what is causing my hiccup?
04-23-2007, 09:30 PM
#1
Senior Member
Thread Starter
My Feedback: (52)
Join Date: Oct 2004
Location: Logan,
UT
Posts: 779
Likes: 0
Received 0 Likes
on
0 Posts
what is causing my hiccup?
My motor has been doing the occasional hiccup/cutout. heres my analysis:
It seems to do it when i am going vertical... doesn't have to be a hard G tho...
all other maneuvers seem fine and i haven't had it hiccup in any other maneuver... blenders, upside down whatever, hovering is fine.
it does it when its pointing about 45 degrees... usually on the way to the vertical line but not always
the motor has never quit due to the hiccup.
The motor seems to be running/tuned rather fine despite the hiccups... they only happen once or twice in a 13 minute flight. But they need to end...
oh and as far as where i am at on the throttle when it happends doesn't seem to matter... that is why i don't think its tuning but i'm not going to rule it out.
i did check the tank just 8-10 flights ago and it seemed fine. I also looked for airleaks.
any ideas? i'm trying to keep an open mind, not ruling out anything at this point.
It seems to do it when i am going vertical... doesn't have to be a hard G tho...
all other maneuvers seem fine and i haven't had it hiccup in any other maneuver... blenders, upside down whatever, hovering is fine.
it does it when its pointing about 45 degrees... usually on the way to the vertical line but not always
the motor has never quit due to the hiccup.
The motor seems to be running/tuned rather fine despite the hiccups... they only happen once or twice in a 13 minute flight. But they need to end...
oh and as far as where i am at on the throttle when it happends doesn't seem to matter... that is why i don't think its tuning but i'm not going to rule it out.
i did check the tank just 8-10 flights ago and it seemed fine. I also looked for airleaks.
any ideas? i'm trying to keep an open mind, not ruling out anything at this point.
04-23-2007, 09:34 PM
#2
Join Date: Jun 2006
Location: Glenview,
IL
Posts: 9,967
Likes: 0
Received 0 Likes
on
0 Posts
RE: what is causing my hiccup?
Try richening it a few clicks and check the return line form the muffler. There is quite a mixture change once you get up in the air as oppsed to the test run-up on the ground.
Good luck!
Good luck!
04-23-2007, 09:50 PM
#4
Join Date: Jun 2006
Location: Glenview,
IL
Posts: 9,967
Likes: 0
Received 0 Likes
on
0 Posts
RE: what is causing my hiccup?
ORIGINAL: erikpmort
low or high end, or both?
thats a good idea to check the return line, i haven't done that
low or high end, or both?
thats a good idea to check the return line, i haven't done that
The low is for throttle response, incidentally...how is the throttle response?
04-23-2007, 09:50 PM
#5
RE: what is causing my hiccup?
Lean the high end untill it sags and slows.
Richen it back up to max RPM and then richen it again--about 1/8th turn.
Fly it like that and see if it's still got a hicccup.
Ignition battery charged? Good heavy duty switch on the ignition? Good size battery on the ignition?
Spark plug lead loose on plug? Plug loose? Plug cap vibrating around on the plug? Bosch pug cap?--Maybe the hose clamp is loose?
Ground strap?
Plug fouled? Too rich?
Gas engines will surge up and down real fast when they are lean. It will surge up and down on the bench. It does it fast. I've never tached one lean like that--but I'd bet it's surging up and down 500RPM. Maybe just a teeny bitt too lean? Not enough to surge, but enough to make it heat up just a bit in the air?
Richen it back up to max RPM and then richen it again--about 1/8th turn.
Fly it like that and see if it's still got a hicccup.
Ignition battery charged? Good heavy duty switch on the ignition? Good size battery on the ignition?
Spark plug lead loose on plug? Plug loose? Plug cap vibrating around on the plug? Bosch pug cap?--Maybe the hose clamp is loose?
Ground strap?
Plug fouled? Too rich?
Gas engines will surge up and down real fast when they are lean. It will surge up and down on the bench. It does it fast. I've never tached one lean like that--but I'd bet it's surging up and down 500RPM. Maybe just a teeny bitt too lean? Not enough to surge, but enough to make it heat up just a bit in the air?
04-23-2007, 09:52 PM
#6
Join Date: Jun 2006
Location: Glenview,
IL
Posts: 9,967
Likes: 0
Received 0 Likes
on
0 Posts
RE: what is causing my hiccup?
ORIGINAL: Rcpilet
Lean the high end untill it sags and slows.
Richen it back up to max RPM and then richen it again--about 1/8th turn.
Fly it like that and see if it's still got a hicccup.
Ignition battery charged? Good heavy duty switch on the ignition? Good size battery on the ignition?
Spark plug lead loose on plug? Plug loose? Plug cap vibrating around on the plug? Bosch pug cap?--Maybe the hose clamp is loose?
Ground strap?
Plug fouled? Too rich?
Lean the high end untill it sags and slows.
Richen it back up to max RPM and then richen it again--about 1/8th turn.
Fly it like that and see if it's still got a hicccup.
Ignition battery charged? Good heavy duty switch on the ignition? Good size battery on the ignition?
Spark plug lead loose on plug? Plug loose? Plug cap vibrating around on the plug? Bosch pug cap?--Maybe the hose clamp is loose?
Ground strap?
Plug fouled? Too rich?
04-24-2007, 12:26 AM
#10
Junior Member
My Feedback: (1)
Join Date: Apr 2004
Location: Woodinville, WA
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
RE: what is causing my hiccup?
One area to check that can cause unusual and unpredictable engine stubles is sudden changes in carb inlet pressure. Sudden changes in aircraft attitude and direction can cause this. Do you have about 3x the exit area in the back or bottom of the cowl as the front inlet area? My BME 110 exhibited the same type of stumble in a large Katana until I opened the bottom of the cowl. This also works with glow engines. Good luck.
