pepito9

Hi guys,
this is my first gas engine, so my knowledge is very very basic, i´ve mounted it on a stand to begin the break in process using a 40:1 mix.

I have to use the starter to get the fuel moving into the carb, no amount of hand cranking will get me there, the tank is in line with the carb.
I choke the engine and it fires, once i remove the choke it runs for a few seconds and then dies, the only way to get it to start again is to re-choke, same results.
If i accelerate it will run for the same time and die.

Any ideas on where to start looking for the problem?

[link=http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6462]This is the engine[/link]

Thanks,

Diego

soarrich

My Feedback: (98)

I have one, it's a nice engine.

The first thing I'd check is that the "H" needle is farther away from the cylinder than the "L" needle, if it is your carb is oriented on the engine correctly.

There is a pressure pulse hole in the bottom of the carb that lines up with the hole in the black block, make sure you have the carb so that hole lines up with the hole in the black block. Make sure the gasket 's hole lines up with both. In the engine's picture you'll see a large screw in the center of the plate on the carb, remove that plate then squirt some gas on the small flappers to wet them. Put the plate back on. I would think your engine would run now. BTW, you tank placement should NOT matter with a gas engine.

This is something I wrote before, but it may help you.

Get Pennzoil, run it at 32:1 all the time.

Do check the timing, here's my way:
The easy no math timing.

Cut a strip of paper 1/4" x 5".

Rap the paper around the prop drive, back by the crankcase where the magnet is. Overlap the paper then cut with a #11 blade cut though both layers of the paper.

Now you have a piece of paper the exact circumference of the prop drive.

Cut it in half, take one of the halves and cut that in half again, take that and cut it in half also. Now cut it so it's in 1/3 and 2/3 pieces.

The 2/3 piece is how much before TDC the engine should fire, (30*).

Now find TDC by removing the spark plug, then sticking something in the hole, a pencil works fine. Move the crankshaft until the piston. is at the top of the cylinder, you'll find that about 5* either side of the TDC it doesn't feel like the piston is moving. Wiggle the crank back and forth until you can find the center of this piston not moving zone, that's TDC.

Now with a marker make a line across the edge of the prop drive onto the crankcase, it doesn't matter where, just that it's easy to see.

Now turn the prop drive clockwise a distance equal to the 2/3 piece of paper.

Plug the ignition into a 4.8v battery, and turn it on.

Now with the two screws loosened move the sensor off the magnet until you hear the ignition pop.

Tighten the screws for the sensor down, then confirm that the timing is still set that 2/3 piece of paper before the TDC mark.

You may have to lengthen one of the grooves in the sensor mount to get the timing correct.


1.Start the engine, set the throttle so the engine is going 3500 rpm.

2.With the engine running I turn the "L" needle in, it is always the needle that is closest to the engine, when the engine speeds up to 4000 rpm I adjust the throttle to bring it back to 3500 rpm. You keep repeating this step until your engine doesn't speed up anymore when you turn the "L" needle in.

3.Turn the "L" needle out 3/16th of a turn.

4.Open the "H" needle 2 turns out, open the throttle all the way open. Now slowly turn the "H" needle in the engine will increase in rpms. Turn the needle about 1/16 at a time, when you get no more increase in rpm the "H" is set properly.

5.Set you idle speed with your throttle trims, it's best to take the idle stop screw completely out, you should have it so the idle is correct with the trim in the middle, and the low trim kills the engine.

6.With the engine running at the idle speed that you fly at you should now be able to snap the throttle open and the engine quickly speed up. If it just dies, turn the "L" needle out 1/16th of a turn, repeat this step until is quickly speeds up. If when you snap the throttle open it stumbles then speeds up turn the "L" needle in 1/16th of a turn until it cleanly and quickly speeds up.

7.Close the hole or notch up in the choke plate, I'll post a picture of what I mean, I do it with soldiering the hole close, some use glue or a bolt.

After you modify the choke plate the way to start the engine is:
a. Close choke completely.
b. Open throttle half way.
c. Flip engine with ignition on until the engine coughs.
d. Take choke fully off.
e. Set throttle just above idle, flip until it starts, usually 3 to 5 flips.

RTK

My Feedback: (1)

Probably pulse, if it will run after a choke then it has to be the carb, make sure there are no obsturctions or clogs anywhere too. Sooarich gave a lot of good info.

pepito9

Thanks a lot will do as told today...

pepito9

I got the timing set, i suppose clockwise is from the front of the engine, meaning against running direction, what i don´t get is why when done clockwise the pop comes at 30º but if i go counter clockwise it pops at 15º

I see what hole needs plugging on the choke plate, i had my doubts at first but after trying to choke with no luck i stuck my finger into the air intake and gas started flowing hole found...

Still i got the same results as yesterday, so i took the carb from the engine but found two holes, both were plugged with sealant, so i took the plastic base out and found the right one, unfortunately tore the paper gasket in the process.

There was sealant on both sides of the base, covering both gaskets, is this necessary? i mean when i put it all together with new gaskets tomorrow i´ll need to be careful not to plug the hole again with sealant.

that´s how it is.

soarrich

My Feedback: (98)

The magnet is about 15* wide, but you just need it timed to run forward, so don't worry about the timing in the other direction.


I posted a picture, look into the carb throat, that's the hole soldiered closed on my choke plate.


I don't think you need any sealant with the gaskets.

Woody218

My Feedback: (24)

When you DO get it running, you will be impressed with just how smooth this little engine is! While it's not the most powerful 26cc I have run, it is without a doubt the smoothest running gasser I have!

pepito9

I got it running, the idle sucks and still dies at idle, if i keep it at 1/4 throttle and above it runs smoothly.
I suppose i have to break it in before doing all the adjustments you mention to the high and low needles right?
What RPM should i aim for breaking in for how long?

thanks

arobatx

Let the engine warm up, then tune it right away. Otherwise you are doing yourself no good at all during the break in period.

soarrich

My Feedback: (98)

No, I think you'll find if you do like I wrote at the end of the tuning it will idle well.
It's best to fly them to break them in, but if you must I'd run it at about 3000 rpm with the cowl off for 30 minutes, then go through 4 cycles of running at full power, then turning it off and letting it cool for 10 minutes, that helps stabilize the metal.

PS When tuning it block the prop blast from blowing across the carb, it affects the tuning.