Rather then try to post to that thread with obvious issues I started a new thread. First off I have attached the owners manual for that engine that will show the plumbing. Notice the use of two filters and a check valve, these are mandatory. YS engines are a bit different as they pressurize the fuel tank. Any leaks in the system and the engine will not run correctly. To test the system you will want to turn the engine over with a starter for a few seconds without glow power hooked up. Let it sit for 5 minutes and pull the vent line free. You should still have some pressure in the tank. If not you have a connection with a leak or the regulator is not sealing correctly.

When starting a YS, never advance to full throttle without allowing the tank to reach full pressure first. This takes about 15 seconds at a high idle. Make very small adjustments and then always cycle the throttle to check the mixture adjustment. Once dialed in you should be able to go months without any adjustments. On the day you feel like an adjustment is required and it is more then just a couple clicks, something changed other then the needle setting, find the problem, tweaking the needle is not a fix when deviating more then a couple clicks from what has been working for a while.

Some of the 4 stroke mufflers are quite small. It's important when installing the muffler that the header pipe bottoms out in the head and you are using the copper gasket. If not be prepared to loose the muffler and possibly stip out the head.



fz120.pdf