O.S 46 AX problems
 

I'm currently trying to break in my new O.S 46 AX in my boomerang trainer and i have run into some problems. I opened the needle to the starting position in the manual (1 1/2 - 2 turns open) and it started just fine until it suddenly stopped after using about 1/4 of a tank of fuel, so i tried starting it again but now for some reason when it starts it starts revving up and down like I'm moving my throttle up and down (but I'm not touching my throttle at all) until it just stops all together and it just keeps doing it every time i start it.. i have made sure its not flooded and it is getting fuel so I'm not sure whats wrong. This is only my second glow engine, so i don't really know much about them[&:].

RE: O.S 46 AX problems
 

Oops, made a mistake - my bigger AX says 2.5 to 3 turns open, 46AX says 1.5 to 2 turns open.

Make sure you are two FULL turns open, and not two 'half turns' open; common mistake.

Sounds to me like it's starving for fuel assuming it's going down to almost quitting. Is it a gradual increase and decrease in RPM, or is it going from WOT to almost dying and back up again?. Check your fuel lines, including the ones in the tank, make sure the clunk is free in the tank, etc.

RE: O.S 46 AX problems
 

Firstly this up and down reving is a sign of the engine running [ too lean ] so don,t run the engine until you have checked and done the following; is the fuel tank vent pipes and main feed clunk set up correctly ? check to make sure there are no air leaks in the fuel tank stopper cap as well as the fuel lines where they meet the fuel tank, tip [ block off all vent lines and blow into one only line to see if the tank builds up in pressure ] if you have only 2 lines which is 1 for carby and 1 for pipe pressure make sure you re attach the fuel line to the muffler pipe before starting and if you have 3 lines make sure the third line is also blocked off when starting and running. if all is fine with the above its time to look at the Carby, disconnect both lines from the remote needle valve to fuel tank and remote needle to carby then take the needle valve out completely, with some spare fuel tube connect this to the remote needle unit and blow through to make sure any crap is dislodged also do this to where the needle valve goes. now open the carby to wide open position and connect the spare fuel; line to the carby and blow through as before, if all seems clear re-connect all fuel lines and re fit the remote needle valve by screwing it all the way in [ but not tight ] then back out this needle to 2 & 1/2 turns [ not 2 turns ] now its time to re start the engine; fill up the fuel tank [ with good fresh fuel ] open the throttle to full with radio on and flick the prop over a couple of times only whilst having a finger covering the carby vent, now bring the radio stick back so the carby barrel is only open about 1/16 to 1/8 th of an inch max. now fit the glow plug starter and start up the engine, let the engine warm for about 45 seconds then open up the throttle to full and go from there with the recommended run in specs that you have in the O.S. booklet. i am sure you won,t have any problems with this fantastic engine, take your time.

RE: O.S 46 AX problems
 

Thanks both of you for your replies. Silly me, i was using the line with the clunk on it to fill it up with fuel.. and the line i am SUPPOSED to be using to fill it with fuel on the engine... oops, i have swapped them back over now and i just successfully ran a full tank through using the run in instructions in the manual. I am very pleased with this engine as it is extremly quiet and blows no smoke at all (is that normal?). Anyway, thanks again.

RE: O.S 46 AX problems
 

it would be nice to see some smoke blow coming from this new engine whilst running in also make sure theres heaps of oil splatter coming from the pipe outlet. keep you fuel mixture at 20% oil plus its good to use an oil mix of 50 - 50 meaning half synthetic and half castor. a couple of slight mods you should do to the great Boomerang trainer is fit larger diameter wheels , replace the rear undercarriage with a Dubro fibreglass type and glue in a support block inside the fuselage to where the steering cable outer tube runs from bulkhead number 2 to the rudder servo, the distance between these 2 points causes too much slop in the cable which makes taxi steering with the front wheel more difficult, the block wedge provides great support.

RE: O.S 46 AX problems
 

There definitely is a lot of oil splatter coming from the pipe, the whole right side of the fuselage was completely coated in oil after the first tank and i had to mop it up with a rag. As for my fuel mixture, I'm just using the fuel my local hobby shop recommended i use (which i don't have with me at the moment but i think its Glo-Max R/C 5% or something?). And i will definitely put that support block inside my fuselage for my nose wheel steering as it only turns well one way, because of the slop in the cable.

RE: O.S 46 AX problems
 

A good way to check that you are not too lean is to very briefly pinch the fuel line to the carb - pinch and release. You should hear an increase in RPM when you pinch the line for a split second. If the engine just sounds like it wants to die you are too lean.

RE: O.S 46 AX problems
 

While people talk about smoke from their engines, it's really a function of the type of oil in the fuel, the amount of oil in the fuel, and the mixture setting on the engine. Some fuels will smoke a lot when the engine's properly-set, other fuels will not. You cannot rely on the amount of smoke exhausted to determine if your engine's properly-set. You must listen to it and/or tach it. You want the engine running rich of peak RPM.

Oil emitted from the exhaust port or pipe on the muffler can land on the model, and it's normal for the model to get quite a lot of fuel on it, depending upon the location of the exhaust outlet. Adding a diverter to the the outlet may reduce the oil on the model, but it may also induce overheating of the engine, because a diverter adds a little bit of back-pressure, and it can be just enough to encourage overheating. You can only find this out by trying the diverter.

Just carry rags or other types of wipes to remove the oil that accumulates on the model. If you fly glow, this is a normal thing.