I have a US 25cc gas. The eng is not running good at all. It will not rev up. If I put my finger over the intake the rpm will come up. I backed out the hi side needle valve and it is not working. I think Im doing it right, that the eng is running Lean but not sure. help me out.
Thanks

Check all of you lines to make sure they is no air leak. Check all of the screws/bolts on the enine to make sure they are not loose. If you have an inline filter between the tank and the carb, try removing it and using a piece of copper tubing as a temporary measure and restart the engine and see if it changes. Remove both needles and clean them.

Your low speed needle may be too lean which will also cause this problem

The little screen on the pump side of the carb may be clogged as well. It might also be time to replace the diaphrams on both sides of the carb (both pump and pressure.

Also, another thing to try is to open both needles two full turns. NOw lean the low end a little at a time until the engine no longer transitions to full throttle. Do not worry that you are not getting full rpm just yet because you are very rich. NOw lean the high speed until you get max rpm then back off 200rpm. This way the engine does not go lean in the air.

You didn't say if the engine was new or used but if it's new, follow what bubbagates said about setting the low and high two full turns open and tweaking from there. If it has a lot of time on it, then follow what he first said in his post. Very good advise.

It is a old eng but there is not much time on it at all.. I got it about 5 yrs a go. I have about 2 hr run time on it.. I got the hi set just find but now when it idles it vibrates so bad that it shook my my wieght off the plane.. The prop is balance just fine.. it is like it is miss fireing bad.
Help me out all.
Paul

tellspin_37,

like bubbagates said, Remove both needles and clean them and the little screen on the pump side of the carb may be clogged as well. It might also be time to replace the diaphrams on both sides of the carb (both pump and pressure).

Open both the low and high needle valves 2 turns, next start the engine, let the engine warm up and give it full throttle. If it does not hesitate then lean the low end 1/8 turn and try again. Keep doing this until when you go from idle to full it hesitates and then richen it up 1/8. Now go to your high needle and with a tach tweak it until you get your highest rpm and then back it off 1/8 turn. If you are unable to do this because the engine simply will not respond then try changing the plug. If it has been setting around for that many years you may need to change some gaskets and clean it good.

I will give it a try and let you all know how it terns out. Thanks for all the info you all have giveing me
Paul