I have a saito 180 on a caps 231 ex, with an apc 18-6 wide prop, and I'm using omega 4-stroke fuel, and I believe my high and low side are getting close, do you think its the valves needing adjusting, or what???HELP!!!

Hey Knees, have you used a tach to set your high end needle? If not, that may be your problem, too lean. Buy, borrow a tach and adjust the high end to max rpm and richen it until you get about a 300-400 rpm drop and see if that helps. A new plug may be needed too. I don't think the valve adjustment would cause backfiring, unless you had a tight one. Of coarse it wouldn't hurt to check them anyway. Anyone else have any ideas that may help?

Close ! your too lean , not very often would you look to the valves as a cause as Suptter said.
The only time I have gotten a backfire on any of my Saito's was they were too lean MY FAULT.
Another thing is to look at amybe the prop size 18/6W is about the top of the prop list .
I have had a backfire with a prop on the big side of the engine range on spool down (CHOP Throttle) BANG! a heavy prop and leanish condition will do that too.

Use a Tach



Den

It's not always lean on top end that causes a backfire. Mine seem to be more prone to backfire comming up off idle.

You can have a lean idle and it will idle all day but if you jam the throttle up, it will pop and it's all over.

Play with your engine some and enrichen the idle a little. You may have to run your trim up some to keep it idling?

Also bring your throttle up slowly to keep back fires down.

Good luck,

Jim

Thanks guys lots of help...I was in a hurry to get a flight in after putting on that new prop, didn't tach it ,but, still backfired even with a smaller prop...But I got the same info on the 300-400 rpm richer on the high side after peak rpm...I'll try that next time for sure...Thanks again...Knees