August 6th, 2017, 05:05 PM | #1 |
ninjette.org newbie
Name: Nicholas
Location: Chicago/Boston
Join Date: Jul 2017 Motorcycle(s): '09 Ninja 250R Posts: 4
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Shimmed my 250R, now dies when revved
Hey all,
I had my 09 250r taken apart for paint, and decided to go ahead and desnorkle and shim the carbs while I had it apart. I added 2 washers to each needle. It previously seemed a bit lean (ran fine once warmed up, but needed a fair amount of choke to get it warm). Now, I started it up, warmed it up (with a bit of choke despite the shims) and when I tried to ride off, it seemed to hit a lean spot around 3-3.5k revs. I can barely get it past it if I modulate the throttle a little, but it generally dies after it hits 3-3.5k. I figured this was it running lean, and decided to put the snorkel back on. This did not seem to affect the issue. I'd rather not open my carbs back up if I don't have to, it was a pain in the ass the first time. Any advice on what could be happening here? |
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August 6th, 2017, 07:11 PM | #2 |
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So the 3-3.5k-rpm behavior is worse now than before?
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August 6th, 2017, 07:38 PM | #3 |
ninjette.org newbie
Name: Nicholas
Location: Chicago/Boston
Join Date: Jul 2017 Motorcycle(s): '09 Ninja 250R Posts: 4
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Yes, significantly. It used to just need to be warmed up for a couple minutes with choke, and seemed a little lacking in the low end of the rev range but not terrible. Now it revs up to 3-3.5 and then either takes several seconds to get past that or just slowly drops in rpm and stalls out/dies.
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August 6th, 2017, 08:01 PM | #4 |
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Name: AKA JacRyann
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What quantitative data have you collected and analyzed to indicate that you have lean mixture as causing your issues in the 3-3.5k-RPM range?
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August 6th, 2017, 08:37 PM | #5 |
ninjette.org newbie
Name: Nicholas
Location: Chicago/Boston
Join Date: Jul 2017 Motorcycle(s): '09 Ninja 250R Posts: 4
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Like I said, it was just a guess. AFAIK, it's either dying because it's rich or lean and I don't smell unburnt fuel. Doesn't seem like I messed up the throttle or choke cable, if there's another reason for it to be dying I'm eager for advice.
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August 6th, 2017, 09:03 PM | #6 |
ninjette.org member
Name: Nein
Location: Canada
Join Date: Jun 2017 Motorcycle(s): 2011 Ninja 250r se Posts: 100
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Heh did you make sure your needles are seated properly in the slides and sitting down in the jets? Once i have them lined up i give them a very gentle push with the blunt side of my tweezers. That'd be my first guess... easy mistake to make. or did you cover one of the holes in your slide diaphragm with the foot on one of your springs? (the white part on the end of the spring has feet, down in the hole there is a small hole that lets your slide actuate freely if obstructed it may cause an issue)
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August 6th, 2017, 09:11 PM | #7 | |
ninjette.org newbie
Name: Nicholas
Location: Chicago/Boston
Join Date: Jul 2017 Motorcycle(s): '09 Ninja 250R Posts: 4
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Quote:
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August 6th, 2017, 09:14 PM | #8 | |
ninjette.org certified postwhore
Name: AKA JacRyann
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Quote:
A lot of bikes have a problem with richness in mid-range. Due to helmholz resonance effects, air goes in, is pushed back by pressure-wave, and sucked back in again, leading to three passes through carbs and way too much fuel. Last futzed with by DannoXYZ; August 6th, 2017 at 11:29 PM. |
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August 6th, 2017, 11:20 PM | #9 |
in your machine
Name: Scott
Location: Summer Shade, Ky.
Join Date: Oct 2014 Motorcycle(s): 98 Ninja 250/F12 aka ZX-2R "SERENITY", 91 Ninja 500/A5 aka ZX-5R "Phoenix", 84 Honda GL1200A "SIREN" Posts: A lot.
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Take a good look and make sure the diaphragms are seated properly, and not pinched, damaged, etc....
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August 7th, 2017, 05:58 AM | #10 | |
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Quote:
Suggestions....remove the shims...turn each pilot screw out in 1/4 turn increments riding, testing warmup charactaristics with each change. This entails allowing to fully cool between sessions and may require carb removal, drilling and removal of the pilot screw tamper caps (if not already removed). Avoid the temptation to make huge, radical, all at once changes. Patience, testing between changes. *********************************************************** Coincidentally, I'm currently working on an owners 250 carb set with pilot jets drilled to a MASSIVE oversize. Owner, understandably, reports black, fouled spark plugs, inability to easily start/idle/transition. Undiagnosed (till now) ...likely the real reason the bike was sold/changed hands. Though they are marked as stock 38 pilots...stock is .016" these drilled to .036" WOWSERS! Obvious solution? Return to new, stock size 38 pilot jets (which I keep in stock) A very poor decision to drill pilots to such an extent. Radical jetting changes as this are rarely (if ever) needed. Small, measured, deliberate steps, always testing between...and only for good reason, IMHO.
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gordon@customcarbservices.com Custom Carb Service www.customcarbservices.com Last futzed with by ducatiman; August 7th, 2017 at 02:40 PM. |
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August 7th, 2017, 06:25 AM | #11 |
Rev Limiter
Name: Jay
Location: WI
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Did you remove the caps on the idle mixture screws while the carbs were off and set them to a base of 2.5 turns out? That usually helps get better running in the idle to 1/8 throttle range.
When working with carb issues, think in terms of throttle position (1/8, 1/4, 1/2, etc) and not RPMs. 2 shims may be too much for you, or something is not assembled correctly in the carbs. |
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