Octane of gas doesn’t create that much of an issue unless its been sitting for a long while. 86+ octane will be fine if used up within a couple weeks/months.
100% check the gap on plugs… manufacturers have gotten really lax on this over the last decase. If they aren’t gapped right that will be why you are getting unburned fuel passing though the carb and getting popping in the exhaust.
Your carb should have a adjustment screw… run the engine, throttle all the way down and adjust the carb so that the RPM is consistently running at 1400 +/- 150. Once thats set the carb will be running the proper fuel/air mix. Now you can throttle up and adjust the pin on the governor spring to max out at 3600RPM.
I picked up some stabil maybe will put some in the tank I drained the high grade regular and put ethanol free in the tank yesterday
I checked the plugs they are a little closer than the old ones but they’re .25in Not sure how to adjust valves
Not sure how to check rpm’s
The gas was setting about 2 weeks until yesterday I changed to Rec 90 and ran it for awhile it was still backfiring but mainly while in bypass. It does surge though at low idle. And while I’m actually going into bypass there’s a surge there too almost like it’s bogging a little. I have doubts about the quality of gas as it said “not a chevron product” on the rec 90 that I got. Not sure how to check rpm’s if there’s a gauge for that. As far as the plugs they looked brownish and were at .25 in. when I checked them.
From the owners manual .028 - .031 on the plug gap for gx630 - gx690. I aim for .028 as the gap will increase with use. Valve adjustment is probably a YouTube video away. They slowly stretch with heat and time, decreasing valve clearance.
I went ahead yesterday and changed the gap on the plugs. I brought it to somewhere between .012-.016 I ran the machine for about 10-15 minutes w/50 ft. of hose and it ran well only one or two quiet pops. Not firecrackers like before. HOWEVER, when I got to the job I had today and fired up the machine then it started popping as bad as before. Terrible sound. On top of that I forgot to take off my muffler extension and this happened (see pics) I almost blew up the whole machine but I ended up finishing the job at about 60-70% throttle because there it wasn’t backfiring. The backfiring is only in bypass when running about full power or just below.
Adjust your valves every 300 hours. Maintenance is much easier than troubleshooting. .028 - .031 is what the paper manual that came in the box specifies.
