ABC engines have a universal break in procedure that works. Make sure that the engine is completely broken in before messing with the low speed setting.

For a .46, use a 9x6 prop...this will allow the engine to get into a 2 cycle scream without a huge heat build up.

Set the engine for wide open throttle and leave it that way for 2- 3 tank fulls of fuel.

With the nose of the model pointed up, bring the engine up quickly to peak rpm, then back the high speed needle down to the richest setting that allows the engine to run in a clean [but rich] 2 cycle scream. You don't want to hear any "4 cycle" blubbering. If you are using fuel with a significant castor content, there should be smoke billowing out. I add enough castor to a fresh jug of LHS fuel to top it completely off.

At this point, monitor the engine's rpm for any signs of sagging and periodically sample the exhaust spray with your finger. The idea is to see the spray clear with no signs of metal sloughing off [mainly the piston]. It is common for the engine to REQUIRE the needle to be opened up slightly during the break in because as the piston / liner fit becomes optimal, the fuel requirement will increase [more horsepower being developed]. Keep doing break in runs at full throttle and with the tank under the engine [not level with] until the needle setting stabilizes and the exhaust spray runs clear.

Now you are ready to play with the low end settings, the high speed will also be slightly effected by too much of a low speed correction, so bear that in mind. Always set the high speed with the nose of the plane pointed up.

Fuel that has absorbed more than 10% water will not run well and can be frozen, then the ice that forms at the top skimmed off. Fuel with up to about 10% water will run decently, this fact was presented in a magazine article years ago, I believe it was published in Model Aviation or RCM?