Carb question

sombo · March 22nd, 2010, 04:42 PM

Ok, this isn't for my bike which is running like a prize winning champion. Today I met a guy at work that has a 2003 ninjette that had been sitting for several months and before taking it out he had cleaned the carbs. However, now he is having throttle response and top end power issues. I took a little spin on the bike and it pretty much stopped at around 8k rpms which of course is right when it starts to get into it's powerband.

I'd like to give him some more accurate advice on what he needs to look for to try and fix the issue. Like I said, he had taken them apart and cleaned them and now it doesn't run right. So it could be that something wasn't put back properly. I gave him this site and the nina250 info site to check out so hopefully he looks them up.

Now, another issue that we had a disagreement on. His bike is still in stock configuration and he claims he has pegged the speedometer at 120mph and was even pulled over by a cop telling him he clocked him at 121mph. I proceeded to inform him of the factory rated top speed, the 10% difference in the speedo, and the current top speed competitions going on with modified bikes. All this to help explain how there is no way he could be doing 121mph on a stock 2003 ninjette. He says once he gets it going again we can go find out. I told him to try and keep up with mine (jetted and 2-into-1 yoshi pipe) and we'll find out.

Samer · March 22nd, 2010, 04:51 PM

This should probably be moved to the pre-gen section.

However, I believe general consensus is about ~100 actual top speed. Indicated could be a bit more. I think the pre-gen might have marginally more power at the top end. However, I guarantee that it would take major mods to go to 120 mph and even then I'd be very skeptical. Top speed goes with power cubed so there is a huge power difference between 105 and 120 mph.

sombo · March 22nd, 2010, 06:26 PM

Quote:

Originally Posted by Samer

This should probably be moved to the pre-gen section.

However, I believe general consensus is about ~100 actual top speed. Indicated could be a bit more. I think the pre-gen might have marginally more power at the top end. However, I guarantee that it would take major mods to go to 120 mph and even then I'd be very skeptical. Top speed goes with power cubed so there is a huge power difference between 105 and 120 mph.

Crap, thought I was in the pre-gen section when I posted this, my bad. I could have swore that I clicked on the pre-gen section on the forums list. Sorry bout that.

Even with the slightly more top end the pre-gens are only factory rated at 110mph top speed in stock configuration. And this bike is 100% stock.

Now as for the actual problem he is having with the bike not wanting to rev properly or be stable at idle and not going past 8k in gear (tested that myself). What things could be causing that? Three different people (myself included) figure it has to be something he did within the carbs when he took them apart to clean them. But not really sure what exactly.

Momaru · March 22nd, 2010, 07:10 PM

If it was working before he messed with the carbs and that's all he messed with...

There's a very fair chance I'm wrong but: high-end issues may be a main jet or needle, stability @ idle being off sounds like a carb synch issue. It's worth noting these bikes come with 2 different needles from the factory and the mix screws set asymmetrically. Depending on how thorough/careful a carb cleaning he did, it's possible he switched needles on accident. If that's not it, I'd just go thru the whole carb troubleshooting/tuning sequence. There's almost certainly more but here's some to get ya started:

Are the runners securely attached from the airbox and to the engine?
Check the fuel/vacuum hoses for same
Check cable play & attachment
main jets - are they clear & snugly attached?
needle - right needle in the right carb? are they seated properly?
diaphragms - were they re-seated completely? is one torn?
mixture screws - were they messed with?
carb synch - how far off is it?
idle speed - what rpm is it idling?

Could probably check the float bowls too, but I haven't messed with it myself so can't help ya there.

kkim · March 22nd, 2010, 07:40 PM

yeah, find out exactly what he did when he "cleaned" out the carbs. Did he remove the jets and blow them out clean? He may have some crap still stuck in the jets.

from the sound of his top speed claims, I'm willing to bet he doesn't know much about bikes and maintaining them.

Alex · March 22nd, 2010, 09:14 PM

/moved to pregen tech

nate-bama · March 22nd, 2010, 09:27 PM

110 top speed LOL, off a cliff perhaps

March 22nd, 2010, 04:42 PM	#1
sombo Newb..... on a steeek! :D Name: Mike Location: Windermere, FL Join Date: Feb 2009 Motorcycle(s): 2012 Harley Davidson XL883L Sportster Superlow Posts: A lot.	Carb question Ok, this isn't for my bike which is running like a prize winning champion. Today I met a guy at work that has a 2003 ninjette that had been sitting for several months and before taking it out he had cleaned the carbs. However, now he is having throttle response and top end power issues. I took a little spin on the bike and it pretty much stopped at around 8k rpms which of course is right when it starts to get into it's powerband. I'd like to give him some more accurate advice on what he needs to look for to try and fix the issue. Like I said, he had taken them apart and cleaned them and now it doesn't run right. So it could be that something wasn't put back properly. I gave him this site and the nina250 info site to check out so hopefully he looks them up. Now, another issue that we had a disagreement on. His bike is still in stock configuration and he claims he has pegged the speedometer at 120mph and was even pulled over by a cop telling him he clocked him at 121mph. I proceeded to inform him of the factory rated top speed, the 10% difference in the speedo, and the current top speed competitions going on with modified bikes. All this to help explain how there is no way he could be doing 121mph on a stock 2003 ninjette. He says once he gets it going again we can go find out. I told him to try and keep up with mine (jetted and 2-into-1 yoshi pipe) and we'll find out.

March 22nd, 2010, 07:10 PM	#4
Momaru ninjette.org certified postwhore Name: Paul Location: Roanoke, VA Join Date: Jun 2009 Motorcycle(s): 2008 Candy Plasma Blue 250R Posts: A lot.	If it was working before he messed with the carbs and that's all he messed with... There's a very fair chance I'm wrong but: high-end issues may be a main jet or needle, stability @ idle being off sounds like a carb synch issue. It's worth noting these bikes come with 2 different needles from the factory and the mix screws set asymmetrically. Depending on how thorough/careful a carb cleaning he did, it's possible he switched needles on accident. If that's not it, I'd just go thru the whole carb troubleshooting/tuning sequence. There's almost certainly more but here's some to get ya started: Are the runners securely attached from the airbox and to the engine? Check the fuel/vacuum hoses for same Check cable play & attachment main jets - are they clear & snugly attached? needle - right needle in the right carb? are they seated properly? diaphragms - were they re-seated completely? is one torn? mixture screws - were they messed with? carb synch - how far off is it? idle speed - what rpm is it idling? Could probably check the float bowls too, but I haven't messed with it myself so can't help ya there. __________________________________________________ Proud member of the Blue Army

March 22nd, 2010, 09:14 PM	#6
Alex ninjette.org dude Name: 1 guess :-) Location: SF Bay Area Join Date: Jun 2008 Motorcycle(s): '13 Ninja 300 (white, the fastest color!), '13 R1200RT, '14 CRF250L, '12 TT-R125LE Posts: Too much. Blog Entries: 7	/moved to pregen tech __________________________________________________ Montgomery Street Motorcycle Club / cal24.com / crf250l.org / ninjette.org ninjette.org Terms of Service Shopping for motorcycle parts or equipment? Come here first. The friendliest Ninja 250R/300/400 forum on the internet! (especially Unregistered)

March 22nd, 2010, 09:27 PM	#7
nate-bama North Alabama Mtn. ryder Name: Nate Location: Alabama Join Date: May 2009 Motorcycle(s): 2006 Posts: 537	110 top speed LOL, off a cliff perhaps __________________________________________________ QTRltrPWR

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March 22nd, 2010, 04:51 PM	#2
Samer ninjette.org guru Name: Samer Location: Jupiter, Florida Join Date: Sep 2009 Motorcycle(s): 09 Ninja 250R SE Posts: 376	This should probably be moved to the pre-gen section. However, I believe general consensus is about ~100 actual top speed. Indicated could be a bit more. I think the pre-gen might have marginally more power at the top end. However, I guarantee that it would take major mods to go to 120 mph and even then I'd be very skeptical. Top speed goes with power cubed so there is a huge power difference between 105 and 120 mph.

March 22nd, 2010, 07:40 PM	#5
kkim Join Date: Nov 2008 Posts: Too much.	yeah, find out exactly what he did when he "cleaned" out the carbs. Did he remove the jets and blow them out clean? He may have some crap still stuck in the jets. from the sound of his top speed claims, I'm willing to bet he doesn't know much about bikes and maintaining them.