dmccormick001
Posts: 133
Joined: 2/13/2005
From: Soddy Daisy, TN, USA
Status: offline
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It's really important on these engines to follow a proven, methodical system of adjusting carb and regulator. If you don't, you can wind up chasing the correct settings all day long and still not achieve a good running engine. First, make sure the check valve is a YS valve, not a Tettra brand. The Tettra valve won't work right, there's something different about the way it's made. And make sure it is oriented properly, so that it allows flow (air) from the engine towards the tank. Next, remove the cover of the regulator and make sure it's clean. Note the position of the cover, and be careful not to lose the gasket, the plunger, or the diaphragm that's inside it. Pump some fuel through it to clear the passages, and reassemble it. Some guys will tell you to throw away the stock gasket and get an aftermarket version, but I've used the one that came on my 140 Sport for quite a while and it's survived a lot of disassemblies. You can do which ever you see fit. Next, position the screw on the regulator so that it is appoximately flush with the regulator cover. Start the engine, and adjust the top end first, by turning the high speed needle valve in (clockwise) until you hear or read on a tach maximum RPMs, then back it up a few clicks to richen it slightly. You should hear or see a drop of just a few hundred RPMs. Now go to about 4000RPMs and adjust the regulator until you get a good, smooth run. Too lean, and the engine shouuld speed up and die, too rich and it should run rough. Adjust the regulator until it runs smooth at 4k and will transition smoothly to full power. Go back and readjust the high speed needle again, and check the 4k setting again. If you change one, you'll need to at least check, and possibly readjust, the other. Get them both as perfect as you can before you try to set the idle, because they will affect it. Now idle the engine down to as close to 2000 RPMs as you can keep it running, and begin to adjust the idle air bleed screw. Remember, it's an air bleed, so it works backwards from a needle valve. Turn it in (CW) to richen, out (CCW) to lean. Adjust for a smooth idle. Watch the smoke coming out of the muffler, it will tell you a lot about whether the engine is running rich or lean. If you have trouble getting the engine to idle smoothly, and if it seems to be running too rich (smoking a lot) despite what you do to the bleed screw, the regulator may still be a little rich, allowing too much fuel through at low speed and flooding the engine, so turn the regulator screw in (CW) about 1/8th a turn to lean it. Whenever you change any setting, give the engine several seconds to respond. Be patient. When you get close to the correct settings, your adjustments will become very small and slight. Keep reducing the idle speed until you get it to idle smoothly at around 2000-2500 RPMs. Take your time and don't make any major changes. You should be able to dial it in 'til it purrs like a kitten.
Hope this helps. It can be frustrating, but it's worth it. The YS engines are in a class by themselves.
David
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YS FZ 110 Tuning Help - 
