[SOLVED] Popping and hesitation on throttle

[50cc]

Hi guys,

After my aftermarket filter broke off it's hose I got tired of experiments and put my old air box back on. I re-jetted to its original jets - the #30 idle and the #85 main (as in my bike's specs).

Since then I get this strange hesitation on takeoff with few popping sounds from the exhaust and deep drop in RPMs - bike hesitates for like 1 to 2 seconds, RPMs go really low, but then suddenly it accelerates fast and runs great overall. Sometimes, when I decelerate quickly, I hear a single strong 'POP!' from the exhaust. I thought it's running lean and put a #90, but that was too much and bike ran like crap and didn't fix the problem. Now I am with the #85 again since #80 is too lean (I have #70 #75 #80 #85 #90 #95 sizes only).

Mixture screw is at 2 1/2 turns out, exhaust is only visually modified, air box is not modified at all, all hoses are great, I have no air leaks at neither side of the carb and intake is 2 months old, carb's diaphragm is new as well, needle clip is in the middle slot, chops are tobacco brownish, perhaps a hint lighter.

Any ideas?

Thanks in advance,
Ivan

[edfr]

Popping on throttle up is a RICH condition.
Popping on deceleration is LEAN condition(Pilot jet or idle to low) or your ACV valve is not working--IF your carb has one.
Lefty

[50cc]

Feb 14, 2013 12:58:41 GMT -5 edfr said:

Popping on throttle up is a RICH condition.
Popping on deceleration is LEAN condition

And popping on throttle up AND on deceleration? Last time I changed jets I pushed the valve and it was squirting fuel well.#

Also, as I already wrote in the new ScootDawg:

the popping occurs only when waiting long on a traffic light without touching the throttle - if it's a short light or I tinkle from time to time with the throttle it does not happen

[millsc]

could be an exhaust leak, mine popped also i put gasket sealer on the exhaust and retightened it, stopped the popping.

[edfr]

I am not on the NEW SD so I would not know what you wrote there.

Sameo Sameo on IDLE(LEAN) or like I said idle is to low the BUTTERFLY is closed to much.
What is your idle at the stop light?
Lefty

[50cc]

Idle is not steady and was better before, but also it doesn't die.. just lowers RPM like it's about to then it picks up again and RPM raises.. Yeah, it's not idling perfectly.

Feb 14, 2013 13:58:22 GMT -5 edfr said:

I am not on the NEW SD so I would not know what you wrote there.

I was just giving some additional info, mate.

[edfr]

So was I just letting you know I am not on the other forum and would not know what you wrote on there no biggy mate.

But you said the magic words IDLE BOUNCEING(LEAN), Now any bounceing can also be caused by AIR LEAKS and or Fuel Ratio Mixture is to LEAN. So First check for AIR LEAKS, intake manifold where it connects to the head, cracks in the manifold, loose clamps, cracked where the clamps tighten onto the carb, also AIR FILTER side, tubing cracked, air box cracked etc..
All that is good then richen up the Fuel Ratio Mixture screw(counter clockwise 1/4 turns at a time).
Lefty

[50cc]

So guys, problem solved - scoot was running too rich. Played with the clip this morning and tried all positions and it runs like before only with the clip at the very top and that makes me think I can go down to #82, #83 or so, but since I have only #80 I'll just stay with the #85, because it runs great now and just as I like it - a tiny bit on the rich side. The bad thing is in summer I'd have to probably downjet to the #80 mj I have, but summer's still far away.

Thanks again to all of you!! Marking thread as 'Solved'.

[super9]

glad you got it fixed