Hello All,

I'm Posting for a buddy who doesnt have access to RCU. I hope you gas guys can solve his problem. I'll give all the info I know then the problem, OK?

35% Edge
DA 100 twin stock exahust, no cannister, 1500Ma Ignition Battery.
Engine has 7 gallons total Run through it. 4 with breakin oil, 3 with AMS oil 50:1.
93 octain fuel, fresh
All purchased New

Here's the Problem; The engine Runs smooth and Flawlessly from 1/4 stick UP.
From Idle up to 1/4 throttle the engine hesitates when throttle is added, He described it like; below 1/4 throttle the engine sounds like a rich 2 stroke, but throttles like a lean engine. The idle is also rough.
There is no excess oil on the bottom of the plane.
He thinks he needs to tweak the low end, but not sure which way to go.

I hope I gave enough info for Ya'll to diagnose the problem.
Any Help or Advice will be appreciated.

Thanks,
David

Sounds like the needles need to be turned a little. No reason to be afraid to do it. Factory settings are NEVER, EVER perfect, and every engine made by anyone is required to have the needles to be tuned for the best and reliable performance. There are several posts and threads currently in the first two pages of the engine forum that cover the proceedures extremely well.

To me, it sounds as though the low end is rich. However, be sure the carb, and carb block bolts are tight. Air leaks cause problems like you describe as well. It may also be stumbling because the mixtures are different between the high and low end. If you look in the carb throat, you'll see that there are two holes in the throat of the carb. The first one is the primary idle, the next is the secondary idle. In the middle of the venturi is the main port (You can't really see this one). The two lower openings operate until you are in the top third of throttle travel. Mixture differences occurring between the secondary and main needles can cause burble and rough running. Get a good tach, and set the high end first. A setting 200-300 rpm rich of peak is what you're looking for. Then, start leaning out the low end. When the engine is warm, and you can advance the throttle quickly from idle to full without the engine stumbling, stop. Check the high end again and see how close you are to the peak setting you had earlier. You may need to richen it slightly again. Advance the throttle slowly from idle to full. If you can get from idle to full and not have the burble at the two thirds setting, you're good to go. A tach will make this easy.

Check the ignition plug. make sure its not backwards.( red to red, black to black and so on.)
It is real easy to get these wires backwards and the engine will run, but it runs like what your describing.
Just a thought.
Been there done that.

Ask him to open the idle screw (CCW) and see if the engine speeds up.
If it does, then it is lean. Adjust the ATV to get the engine back to a good idle, then open the idle screw again.
Keep doing this until the engine stops speeding up.
From this, adjust the idle so that you get good transistion and solid idle.

Once this is done, then adjust the high speed screw to get good WOT power and uplines.