Saito FA-180 Gas conversion IDLE PROBLEM
 

Hoping someone may be able to give me some advice, I had completed my Saito 180 conversion last week, installed ignition system and gas carb conversion. I am still running it on the ground was running it today to get it ready to go fly it for the first time and I have developed a problem. I have previously ran this engine about 20 times, over a tank of gas, had a good steady Idle about 1550-1600 RPMS, good transition, and good full throttle about 7500 with a 16x10x3 prop. The problem just started happening ,What it is doing is at idle, I rev it, and then when I bring it backdown it will Idle Erraticly, mostly it will idle really high, and kind of surge, I can move the throttle up and back real quick and it will come down for a second then go right back to a really high Idle, I can try to bring the idle down,using the radio to a reasonble setting and it will Die, ,I will have to choke it to get it started again, then get it running, and it will do the same thing, only I will have to change the radio settings again to get it running and the Idle will be really High again. I removed the carb thinking I may have an air leak, I made all new (3) gaskets for between the carb and block, as well as the intake tube to adapter plate. Put it together, and Still the same problem, I cleaned the area where the tube goes into the head, same problem, I thought maybe its the servo, in the plane, I replaced the servo, same problem. I am running the same fuel, same prop, full battery, not sure what could have changed?? I had the needles perfect, not sure how anything could have changed, I have tried retuning with the needles, and no amount of adjustment on the needles will settle the idle down. Any advice of what else to check I would definately appreciate it. My next idea is to get it running and spray a little starting fluid around the intake tube and carb, maybe even where the head is bolted to the crankase, and see if there may be an air leak? Not sure what else to check??

Regulator diaphragm in the carb may have gone stiff?

Ok, so here is where I am, I have removed the carb, dis-assembled, cleaned every port out with carb cleaner, the screen was spotless. diaphragm and fuel pump still like new. put it back together, made new gaskets for carb mounting, put back on the engine, does the very same thing. So I went to plan B,,, I have 2 180s, I am putting in a B25. I grabbed the other 180, mounted it up, Put the conversion kit on it, timed it at 30degrees (BTW the timing ring had not moved on the first engine) I got it all hooked up, primed and within a couple flips this engine was running, warmed up, same exact problem. Now I know this is either a carb issue, or perhaps the plug? tested ignition with my tester, its working good. I am stumped, the thing that fools me the most is this was running perfect until a few days ago.

Check them out with newly mixed gas, I have had similar problems with gas that has been old or gotten water in it.
Larry