Basic engine tuning.

[acerc]

I'd like some ideas on starting my da 70. I've been flying in 90° weather lately with 80%~ humidity. It'll start and run fine the first time of the day, but after I've landed, fueled, and waited for my turn again, it's a real pain to start. I have to come for 3-4 flips, choke off 3-4 flips and it runs for 1-2 seconds. Choke 3-4 flips, choke off for 3-4 flips and its going for 2-3 seconds. Repeat this process 6-8 times and your arm is tired, sweat is running into your eyes, and if your lucky the engine will start.

Then, once it is running it'll struggle to pickup speed. I have to sit there and goose it several times to get it to rev up.

Earlier in the spring and winter it ran just fine...

FYI @ericrs has an eme70 that is acting about the same now that it's hot out.

Sounds like it is to lean.

 

[Flyingjon]

@Flyingjon it sounds like you may be running into a vapor lock scenario. How soon after landing are you trying to fire the engine up again? Check the fuel line location and see if there is a way to move it further away from the exhaust. Also, check to see if there is a way you can get some more air flowing through the cowl or just open it up a bit more so it will cool better when sitting between flights.

Just my thoughts based on the symptoms you provided

We figured must be a vapor lock issue but didn't have much for ideas on curing it. Will check the fuel lines out.

One of my DA50's does that. If you try to just land, fuel up, and fly again it's a total pain to restart. If you let it cool for say 15 minutes, it will start on the first flip almost every time. If you wait more than an hour you have to choke it again.

The crazy deal is, if you kill it, refuel it, and start it right away again, then it starts easier. I wonder if maybe a fuel line close to the muffler has more time to vaporize if it sits there a bit....?

Sounds like it is to lean.

I did richen it up close to an 1/8 and that helped the issues of not throttling up smoothly, but didn't notice any difference in how it started.

 

[sparkx38]

Very helpful info Terry. Just curious. Why is this method specific to the 100cc class engines? Do you have a different method for say the 60cc class and the 170cc class? My DA 170 is also running a tuned pipe which makes tuning even more different. Any help there? Thanks again for the 100cc class info. Will come in handy for my DLE 111.

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[Bluepilot2003]

Last week I had the same issue with my DA-50 about getting it started on a hot day after the first flight. I actually could see the bubble in my fuel line (which was no where near the exhaust). But it was 100 degrees sitting in the Arizona sun. So I don't blame it for not wanting to run again! So hot days, I get the plane into the shade right away to help out.

 

[Phil.Griffin]

We figured must be a vapor lock issue but didn't have much for ideas on curing it. Will check the fuel lines out.



The crazy deal is, if you kill it, refuel it, and start it right away again, then it starts easier. I wonder if maybe a fuel line close to the muffler has more time to vaporize if it sits there a bit....?



I did richen it up close to an 1/8 and that helped the issues of not throttling up smoothly, but didn't notice any difference in how it started.

I have this EXACT same thing going on. As long as I let my engines cool before restarting or, fuel and start immediately, they crank up fine. If they sit a few minutes after a flight I can forget them starting again until they cool off. In my totally uneducated opinion, if they sit too long, the carb gets heat soaked and will need to cool again below some certain temp before restarting. I've had others tell me their DA's will start regardless but mine will not.

 

[Flyingjon]

That same thought had crossed my mind that the carb is heating up and causing issues. Seems like there would be an easy cure other than setting a fan in front of the motor when you shut it down...

 

[Phil.Griffin]

That same thought had crossed my mind that the carb is heating up and causing issues. Seems like there would be an easy cure other than setting a fan in front of the motor when you shut it down...

I plan to try an EFI 120 at some point in the next 12 or so months. I'm anxiously awaiting the inevitable price drop, and the ability to send an existing engine in for the upgrade. I want to compare, in my own airframes, the new technology with the old.

 

[49dimes]

It's that time of year again. Hot Humid weather causing lean conditions . Just opening the L needle a tad usually solves the problem. Shade and cool down after a flight is a must for me. See.....my personal "onboard" pump needs it too .

 

[Terryscustom]

Very helpful info Terry. Just curious. Why is this method specific to the 100cc class engines? Do you have a different method for say the 60cc class and the 170cc class? My DA 170 is also running a tuned pipe which makes tuning even more different. Any help there? Thanks again for the 100cc class info. Will come in handy for my DLE 111.

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I didn't say the info was specific to 100cc engines, just the needle settings that I talk about. You will find basic needle settings in your manual or from the mfg. of the engine.
Tuning an engine is not rocket science, they all tune the same with the process I noted. Use the same thing for my 20cc all the way up to 180cc. If the tuning process is leaving you with issues either A - The process was deviated from or B - there is a problem with your engine or setup to start with.

 

[sparkx38]

I didn't say the info was specific to 100cc engines, just the needle settings that I talk about. You will find basic needle settings in your manual or from the mfg. of the engine.
Tuning an engine is not rocket science, they all tune the same with the process I noted. Use the same thing for my 20cc all the way up to 180cc. If the tuning process is leaving you with issues either A - The process was deviated from or B - there is a problem with your engine or setup to start with.

Misinterpreted what you was saying and couldn't figure out why it would make a difference. Makes much more sense now. Thanks

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