two weekends in row, first flight problem.

[Zman39]

Hey Guys.

I thought it was a fluke last weekend but did same this weekend, here is what happened, any ideas welcome.
Last weekend I fired up the spectra with TRM and put it in a hover, seemed smooth sounded good so into FFF she went, on the second circuit I rolled her and when inverted the engine sounded like it was about to quit and then immediately came back to life as soon as she was back upright. I did it a few more times after that (with a little more altitude :) ) and it never did it again.
This weekend, I did the same thing, brought it up in hover, sounded good and put her in FFF and on the second or third circuit I slowed her down to do some flips. On first flip the engine did it again as soon as heli was inverted. it recovered as soon as upright and never did it again. Anyone have any ideas what might be going on? Is there some air sitting there from heli sitting during week. Both times I brought heli in and checked bulb and it was 98% full, just a few air bubbles sitting at top.

Thanks
Mike

[Peter]

yeah .. mine sometimes do that 1st flight of the day if i dont let the motor warm up a bit ..... now I do a minute or so of FFF , then let her rip !!! It's got to be a carby thing , I suppose , not much else to them !! maybe theres something that needs to fill up ?

[Zman39]

I was thinking next time, I would bring it up in a hover and warm it up and then spool it back down and turn throttle hold on and then physically turn the heli upside down and see if there is some air bubble that passes through???? not sure what else to try.


Mike

[rbort]

I see this alot and I have learned over the years many things:

a) ALWAYS do your first flip 200 feet up over the runway so if it quits during the flip you can complete the flip, regain rotor speed on the way down and land.

b) If you richen the mixture on the low end slightly, this seems to either reduce this "cough" or eliminate it. But sometimes the mixture might be too rich to fly around (that eliminates this) so its a balancing game. If you lean the low mixture too much, the cough becomes worst and could be a dead stick.

c) If you push the primer bulb several times before you start the engine after every refuel, this also seems to help either eliminate it or reduce these occurances.

d) Recently I found the stents clunk that is supplied with the kit to be restrictive in fuel flow (gets blocked after some time with certain conditions (read my post on RR about this). I changed over to a Walbro clunk which I feel is much better.

e) know that if it coughs/sucks a bubble or something on the first flip or two, once that is over with you are good for the rest of the flight. So always do a) above before trusting the machine to any low flips to avoid uncessary heartache.

f) waiting for it to warm up did not seem to help for me. I've flown around level before for a few minutes but then when I went for my first flip it did cough in some occassion. It doesn't always do it, but the point here is that warmup didn't seem to fix it when it was going to do it.

-=>Raja.

[ka6fty]

I've always found it does it when the carb is previously run dry. I don't defuel or run the engine out of fuel at the end of the day and it never does this unless I run it out.