Popping and hesitation on throttle after putting air box back on

50cc · 02-14-2013, 10:48 AM

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

scootnwinn · 02-14-2013, 11:00 AM

Try moving your needle clip to the top position hesitation and popping followed by brisk acceleration make me think its too rich...

50cc · 02-14-2013, 11:45 AM

Will do that.

Also, 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.

50cc · 02-14-2013, 01:40 PM

Also, edfr mentioned in the old forums that the cause could be the ACV valve of the carb, but the last time I changed jets I pressed it and it was squirting ok.

**Admin** · 02-14-2013, 02:43 PM

I agree, sounds like a needle adjustment issue.

50cc · 02-14-2013, 02:50 PM

Ok guys, thanks again. Tomorrow morning I'll lower the needle and will report.

**inuyasha** · 02-14-2013, 03:42 PM

Hi
Sounds like she's running lean to me
Check for airleaks, since you just put back the airbox i would start there
Take care and ride safely dear friend
Yours Hank

savy09 · 02-14-2013, 05:44 PM

Go back to the stock 75 jet first, correct the idle and ride.

millsc · 02-14-2013, 10:12 PM

the acv valve is on 24mm carbs the 50's have a fuel pump on the bottom. You don't have an acv valve.

50cc · 02-15-2013, 07:29 AM

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!!

scootnwinn · 02-15-2013, 10:17 AM

Glad you got it going I know how it is when they aren't quite right it can drive you mad...

50cc · 02-15-2013, 10:42 AM

Quote:

Originally Posted by scootnwinn

Glad you got it going I know how it is when they aren't quite right it can drive you mad...

Yeah, I really care about the machine and want to run it with correct mixture only. My heart breaks when I feel it's out of tune. I guess I'm too rigorous..

scootnwinn · 02-15-2013, 10:48 AM

Nah can't happen. 2 wheel vehicles require OCD type of attention to all details. You have the perfect mindset

**Admin** · 02-15-2013, 02:52 PM

Awesome, glad ya got it all worked out!

02-14-2013, 11:00 AM	#2
scootnwinn Join Date: Aug 2011 Location: Tierra Azul, NM Posts: 739	Try moving your needle clip to the top position hesitation and popping followed by brisk acceleration make me think its too rich... __________________ Do not fear mistakes. You will know failure. Continue to reach out. - Benjamin Franklin Join the HARDCORE 1983 Honda GL650I SilverWing
	0

02-14-2013, 01:40 PM	#4
50cc Join Date: Oct 2012 Location: Germany Posts: 140	Also, edfr mentioned in the old forums that the cause could be the ACV valve of the carb, but the last time I changed jets I pressed it and it was squirting ok. __________________ 50cc 139QMB, 7g sliders, manual petcock w/ transparent lines, Naraku CDI, Naraku belt, high output racing coil, 18.4mm CVK clone w/ #85 mj and #38 idle, needle @ leanest, OEM pipe mod, Kenda tires, NGK Iridium, lots of LED mods, 2.61L/100km (90 MPG)
	0

02-14-2013, 02:50 PM	#6
50cc Join Date: Oct 2012 Location: Germany Posts: 140	Ok guys, thanks again. Tomorrow morning I'll lower the needle and will report. __________________ 50cc 139QMB, 7g sliders, manual petcock w/ transparent lines, Naraku CDI, Naraku belt, high output racing coil, 18.4mm CVK clone w/ #85 mj and #38 idle, needle @ leanest, OEM pipe mod, Kenda tires, NGK Iridium, lots of LED mods, 2.61L/100km (90 MPG)
	0

02-15-2013, 07:29 AM	#10
50cc Join Date: Oct 2012 Location: Germany Posts: 140	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!! __________________ 50cc 139QMB, 7g sliders, manual petcock w/ transparent lines, Naraku CDI, Naraku belt, high output racing coil, 18.4mm CVK clone w/ #85 mj and #38 idle, needle @ leanest, OEM pipe mod, Kenda tires, NGK Iridium, lots of LED mods, 2.61L/100km (90 MPG)
	0

02-15-2013, 10:17 AM	#11
scootnwinn Join Date: Aug 2011 Location: Tierra Azul, NM Posts: 739	Glad you got it going I know how it is when they aren't quite right it can drive you mad... __________________ Do not fear mistakes. You will know failure. Continue to reach out. - Benjamin Franklin Join the HARDCORE 1983 Honda GL650I SilverWing
	0

02-14-2013, 03:42 PM	#7
inuyasha Join Date: Sep 2012 Location: West Haven CT Posts: 1,165	Hi Sounds like she's running lean to me Check for airleaks, since you just put back the airbox i would start there Take care and ride safely dear friend Yours Hank __________________ "4wheels move the body 2 wheels move the soul" Duty, Honor, Country. Those three hallowed words reverently dictate what you ought to be, what you can be, what you will be. Douglas MacArthur
	0

02-14-2013, 05:44 PM	#8
savy09 Join Date: Aug 2009 Location: BOCA RATON, FL Posts: 51	Go back to the stock 75 jet first, correct the idle and ride.
	0

02-14-2013, 10:12 PM	#9
millsc Join Date: May 2012 Location: missouri Posts: 164	the acv valve is on 24mm carbs the 50's have a fuel pump on the bottom. You don't have an acv valve. __________________ B.A.M.F. tapout scoot 24mm carb 150cc intake performance exhaust A9 cam hoca big valve head 16/50 gears 9.25 gram dr pulley sliders koso variator 1.5k torque spring orange coil orange unlimted cdi uni filter gates premium belt 2012 taotao vip cy50a scrappys 110cc big bore kit 52mm "88cc" 100 main jet 38 idle iridium plug custom paint, leds and decals alarm system naraku hd crankshaft
	0

02-15-2013, 10:48 AM	#13
scootnwinn Join Date: Aug 2011 Location: Tierra Azul, NM Posts: 739	Nah can't happen. 2 wheel vehicles require OCD type of attention to all details. You have the perfect mindset __________________ Do not fear mistakes. You will know failure. Continue to reach out. - Benjamin Franklin Join the HARDCORE 1983 Honda GL650I SilverWing
	0

02-15-2013, 02:52 PM	#14
Admin Join Date: Apr 2011 Location: NY Posts: 990	Awesome, glad ya got it all worked out!
	0