ASP 120 4 str Not playing ball!

Well, rather than going to the slope I decided to stay at home in the cold drive and get the ME109 engine running. Wished I had gone sloping!

The new engine starts okay but will not pick up from idle or maybe a little fast idle. Runs for a half a minute and stops. I have fiddled and flicked till I was tempted to go into the garage and find the original 90 2 str and stick it back in. But I don't want to succumb to defeat yet. The reason for a four stroke was for scale effect and the fact that when the 2 str was in I had to start it with the model inverted

I tried walking away for a break and a cup of tea but this didn't help either.

Any thoughts and things I may have missed?

My ASP 70 FS took ages and a lot of input from others before finally I had an engine that worked. I spent weeks starting the model at the field, with it cutting on me when I throttled up.

The idle screw was the culprit. It went in about 2.5 turns from as delivered state and is very very sensitive.

One bit of advice I was given was how to set the idle initially. Take off the fuel feed to the carb and replace with a short length of clean pipe. Then, with the needle valve closed, blow into the fresh pipe and adjust the idle crew until it is just letting air through. It won't be right, but it will run. You can then tune it to get reliable running.

Later on, after many flights without engine problems, I couldn't start it at all. I replaced all the pipes and found that the one connected to the silencer was blocked with exhaust muck at he silencer nipple. A new pipe cured that.

Only had these problems with the ASP.

I have done most of what you have suggested. I took the engine back out of the me109 and mounted it on my test bed. Not ideal as it really suits two strokes and their carb faces a upwards. Four stroke will be pointing down so choking it is not that easy at all. Got it running at a fast idle for about a minute or so but it died before I could tweak it. I have to keep turning the engine upside down to get fuel into the manifold. Getting covered in it too! Light failing so gave up for now.

You just know you have crap engine from day one!

However, where it has been running the compression has come up well so the ring has started to bed in.

Might have stick it back in the me109 to play with it unless someone has a jig for four strokes.

In future I am sticking with electric, less fuss and clean

Have found an old thread regarding these ASPs and the factory jet settings are: low 4 1/2 turns in from fully out. High is: 2 1/2 turns from closed. That's a starting point at least (excuse the pun) I'll have another go maybe tomorrow.

Here it is so far. Blowing down exhaust pressure line I can get fuel pouring out of carb line. Put a few drops of fuel down carb mouth and it'll fire and run for few seconds, probably the fuel chucked down the carb. Next, I opened throttle fully and again blew down exhaust line expecting to see fuel going down carb venturi. Nothing!

I am wondering if the carb needle is actually moving with the barrel?

Hi Phil

I have had this happen several times and the problem was always hair strands in the carb and jets - these can be very difficult to see, even with a x9 eyeglass.
As a matter of course, I always strip the carb and blow out the jets with compressed air if an engine keeps cutting out unexpectedly.

Ron