gcoron Posted July 29, 2017 Share Posted July 29, 2017 Any clues for me? I have a Black Hawk w/corsair 175 M25Y engine that has ~40 hrs on it. (It sat idle in a hanger for quite a few yrs before I bought it from a friend).It used to consistently reach max rpm of ~7800 on the ground & ~7400 airborne. It has recently started having problems getting above ~6200 before it starts sputtering, but it will get up to ~7400 after a few minutes airborne. Some background: ~6 engine hrs ago it became hard to start and would sputter & die if I even tried to throttle up from idle, so I put in a new plug NGK BR9ES, overhauled the carb WB (found some litter in the screen). I have always used the all black fuel pump diaphragm but this time I followed advice from Alex Varv's web-page and used the tan/clear diaphragm... And everything seemed fine for a few flights (~2 engine hrs) but the sputtering came back. Then I discovered that he spark plug cap/boot was bad so I replaced that, and now the last 2 flights I am having problems reaching 7800rpm after warmup before launch. I am thinking I should install the old style black fuel pump diaphragm first and go from there. Other notes: Under plug CHT has shown no more than ~380F max during any of this. I warm my engine up to ~200F before all run ups or launches. Thanks! Greg C. in Va. Quote Link to comment Share on other sites More sharing options...
Casper Posted July 29, 2017 Share Posted July 29, 2017 Remove the CHT, you might have a leak there. Quote Link to comment Share on other sites More sharing options...
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