Motorcycle Repair: ATV 50cc carb., air fuel mixture, 50cc atv

Question
I have a 50cc ATV(Chinese) with a Honda clone engine(The old trail 50 motor) The carb is a PZ19 Kliene(not sure of the spelling) I have had 2 brand new carbs on it and it has the same problem. Idle's great but when you throttle up fast it dies,,low end rpms are boggy. High rpms are fine once you get there. All intake bolts are tight. Needle changes up or down only worsen the problem. Air flow is unresticted. This engine is brand new. It does have a small paper fule fiter but as I said High rpm is good and its new. I am lost as to what to check. Float? adjustment? The plug is new ,same as the Trail 50 uses.

Answer
Hi Steve,

Too much air is being drawn into the engine upon quick throttle demand. The air intake needs a bit of air restriction to correct this problem.

Boggy low end may be fuel contamination or incorrect air-fuel mixture.

Try adjusting the air-fuel screw (pilot screw). With engine off, gently seat the screw counting the number of turns in as you go. Remember this number. Return the srew out and make 1/4 turn incriments both directions. Note engine performance as you go.

Wehn tuning carbs, make one adjustment at a time to know what effects each change has on engine performance.

Fuel service level (float height) should be fine. Engine seems to be working well at higer RPM's.

Visit the folowing websites for more information:

www.hondatrail70.com/

www.oldhonda.com/trail702.htm


Respectfully,
Mark Shively