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Old September 7th, 2018, 03:11 PM   #1
overtninja
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Question Bike starts fine first time, won't idle or rev subsequent times.

Hello all,

I bought a 2012 Ninja 250R (first bike!) and have been working tirelessly to get the darn thing to run smoothly (to no avail). Here's what's happening.

If I let the bike sit overnight (or at least a couple of hours) with the fuel switch set to PRI/prime, I can get it to start almost no problem. It takes a little bit of throttle for it to catch, but then it will rev as it should. However, as soon as I let off the throttle, the bike dies. Any further attempts to start still require the throttle, but the engine will no longer rev. It caps at somewhere <1,000RPM (I can't tell exactly, the tachometer doesn't work) even with the throttle maxed. This is still a slight improvement over the condition the bike was in when I bought it .

So, here's what I've done in an effort to correct this problem.
  • Removed the carburetors and cleaned them thoroughly, being careful to remove the jets and clean them as well. The pilot jets were already clean as a whistle, but I still cleaned them again.
  • I have checked that the vacuum lines were in the correct placement - they weren't when I got the bike.
  • Replaced the spark plugs, which after two days and probably 30min total of running the engine were totally fouled with black grime when I checked them again.
  • Because the spark plugs indicated the bike was running rich, I adjusted the air/fuel mixture screws on the carbs to run leaner. The caps were already removed, so I'm assuming they had been toyed with before. They were at 2.5 turns out, I set them to 1.5 turns out.
  • Replaced the battery because it was showing 0v.
  • Cleaned the air filter and re-oiled it. It wasn't terribly dirty, but it needed to be done anyway.

Now, some notes about the bike in general (to provide context b/c it could be useful?).
  • Only 1399mi on the odometer.
  • It's straight-piped (I'm working on getting a muffler for it).
  • It's missing the headlights. In fact, the front cowling is entirely after-market or swapped from another bike.
  • It does not have any of the fairings save two side panels (that cover the air-filter access panel on the right side) and the rear fender.
  • The cables are all in working order. The clutch is responsive, the throttle is snappy, and the choke chokes.

I've now just about exhausted my knowledge of how to work on this bike and would love to avoid taking it into a shop. I spoke to a fellow rider at a Cycle Gear (great guy) who thinks it could be a blown head gasket, the way it dies on idle. Does anyone have any ideas what could be the root of the symptoms? I'm willing to do it myself, I just don't want to set out on a crusade until I'm at least 50% certain I need to .

Thanks in advance for any replies.
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Old September 7th, 2018, 04:13 PM   #2
Triple Jim
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Hi Johnny, welcome to the board. My money would be on the carbs still not being truly clean. Another possibility is restricted fuel flow, since after sitting it seems nearly OK for a little while.
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Old September 7th, 2018, 06:29 PM   #3
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I would check to see if the slide diaphragm's are seated correctly or torn. 1.5 turns is super lean on these bikes I bet something else is causing your fouled plugs like float height or way too big main jets.
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Old September 7th, 2018, 08:59 PM   #4
overtninja
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Thanks for the replies!

Quote:
Hi Johnny, welcome to the board. My money would be on the carbs still not being truly clean. Another possibility is restricted fuel flow, since after sitting it seems nearly OK for a little while.
I took the carbs off again and gave them a very in depth cleaning. Main jets were clogged again, but the rest was fine. I was very careful to get in every crevice as best I could with carb cleaner and compressed air. Same result :/ At least I'm getting really good at removing the carbs

I've also thought it could be restricted fuel flow, so that's my next direction I think.

Quote:
I would check to see if the slide diaphragm's are seated correctly or torn. 1.5 turns is super lean on these bikes I bet something else is causing your fouled plugs like float height or way too big main jets.
Diaphragms are looking solid, and I believe the jets are stock. Any way I can check their size? Also, how would I check/adjust the float height?

Again, thank you both!
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Old September 8th, 2018, 03:02 AM   #5
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check petcock. u should never need prime to get it started. remove cover plate, check diaphragm, sometimes the spring over time or not running often will need a slight pull to lengthen spring a bit. my green bike that sat for 8 years needed max choke to stay running. i flushed fuel tank, clean carbs(not a deep cleaning) and it fired right up, everything normal. pilots jets had lots of crud in them. many on the board will say if ya don't have the proper equipment it's impossible to get carbs back to a factory new state. one of the members does run a carb rebuild/ cleaning service. he is very good at his trade. his handle is ducatiman. custom carb services
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Old September 8th, 2018, 03:14 AM   #6
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their is also a very small inline fuel filter that sits inside the inlet connection. sometimes it will hidden or up is your fuel line near connection. check and clean
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Old September 8th, 2018, 07:09 AM   #7
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Quote:
Originally Posted by maverick9611 View Post
check petcock. u should never need prime to get it started.
I realize that this probably does not apply here, but when my 250 has been sitting for a couple weeks and the gasoline in the float bowls has evaporated enough that the level is down, trying to start without priming the carbs requires a lot of cranking.

Maybe "hardly ever" would be more correct than "never".
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Old September 8th, 2018, 09:46 AM   #8
overtninja
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Quote:
Originally Posted by maverick9611 View Post
their is also a very small inline fuel filter that sits inside the inlet connection. sometimes it will hidden or up is your fuel line near connection. check and clean
Should I be checking for this piece on the carb inlet connection? I can't seem to find it on any of the diagrams in the service manual

EDIT: Found it in the carb diagram right after posting, haha. Part 49019, why have you forsaken me?

EDIT 2: Found another issue. That particular filter is missing from my bike. Pretty soon I'll be rebuilding the petcock anyway, so I'll check the filter on that fella as well.

Last futzed with by overtninja; September 8th, 2018 at 10:16 AM. Reason: Updated with more information.
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Old September 8th, 2018, 12:24 PM   #9
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Rebuilding petcock is good start. Sounds like vacuum diaphragm is not working properly to stay open and let fuel flow. Also check main jet, very common for people to go up in jet size rather than clean/floss the hidden fuel passasges in their carbs. Please review this thread and linked threads within on proper carb-cleaning procedure. https://www.ninjette.org/forums/showthread.php?t=323737
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Old September 14th, 2018, 07:56 PM   #10
overtninja
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Hello everyone!

Just wanted to update this thread in case anyone else ever has a similar issue. Took the Ninja to a local mechanic and had them diagnose it.

Although I was correct that my jets were stock, it turns out the previous owner had drilled out the pilot jet to be larger. This was causing the engine to flood, thus no idle.

Thank you to all for your help! I now have a running bike!

Cheers.
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Old October 11th, 2018, 06:40 AM   #11
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the jet needle may need to be cleaned sounds like its rich tho from the black spark plugs you could try adjust the needle
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Old October 11th, 2018, 07:16 AM   #12
DannoXYZ
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Quote:
Originally Posted by overtninja View Post
Although I was correct that my jets were stock, it turns out the previous owner had drilled out the pilot jet to be larger. This was causing the engine to flood, thus no idle.
What is it with people drilling out jets?@#$!
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Old October 11th, 2018, 10:36 AM   #13
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Originally Posted by DannoXYZ View Post
What is it with people drilling out jets?@#$!
Murica! more is always better, right?
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Old October 11th, 2018, 04:58 PM   #14
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"More is always better" - guy here posted in a local forum about a guy who bought a new bike, KTM, I think, and came in three weeks later, livid because the bike was spewing white smoke. Guy had filled the oil to the tippy top because "the more oil they have, the better they run."

Got to wonder about some people.
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