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YS Engine Help
[b]
Need some help with a YS AC 120 Glow engine. Engine recently rebuilt by YS and ran great for the first few flights. Now the engine surges and changes rpm on its own. I have checked the fuel tank, needle valve, all fuel lines, throttle servo, and all the other likely suspects with no results. Has anyone had a similar experience that can lend some advice? |
RE: YS Engine Help
If the engine surges, then: 1) The high end is too lean 2) The midrange is too lean 3) Fuel line has a tiny hole in it.
Try richen up the regulator screw about 1/8 of a turn. |
RE: YS Engine Help
If it's a constant surging, up and down with the RPM's for no aparent reason, is a classic YS problem.
Normally that means escaping air between the ring and the liner, very popssibly due to the fact that things aren't steating properly due your strip down. Do a ring change and it should go away for a while confirming the problem. It could very likely come back within 50 runs confirming you'll need to change the ring and the liner, better still replace the ring, piston and liner. It's a classic problem. Better still just send it to YS performance and have a complete strip down rebuild and have them run it up. they can do a small gas porting mod to the piston to help get a better ring/liner seating. You'll have what esentially a brand new engine. Try what was suggested in the post above, hopefully it'll work, if it doesnt. get a ring. |
RE: YS Engine Help
Suggest you go to the YS section of the Engine Manufacturers Direct Support boards. Dave Shadel is very good at helping solve YS problems. You may wish to look through the existing postings for a solution before making your own post.
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RE: YS Engine Help
ORIGINAL: bla bla If it's a constant surging, up and down with the RPM's for no aparent reason, is a classic YS problem. Normally that means escaping air between the ring and the liner, very popssibly due to the fact that things aren't steating properly due your strip down. Do a ring change and it should go away for a while confirming the problem. It could very likely come back within 50 runs confirming you'll need to change the ring and the liner, better still replace the ring, piston and liner. It's a classic problem. Better still just send it to YS performance and have a complete strip down rebuild and have them run it up. they can do a small gas porting mod to the piston to help get a better ring/liner seating. You'll have what esentially a brand new engine. Try what was suggested in the post above, hopefully it'll work, if it doesnt. get a ring. --------------- Is the gas porting mod the old trick of drilling a hole down into the top of the piston and to the ring land, in order to force the piston ring against the cylinder walls? |
RE: YS Engine Help
Yeap it is.
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