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Old May 27th, 2015, 12:15 AM   #1
dannyb
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High idle issue

Hi everyone,

I just got a stock 2005 Ninja 250 with around 7,000 miles on it. It has a problem where it idles high (around 3000rpm) sometimes, and I'm wondering what you guys think the problem might be?

Here is a video of the issue:
https://youtu.be/-gNxZgNplfM


Link to original page on YouTube.

As you can tell, it idles pretty normally until it warms up (temp guage in the middle), then it will go up to around 3000rpm. If you rev the bike, it will fall back down to normal (~1500rpm) and then go back up to 3000rpm after a few seconds.

The previous owner didn't do any maintenance except cleaning the carbs, apparently. I'm assuming it was broken in properly by the original owner, but I don't know for sure. I'm the third owner.

My friend and I took off the carbs, removed the caps on the idle mixture screws and set it to 2.5 turns. This didn't really fix the problem though. We also looked at the air filter, which seemed fine. Next, we're planning on cleaning and syncing the carbs, checking for vacuum leaks, as well as adjusting the valves. Let me know if there's anything else we should look in to.

Thanks!!

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Old May 27th, 2015, 01:04 AM   #2
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Okay here's some of my personal tips for you,



Quote:
Your initial setting should be 3 full turns out from the bottom, remember just slightly tighten them, don't go all Conan on them.



Then warm it up, slowly turn 1 side pilot screw in until the rpms drop, then back out till RPM's peak (and no further)* Twist throttle...see how it reacts...tweak to taste.
Repeat on other side... test ride. You're looking for best throttle response and transition from just cracked to 1/4 throttle opening or so.*

Thats a quickie, 10 cent tutorial on setting pilot screws.**

Quote:
You can sync with the carbs in hand. Back the idle adjustment off to close that carb then match the second carb to it with the sync screw. You can then turn the idle adjustment up while using a thin feeler gauge (maybe .002") between the throttle plate and the throttle bore, adjust to just fit, and then check the second one and adjust to match. If you have good feel for this it will run fine once installed.

It would do folks well to take a minute to review and understand what a sync tool does, how it works. And take another minute to look at the carb linkage and sync adjustments available to fix irregularities that might occur. It can help take some of the mystery out of this as well as stop unnecessary carb sync screwups.

Meaning, that the carbs were right once, the butterflies were matched and it performed well, but then changed. Undecided And the problem somehow occurred in the butterfly direct shafts, or the sync screw turned or wore that pad that it rests on, or the carburetor pairing/ bridging brackets twisted in relation to each other, and enough so that the butterflies no longer operated in sync, such that performance noticeably suffered. And a fix will be accomplished by changing the butterfly position, the only thing the sync adjustment does. Hmmm. Really? Undecided

Meanwhile, the tool measures vacuum at each individual runner. That's all it does, how it works. And vacuum is effected by a huge list of things, butterfly position being only one of them, and the only one addressed with that tool while turning those sync screws. The rest of that list includes, valve adjustment, jetting, float level, compression differences between cylinders caused by wear as well as factory CC differences in the head, intake runner, as well as flow by port variations, etc. Variations in cams, wear or factory tolerance. Then there's the potential big one, pilot jets and pilot screw mixture settings. All of those effect the vacuum and will be read by the sync tool, accurately identifyng the difference that exists, and with the only adjustment being used to "correct" the problem, move the butterfly relationship, one to the next.

It's that clear understanding that has me of the opinion and long time practice to not touch the sync screws on a set of carbs that were right once and were never dismantled from the rack. And jet cleaning as well as float needle changing doesn't require that they be dismantled. And further, if I DID dismantle a set of carbs, I just matched the butterflies on the bench at assembly, using a feeler gauge, and then never touched them again, never gave them another thought.

That method, properly executed, will have THAT portion of the complete equation, balanced flow to each cylinder in a multi-cylinder/ carb application due to butterfly position, satisfied entirely adequately. And in fact, it has worked for me every time I've done it on every bike (as well as individual runner/ butterfly V-8 intakes, all eight) that I've ever owned or any that I've fixed for others. And the times I fixed for others was usually after an attempt by others to sync the carbs, chasing a problem, or sometimes not even chasing a problem, but one they created wth a sync tool, chasing a problem from that list, that was never a butterfly position change problem. Those linkages are so direct and simple that they don't know how to screw themselves up. Not enough to care about.

I'm sure this will start a lot of controversy so I won't argue it, just offering it for those who understand the whole picture that I outlined and might make good use of it. It is what I've done, on every engine I ever worked on, including blue printed racing engines as well as regular old, high mileage street stuff. I've had at least four, four cylinder bikes with over 100,000 miles that ran quite well, the whole time, and never had a carb sync performed. When they did finally get a total disassembly, this is how I set them up, on the bench. Over the years I've straightened out at least a half dozen messed up ones, probably more, and on the bench, after fixing the original problem which was fouled pilot jets.

I only posted this because it seems like its coming up fairly often, especially with problems from a sync gone bad. One I would suggest was never a sync problem to begin with. A big or sudden change in performance is NEVER a sync problem. NEVER. Remember that. Cool If there is a problem, and you connect the gauges? YES, there will definitely be an imbalance indicated. But because that hole has a problem that is from the rest of the list. A bad plug, a plugged pilot jet, a screwed up float, a bad valve or setting, etc. Every one of them effecting the vacuum in the intake but NOT from a sudden move of a butterfly position, a sync adjustment.
Quote:
You need to verify the petcock is petcocking, err, i mean working properly.

PETCOCK TEST
install a fuel hose from the petcock fuel outlet into a catch can. Pull the vacuum hose from the engine side. Leave it connected to the petcock.

Now...petcock set to on.... fuel should NOT be flowing. Apply suction to the vacuum hose (which is connected to the petcock ONLY) ...fuel should now flow.

Make sure the vacuum line doesn't have any pinholes or cracks!

Post your findings.
If your in need for either carburetor services or parts pm @ducatiman


Hope this helps, any questions feel free to ask.
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Old May 27th, 2015, 04:59 AM   #3
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Welcome Danny!!!
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Old May 27th, 2015, 06:24 AM   #4
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Old June 5th, 2015, 07:47 AM   #5
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check the easy things first, the choke cable pinched, binding or somehow pulling the choke 'on'

also check for a vacuum leak in any of the emissions plumbing. I dunno if VC has draconian emissions laws like CA, but if you have all that jibber-jabber stuck on your bike, best check it out.

my bike had a persistent wandering/high idle when i first got it running after cleaning the carbs. A couple good rips on the highway at 75 mph blew all the junk out and got things running smooth... the old 'italian tune up'
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Old June 24th, 2015, 11:57 AM   #6
jhey42.1
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High Idle thoughts

I just went through this on my 07. It turned out to be a choke slide screw that was to tight and binding, not letting the chock return spring do its job. At the handle bar the choke was off, at the other end of the cable the choke was still one because it could not slide back to the throttle/brake side of the bike.

SO before you go taking everything apart, get your finger down in there and check that there is no binding on the mechanism.

My two cents.
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Old July 4th, 2015, 09:12 PM   #7
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Tried all of the above I HATE THIS BIKE
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Old July 5th, 2015, 02:03 PM   #8
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Quote:
Originally Posted by Milsparro View Post
Tried all of the above I HATE THIS BIKE
Now...now...

You need to have patience and think of finding the cause as a challenge.

Check that the carb clamps are all tight and the carbs are seated correctly in the boots. Make sure you have adequate slack on the throttle cable. Check for a vacuum leak. Check that the slides rise and fall smoothly.

The carbs may also need adjustment and syncing or a thorough cleaning.
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Old July 5th, 2015, 02:14 PM   #9
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You need to double check things again.
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Old July 5th, 2015, 03:35 PM   #10
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I had the same problem in the past. Grabbed a bottle of starting fluid from Walmart and sprayed all 4 boots (2 from airbox to carb and 2 from carb to motor). Sure enough, one of the boots was leaking. Rpm changed immediately. Tried tightening the clamp, but that didn't help. Replaced boot and all was good again.
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Old July 5th, 2015, 05:50 PM   #11
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As you've inherited this bike as is, i'd surmise the PO whacked out the carb adjustments during his cleaning.

Did you actually remove them and eyeball the throttle plates?
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Old July 5th, 2015, 09:06 PM   #12
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Intake air leaking in? Last valve adjustment?
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Old July 5th, 2015, 10:58 PM   #13
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Old July 6th, 2015, 05:07 PM   #14
Milsparro
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Quote:
Originally Posted by jkv45 View Post
Now...now...

You need to have patience and think of finding the cause as a challenge.

Check that the carb clamps are all tight and the carbs are seated correctly in the boots. Make sure you have adequate slack on the throttle cable. Check for a vacuum leak. Check that the slides rise and fall smoothly.

The carbs may also need adjustment and syncing or a thorough cleaning.
Carbs are thoroughly cleaned for the second time, bench synced, if you set the idle high enough to idle at 1200 it'll hang at 5000.

The STUPID store is out of the product I need to check for boot leaks.

Edit: Never mind. It's missing below 2500 on one side.

Last futzed with by Milsparro; July 6th, 2015 at 06:31 PM.
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Old July 11th, 2015, 06:58 PM   #15
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Quote:
Originally Posted by Milsparro View Post
Carbs are thoroughly cleaned for the second time, bench synced, if you set the idle high enough to idle at 1200 it'll hang at 5000.

The STUPID store is out of the product I need to check for boot leaks.

Edit: Never mind. It's missing below 2500 on one side.

Solved. First time in 14 months (and 9800 miles) it's idled. Carb cleaned again, freed a sticky piston in the idle enricher, checked for boot leaks with propane (none), did the valves (2 exhaust were way too tight) and wuddya know. It idles. Like a normal motorcycle. 3 turns out on the A/F screws, haven't tweaked, may not, it comes off throttle fine.

I did all of the above after I got the bike, but I remember not taking the idle enricher apart last year, as at that point I didn't recognize it as a thing. So, uh, yah, make sure that piston isn't all varnished with gas too.
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