May 26th, 2015, 07:25 AM | #1 |
ninjette.org newbie
Name: Michael
Location: Denver CO
Join Date: May 2015 Motorcycle(s): 97 Ninja 250 Posts: 5
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Rejetting for Altitude
Hey guys, I bought a 97 250 last October and it ran great for a month, then when warmed and ridden after about 20 minutes it just bogs down and dies. If I let it sit for 30 minutes or so it will crank back up and go for another 10-20 minutes before bogging down and dying. There is a nasty hanging idle, If I rev it above 4-5k it comes back down to 1500 very slowly. Saw the thread below this and I'm going to check the air filter/box, as well as the slides. I was told a hanging idle could be vacuum leak?
Now that summer is on it's way I plan on pulling the carbs for my first time and cleaning them. While I'm in there I was curious about rejetting for the Denver altitude. I've been told that it isn't needed and to not worry about it, but I've found a couple topics around different forums that state a #102 main jet and #35 pilot jets. Most of my riding will be around 5-6k feet but I do plan on some mountain riding and could be around 9-10k. Any advice here? Thanks in advance. Last futzed with by micellis; May 26th, 2015 at 07:50 AM. Reason: Content |
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May 26th, 2015, 08:27 AM | #2 |
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If the pre-gen is anything like the new gen you'd actually want to go down in size... Modified exhaust/intake? I have a very open air box and slip-on and I'm still rich on the top end with a #100 in there...
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May 26th, 2015, 08:29 AM | #3 |
Rev Limiter
Name: Jay
Location: WI
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Not sure if compensation for altitude would be required or not. I believe that increased altitude will cause you to run richer (less dense air charge).
As far as the other issues, it does sound like a vacuum leak causing the revs to hang-up. Spray some carb cleaner around the boots from the carb to the engine and listen for a change in rpms. The other issues sounds like fuel-starvation for one reason or the other. Either the tank is not venting (open it when it quits and listen for air rushing in) or a restriction in the fuel flow to the carbs that eventually won't let them fill to an adequate level. That would most likely be an issue with the petcock or debris in the tank clogging the filters/screens and reducing flow. |
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May 26th, 2015, 08:29 AM | #4 | ||
ninjette.org newbie
Name: Michael
Location: Denver CO
Join Date: May 2015 Motorcycle(s): 97 Ninja 250 Posts: 5
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Quote:
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May 26th, 2015, 08:33 AM | #5 |
Rev Limiter
Name: Jay
Location: WI
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Did you store it with a full tank? If not, you may have enough condensation in the tank to cause running issues.
I always suggest completely removing and replacing the fuel - if there is any question at all - before going into more complicated troubleshooting. Use ethanol-free 87 if possible. A vacuum leak would be caused by leaking intake boots most likely, but you should check the condition of the vacuum like going to the petcock from the carb. If that was damaged and leaking it could cause what you described. |
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May 26th, 2015, 08:35 AM | #6 | |
ninjette.org newbie
Name: Michael
Location: Denver CO
Join Date: May 2015 Motorcycle(s): 97 Ninja 250 Posts: 5
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Quote:
It was about 3/4 full, with seafoam added for stability. I've ran it every 2 weeks for about 30 mins, even just idling to cycle gas through. |
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May 26th, 2015, 08:38 AM | #7 | |
Rev Limiter
Name: Jay
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Quote:
In the future, add the stabilizer and fill the tank to the top, then drain the floatbowls. Best thing to do is change the oil and filter before storing and not start it again until it's time to ride. Starting and idling just contaminate the fresh oil that is coating and protecting the engine internals from corrosion. |
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May 26th, 2015, 08:42 AM | #8 | |
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No need to replace the lines, fuel filter or any parts if you can clean them. If ANY lines however are cracked, brittle or hard it would be best to replace them... It sounds to me like this might be a compound issue. Gummed up carbs can also cause your symptoms, so it would be best to start taking things apart and investigating further... If you require any assistance, I'm in Golden... I'll be gone the first 2 weeks in June, but after that I'd be happy to assist where needed. Post up some pics as you take things apart and we can help you further on here.
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May 26th, 2015, 09:14 AM | #9 |
I'm crazy,your excuse is?
Name: Winston
Location: Connecticut
Join Date: May 2013 Motorcycle(s): 250 2007 ninja Posts: A lot.
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Did you buy this bike at a lower elevation and then took it up high?
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May 26th, 2015, 09:31 AM | #10 |
ninjette.org newbie
Name: Michael
Location: Denver CO
Join Date: May 2015 Motorcycle(s): 97 Ninja 250 Posts: 5
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May 26th, 2015, 11:33 AM | #11 | |
EX500 full of EX250 parts
Name: Bill
Location: Grand Rapids-ish, MI
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Quote:
For a quick check, just use a spare key and open the gas cap when the problem happens. That'll allow air into the tank so the fuel can run out properly. Obviously it's not a permanent fix, but it's a free and easy way to verify if that's the problem.
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May 26th, 2015, 11:38 AM | #12 | |
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Example: The performance of a 600cc inline 4 will fall off before a 600cc v-twin. And the 600cc v-twin will fall off before a 600cc single cylinder engine. Both bikes have to contend with the reduced amount of oxygen in the atmosphere but there's a secondary effect of high altitude: the reduced atmospheric pressure causes the Volumetric Efficiency of the engine to fall off. While the effect of reduced oxygen percentage is equal for all engines running at that altitude, the effect of reduced atmospheric pressure is not equal. The effect of reduced atmospheric pressure is that the individual cylinders begin having difficulty "filling" themselves (using intake suction to accelerate a gulp of atmosphere into the cylinder). A small fast-moving cylinder will have a bigger problem than a large slower-moving cylinder. Even though it's not absolutely correct you can get a pretty accurate idea of the problem by imaging that the atmosphere gets "stretchy" at high altitude, so the "long pull" of a big, slower moving piston will be better at moving it. This means the EX250 isn't a very good choice for high altitude riding. |
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May 26th, 2015, 03:04 PM | #13 | |
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Quote:
Yes, good recommendation for the test, just wondering for my own edification.
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May 26th, 2015, 03:25 PM | #14 | |
EX500 full of EX250 parts
Name: Bill
Location: Grand Rapids-ish, MI
Join Date: Jul 2012 Motorcycle(s): '18 Ninja 400 • '09 Ninja 500R (selling) • '98 VFR800 (project) • '85 Vulcan VN700 (sold) Posts: A lot.
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Quote:
It's a huge problem on the VN750 (they even gave it a name - Phantom Out Of Gas Syndrome, or POOGS) and pretty common on the EX500. I've seen posts about the vent here before, so I'm just assuming it's similar. On the 500, there's an overflow drain tube that's connected to the area around the fill hole. But the air in the tank still has to go through the vent system to breathe out to that area. The tank has to have some sort of vent. If air can't get in to replace the fuel that's leaving, it'll vacuum-lock and the fuel will stop flowing. They use a few rubber discs in the vent so that it's not just completely open to the atmosphere, which would allow for faster evaporation, contamination, and more spillage if it tipped over. Over time those rubber discs get hard and stop working properly, leading to that vent not actually venting.
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*** Unregistered, I'm not your mom and I'm not paying for your parts, so do whatever you want with your own bike. *** Last futzed with by InvisiBill; May 26th, 2015 at 03:39 PM. Reason: start != stop |
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May 26th, 2015, 03:31 PM | #15 | ||
Daily Ninjette rider
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Quote:
http://forums.ninja250.org/posting.p...&t=81112&tro=1 Quote:
http://faq.ninja250.org/wiki/Why_wou..._my_jetting%3F http://faq.ninja250.org/wiki/How_to_...e_your_jetting
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May 26th, 2015, 05:49 PM | #16 | |
Long Time Rider
Name: Blue
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May 26th, 2015, 07:12 PM | #17 | |
ninjette.org certified postwhore
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May 27th, 2015, 07:46 PM | #18 | |
ninjette.org newbie
Name: Michael
Location: Denver CO
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Quote:
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May 27th, 2015, 08:50 PM | #19 |
ninjette.org certified postwhore
Name: Spooph
Location: Golden, CO
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update us when you can, PM me if you need any hands-on assistance after mid-June...
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