Running too Lean?, dies when given throttle

RustToRedemption · June 17th, 2021, 07:35 AM

Bought a non-runner for $100, took the carbs out and cleaned them (not my first carb rodeo; ultrasonic cleaned and then blew compressed air through all the passages, cleaned the jet orifices with fine wire). Installed new diaphrams, as one of the old ones had a tear in it. It now starts right up and idles perfectly, but will die immediately if you touch the throttle. Thinking its way too lean; I've re-oiled the filter and that only changed that you can now rev it with the choke on. Changed the AF screw to 2.75 turns out on both carbs. Checked the intake manifolds for leaks and there was no fluctuation in idle RPM when spraying carb cleaner around them. I feel like I have to be missing something, but Im stumped right now. Any really common problems on these bikes that cause a lean condition? Any help is appreciated.

**Ive searched the forums, and it seems like most people who have this problem put their carbs together incorrectly/with missing pieces. Im fairly confident I've done this without a mistake.

jkv45 · June 17th, 2021, 07:53 AM

Take the air filter out and try it.

Better or worse?

RustToRedemption · June 17th, 2021, 08:09 AM

Quote:

Originally Posted by jkv45

Take the air filter out and try it.

Better or worse?

Worse. Much worse. Wont start with it out.

Triple Jim · June 17th, 2021, 09:13 AM

10 to 1 you missed something when cleaning them. These carbs are not simple to get truly clean.

RustToRedemption · June 17th, 2021, 10:33 AM

Quote:

Originally Posted by Triple Jim

10 to 1 you missed something when cleaning them. These carbs are not simple to get truly clean.

I cut my teeth on cleaning 70s/80s carbs. These are pretty simple compared to some of those. Is it possible I screwed something up? Sure. Would I take a 10:1 bet that its something else? Every single day of the week and twice on sundays.

Triple Jim · June 17th, 2021, 12:31 PM

Quote:

Originally Posted by RustToRedemption

I cut my teeth on cleaning 70s/80s carbs. These are pretty simple compared to some of those. Is it possible I screwed something up? Sure. Would I take a 10:1 bet that its something else? Every single day of the week and twice on sundays.

Well, when they're clean and properly assembled they don't have any lean spots.

ducatiman · June 17th, 2021, 01:03 PM

stock exhaust?
both needle jets present & accounted for?
petcock confirmed delivering adequate fuel?
try again with an open fuel cap?
what jet sizes, both main & pilot?

RustToRedemption · June 17th, 2021, 03:14 PM

stock exhaust? Yes

both needle jets present & accounted for? Yes

petcock confirmed delivering adequate fuel? Maybe? The bowls have been full the two times I’ve taken the carbs off the bike

try again with an open fuel cap? Nope, but I’m assuming if I have adequate fuel, checking for a blocked fuel vent won’t matter

what jet sizes, both main & pilot? Main is a 105 and pilot is maybe a 38? Hard to read.

ducatiman · June 17th, 2021, 05:01 PM

carbs wet tested when off the bike after your clean? Float levels nailed?
pilot screws get new orings?
new float valves?
carbs in reasonable synch?
transition ports checked, confirmed clear?
adequate valve clearances present?
carb vent hose clear? not plugged or kinked?

RustToRedemption · June 18th, 2021, 06:22 AM

carbs wet tested when off the bike after your clean? Dont know exactly what you mean by this, but I function checked the float valves to make sure they flowed fuel, and stopped the flow of fuel
Float levels nailed? Checked statically with calipers, within spec.
pilot screws get new orings? Yes, and made sure it still had the washer in there as well.
new float valves? No, but inspected the tips for damage and found none, and the spring return nipple on both needle valves are in good working condition.
carbs in reasonable synch? Yes, bench synced them, and will do vacuum sync after I can get it running reasonably well
transition ports checked, confirmed clear? Yes
adequate valve clearances present? Need to check this; adjusted at a shop 1000 miles ago (according to a receipt), so they should be fine, but I need to get in there and confirm too.
carb vent hose clear? not plugged or kinked? Yep

jkv45 · June 18th, 2021, 08:18 AM

Did you replace any of the jets?

Slides lift and fall smoothly (manually)?

Seems to me that the idle circuit is working, but it fails to pull fuel into the venturi when the slides/needles rise.

With it idling, can you watch the slides as you open the throttle to see if they are lifting?

Where did you get the diaphragm you replaced? OEM?

June 17th, 2021, 07:35 AM	#1
RustToRedemption ninjette.org newbie Name: Josh Location: Iowa Join Date: Jun 2021 Motorcycle(s): 2007 Ninja 250 - 2008 Hyosung GT250 - 1981 Honda XL500S - 1978 Kawasaki kz200 Posts: 7	Running too Lean?, dies when given throttle Bought a non-runner for $100, took the carbs out and cleaned them (not my first carb rodeo; ultrasonic cleaned and then blew compressed air through all the passages, cleaned the jet orifices with fine wire). Installed new diaphrams, as one of the old ones had a tear in it. It now starts right up and idles perfectly, but will die immediately if you touch the throttle. Thinking its way too lean; I've re-oiled the filter and that only changed that you can now rev it with the choke on. Changed the AF screw to 2.75 turns out on both carbs. Checked the intake manifolds for leaks and there was no fluctuation in idle RPM when spraying carb cleaner around them. I feel like I have to be missing something, but Im stumped right now. Any really common problems on these bikes that cause a lean condition? Any help is appreciated. **Ive searched the forums, and it seems like most people who have this problem put their carbs together incorrectly/with missing pieces. Im fairly confident I've done this without a mistake.

June 17th, 2021, 07:53 AM	#2
jkv45 Rev Limiter Name: Jay Location: WI Join Date: Jul 2013 Motorcycle(s): '06 SV650n, '00 Derbi GPR, '64 CA77 Dream 305, '70 CL450 Scrambler, numerous dirt bikes Posts: A lot. MOTM - Jun '18, Oct '16	Take the air filter out and try it. Better or worse?
	1 out of 1 members found this post helpful.

June 17th, 2021, 09:13 AM	#4
Triple Jim Guy Who Enjoys Riding Name: Jim Location: North Carolina Join Date: Jul 2016 Motorcycle(s): Ninja 250 Posts: A lot. MOTM - Oct '18, Aug '17, Aug '16	10 to 1 you missed something when cleaning them. These carbs are not simple to get truly clean.
	1 out of 1 members found this post helpful.

June 17th, 2021, 01:03 PM	#7
ducatiman ninjette.org certified postwhore Name: Gordon Location: new york Join Date: Sep 2009 Motorcycle(s): '95 DUCATI 900SS/SP '07 DUCATI SS800 '19 HONDA CBR650R Posts: A lot. MOTM - Nov '18, Mar '17	stock exhaust? both needle jets present & accounted for? petcock confirmed delivering adequate fuel? try again with an open fuel cap? what jet sizes, both main & pilot? __________________________________________________ gordon@customcarbservices.com Custom Carb Service www.customcarbservices.com

June 17th, 2021, 05:01 PM	#9
ducatiman ninjette.org certified postwhore Name: Gordon Location: new york Join Date: Sep 2009 Motorcycle(s): '95 DUCATI 900SS/SP '07 DUCATI SS800 '19 HONDA CBR650R Posts: A lot. MOTM - Nov '18, Mar '17	carbs wet tested when off the bike after your clean? Float levels nailed? pilot screws get new orings? new float valves? carbs in reasonable synch? transition ports checked, confirmed clear? adequate valve clearances present? carb vent hose clear? not plugged or kinked? __________________________________________________ gordon@customcarbservices.com Custom Carb Service www.customcarbservices.com Last futzed with by ducatiman; June 18th, 2021 at 05:40 AM.

June 17th, 2021, 03:14 PM	#8
RustToRedemption ninjette.org newbie Name: Josh Location: Iowa Join Date: Jun 2021 Motorcycle(s): 2007 Ninja 250 - 2008 Hyosung GT250 - 1981 Honda XL500S - 1978 Kawasaki kz200 Posts: 7	stock exhaust? Yes both needle jets present & accounted for? Yes petcock confirmed delivering adequate fuel? Maybe? The bowls have been full the two times I’ve taken the carbs off the bike try again with an open fuel cap? Nope, but I’m assuming if I have adequate fuel, checking for a blocked fuel vent won’t matter what jet sizes, both main & pilot? Main is a 105 and pilot is maybe a 38? Hard to read.

June 18th, 2021, 06:22 AM	#10
RustToRedemption ninjette.org newbie Name: Josh Location: Iowa Join Date: Jun 2021 Motorcycle(s): 2007 Ninja 250 - 2008 Hyosung GT250 - 1981 Honda XL500S - 1978 Kawasaki kz200 Posts: 7	carbs wet tested when off the bike after your clean? Dont know exactly what you mean by this, but I function checked the float valves to make sure they flowed fuel, and stopped the flow of fuel Float levels nailed? Checked statically with calipers, within spec. pilot screws get new orings? Yes, and made sure it still had the washer in there as well. new float valves? No, but inspected the tips for damage and found none, and the spring return nipple on both needle valves are in good working condition. carbs in reasonable synch? Yes, bench synced them, and will do vacuum sync after I can get it running reasonably well transition ports checked, confirmed clear? Yes adequate valve clearances present? Need to check this; adjusted at a shop 1000 miles ago (according to a receipt), so they should be fine, but I need to get in there and confirm too. carb vent hose clear? not plugged or kinked? Yep

June 18th, 2021, 08:18 AM	#11
jkv45 Rev Limiter Name: Jay Location: WI Join Date: Jul 2013 Motorcycle(s): '06 SV650n, '00 Derbi GPR, '64 CA77 Dream 305, '70 CL450 Scrambler, numerous dirt bikes Posts: A lot. MOTM - Jun '18, Oct '16	Did you replace any of the jets? Slides lift and fall smoothly (manually)? Seems to me that the idle circuit is working, but it fails to pull fuel into the venturi when the slides/needles rise. With it idling, can you watch the slides as you open the throttle to see if they are lifting? Where did you get the diaphragm you replaced? OEM?

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