Small bubbles in the line from the regulator to the carb can be a normal. These are not always a concern. What happens is the line into the regulator is under pressure. About 6-8psi. When the fuel gets past the regulator and in the line to the carb its no longer under this higher pressure. The resulting expansion can make a tiny tiny bubble from a foamy fuel tank bigger and you will see it.

This doesn't always mean that your engine is not working properly. However if you have a leak then lots of bubbles can be in this line and this is not good.

Small bubbles by themselves are not an issue. If the engine is running properly then usually some small bubbles can be seen in this line...Not always and it usually has to do with your fuel tank setup and if you are getting foaming issues because the tank is vibrating.

If the engine is running a little lean on the low end this can happen. try to richen it slightly to where it wants to load up just a little on the first start up. This will affect you taxi and idle when the engine is cold. It takes a few minutes to get up to temps. If your idle is perfect from a cold start its likely slightly lean. A lean condition like this can ruin a glow plug in the first run. So 10 flights well....these engines don't use spark plugs like in your car. The plugs can be fragile and sometimes you can get one that is not right out of the package. Its rare but happens. I have seen running the engine out of fuel in the air destroy a brand new plug in the first flight.

This goes for any glow engine and is not really specific to the YS...however all 4 strokes tend to be a little more critical on glow plug performance. Just because it glows doesn't mean its good. It like my father in law says about tires. All it has to do is hold air and roll......yep that makes it a tire...but you don't put that tire on your Ford Expedition and hit the highway at 70-mph. YS engines are high performance engines. They can sometimes be finicky about glow plugs...it depends on your choice of fuel, prop and environment. Usually the higher the nitro you run the less critical all these little things become. Try to do it on 15% and you will have to have things right on the money. Throw some 30% heli in it and since everything is now get adjusted richer the settings are much less critical, and the abuse on glow plugs and so on is less

Troy Newman
Team YS