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Old July 8th, 2018, 06:13 PM   #1
DirtyMike
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[1987] Pilot/Main jet for altitude

I have had my carbs cleaned twice now (once by me and also professionally) and they are saying I need to replace my jets to get it to idle correctly. Odd thing is my bike now doesn't want to go past 7k rpm.....it was redlining fine before just wouldn't go before 3K idle.

I live in Colorado around 5500 altitude.
Any advice on if the jets are actually the issue? I feel like stock should work...
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Old July 8th, 2018, 08:07 PM   #2
DannoXYZ
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At that altitude, you'd want to go down 2 jet-sizes to compensate for thinner air. Most likely not your issue as richer-than-ideal mixture won't cause it to not redline.

Most likely you have an insufficient fuel issue due to clogged fuel-circuits. Or clogged vacuum circuits leading to slides not opening enough. Are you able to disassemble carbs down to last nut and bolt to clean?
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Old July 9th, 2018, 06:22 AM   #3
jkv45
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Originally Posted by DirtyMike View Post
I have had my carbs cleaned twice now (once by me and also professionally) and they are saying I need to replace my jets to get it to idle correctly. Odd thing is my bike now doesn't want to go past 7k rpm.....it was redlining fine before just wouldn't go before 3K idle.

I live in Colorado around 5500 altitude.
Any advice on if the jets are actually the issue? I feel like stock should work...
Most likely the carbs are not right. What did it do before having the carbs worked on?

Possibly the diaphragms are damaged or not seated correctly. Confirm that the butterflies on the carb are opening all the way when you open the throttle by watching them rotate on the right side of the carb. With the throttle wide open (engine off) see if you can rotate the shaft more.

Reach in the airbox and lift the carb slides (engine off). See if the rise and fall smoothly and evenly.

You should be able to get it to idle properly with the Idle Mixture adjustment screws on the bottom of the carb. Because of the altitude, you would need to have the adjustments set farther "in" than normal. Normal is in the range of 2.5 turns out, so you would be closer to 2 turns out.

If it's running rich at wide open throttle and high RPMs, you would need to change the Main Jet to a leaner one - but i don't think that is your problem.

Leaning the Main Jet may help it to pull cleaner and make optimum power, but it should run decent (and rev to 10,000) with the stock jets.

Here is some general carb info - https://faq.ninja250.org/wiki/Intake

Adjustments for altitude and temp - https://faq.ninja250.org/wiki/Jettin...26_temperature
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Old July 9th, 2018, 07:29 AM   #4
wiguzziman
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Carb float height

As long as we're on the subject of carburetors; does anyone have the float height measurement for the 2006 250 Ninja carbs handy? THANKS!!

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Old July 9th, 2018, 09:12 AM   #5
jkv45
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Originally Posted by wiguzziman View Post
As long as we're on the subject of carburetors; does anyone have the float height measurement for the 2006 250 Ninja carbs handy? THANKS!!

wiguzziman
17mm

https://faq.ninja250.org/wiki/How_do..._the_floats%3F
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Old July 9th, 2018, 11:11 AM   #6
wiguzziman
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Float height measurement

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Originally Posted by jkv45 View Post
THANK YOU!!!!!!
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