I want to build my first engine

[Makintrax73]

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.

RE: Oil. Yes I purchased some pure cold pressed castor oil off Amazon. Hopefully that is the right stuff. From what I read castor oil is the go to. I also have some 2 stroke "Sea and Snow" oil I could substitute. I tried two different mixes with the same result: 25 castor, 35 JD ether, 35 kero, few drops of cetane boost and 25 castor, 35 JD ether, 45 kero, few drops cetane boost.

Ok so the above video I grabbed on the quick this afternoon. Thank you for the suggestion. What I am seeing is with an air bubble in the fuel line as a visual reference and the mixture needle wide open I do not get any fuel flow seen at all. Clearly there is a problem with either the internal airflow, or with the venturi in the carb.

I'm going to see if I can find a degree wheel I can print out and glue to some cardboard and map out the events. Apparently I gave away my old hotrod days degree wheel when I sold my Camaro. There is a lesson there about EVER doing away with tools because you never know.

 

[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.

I listened closer, to my ear I get a pfft when the exhaust ports are opening, and perhaps a barely audible pfft when the transfer ports open. Not sure what's going on there.

 

[Just for fun]

Beautiful job on the engine. Keeping my fingers cross you will get it working in short order.

 

[Flyinfool]

Check the needle valve to spray-bar fit for air leaks. Also the spray bar to venturi body for air leaks.

Put a piece of clean fuel tube onto the spray bar and see if you can blow through it. If you can not blow air thru it will not suck fuel either.
If you can not blow thru check for debris plugging it up. Maybe a piece of dirt from the new fuel system or a chunk of swarf from making it.
Dumb question but I am good for those, you did remember to drill the cross hole to allow fuel out of the spray bar?
The hole in the spray bar should be mounted facing perpendicular to the air flow.

Can you post a pic looking down the assembled carb. All should be good but a sanity check should be good.

 

[Makintrax73]

Check the needle valve to spray-bar fit for air leaks. Also the spray bar to venturi body for air leaks.

Put a piece of clean fuel tube onto the spray bar and see if you can blow through it. If you can not blow air thru it will not suck fuel either.
If you can not blow thru check for debris plugging it up. Maybe a piece of dirt from the new fuel system or a chunk of swarf from making it.
Dumb question but I am good for those, you did remember to drill the cross hole to allow fuel out of the spray bar?
The hole in the spray bar should be mounted facing perpendicular to the air flow.

Can you post a pic looking down the assembled carb. All should be good but a sanity check should be good.

The machining instructions I was following said to put spray bar hole facing down toward the crank. I was sitting there thinking about this last night and remembered Bernoulli's principle thinking I'm not sure that is right? Your comment now doubles my concern.

The fastest air is the lowest pressure, and that would be on the side of the spray bar at the point of greatest constriction, yes?

Anyway I was trying to tighten up the spray bar fit just as you suggest to check for leaks and the narrow cross section brass did not like that. Snapped right in half........so I will be remaking the spray bar for about the 4th or 5th time either way.

I did degree wheel the timing as well as I could. I'm out no more that 5 degrees on any given timing event per the diagram on the plans. There is the slightest bit of overlap between the inlet opening and xfer port opening which the plans say shouldn't be.....about 4 degrees overlap. Hopefully not fatal. I could shave the cylinder mounting boss a few thou and lower the xfer ports which would reduce that if needed.

 

[Flyinfool]

There are 2 separate pressure things happening around the spray bar.
One is Bernoulli that says the pressure is lowest at the narrowest point.
second is that the spray bar is a restriction to airflow thru the carb so below the spray bar will have negative pressure. Kind of like the way a choke works. I can only guess which way is better for your application. As I said above make sure the spray bar is allowing fuel flow by blowing thru it with a clean piece of fuel line (unless you like the taste of kero). You were spinning it over plenty fast that is should have been drawing fuel.

The fact that it will run off the prime means that once it gets the correct amount of fuel it will run.

 

[Makintrax73]

Not much new but I did get it to kick out smoke for a couple seconds while turning it over with a drill......
It is now sucking fuel for sure after I redid the spray bar and needle. Jet hole is straight back at the narrowest point of constriction.

View attachment 20240306_134044.mp4

Unfortunately I don't have a tripod for my phone so not a very good video

 

[Chris Hamel]

Don't know if this helps but many years ago when I first started flying rc planes I rigged up a drill instead of a starter and it didn't work. This was on a glow fuel engine but apparently the drill didn't spin it fast enough. Didn't make sense to me but when I used a for -real starter engine started fine. If you know anyone with an actual starter might be worth a try.

 

[Makintrax73]

Don't know if this helps but many years ago when I first started flying rc planes I rigged up a drill instead of a starter and it didn't work. This was on a glow fuel engine but apparently the drill didn't spin it fast enough. Didn't make sense to me but when I used a for -real starter engine started fine. If you know anyone with an actual starter might be worth a try.

Yeah, it definitely doesn't work correctly. I can feel it slapping the fingers I put on the adapter when the engine fires, which can't be good. It feels like it wants to spin and overruns the drill. Unfortunately I don't know anyone that has a real starter. I kind of find myself wondering if I machined something with a 1 way bearing if it would work. IDK if a small one way bearing would be strong enough, but the current setup is getting in the way.

 

[Chris Hamel]

This is kind of starter you need. It grips on a spinner in front of the prop.

Model Airplane Starter | eBay

Model Airplane Starter.

www.ebay.com

Although, now that you have it popping, it might start by flipping the prop.