Starting difficulties
 

Hi everyone....its me again asking about my TT F-75S

Since it is my first 4 stroke I don't know if it is normal....

I have the engine mounted about 135 degrees, the engine is cowled, and I can't prime it properly, what I do is open throttle, block the exhaust and flip, or I blow a little through the line where I fill the tank, blocking also the exhaust... if the engine is cold...first start of the day, I can start it with a back flip, it starts always.

But if the engine is warm...I have to tinker with it a considerable amount of time to get it started... (if I can't borrow a starter from the collegues...). When I prime it again it will always start backwars (when it fires at all), no matter if with a back flip, or cranking it cw....ccw is quite dangerous (I use a stick or the grip of a big screwdriver) because the engine is always violent! I even damaged a propeller...

So if I don't have a starter handy...it's quite impossible to get it run! It wil start backwards...if I give throttle...it will throttle backwards, quit funny indeed, but also dangerous... the problem is that I don't know how to fly the plane backwards and I don't want to fly just the propeller (hard to get the servos there eh!)

Yesterday at the field, for the first flight, I could start the engine with the back flip at the first try, headed and the plane went on his nose...it took me about 10 minutes to start it again...I waited and let it cool...but erghhhhh

With a starter it works instantly...but I don't have one yet, and I don't know when I'm going to get one....and personally, I like to start the engines by hand as they suffer much more less...

The engine runs fine, everything is just ok... but I was wondering if there is something to look at? valve clearance (backwards) ....
Fuel is ok...I misched it about 2 weeks ago 15% Molsyn 150k, 3% castor and 10% nitro (it works super!), plug is o.s F...

I appreciate any inputs/suggestions


Saludos,

Jorge

RE: Starting difficulties
 

Sounds like you have two items;
A slightly over-compressed engine, and a prop that is too small for the engine, providing too little flywheel mass.
add a gasket under the cylinder foot, readjust valve clearance and fit a larger, heavier prop. Maybe cut down on nitro content as well.

RE: Starting difficulties
 

The TT F-75S has a typical compression ratio comparable to OS and Magnum. Be careful priming in that position as you may end up with too much fuel in the cylinder. Running backwards is a sure sign of being wet or having fuel in the muffler. Violent kickbacks when hot are usually due to over priming and a slow flipping action.