I want to build my first engine

[Makintrax73]

Thanks for the continued support guys. I was able to get it assembled and decided it was too tight. It wouldn't "flip" over by hand just drag (in other words it could be turned over by hand, but would not free wheel really for the bottom half of the stroke). I pulled it back apart and lapped the piston for about 10 seconds. This felt much better. It now could be flipped, but compression still felt OK.

I mixed some fuel with the JD80% ether, and put it on the test stand. I have been able to get a couple short "brapps" and a couple wisps of smoke from the exhaust. So this is a major improvement over last time. Hopefully with some fine tuning of compression and fuel I can get it to actually fire up for more than 2 or 3 cycles.

 

[Chris Hamel]

Sounds promising

 

[CraigH]

Looks nice - I also built my Sparey 5cc crankcase from a block of aluminum - mistakes were also made.

 

[Makintrax73]

Looks nice - I also built my Sparey 5cc crankcase from a block of aluminum - mistakes were also made.

Thanks Craig. I've about lost hope this thing will run. Something with the fuel flow I can't figure out at all. I've rebuilt the spray bar already.

This week I rebored the crank bearing, remade the crankshaft for a better fit, and fixed issues with sealing the crankcase.







Overall everything fits better, the inlet port is better located, even purchased fresh from the pump kero, etc......I tried to start it again this morning. Get an occasional "brap" (burning off the prime) and no amount of fiddling with the fuel needle gets it to start.

Think its time to move on unfortunately

 

[Olli-Matti]

You have persisted and put a great effort to it definately, the success will come eventually I am sure!

Can you hear a hissing sound when turning the propeller over TDC slowly and piston coming back down? There should be an audible pfft when the transfer ports open Also when piston goes up you might hear the pfft when the inlet opens but the transfer sound is usually a bit more audible.

 

[wachuko]

Thanks Craig. I've about lost hope this thing will run. Something with the fuel flow I can't figure out at all. I've rebuilt the spray bar already.

This week I rebored the crank bearing, remade the crankshaft for a better fit, and fixed issues with sealing the crankcase.

View attachment 480801

View attachment 480802

View attachment 480803

Overall everything fits better, the inlet port is better located, even purchased fresh from the pump kero, etc......I tried to start it again this morning. Get an occasional "brap" (burning off the prime) and no amount of fiddling with the fuel needle gets it to start.

Think its time to move on unfortunately

I just want to say that it is so cool to see you are using a Logan lathe... and seeing how you are using the face plate, and other contraptions. Very cool.

 

[Makintrax73]

You have persisted and put a great effort to it definately, the success will come eventually I am sure!

Can you hear a hissing sound when turning the propeller over TDC slowly and piston coming back down? There should be an audible pfft when the transfer ports open Also when piston goes up you might hear the pfft when the inlet opens but the transfer sound is usually a bit more audible.

Unfortunately I'm away from the shop for the weekend or I would try to post a video with sound. I don't remember hearing anything upon opening the transfer ports, but didn't really listen for that either.

What I know for sure:

Crankcase IS pressurized as piston falls. Reason I know that is I had bubbles forming from the cylinder to block joint. I recut a thou off the seat and now I don't see that happening so the pressure should be pushing through the ports.

Still getting a little compression squeezing by the piston based on fuel bubbles as it goes up if you turn it slowly, but apparently within spec because it does pop the prime fuel (inconsistently unfortunately)

I assume the carb is capable of pulling fuel because when I prime the fuel line by turning it over with my thumb covering the barrel it pulls fuel smartly from the fuel tank. I know not to over do it on this or it will flood.

This design has what appears to me to be a large transfer port area. I wonder if this decreases the velocity of the charge at low rpm and creates hard starting if everything isn't just right?

 

[Flyinfool]

Try spinning it with an electric starter. I have had some engines that no amount of hand flipping would ever start but started and ran fin using a starter.

Just pay attention to where the thrust load of the starter is going so you are not pushing the crank into the back plate. Normally the thrust load is taken up by the thrust washer against the front of the crankcase. Also when spinning with a starter if the carb is working you will see it draw fuel.

Do you have oil in your fuel mix? You only mentioned the ether and the kero. I have also only used actual pump diesel fuel, it has more BTUs for a given volume and makes more heat.

 

[Chris Hamel]

Before you totally give up on the project, have you considered remaking the cylinder head and converting it to a glow fuel engine? I ran glow engines for years it seems they are less finicky than diesels.

 

[Makintrax73]

View attachment 20240303_144805.mp4