JUst got my RCS1.40 up and running again after it has been sitting around a while. I have always had a problem with what sounds like a miss in the engine, anyways first i tried the supersonic muffler in place of the previous pitts muffler, this was quite noisy and due to not wanting to disturb the neighbours to much i only run the engine for about 5 minutes, i noticed the miss was still apparent at top end.
Then using the exhaust stub that comes with the RCS, i managed to mount a super tigre 90 quite silencer onto the engine, once running this sounded a lot better, a lot easier on the ears and the miss was not apparent, does this make sense?

Lastly i am running a MAS 16x10 3 bladed prop, top RPM 6400 low stable is around 1900, it will go down to 1600 but fluctuates, is this in the ball park for this motor?

I have two of these motors on a twin and am getting a 16 x 8 up to nearly 9000 RPM. I flew the model with different props tached at about 7300 before. The difference in power is very noticable - these engines like to spin up. I would say that you are over proped, a 16 x 10 3 blader may be too big.

Before the crash it was turning a 17x10, i always what sounded like a miss which i could trace out, swapped a couple of things, anyhow i figure i am going to try and get this engine properly on a test stand before finding another plane for it.
There is also quite a bit of black goo coming out of the exhaust, is this normal?

Is the noise truely a miss or a gurgle? Perhaps the engine is a little too rich on the upper end. The black goo: It takes awhile for the engine to be fully broken in.

I used to get about 7200 with a 18 x 8 with that engine. I think you have it over propped.

Elson

fly109
what brand or prop r u running. I am running a 18 x 6 Mejzlik on mine but i do have an apc that i have not tried on this new project.

Too much spark advance will cause a miss at WOT....You might try retarding the spark..You want it timed right at at or slightly past the point where it starts to cause a loss in rpm..28 to 30 degrees BTDC is the magic number...[8D]

How do you adjust the advance on these, the pickup is fixed to the crankshaft and the pick up point is dependent on the way the back plate is installed, there is no way to move or adjust it mechanically that i can see.

I am running two kinds of props due to the fact that this twin uses one conventional motor at the nose and a pusher in the tail. At the rear I am using a Bolly 16 x 8 Wood and I have an APC 16 x 8 at the front. I also have a Bolly 16 x 8 wood for the front.

Timing can't be adjusted on some engines, you just have to trust the factory...

IOW put up with it...., should be getting another plane for the engine soon, so will give it another try and see what happens.

The ignition quit working on mine. I removed the back plate and found that the little magnet was gone from the timing disk. I guess it went out thru the engine exhaust.
I replaced the timer with one on the front drive rotor like other engines have.

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You can't, so you are going to have to reduce the load on the engine. Lower the demand the prop places on the engine by reducing pitch/diameter. As mentioned previously, this engine likes to rev up a bit.

Yes, you may have gotten away with running too much prop under certain conditions, but you may be right on the edge where ambient weather conditions can push the engine into running too hot (in terms of spark advance with a given load).

I am mounting the engine into an old Giles at the moment, i am going to see what i can do to get a 17x6 or 17x8 wood prop to start off with and see how it goes, the 16x10 carbon runs real good, i was getting 8050 a couple of days ago on the test stand, good transition and no miss.