hey all.

took the extra out for a flight yesterday as it was such a nice day,[8D] got everything set up, the first flight was great, nothing major just a few rolls, loops as this is only my second plane so being steady with it, anyway filled up for the second flight, started the engine, it idled then cut out, this went on for about 5 attemps, eventually got it running, got ready to take off and it lost power going down the runway, it took us another 5 or so attemps to get to go, adjusting the needle etc. anyway eventuall got it in the air only for it to go dead stick after about 2 mins. the engine is an os .61 and its only had about 7 flights on it since it was new, it was fine up untill last week when it did the same thing, the first flight is fine then it plays up. any ideas? maybe its overheating? as its fully cowelled but there is plenty cut away round the head and exhaust, tried a new plug, checked the pipes etc. dont fancy another dead stick landing.[]

you not only have to have airflow coming into the cowl...but airflow exiting the cowl as well..make sure you have an exit at the bottom of your cowling to ensure you have good flow through the cowl..also make sure the engine mixture isn't too lean. you should see a "smoke trail " in the air..adjust the high speed needle so the engine is at peak power by sound, if you lean anymore you hear the engine slow down. stop.. richen until its back to peak power and stop.now richen the needle a 1/4 turn.
hope this helps ya out

Fuel - is very important to an engine - - what type and what is in the fuel ... Caster oil ... is a must for 2 stroke engines.

What you are describing is an engine over heating and seizing up. [X(] [&o]

The reason could be air flow... as suggested make sure that the air can exit the cowl for proper cooling.

BUT!!! also make sure that you fuel has at least 18% caster oil (check the manufacturer's recomendations and compare them to your fuel's ratings).

This keeps the engine lubricated and cool and prevents seizing up.

On a cowled engine, you need an exit hole for the air. The air passing around and cooling the engine expands with the heat so you need a larger exhaust opening. The rule of thumb is your exit area needs to be at least twice the size of the inlet area.

ok thanks for the suggestions, ive been useing duraglo 5 fuel, not sure on the oil content with out looking, maybe i do need to enlarge the exit holes a bit, didnt want to cut the cowl up to much if possible as it looks really good..... but would definatly prefer an engine that keeps running as dead sticks are not my favourite way of landing, the cowel has the standard opening at the front, (ita a seagull extra 300s) and ive cut a large circle where where the head sticks out and cut around the exhaust at the bottom/side. looking at it it prob does need some more off it. thanks.

Huh? What's wrong with synthetic oil?

A statement born of lack of knowledge.

Ed S

hey all, took the plane out again last night, (wed) it ran perfectly for 3 flights, was starting to get a bit dark then so had to stop. anyway i cut some more out of the cowling from underneath and some more round the head, plus took the carb off and blew it out to make sure it wasnt clogged up, and it was perfect so hopefully thats curred it..... touch wood. i can hopefully get a load of flights in now before the nights draw in and the weather gets to cold. roll on sunday so i can go again.

You don't have to hack the cowl to get a larger exhaust opening.

You want the opening to be directly behind the engine. Air that goes into the cowl anywhere other than directly around the engine actually shoves the warm air out of the way. Cool air follows cool air and is easier to move than warm. So the cool simply finds the exits and keeps the warm from leaving. Put the opening behind the engine and some of that problem is solved. Take a wedge out of the corner of the fuse/firewall right behind the engine. Slap some scrap wood in to line the "tunnel", and paint it with epoxy. Make it extend just beyond the end of the cowl and it'll work like a vacuum cleaner.

If the engine is fairly new, you just might solve the problems by adjusting the low speed needle. Use the pinch method to check the idle whatever you do next. It's amazing how often a new engine starts to give problems after it's first outing or two and they go away after the low end is adjusted.

how will i know if the low speed needle is set right, when you pinch the pipe what should it do. sounds a bit obvious i know , but will it speed up first, die straight away etc. thanks for all your help.

The pinch test has been around for years doing excellent work for everyone who learns to do it.

With a warmed up engine, run it WOT to clear it out. Go to idle and let it settle out on it's own. Set the idle trim to get a low enough idle that the airplane will jsut sit there. And if you have to reset the trim, start over with the clearing out etc.

When it's idled 8-10-15seconds or so, pinch the fuel delivery hose up near the carb. Lots of guys use a hemostat or needlenose pliers to do this. Pinch and hold and listen.

If the engine speeds up and dies, the low speed was too rich. If it just suddenly dies, it was probably too lean.

Until you get some experience doing this, adjust the low speed needle just about 1/8 turn each change. Always test right after, and start from the WOT clearing out.

One detail I've seen overlooked is to verify that the carb actually has a low speed needle and isn't an airbleed carb. Airbleed is a bit more complex in how you change it's setting.

Airbleed carbs have a hole that lets air in on lower throttle settings to affect the mixture. Turning the screw that partially blocks the air hole can richen or lean the mixture depending on how far the screw is into the hole.

We had a guy spend almost an entire day driving himself nuts with an airbleed carb. He'd never heard of one. And almost refused to believe they existed in spite of the fact he owned one and was shown what and why. And they're actually easier to tell what their initial setting is 'cause the hole is right there in front of you and the screw position is easy to understand.

Usually when an engine dies like that specially at idle it is the plug, if not then i take out the high needle adjustments and turn the engine over to see if the fuel is comming out, it could be plugged, i have run into that a few times. Check all your lines for a pin hole will also do it. Good luck.