but then it levels off and doesn't get overly coated. Deep cleaning has trashed the performance of many larger steel engines.
Rusty

andrew_v wrote:Fuel was 20% nitro with 20% castor, mixed about 2 weeks ago by a reputable hobby store. Unfortunately we don't have the luxury of buying premixed fuels here in Australia. I am confident in the fuel, as I have tested about 8-10 of my reed engines and its been fine in all of them showing excellent performance.

Your mix sounds fine to me.  I generally home-brew 25%-25% fuel & it seems fine, although I tend to more often use a premixed buggy fuel (something that is far more readily available) with castor oil & nitro added to come up to 25%-25%.  This actually seems to run slightly better in my .049s.

You can get premix here http://www.rcfuelsupplies.com.au/index.php but the freight may be a problem.  I've only ever personally picked up some nitro & castor from them on a holiday to Queensland.  I'm sure they would probably even pre-mix whatever blend you want.

Rod.