July 3rd, 2019, 11:34 PM | #1 |
ninjette.org newbie
Name: Aaron
Location: Denver
Join Date: Jul 2018 Motorcycle(s): Ninja 250r, ZG1000 Posts: 4
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Low Speeds High RPMs HELP!
2012 Ninja 250r
Bought "used" with 70 miles on it. The bike now has almost 3k miles on it but its had this issue since day one and I only feel like its getting worse. The bike has no problem idling or running, but its top end speeds are greatly reduced from what I've seen other people have on similar stock bikes. Since day one I've been trying to find the source of the problem cleaning the already flawless carbs, adjusting the Fuel/Air ratio, checking the air filter spark plugs, gear ratio, all to no avail. I haven't paid much attention to low gears but recently I've been getting around 60-65mph at around 9.5-10k rpm, If I WOT I can squeeze around 80mph out of her at red line after probably 30 seconds from 60mph. Just today it was particularly hot outside and it dropped to 55mph at 10k rpm. I work about 30 miles away from where I live and like the bike for its gas mileage but I hate making the engine scream just to keep up with traffic and I find it quite dangerous that I have no top end left in case of emergency. I've scoured the web and found no real answer. Last thing I can think to mention is that early on I discovered spotty Y hose connectors and hoses routed to the wrong places in the carb. I rectified all the problems and the routing is back to stock. After speaking with a long time bike mechanic we think the bike came from Cali and had work to meet stricter regulations there. I think this is what is causing this issue if they changed something that I haven't looked at yet but maybe not. |
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July 4th, 2019, 03:45 AM | #2 | |
ninjette.org member
Name: Garry
Location: Bungendore Australia
Join Date: Jan 2019 Motorcycle(s): GPX250 1989 model and 1990 model Posts: 98
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Quote:
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Perpetua Culpa Alterna Vagus |
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July 4th, 2019, 05:34 AM | #3 |
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count your sprocket teeth. I had very similar speed vs rpm relationship when I was running +2 gearing on the rear sprocket. stock is 14/45 IIRC
but yes, check the clutch adjustment. very possible for the lever to not allow the clutch to fully disengage if the barrel adjuster is too tight. |
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July 4th, 2019, 11:47 AM | #4 |
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July 4th, 2019, 12:16 PM | #5 |
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^ attempted adjusting of the pilot screws would make sense, no?
You need to verify the carb innards are absolutely correct and assembled correctly for your version 250, nobody been in there "modding"...screwin' around, swappin' stuff at any time....other than Mr and Mrs Keihin, that is. On BOTH carbs verify the size of pilot jets, main jets, # on needles, visually assure the needle jets are BOTH present in all their shining glory (as these commonly "go missing" and could very well be responsible for transition issues) Verify the pilot screw springs, washers and orings are present too. Always remember....Clean Carbs Matter.
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gordon@customcarbservices.com Custom Carb Service www.customcarbservices.com |
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July 4th, 2019, 03:21 PM | #6 |
ninjette.org newbie
Name: Aaron
Location: Denver
Join Date: Jul 2018 Motorcycle(s): Ninja 250r, ZG1000 Posts: 4
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The two flat head screws on the bottoms of the carbs. I had adjusted them previously cause it was running really rich, but I put them back to stock (left 2 1/2 turns, right 1 3/4 turns)
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July 4th, 2019, 03:29 PM | #7 |
ninjette.org newbie
Name: Aaron
Location: Denver
Join Date: Jul 2018 Motorcycle(s): Ninja 250r, ZG1000 Posts: 4
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Looks like the clutch disengages all the way and has the 2-3mm of slack. Sprockets are stock
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July 4th, 2019, 04:34 PM | #8 | |
ninjette.org certified postwhore
Name: AKA JacRyann
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Quote:
Would be helpful to know exact AFR at time it's bogging at WOT going 55mph or 80mph. Should inspect your slide diaphraghms for sealing issues or pinholes. Also with warmed-up engine, measure manifold vacuum at idle and 3000rpm. |
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July 4th, 2019, 04:47 PM | #9 |
ninjette.org newbie
Name: Aaron
Location: Denver
Join Date: Jul 2018 Motorcycle(s): Ninja 250r, ZG1000 Posts: 4
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Youre going to hate me for this response, but I was going off of exhaust fumes (If it smelled really rich id lean it out) Which I feel caused it to be really lean because it was running pretty hot.
Im not exactly sure about your second comment but its basically constant slow acceleration up to 80. I dont really feel a loss of power its just red lining at slower speeds than I would think. I dont really want to pull the carb again, its a pain in the ass on this bike and it seemed alright to my untrained eye (about a year ago) but if you think its a leading suspect I can give it a look. Worst case I can take it over to the shop and they can have a gander. Expensive though :/ |
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July 5th, 2019, 05:59 PM | #10 | |
ninjette.org certified postwhore
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Let's step back a little....
A bike that's been ridden less than 1-mile/month for past 7-years is most likely going to have dirty and clogged carbs. Spray "carb cleaners" do not work! They no longer have chlorinated compounds and are no better at cleaning your carbs than pee! At least that has some ammonia in it and can do some actual cleaning. These carbs ran perfectly fine when bike rolled off showroom floor. The only reason yours isn't running like scalded cat is because carbs in your bike aren't factory-fresh clean. Quote:
https://www.youtube.com/watch?v=AwXRvgyFUG4 https://faq.ninja250.org/wiki/How_a_...arbs_explained Due to limitations of mechanical-computing, carburetor needs multiple fluid circuits to deal with wide range of airflow and load conditions that exist in motorcyle engines. Some circuits deal with idle mixture, others mid-range and others fulfil WOT high-end operations. As you can see, adjusting pilot screws for low-end makes zero effect to high-end/high-load mixtures. That's why I asked for actual air-fuel ratio while you are going full-throttle at 55mph and 80mph. AFR under those conditions will be wildly different than sitting at idle. Again, these carbs worked great when bike left showroom floor, therefore no adjustment is needed away from factory settings. You just need to restore them to factory-fresh clean condition. Please review these threads on what actually needs to be done to fully clean and restore carbs to factory-fresh conditions. Be prepared to remove carbs from bike at least 4-5x more. https://www.ninjette.org/forums/showthread.php?t=333176 https://www.ninjette.org/forums/showthread.php?t=334365 https://www.ninjette.org/forums/showthread.php?t=330213 https://www.ninjette.org/forums/showthread.php?t=330960 https://www.ninjette.org/forums/showthread.php?t=323737 https://www.ninjette.org/forums/showthread.php?t=323452 https://www.ninjette.org/forums/showthread.php?t=322846 https://www.ninjette.org/forums/showthread.php?t=321223 https://www.ninjette.org/forums/showthread.php?t=317977 https://www.ninjette.org/forums/showthread.php?t=317810 https://www.ninjette.org/forums/showthread.php?t=316395 https://www.ninjette.org/forums/showthread.php?t=315193 https://www.ninjette.org/forums/showthread.php?t=299855 https://www.ninjette.org/forums/showthread.php?t=280658 NOTE: there's clue in those threads on how you can get away with removing your carbs just one time more... Last futzed with by DannoXYZ; July 6th, 2019 at 06:33 AM. |
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