alticrashi

i have a .91 4 stroke engine mounted inverted.-needle valve about 1" below the c/l of the tank.am using a dubro quick fuelling valve. i cannot change the position of engine or tank. when i try to start it ,it kicks back and knocks the prop loose. can anyone tell me the problem?

Sport_Pilot

Kicking back the starter is usually a problem of being over lean. The plane in my avitar had a simi inverted engine and the needle was about 1/2 inch below the tank. It would not siphon because it was a tail dragger, however it did have the problem of going from rich to lean during the flight. I simply switched the tank to a uniflow setup and it cured that problem. With the tank that far below and siphoning I would consider either the Cline or Iron Bay regulator.

MinnFlyer

My Feedback: (4)

Try flipping it backward - this often causes the engine to kick back and run the right way

John 38

With the highish tank level, engine may be getting quite wet before you even turn it over, which should make it even easier to start. However, if it is too wet and/or your throttle opening is more than just idle, then pre-ignition and resultant back start is almost certain to happen.

flicking backwards is a favourite way to start and also to overcome this. I also hand flip over several times before connecting plug to clear any excess wetting - ie flooding - before I use starter, to avoid bending conrod.

trust this is usefull

John

warhwk

My Feedback: (3)

It sounds like you are Hydro-Locking the engine with too much fuel. This will cause the piston to lock and the spinner to come loose. ALWAYS turn over a 4-stroke by hand first and make sure it turns before using an electric starter or even a "chicken-stick"

If this is the case, remove the glow plug and remove the exces fuel

John 38

On an inverted engine , if flooded it wont fire or backfire as the plug is under fuel and not hot enough.

The backfire can throw the prop as the sudden reversal of rotation can be enough to shock the prop nut(s) loose.

This is why modern 4 stroke now come with locking nuts, almost but not quite foolproof as even then a strong backfire can still shock them loose.

It is also why safe practice is never to stand at the side in line with the prop when someone is starting their engine, particularly 4 strokes

John

rc-sport

My Feedback: (12)

Close your throttle to an idle position when you start it

pc55bomber

I had this problem with my PT 26 and eventually solved it by changing to the Uniflow tank system.
Its all to do with atmospheric pressure. Look here http://www.fraserker.com/heli/uniflo...flow_works.htm
and here is a thread on the subject. http://www.rcuniverse.com/forum/m_31...tm.htm#3131525

Cheers
Paul

rclement

My Feedback: (1)

I've been running a Saito 82 inverted on a U Can Do for a couple of years now and it works great for me. Here's what I do. I prime the engine, for the first run of the day, by opening the throttle about 1/2 way. Then I put my thumb over the carb and crank the engine over with my starter. I then close the throttle down to idle and put the glow driver and starter on and it fires right up. After the first run of the day I just put the glow driver on and fire it up. Hope that helps.

John 38

Rob,

my starting procedure for my inverted Saito 90 is exactly same as yours.

word of advice - dont forget to close down to idle - I forgot one day and with the throttle almost full open, I had the grand-daddy of backfires which seperated the bulkhead from the plane and shocked the main bearings necessitating an engine dismantle to replace all bearings. fortunately all repaired well and engine still purring along as Saito's do

John