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Old June 9th, 2018, 04:28 PM   #1
Runeknight95
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No power on full open throttle, petcock question etc.

Friends bike she asked me to look at, 13k miles 08 ninja 250r. No power on full throttle and some odd backfires here and there.

Sat for 2-3 months, ran like junk, new gas still ran bad.

I pulled the carbs and cleaned them, cleaned primary jets, secondaries and the bowls and upper area spraying it all down.
Still runs poorly

I noticed the petcock was puking in the "on" position, so i stretched the spring like I did on my bike 4-5 years ago (see https://www.ninjette.org/forums/showthread.php?t=141972). Fuel stopped puking but still have no power under full throttle, I have power to about 50-60% throttle then its gone.

Any other ideas would be helpful. I think I will replace the petcock first and diagnose from there its just a bummer its like $93 bucks now, unless anyone knows of a good rebuild kit or a good aftermarket one.

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Old June 9th, 2018, 05:12 PM   #2
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Do this test with stopwatch:

1. Aim petcock fuel-outlet hose into measuring cup
2. Apply vacuum to petcock activation port
3. How long does it take to flow 2-cups???
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Old June 9th, 2018, 05:20 PM   #3
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It would take a few seconds for insufficient petcock flow to make the power drop at full throttle. If it does it immediately, something else is wrong. My guess is that the carbs are still not completely clean.
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Old June 9th, 2018, 05:59 PM   #4
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Quote:
Originally Posted by DannoXYZ View Post
Do this test with stopwatch:

1. Aim petcock fuel-outlet hose into measuring cup
2. Apply vacuum to petcock activation port
3. How long does it take to flow 2-cups???
What is a normal variable or specification i.e. how many seconds would be normal to fill 2 cups?
I mean the bike is 10 years old, rubber seals and diaphragms do deteriorate. Even though it stopped leaking while in the "on" position who knows what else is wrong, Ill check this thank you!

Quote:
Originally Posted by Triple Jim View Post
It would take a few seconds for insufficient petcock flow to make the power drop at full throttle. If it does it immediately, something else is wrong. My guess is that the carbs are still not completely clean.
Hard to say what immediately is vs few seconds as it loses power after 60% throttle it bogs down.
When cleaning the carbs, the primaries had little light coming through and after the cleaning a lot of light. Secondaries were cleaned I did not notice much difference.
I cleaned junk out of the bowls and sprayer the upper area but never removed the floats as they seemed to flex with ease. What other areas should I focus on? I will watch a video to double check what I did but if you know off the top of your head it would be appreciated.
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Old June 9th, 2018, 06:55 PM   #5
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I'm not sure what you mean by primaries and secondaries. There's the main jet circuit, and then the needle in its jet, is that what you're referring to? Also there's the idle circuit, but that won't be in effect for WOT.

You should be able to tell if the problem is immediate upon opening the throttle all the way, or if it produces full power for a few seconds and then stumbles.
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Old June 9th, 2018, 07:51 PM   #6
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Quote:
Originally Posted by Triple Jim View Post
I'm not sure what you mean by primaries and secondaries. There's the main jet circuit, and then the needle in its jet, is that what you're referring to? Also there's the idle circuit, but that won't be in effect for WOT.

You should be able to tell if the problem is immediate upon opening the throttle all the way, or if it produces full power for a few seconds and then stumbles.
there are 2 jets, large one and a small one in each bowl.

Does not produce full power at all.
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Old June 9th, 2018, 08:04 PM   #7
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That would point to something besides the petcock. Danno has some good photos of what needs to be cleaned in these carbs, maybe he'll post them once again.
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Old June 10th, 2018, 06:09 AM   #8
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possible fuel delivery issue? did you check the in line fuel filter? its quite small clogs easily. its down by fuel intake to carbs. i chuck em and put vw style filter on
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Old June 10th, 2018, 07:09 PM   #9
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My guess is either carb/jets are not completely clean or the diaphragms are damaged.

Did you remove the caps over the idle mixture screws and check the passages and o-rings, then set the screws to 2.5 turns out?

"Carb cleaning" is a very general term, and means different things to different people. Complete disassembly and cleaning of all jets and passages can often take more than simple tools and a can of carb cleaner.
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Old June 10th, 2018, 10:59 PM   #10
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I get about 2.0-hrs of full-thottle track time out of 3.5-gallons of fuel in tank. You can figure out drain-rate from tank with those numbers. I bet your petcock is flowing more than that by significant amount.

Quote:
Originally Posted by jkv45 View Post
My guess is either carb/jets are not completely clean or the diaphragms are damaged.
Yup, most likely fuel flow inside the carbs is problem (clogs or damage). I'll dig up photos of secret passages and disassembly photos when I get to a desktop.

Carbs aren't completely clean. Search here and you'll find that even experienced DIY guys who rebuilds engines on their kitchen tables with both arms tied behind their back, have had to tear their carbs apart 4 times before they got them clean enough.

EDIT: check out this thread for photos of where to clean https://www.ninjette.org/forums/showthread.php?t=317977

Most likely if you didn’t do following, carbs really aren’t as clean as factory new condition:

- soak in heavy-duty industrial chemicals (not spray carb-cleaner)
- hot ultrasonic bath
- flossed all hidden passages with wire/string
- soda blasted all orifices and circuits

Last futzed with by DannoXYZ; June 11th, 2018 at 09:43 AM.
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Old June 11th, 2018, 07:02 AM   #11
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There's a guy on these forums (unfortunately I can't remember his username) who provides carb cleaning services and gets rave reviews for his work. Hopefully someone will know who I'm talking about and ping his name.
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Old June 11th, 2018, 07:07 AM   #12
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Quote:
Originally Posted by Ralgha View Post
There's a guy on these forums (unfortunately I can't remember his username) who provides carb cleaning services and gets rave reviews for his work. Hopefully someone will know who I'm talking about and ping his name.
@ducatiman (Gordon)
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Old June 11th, 2018, 09:48 AM   #13
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Check out a small sampling of ducatiman-Gordon's work here with before & after pictures:

https://www.ninjette.org/forums/show...6815&p=1170700

Lots of other threads & posts detailing his meticulous work.
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Old June 11th, 2018, 01:29 PM   #14
Runeknight95
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Quote:
Originally Posted by jkv45 View Post
My guess is either carb/jets are not completely clean or the diaphragms are damaged.

Did you remove the caps over the idle mixture screws and check the passages and o-rings, then set the screws to 2.5 turns out?

"Carb cleaning" is a very general term, and means different things to different people. Complete disassembly and cleaning of all jets and passages can often take more than simple tools and a can of carb cleaner.
Did not mess with idle screws, all seems ok now though.

Quote:
Originally Posted by DannoXYZ View Post
I get about 2.0-hrs of full-thottle track time out of 3.5-gallons of fuel in tank. You can figure out drain-rate from tank with those numbers. I bet your petcock is flowing more than that by significant amount.

Yup, most likely fuel flow inside the carbs is problem (clogs or damage). I'll dig up photos of secret passages and disassembly photos when I get to a desktop.

Carbs aren't completely clean. Search here and you'll find that even experienced DIY guys who rebuilds engines on their kitchen tables with both arms tied behind their back, have had to tear their carbs apart 4 times before they got them clean enough.

EDIT: check out this thread for photos of where to clean https://www.ninjette.org/forums/showthread.php?t=317977

Most likely if you didn’t do following, carbs really aren’t as clean as factory new condition:

- soak in heavy-duty industrial chemicals (not spray carb-cleaner)
- hot ultrasonic bath
- flossed all hidden passages with wire/string
- soda blasted all orifices and circuits
Quote:
Originally Posted by Ralgha View Post
There's a guy on these forums (unfortunately I can't remember his username) who provides carb cleaning services and gets rave reviews for his work. Hopefully someone will know who I'm talking about and ping his name.
Quote:
Originally Posted by jkv45 View Post
@ducatiman (Gordon)
Quote:
Originally Posted by DannoXYZ View Post
Check out a small sampling of ducatiman-Gordon's work here with before & after pictures:

https://www.ninjette.org/forums/show...6815&p=1170700

Lots of other threads & posts detailing his meticulous work.

Thanks all, it seems the bike is good to go. I pulled the carbs again, cleaned them every port/hole with carb cleaner and compressed air, cleaned jet needles etc.
I also cleaned the fuel filter which had some nasty stuff in it.

I was able to open full throttle and had power , could only do 40 mph in parking lot it was raining will test again tomorrow but I think shes good to go! Thank you guys!!

Fuel filter.jpg
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Old June 11th, 2018, 01:54 PM   #15
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Quote:
Originally Posted by Runeknight95 View Post
Did not mess with idle screws, all seems ok now though.
Glad it's running at WOT now, but you really want to be able to make idle mixture adjustments. It's part of tuning.

That means pulling the caps when the carbs are off. There are o-rings on the screws that can fracture and get lodged in the passages, and the passages can become partially plugged. Doing that is all part of "carb cleaning". Syncing the carbs when you are finished (syncing them on the bench also - which should be close unless there is a problem somewhere) is the last part.

That's why I said "carb cleaning" means different things to different people.
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Old June 11th, 2018, 03:42 PM   #16
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Quote:
Originally Posted by jkv45 View Post
Glad it's running at WOT now, but you really want to be able to make idle mixture adjustments. It's part of tuning.

That means pulling the caps when the carbs are off. There are o-rings on the screws that can fracture and get lodged in the passages, and the passages can become partially plugged. Doing that is all part of "carb cleaning". Syncing the carbs when you are finished (syncing them on the bench also - which should be close unless there is a problem somewhere) is the last part.

That's why I said "carb cleaning" means different things to different people.
By the time you posted your answer I was already reinstalling

I didn't want to mess with those 2 screws because I found shims (assuming jet kit) and also didn't recall how to set the idles (the 2.5 turns out thank you for that info).
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