c550

My Feedback: (16)

I am having an issue with an 8 year old OS 1.60. It has been running great but now it doesn't hand start and when it runs the idle is not as low as it used to be. The compression when warm is low. Also the needle valve is now not very sensitive. I am thinking it is time to do an overhaul and my question is this; Can I replace just the $25 piston ring or do I need to replace the $85 dollar cylinder as well? Also if I do an overhaul should I replace any other parts? The bearings seem very smooth, I replaced them a few years ago.

Any insight is appreciated.

Regards,

Dave

Cyberwolf

My Feedback: (4)

The first thing I would do would be to check all of the bolts to see if any has worked loose, if not then go with the following.

The only real way to tell what it needs is to take it apart and measure things or just look & feel to see if it has worn a ring ridge which is doubtfull. Also measure the piston to see how much wear it has sustained, check the wrist pin in both the piston and rod to make sure it is still good and tight
I just went thru 2 of mine all they needed was a ring and bearings, do yourself a favor and if you do replace the ring and such replace the bearings while your at it.
Do a light hone job on the sleeve clean and inspect each part for wear and your off to the races.
One note of intrest look at the rod really close and see if it is starting to go egg shape on the main journal. (CRANKSHAFT END) The engine I picked up used had this issue, not much but enough that I could see there was excessive movement in the rod when turned over by hand with the backplate off.
Off subject but I converted one of mine over to gas and won't look back .

Frank Bowman rings can be sought after here
[email protected]
Bearings can be obtained from
rcbearings.com
I feel that both of these after market items are better than the original and at a much lower price tag to boot.

Kostas1

Dave ,

how many gallons have you run through your engine ?

I think piston rings can be found easily.

I had an O.S. 160FX but i didn't run her too much
because it was replaced with a SAITO FA-150s.

c550

My Feedback: (16)

The 1.60 has seen moderate to light use when I had it in a 1/4 scale cub. I put it in a ESM Corsair and have been flying it a bit more, but couldn't guess how much fuel it has seen. I also like the Saito 1.50 I went with the OS because it could be fully cowled and my Saito 1.50 is in a Spitfire.

Scar

My Feedback: (3)

Needle valve not sensitive? Low power? I gotta tell you, first thing I do now is try a new jug of fuel.

In the last 5 years, I've had two (partial) jugs of fuel become almost unburnable. Hard starting, low power, etc. New fuel cured it all. It's worth a try.

Good luck,
Dave Olson

c550

My Feedback: (16)

Scar,

I don't think its the fuel, because I flew my Saito .82 powered TF B-25 on the same fuel on Saturday with no problems. I gues I will disasemble the engine and look for worn parts. I really was hopeing someone would say just replace the $20 ring and I would be good to go. At the price of a liner, pistonring, and conrod I might just replace the whole engine. I am probalbly over thinking it.

Regards,

Dave

Desertlakesflying

My Feedback: (28)

I agree with checking the head.........RUN OS Type F only......You will have so many less problems with all of your engines.

w8ye

My Feedback: (16)

I'd try opening up the low speed needle just a smidgin first

c550

My Feedback: (16)

A little update, Thanks to the generosity of a club member I replaced the engine and took the old one apart. I found that there was considerable scoring on the piston and that it had trapped the ring in its groove. There is some scoring on the liner. I am wondering if I can polish the liner and still use it. A new piston and ring aren't too expensive but at $85 the for a new liner I might just keep the parts around as I don't think it is cost effective to rebuild.

Regards,

Dave

NM2K

My Feedback: (14)

I don't think your engine needs a rebuild from your description of the symptoms. Besides, I would make it run correctly before I rebuilt the engine anyway. Your description of its faults are not typical of a worn out engine.

Most engines, if not all, have less compression when hot than cold. This is normal. Cold compression is more of an accurate indicator of the state of your piston to cylinder seal. Most likely, unless you have fried the ring with a super lean run, or have ingested a lot of dirt, your piston, ring and cylinder are just fine.

Glow plugs, fuel and prop choices can affect the idle, transition, etc., every bit as much as worn or defective parts. Your engine should be checked every few weeks of active flying for such things as loose fasteners, cracks in the metal, blown gaskets, etc.

Your description of your handling problems truly sounds as though the carburetor is partially plugged. Before I did anything more involved than changing out the glow plug, I would disassemble the carb and make sure that it is whistle clean. Good luck and come back and tell us how things worked out.


Ed Cregger

Cyberwolf

My Feedback: (4)

Hi Dave some pics of the inside parts would be very helpfull.

earlwb

well, some scoring does happen. But if the scratches are shallow, it isn't a big deal. A new ring would still work.
Some guys would lightly run a hone through the cylinder to polish it up a little. But you don't want to over do it, or you may need to make a oversize piston for it then. But from your description, it sounds like the piston ring had gotten stuck in the piston. So cleaning out the piston groove (the old ring works good for that) should do the trick.
I would suggest just putting in a new ring and go for it.

Kostas1

And here is the maiden flight of my GreatPlanes Giant SuperSportster....

Watch on HighDef.1.080p...i know the 160FX is good, but listen to that FA-150S....

[link=http://www.rcuniverse.com/forum/fb.asp?m=10469210]Maiden Flight GreatPlanes Giant SS[/link]

the pope

Howdy there Kostas , at the risk of sounding like your mother I think you need to find a way of restraining your model or your friends will be calling you stumpy or mangina . Having seen fingers flying off peoples hands before I tell ya it aint much fun and too late to think about it after its happened. Cheers from the pope