I have noticed that my newly acquired 3W bogs when it's flying. The throttle response is slow and unresponsive. I know its not the throttle cable binding because the engine works fine on the ground. I don't have a fuel pump installed and I am running 40:1 fuel mixture. Any recommends on how I can improve engine performance without taking too much of a toll on the engine itself? Anyone have any good procedures on how to tune a gasoline engine? I'm new to the gasoline world.

3W engines need a long running in period, in which you normally should not ask full power for so long that the engine bogs down. This is a sign of engine distress.
Check your cooling (baffling, air extraction) Also check that the carb is in cool air all the time.
I have some notes on www.prme.nl/forum which may help you get going.

what do u mean by a long running in period? As in warming up before flight? Or break in?

Bogs or sags?

Bog is usually slow acceleration, sagging is slowing down from Max rpm, two different things, two different causes.

The engine is either not fully broken in or is running hot

Or not tuned.

soarrich - slow acceleration. <div>
</div><div>w8ye - running hot might be possible although i seem to doubt it considering the cowling design nor would it be not fully broken in because it is an older engine.</div><div>
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tired old man - thats one of my considerations is the tuning. apparently its tuned to run on the richer side to protect the engine according to the previous owner. whats a good mix for oil? I was told 40:1 of Amsoil Saber 100:1 premix.<div>
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maybe you should richen the high end a bit

OK, it sounds like it's not tuned properly.

Try this even though it's how I do Walbro carbs, I tuned my 3W75 this way and it works on them too.

OK, that sounds like the idle is rich. This is how I would tune it, or any gas engine with a Walbro carburetor.

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.

Switch to Pennzoil 32:1 your engine will last forever.

Before and after pictures of choke plate modified, shouldn't take more than 15 minutes.

Hm...
Learned a new english word generic meaning today.
I thought the two were:
"bog down" (reduces rpm by too much load)
"sag" reduces rpm at constant load

That's OK, you speak better American than we speak Dutch.Colloquialisms are tough to master, and forever changing.

This bog was more like when a drag racer puts too big of a carb on an engine, the engine bogs down when it's given gas quickly. They said the only thing that separates us from the English is we speak a different language.

Book needle settings for my 110 are way too rich! It ran but even better now that it is tuned. As for running hot, make sure it is properly baffled. My inflight temps dropped 70 degrees from proper baffling.

Book needling is to get the engine running. Not more, not less. It is impossible to set a carb by the book and account for engine deviations, carb deviations, propeller load inflicted by the user, and altitude.
Every engine needs to be jetted to suit the engine and use. Tweek the needles until the engine can deliver what it is capable of. That means set the idle and high for good transition and max rpm. Then balance the needles by tweeking them little by little.
You will find that leaner idle needs a bit opening of the High, and vice versa.
Final say is by reading the plug and piston colors, better still EGT (exhaust gas temperatures), but that is beyond mine, and most of our shop equipment. I do have a wish list, And EGT measurement scores high!

will it make a difference if i tune the engine with the cowling on versus off? I have to tune it with it off because I cant reach the carb while it's running. I would assume that the temp readings would need to be taken with it on though.

The cowling many times makes a difference, so does the airflow around the plane once it flies in different attitudes.
Coolingwise, it is best to run the engine with the cowl on, IF you have provided for baffles and air extraction (that is not just a big hole)

It will make some difference, but you can get close, then fine tune after every flight. I put tubing on the needles to make mine adjustable while running, it helped some.

I like the tubing idea! You can make adjustments by turning the tubing further away from the prop?

Yes.

thanks guys for the tips! I got it running alot better now. those needles are damn close to the prop i tell ya lol.

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