December 18th, 2015, 10:58 PM | #1 |
ninjette.org member
Name: Joel
Location: Napa, CA
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Help needed diagnosing carb issue
Hey all,
Havent been on here in a while, but currently have a couple of 250's in the garage and one of them needs some carb work. First off a little back ground on the bike: 2006 with 1304 miles on it. Owner let it sit outside for a few months and I bought it as a non starting project. I can get it to start with the choke on, but once the bike warms up (and it takes a little longer than it should) the idle is rough, dips, hangs if you rev it, sometimes it will rev fine, other times it will stumble and not go past 5 or 6k rpm. Also when i took the carbs off, i noticed there was a decent amount of gas in the boots between the carbs and the motor. So far ive broken the carbs down and cleaned them, replaced the main and pilot jets with fresh 105/35 jets. Idle screws are 2.5 turns out. checked the diaphragms and they look like theyre in good condition. In any case, I could use some help diagnosing what could possibly be wrong and where to go next. Thanks Gitter |
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December 19th, 2015, 01:34 AM | #2 |
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Did you check the float height? Replace the float valves? Verify all fuel circuits are clear with an air compressor?
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December 19th, 2015, 03:04 AM | #3 |
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Haven't checked float height yet. I think I have a spare set of valves I'll drop those in and see how it does. Also, is there a list or maybe some picture ls that show the different passages that need to be checked? I got the obvious ones where the jets are but simply for the sake of being thorough I want to make sure I didn't miss one
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December 19th, 2015, 04:24 AM | #4 |
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Welcome Joel!
Why 105's? Stock airbox and exhaust?
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December 19th, 2015, 04:32 AM | #5 |
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Yeah everything is stock, that's why I decided to go with the stock 105 jets.
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December 19th, 2015, 06:02 AM | #6 |
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Good call on the jets.
As far as passages goes, the jet holes, also make sure the emulsion tubes part# 13091 are clear as well. Make sure the idle circuit is clear, from the jet side, idle mixture screws, and inside the carburetor, check any hole as well. Make sure you've assembled them correctly. Common mistakes are the assembly of the diaphragm, and needles, and the other is part # 16017. Also the small washer and O-ring on the idle mixture screws. If your in need for carburetor services and parts PM @ducatiman, his prices are extremely affordable.
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December 19th, 2015, 07:05 AM | #7 |
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Name: Joel
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Emulsion tubes are clear, pulled them out and checked when i replaced the jets.
Did a quick google search- would a good step be re-clean and blow out all these spots with compressed air? http://n4mwd.blogspot.com/2013/10/se...-passages.html As far as making sure theyre put together correctly, I'll break them down and put them back together again. This is the first 250 ive had that the carb problems havent been solved by swapping in clean jets and cleaning the jet holes. For adjusting the float bowls, is there a walk through somewhere? I found the one in the how to section but i was hoping to find one with pictures |
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December 19th, 2015, 07:07 AM | #8 |
ninjette.org member
Name: Joel
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Also, just to rule it out, at only 1304 miles, valves being out of spec should be a non issue right?
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December 19th, 2015, 07:12 AM | #9 |
in your machine
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Here's a link
http://faq.ninja250.org/wiki/How_do_..._the_floats%3F And picture Float height is very important for the tuning, and one of the most overlooked.
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December 19th, 2015, 08:12 PM | #10 |
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Stock Pilots are 38s that could be a cause of your problem.
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December 19th, 2015, 10:16 PM | #11 |
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Hanging idle is a sign of an air leak in the carb system. A simple vacuum leak will make it impossible to get a consistent idle.
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December 19th, 2015, 10:21 PM | #12 |
in your machine
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I agree, but without being 100% sure the carburetors are right, you'll be chasing your tail.
You need to cover the basics, carburetors are correct, petcock, tank vent, spark plugs, and caps, and valves adjusted.
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December 19th, 2015, 10:48 PM | #13 |
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Not necessary a air leak, it just means its lean. Which could be caused by his small pilots.
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December 19th, 2015, 11:09 PM | #14 |
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didnt even think to double check the pilot jet size before i ordered
took the carbs back apart, blew everything out, checked the floats, put everything back together. Also forgot to add in the original post that i put fresh plugs in. With the idle screws turned out three turns, it will idle fairly well. Seems to pull decently well at neighborhood speeds. Has a bit of a flat spot around 3 or 4k rpm. Gonna let it sit over night and check it again in the morning to make sure it will warm up properly before i button everything back up. I'll post back and let you guys know how it goes. Should i order 38's or just stick with the 35's if they seem to be working? |
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December 19th, 2015, 11:23 PM | #15 | |
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Quote:
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December 20th, 2015, 11:31 AM | #16 |
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the difference between 35 and 38 may seem insignificant, but its not and is very likely causing your issues.
In doing others carbs, I routinely "index" (measure) the pilots...can vary wildly even though marked a given size. "Hogging out" jets is, evidently, a fairly common practice and can reveal causes for weird symptoms. Back to OP's case...the factory called for #38....I'd strongly suggest to get them back in there. |
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December 20th, 2015, 12:26 PM | #17 |
ninjette.org member
Name: Joel
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December 20th, 2015, 01:43 PM | #18 |
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Though not pretty, yes, they CAN be used. The actual metering orifice lies deep within the jet, not affected by the mauled head. If you choose, you can order new ones for next time you go in there.
Just one note...if the outer circumference of the mauled head is nicked (deformed out of round), jet removal may be problematic....high spots may cause interference... not allow the jet to "drop out" of the pilot orifice when loosened. There is not much clearance there. You can carefully file any nicks causing high spots. Correct fitting screwdriver for soft pilot jets essential, using plenty of downpressure during removal....mauled heads are the aftereffect if compromised. |
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December 22nd, 2015, 10:08 AM | #19 |
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Installing new oem jets always gives you peace of mind and a good starting point for tuning. On a used cycle, that's obviously been worked on, you never know if someone has reamed 'em out.
It's just not worth messing around with questionable parts when you are going through a carb. That, and make sure they are totally, completely, absolutely, clean before you call it good. Last futzed with by jkv45; December 22nd, 2015 at 08:23 PM. |
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December 22nd, 2015, 02:42 PM | #20 |
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indexing (measuring) immediately separates the good from the bad....
agree with automatic replacement of hogged out or badly mauled pilots... but if found to be unbastardized nothing wrong with reuse (after thorough clean) |
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December 22nd, 2015, 08:54 PM | #21 |
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How would a normal person measure and index a jet. I have way more tools than the average person, and If it was even in question the jets weren't genuine I would just bin them and buy new ones.
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December 22nd, 2015, 09:25 PM | #22 |
ninjette.org member
Name: Joel
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I'm also curious how this is done. On a side note, put those 38's back in, bike warms up and idles like a champ now. still a bit of a flat spot around 4k, but it lessens once the bike is warm
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December 22nd, 2015, 09:35 PM | #23 |
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I'd say for sure shim your needles, sounds lean at 4k.
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December 24th, 2015, 07:08 AM | #24 | |
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Quote:
examples #35 jet is .35mm= .0137" #38 jet is .38mm= .0149" using drills or guitar string as a "go, no go" reference...kinda like feeler gauges whilst checking valve clearances Impossible to confirm by eyeball...hogged out jets will stand out like a sore thumb using this method. PS I always stock a set of *new* 35's and 38's just in case, along with usable accumulated spares, offering folks the choice. Merry Christmas and Happy Holidays , y'all! |
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