Fairly new to this game just started flyin 9months ago, i've had this engine from the start. A problem arose about a month ago, when i set the needle valve on the ground and then hold my model verticle the engine dies after 5-10 seconds. Now if i adjust the needle when its verticle and get it running o.k, when the model is back horizontal its way too rich. I've checked my tank and piping several times and its fine! Can anyone help me?

Your difficulty indicates a problem with fuel flow. You'll need to check yoru fuel tank to make sure that the fuel pickup isn't in the front of the tank and becoming unported when you hold the model nose-up. That's the most likely difficulty. Another would be that there is a restriction in the fuel line or vent line that prevents proper fuel flow. Holding the model nose-up causes reduced fuel pressure due to gravity, and the the engine now leans and dies.

If the engine will run "all day" horizontally, then there's nothing wrong with the engine, itself. The problem is in the engine/airframe/fuel system combination.

Hi There,
Initial settup is horizontal, with the centre line of the tank running in line with the needle valve. Then as was previously mentioned, Tune the engine for a tad rich, horizontally on the ground. Then lift the nose to vertical slowly and note the engine pitch (sound). It should speed up slightly as you begin. If it cuts out again as the vertical approaches it means the suction at the needle valve in the carby is not good enough to overcome the change in level of the fuel as the tank drops behind the engine. You may have a problem with the tank being too far to the rear of the model, making the fuel level even lower with the nose up. If not that, and if you run muffler pressure, you may have a severe leak in the pressure line. The golden rule is to keep the tank as close to the engine as possible and not to high or low horizontaly. Engines today are biult with very wide choke diameters (Improving Power Output) this reduces the airspeed passing the spraybar in the carby and hence the suction on the fuel supply. (This is why most modellers resort to exhaust pressure feeds). I keep clear of them myself, being an oldie Ha..

Thanks for the reply Bill but i've already checked the fuel intake and its fine! I don't believe theres anything wrong with the engine either cause it will run all day horizontally, untill i go to attempt a prop hang. I've checked my tank and pipes so often now that i just can't understand where the problem lies. Cheers anyway....

philip053,
Have you checked the tubing that goes from the fuel tank stopper to the clunk? If this hose has so much as a pin hole, it could cause the fuel to not be sucked through it especially when vertical. It may be submerged in the fuel when horizontal but when vertical it may surface out from the fuel and cause the engine to stop. It may not even be visible to the eye, ask me how I know this... I had a similar problem and it ended up to be a tiny hole in the clunk tubing. When you point the plane vertical, does the engine speed up just before shutting off? Hope this helps...

philip053,
Have you checked the tubing that goes from the fuel tank stopper to the clunk? If this hose has so much as a pin hole, it could cause the fuel to not be sucked through it especially when vertical. It may be submerged in the fuel when horizontal but when vertical it may surface out from the fuel and cause the engine to stop. It may not even be visible to the eye, ask me how I know this... I had a similar problem and it ended up to be a tiny hole in the clunk tubing. When you point the plane vertical, does the engine speed up just before shutting off? Hope this helps...