Engine troubleshooting

Hi Levent,

thank you for all your suggestions.
The piston moves freely in the cylinder and gives a nice positive "plop" when I turn the prop. The axial play of the shaft is normal.
I like the "dirt in crankcase" hypothesis, and by "like" I mean I think it's plausible. That's the one place I haven't cleaned and it's consistent with what I might expect after a crash. What I don't like about it is that it means I have to remove the drive plate, which absolutely horrifies me. How do you even do it? IS any special equipment required?

So no varnish build up?
May have bent the crank or conrod might be bent a bit.

dirk gently wrote:Hi Levent,

thank you for all your suggestions.
The piston moves freely in the cylinder and gives a nice positive "plop" when I turn the prop. The axial play of the shaft is normal.
I like the "dirt in crankcase" hypothesis, and by "like" I mean I think it's plausible. That's the one place I haven't cleaned and it's consistent with what I might expect after a crash. What I don't like about it is that it means I have to remove the drive plate, which absolutely horrifies me. How do you even do it? IS any special equipment required?

Removing is easy and it can be removed in several ways. I use a propeller screw and a vice to remove it. I attach two pieces of plywood on vice jaws with double sided tape.

Here is a useful information:

https://www.coxengineforum.com/t3062-can-i-reuse-drive-plates?highlight=Removing+drive+plate

There is a tool to re-attach drive plate in Cox International:

https://coxengines.ca/assembly-tool-for-cox-.049-engines.html

Ok, so let's see if I've got this right:
I strip the engine down so that only the crankcase, crankshaft and drive plate is left.
I then screw a prop screw into the crankshaft as far as it will go, making sure there's enough of the screw sticking out to make room for the drive plate as it will be sliding off of the crankshaft.
Then I put the whole thing in a vise, with one jaw pressing onto the crankcase where the tank would normally be, and the other jaw pressing on the head of the prop screw.
As I press, the drive plate rests against the crankcase and the prop screw presses the crankshaft in until it drops into the crankcase.

Is that about right?

dirk gently wrote:Hi all,

I seem to have an issue with one of my Bees.
It's been in a crash, it was thoroughly cleaned inside and out afterwards to make sure there was no sand in it. It seemed intact.
Since the crash, it still starts easily and runs great when cold. I can maybe get two good runs from it at a time. After that, the engine still starts normally, but quits after maybe 20 seconds, and becomes excessively hot. Even the prop drive plate is way too hot to touch. Priming fuel just boils away instantly on the piston, like drops of water on a hot plate, and I think it even boiled off some of the fuel from the tank through the filler vent.
If anyone has any ideas how to troubleshoot this, they would be much appreciated.

Sounds like its running lean, I would looks for leaks in the intake system (needle/reed/tank/gaskets/etc). Good luck.

You are correct in the removal process, but when putting it in a vise to press it apart, put a small block of wood or somathing soft on the rear of teh cramkcase side so as not to damage the case back. And I believe you said it right by stripping the case apart, but just want to re-itterate to make sure the piston is off as well. Don't ask how I know.....

dirk gently wrote:Ok, so let's see if I've got this right:
I strip the engine down so that only the crankcase, crankshaft and drive plate is left.
I then screw a prop screw into the crankshaft as far as it will go, making sure there's enough of the screw sticking out to make room for the drive plate as it will be sliding off of the crankshaft.
Then I put the whole thing in a vise, with one jaw pressing onto the crankcase where the tank would normally be, and the other jaw pressing on the head of the prop screw.
As I press, the drive plate rests against the crankcase and the prop screw presses the crankshaft in until it drops into the crankcase.

Is that about right?

Yes and remove piston before as NEW222 says.

NEW222 wrote:You are correct in the removal process, but when putting it in a vise to press it apart, put a small block of wood or somathing soft on the rear of teh cramkcase side so as not to damage the case back. And I believe you said it right by stripping the case apart, but just want to re-itterate to make sure the piston is off as well. Don't ask how I know.....

Right

Hello friends,

first of all, thank you for all your kind help, I wouldn't have been able to go through with this process without your advice.

I managed to pull the drive plate off the crankshaft. I cleaned the crank and the inside of the crankcase. Prior to disassembly I noticed that if I push the drive plate back and turn it, it grinds against the crankcase, so I lapped the two mating faces using ultra-fine emery paper on a flat glass board, then stropped it with buffing compound. Then it occurred to me the prop would pull the drive plate forward, so it would never actually rub against the crankcase anyway.

I put the engine back together without too many issues, then gave it a test. It completed the first run fine, died abruptly after 10s during the second run. Then it did 3 consecutive full runs turning 15.300k on a 5.7x3'' APC prop, best performance ever. Oh well, I guess it's as good as it's gonna be.

I no longer think the issue had anything to do with overheating, I tested it against another of my engines and it doesn't really seem hotter to touch. Both engines now behave ok and have adequate performance, plus, I learned to handle drive plate (dis)assembly, so all is good.

I never understood the tv show Dirk Gently holistic detective agency

The UK one o the American one?

THE one episode I saw was the pilot on some direct tv channel-- could have been, and probably was, BBC

I assumed there was some back story I was not privy too and most of that episode was just weird and made no sense to me

The American one strayed a lot from the books in terms of plot and character design, but was very true to the spirit of the literary original.
I didn't care for the UK one.