I have an O.S. 46 LA motor and It surges on the ground and when I raise and lower the throttle it transitions very poorly and it will die if I open it up too fast.. The last time I flew it when it was doing this and I had the throttle open all the way but the engine was only going about half throttle. It ended up dying and I had to do a deadstick landing.

It sounds like the idle mixture is tto rich. Try leaning it out slowly in 1/8 turn adjustments. Make sure to do this with the engine not running to keep your hands out of the prop. the idle misture screw is inside the rotating portion of the throttle barrel opposite the high speed needle.

I agree with Bruce and think your mid range mixture control needs to be leaned a tad. The LA series engines do not use a second needle type in the throttle barrel though. The mid range for your engine is a hole drilled directly in front of the carb facing the prop and extending to the right side or straight up Can,t remember which, is a screw that opens this hole and allows air to be pulled in and bleed directly into the venturi. With this type mid range adjustment is opposite of the more common second needle arrangement. In other words to make the midrange leaner during the transition you would unscrew this little screw (counter clockwise). The bleeder types are a little less responsive to adjustment and therefore you can use a little more turn during each adjustment, maybe a quarter turn. This is one reason in addition to being less expensive that they are used in some beginers engines, they are little easier to get a usable tranistion.

In regards to getting good RPM at high throttle there are lots of factors could be as simple as an inappropriate prop size or perhaps you are not getting a good main needle valve setting. This is common when folks are first learning to operate these remarkable little power plants especially if they are getting no experianced help. If that is the case I would strongly suggest you get some experianced help as learning to properly adjust these little engines an experianced ear is important and not something you are likely to learn by just reading forums or instruction.

John

DP

You're right John, I forgot that was a bleed air carb. Thanks for the correction.

In addition to the advice you've already received about tuning the low end, it's important to remember that idle adjustments cannot be done until you've got the high speed needle set correctly.

Aye Matey's 'Teamwork'

I went out and flew today and I adjusted the low end a little at a time and I got higher rpms and the engine quit surging after about 3 full turns. I flew around for about 10 minutes and I could hear it start to surge again so I landed. After reading John's post I realized that when I thought I was making the low end leaner I was actually making it richer. I was tightening the screw without thinking about it which made it richer. I'll try to lean it up tomorrow and see if I can get it to work. Thanks for the help.

I actually made it just a little bit richer again and it worked great. I made an entire flight without it surging. It still doesn't sound as loud as it used to but maybe it's just me. I still might have to fine-tune the high-speed needle a bit.