hthKeep in mind that the low speed flows fuel from zero to about 1/3rd throttle opening. The high speed jets starts flowing from about 1/3rd throttle open to full throttle. Both jets flow fuel above 1/3rd throttle.
Set the high speed jet at least 2 turns out from bottom to start. Set the low speed jet at about 1&½ turns out. Warm the engine on the stand for a few min, rev the engine on the stand a bit while rough setting the low speed jet for idle to rev throttle response. Close the low speed too far, and the idle goes up from a lean condition. Open the low to far and the engine will run rich and die. Stay on the rich side, but make sure throttle response from idle is good. Continue to rev the engine above half throttle, but not holding it in any one position for the last few min, to run the engine with the high speed jet flowing. Shut it down, and check the plug color. The plug should be a dark color like a dark brown or black. The rich settings we start with could possibly foul a spark plug, so you might want to have a new plug or two on hand for tuning. This plug color is good for now, it means we are getting plenty of fuel--at least on the stand.
Now, it is time to run it and tune the high speed jet. Remove any body parts, or roll cage parts you need in order to access the plug easily. You will want to keep a plug wrench and a glove (that plug will be hot) in your pocket while you are out in the field tuning, You want to be able to access your plug easily. Run the Buggy. Run it for 10 sec min, at about ½ throttle after it is warmed up, and stop it at your feet. Quickly shut off the engine, and check the plug (don‘t let engine idle or use lower RPM‘s so the plug won‘t darken, and give you a false reading). If it is still dark in color, that is good for now. Now run the buggy again and use a little higher RPM. Check the plug again. Repeat while creeping up on full throttle, and check the plug often. Keep doing this until you are checking the plug with full throttle runs (you will need a lot of room), and the plug hopefully is on the dark side. If the plug is white, or light in color at any RPM, and you cant get a safe color to it by turning out the HS jet (over 2 turns out approx does not make any difference on the jet), stop running the engine. You most likely have a air leak or a dirty carb/filters, which can also cause a lean condition and damage the top end. If the plug is still dark after your going full throttle, you should be safe. You can start leaning out the high speed jet until the plug is a nice med chocolate brown color AT FULL THROTTLE. After that is done, you can fine set the low speed jet for best acceleration. Going richer on the low speed usually helps the jump off the line, but the idle may suffer.
Note- Make sure you use a tacky filter oil for the air filter or you will suck in dirt. A “Tacky foam air filter oil” can be purchased at any dirt bike shop. Fully saturate the filter element, and squeeze as much oil out of the filter as possible with paper towels. It makes no sense to tune the carb with a dirty filter, so use a clean one.
ya, colemans is so much cleaner burning than gas, regardless of oil used. its not surprising it has very little deposits left behind.I run colmane and my plug barely change colors..its still nice and shinny, almost...... 7 tanks later
yes you do, but you don't have to start all over. i just get it warm and adjust the high speed needle as needed.I don't know where to post it but, here it goes. I am running a fuelie motor with the stock muffler, I now put the performace pipe on, do I need retune the engine? I really don't like messing with carbs.