SC52fs Tuning problem

[Geo.]

Hi Guys..I have just put my trusty sc52fs into a new model. It had not run for about 18months but fired up first time and ran its usual beautiful self. The problem i have that has me scratching my head is, i cant seem to get a slow enough idle that wont pull the model along, which as you can understand is not ideal for landing. The engine runs good with excellent throttle response. There comes a point when another click down on the trim and the engine cuts. I don't know what to try now....any solution suggestions would be greatly appreciated.......Oh the engine is fitted with an OS plug and is fueled with Irvine contest 10 formula.

[stuey]

Sounds similar to the problem I am having with mine. My engine is 10 odd years old, but never run that much so I dont know if newer versions are better. Is it installed inverted? Mine is and I cant get a decent slow idle either despite my efforts. If my on board glow ever turns up, I am hoping that will solve the problem as it idles much better with the glow driver on. Can you get a slower idle with the glow left connected?

[Geo.]

The engine is installed at 90 degrees as it was in last model and it worked perfectly well then. Tried it again after a little fiddle and it slowed to a good idle but only for a few seconds after which it either died or speeded up. I am not an engine type of guy but i noticed the slow speed needle seems kind of far out...ie it's screwed out a bit above the flush. I am assuming its a setting rather than an engine problem as it was a great runner before its lay off. There is not much of a difference with or without the glow stick connected.

[YakMad]

Try replacing the idle needle or just the "O" ring if you can source one, the ASP parts are the same and cheap from Just Engines, I have run ASP .61 FS engines for years and keep a small stock of main and idle needles as the "O" rings get hard and leak air causing the mixture to go lean at idle hence the very fast idle. in fact I only replaced an idle needle in one of my ASP 61's last week with was running fine for the last two years but suddenly started to run very rough at idle, now running like a clock again after the needle change.

[stuey]

Thanks for the heads up on the o ring issue. As my engine is 10 odd years old but not run that much there is a good chance I may be suffering from this. I got a big box of o rings recently, may have the right size to hand. I dont know if the idle needle would be the same in my engine compared to the Mk2 versions available now.

[stuey]

Come to think of it, my main needle seems to be very sensitive where 1 click richer takes a few hunderd rpm off, and 1 click too lean starts to cause the revs to drop off like its getting too hot requiring immediate richening. Perhaps the main needle o ring is leaking causing this?

[YakMad]

Stuey,

 

 

Sounds like the 'O' rings are leaking air, best to change the high and idle needle if you have ones available, it's also worth putting a small piece of fuel tubing on the main needle as well as I found this helps improve the high end tuning on my ASP's, it creates a second seal to prevent air leaks.

[stuey]

Thanks for the heads up, hopefully got some on the way and will give it a try.

[JC]

I had the same problem with an old SC 52 fs. New O rings solved the problem of poor idle and cutting out on take off. Now runs perfectly.

[Geo.]

YakMad,

 

New O rings on the needles has solved the problem. Had a couple of flights this afternoon and the engine is back to its old self with a very good idle. Cheers for the info about the O rings, something else i have learned for future reference.