Hesitation after rolling off throttle

djdirka · September 27th, 2017, 09:07 PM

I thought it was normal until I let someone else ride my bike, but at any gear, if I let off the throttle my bike starts to slow down pretty fast and then as soon as I roll back on the throttle it jerks back.
I have a '92 250r and I think it might be the carbs, but I changed the spark plugs a few days ago, put new tires on, and was going to change the oil and all other fluids before winter. I also added a bit of seafoam when I filled up today so hopefully that can clean the carbs a bit, but I just wanted to know what the problem could be?

Like I said, its a '92 and only has 8000 miles on it, so Im assuming the previous owner really didnt do much to it if they didnt ride it too much. Any thoughts?

Triple Jim · September 28th, 2017, 06:32 AM

I'll be interested to hear what develops here, because if I run mine at mid-high RPM with the throttle closed for a while, like going down a steep hill, and then open the throttle, there is usually a delay before the power comes on. I assumed this was an anomaly of CV carbs.

Seafoam won't do much to clean anything. You can see what's in it by looking up an MSDS for it. Products with Techron (polyetheramine) will actually tend to clean carbs and the fuel system, but of course not like disassembling the carbs and cleaning them the hard way.

jkv45 · September 28th, 2017, 06:50 AM

I think most of what you are experiencing is what TJ noted - a trait of a CV carb. You could make a few common carb adjustments that may help like adjusting the idle mixture screws, idle speed, carb sync, and shimming the needles. Even if they don't cure the problem, the fine tuning will surely make it run better overall.

Something else that may make that a lot more noticeable and annoying is the excessive amount of play in the "cush drive" on the rear wheel.

If you put the bike on the centerstand and put it in gear (not running), then move the rear wheel back and forth you will see the amount of play in the cush drive. Most of the time it's excessive. Shimming it with something to reduce the play will smooth out on/off/on throttle transitions.

Both our Ninja 250s and our Ninja 500 needed quite a bit of shims to snug it up, and it is noticeable.

Here's more info on the cush drive - https://faq.ninja250.org/wiki/How_to...the_cush_drive

Carb tuning info - https://faq.ninja250.org/wiki/Intake

DannoXYZ · September 28th, 2017, 07:22 AM

Drill the slide...

ducatiman · September 28th, 2017, 07:23 AM

All tuning consideration should be predicated on a bike in known good spec...valve clearances confirmed, carbs legitimately cleaned, plugs, filters, etc etc....THEN evaluating your need for changes.

Tuning can be tweaked for performance over fuel efficiency..to YOUR preferences....investing time and effort.

Using calculated MPG vs your ass dyno is in your best interests...as unfortunately we all don't own EGA's and Dyno's.

As was posted earlier...radical intake/exhaust changes dictate radical jetting needs. Jetting trends can be suggested, but YOUR satisfaction can't be precisely anticipated by proclaiming "use jet size XXX" over an internet forum.

I'll submit...the bike will run with any of 3 sized pilots or mains...up to you to find your mix of performance vs efficiency.

Major mods only complicate...rendering "keyboard tuning" near impossible. What is acceptable for one owner, may be unacceptable for another.

Bigger (jet size) is not necessarily better....

Take your time, experiment step by step within logical, reasonable bounds, says I. Be in a position to recognize and reverse any "mistakes".

Sorry for long winded ramble......

DannoXYZ · September 28th, 2017, 08:59 AM

Quote:

Originally Posted by ducatiman

Take your time, experiment step by step within logical, reasonable bounds, says I. Be in a position to recognize and reverse any "mistakes".

Yes! Keep a log of everything you do! Will be able to reverse and/or spot trends in the future!

Ram Jet · September 30th, 2017, 08:41 AM

Quote:

Originally Posted by JacRyann

Drill the slide...

Where? What for? Just curious.

Bill

DannoXYZ · September 30th, 2017, 10:24 AM

Quote:

Originally Posted by Ram Jet

Where? What for? Just curious.

Bill

Improves low-end/mid-range responsiveness.
https://www.ninjette.org/forums/showthread.php?t=10736

Ram Jet · September 30th, 2017, 10:43 AM

Quote:

Originally Posted by JacRyann

Improves low-end/mid-range responsiveness.
https://www.ninjette.org/forums/showthread.php?t=10736

Thanks JR. Interesting article. I won't be doing this as I'm happy with my carbs right now. Good for future reference though.

Bill

September 27th, 2017, 09:07 PM	#1
djdirka ninjette.org newbie Name: Derek Location: 609 State Route 57 E Join Date: Aug 2017 Motorcycle(s): 1992 Ninja 250r Posts: 2	Hesitation after rolling off throttle I thought it was normal until I let someone else ride my bike, but at any gear, if I let off the throttle my bike starts to slow down pretty fast and then as soon as I roll back on the throttle it jerks back. I have a '92 250r and I think it might be the carbs, but I changed the spark plugs a few days ago, put new tires on, and was going to change the oil and all other fluids before winter. I also added a bit of seafoam when I filled up today so hopefully that can clean the carbs a bit, but I just wanted to know what the problem could be? Like I said, its a '92 and only has 8000 miles on it, so Im assuming the previous owner really didnt do much to it if they didnt ride it too much. Any thoughts?

September 28th, 2017, 07:23 AM	#5
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	All tuning consideration should be predicated on a bike in known good spec...valve clearances confirmed, carbs legitimately cleaned, plugs, filters, etc etc....THEN evaluating your need for changes. Tuning can be tweaked for performance over fuel efficiency..to YOUR preferences....investing time and effort. Using calculated MPG vs your ass dyno is in your best interests...as unfortunately we all don't own EGA's and Dyno's. As was posted earlier...radical intake/exhaust changes dictate radical jetting needs. Jetting trends can be suggested, but YOUR satisfaction can't be precisely anticipated by proclaiming "use jet size XXX" over an internet forum. I'll submit...the bike will run with any of 3 sized pilots or mains...up to you to find your mix of performance vs efficiency. Major mods only complicate...rendering "keyboard tuning" near impossible. What is acceptable for one owner, may be unacceptable for another. Bigger (jet size) is not necessarily better.... Take your time, experiment step by step within logical, reasonable bounds, says I. Be in a position to recognize and reverse any "mistakes". Sorry for long winded ramble...... __________________________________________________ gordon@customcarbservices.com Custom Carb Service www.customcarbservices.com

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September 28th, 2017, 06:32 AM	#2
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	I'll be interested to hear what develops here, because if I run mine at mid-high RPM with the throttle closed for a while, like going down a steep hill, and then open the throttle, there is usually a delay before the power comes on. I assumed this was an anomaly of CV carbs. Seafoam won't do much to clean anything. You can see what's in it by looking up an MSDS for it. Products with Techron (polyetheramine) will actually tend to clean carbs and the fuel system, but of course not like disassembling the carbs and cleaning them the hard way.

September 28th, 2017, 06:50 AM	#3
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	I think most of what you are experiencing is what TJ noted - a trait of a CV carb. You could make a few common carb adjustments that may help like adjusting the idle mixture screws, idle speed, carb sync, and shimming the needles. Even if they don't cure the problem, the fine tuning will surely make it run better overall. Something else that may make that a lot more noticeable and annoying is the excessive amount of play in the "cush drive" on the rear wheel. If you put the bike on the centerstand and put it in gear (not running), then move the rear wheel back and forth you will see the amount of play in the cush drive. Most of the time it's excessive. Shimming it with something to reduce the play will smooth out on/off/on throttle transitions. Both our Ninja 250s and our Ninja 500 needed quite a bit of shims to snug it up, and it is noticeable. Here's more info on the cush drive - https://faq.ninja250.org/wiki/How_to...the_cush_drive Carb tuning info - https://faq.ninja250.org/wiki/Intake

September 28th, 2017, 07:22 AM	#4
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	Drill the slide...