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MVVS .45 break-in/tuning problem

Old 03-10-2007, 11:46 AM
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Default MVVS .45 break-in/tuning problem


I've just bought a MVVS .45 engine second hand from a fellow flyer..allegedly he has only used the engine for two flights and then quit, having recently changed from flying fixed-wings to helis. I've fitted it on my 1st ever RCM Trainer 40. As the engine comes with a tuned pipe rather than a 1st, I was a bit worried, thought the engine was too overpowered for my trainer. However, after my maiden flight last seems to be alright, after all, a bit more power doesnt hurt when i need it, does it?

anyway, that is not the problem..the problem I'm having is that the engine does not seem to be tuned right..for prior to takeoff, when I'm 'heating up' the engine, the engine dies quite a lot of times whenever I throttle up and just revs up..and dies. My instructor would normally then fiddle with the needle, find the most suitable mixture and once the engine is running nice (kinda, it still sputters a little bit)...takeoffs. he would then hand me the controls, I'd fly around for a couple of minutes..and then more often than not, I'd get a deadstick before it's time to land. lucky for me, the plane glides so well. =)

subsequently, I cleaned the carb..then borrowed a Rossi plug from a friend..after which the engine seems to be a little bit better, but not much. i still got a deadstick after that. my instructor has told me that the engine has not been properly broken-in yet, since the previous owner used it so seldomly and then let it sit for such a long time. my instructor said that it would take at least 2 gallons of fuel before the engine would perform & run normally. i'm running a 0% fuel.

someone on the RCU forums has suggested to me that the problem occurs because I have mounted the engine upright, making the fuel tank position too low in relation to the engine. he suggested that it be mounted sideways instead.

could this be the possible cause of my engine problems? the thing is, the only way i can mount the engine sideways is by cutting the nose part of the fuselage a little bit, and I'd hate to do this. hehe..see the attached pic.

can anyone help me with this? its really beginning to put the fun out of flying..having to deal with an engine that keeps dying on me. does this problem occur in all MVVS engines..or is this an isolated case?and if so..what is the solution?
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Old 03-10-2007, 12:09 PM
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Default RE: MVVS .45 break-in/tuning problem


Although the engine is mounted a little low, in relation to the fuel tank (the middle of the carburettor barrel should be at the same height as the tank's center-line), it should have no problems running as it is in a trainer.

The problem I see immediately is the fuel line, which is about 10 cm too long.
Cut the excess, so it will just reach the fuel nipple...

Also, has the nozzle been loosened? The nipple must be nearly horizontal.

Once the engine has accumulated a few hours of running time, it should be dead reliable; not dead-sticking.
Old 03-10-2007, 05:09 PM
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Default RE: MVVS .45 break-in/tuning problem

Me too, cut the overly long line, put a filter in and never detach the filtered part from the spraybar.
I further suspect a small sliver of debris to be present in the spraybar. Take out the needle, and use a well fitting dril to clean out the needle chamber.
Use at least some 10% castor in the fuel. Fresh, not old.
How old is the engine? Does it have the new type spraybar where the idle needle is in the spraybar all the time?

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