Hi all. New guy here. I'm having problem with and older Ryobi 790r string trimmer. Amazingly this trimmer has been trouble free for many years but this year have been having trouble keeping the engine running. I rebuilt the carburetor and have been trying to get the jets tuned right. This is an older model which has access to the jets without a special tool. After the rebuild, I was able to get it started but it would not start with the original jet settings after removing the screws, cleaning, and setting them back to the original settings. Again this was a complete teardown of the carb with thorough cleaning and new gaskets, needle valve, etc. So I started from the beginning with the normal procedure of backing the High and low jets off 2 turns and then adjusting the low jet at idle and then the high. I've gone through this procedure several times and seem to get it running well for about 10 minutes, but then it starts to have problems bogging down when I hit the throttle, and stalls. I am able to start it again at idle, but again can't get it to throttle up without bogging. After about 5 minutes more, I can't get it started at all. If I let it sit for an hour or so, it will start but the same thing will happen after it warms up again. Wondering if you all think this is an ignition coil problem or what. Thanks for your input.