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Old April 14th, 2019, 07:10 PM   #1
Robb235
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I Think My Pilot Jets Are Plugged

Got a 2007 250-EX that sat for a couple years. Between having kids and several moves, it just didn't get ridden. I have replaced the gas with fresh gas and added Seafoam to the tank.

It will only start if choked at 75% or more. Even when completely warmed up, if I choke it less than 75% it will die out. Only idles when choked. I can ride it around as long as engine is under load. So as long as the carburetor is in the high speed circuit it's great. Low speed circuit appears to be the problem. So I took out the carb and removed the jets. The main jet I can see straight through. I can also see through the multiple holes on the shaft of the main jet (the holder I think it's called?).

But the pilot jet I cannot see straight through. I cleaned out the multiple holes on the shaft of the pilot jet, and I can see through those, but I cannot see straight through the pilot jet itself like I could the main jet.

I am supposed to be able to see straight through the pilot jet, right??

I've tried soaking both pilot jets in carb cleaner and Seafoam. Can't seem to blast out any more gunk with spray carb cleaner. I tried stripping some spare electrical wire I had and using one of the copper strands to poke through the blockage, but no luck. The copper strand wasn't rigid enough to force through. Still can't see through the pilot jet.

Do I just need to get some new pilot jets at this point?
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Old April 14th, 2019, 08:05 PM   #2
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I think you're on the right track, Robert. Get some lacquer thinner or good carb cleaner and alternate soaking and poking with the wire until you get the hole open. Of course you can buy new jets, but if you do, be sure they're OEM. Aftermarket jets are notoriously inaccurate.

Once you get the pilot jets clean, you may find that other small passages in the carbs also need attention. These carbs are not particularly easy to get truly clean. If you get frustrated, give Ducatiman here a shout. I just had him completely restore my carbs and my 250 has never run so well.

Seafoam is not a very good product. If you want one that can do some good, get one with PEA like Techron. It is capable of loosening blockages if they're not too old and hardened.

And welcome to the board!
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Old April 15th, 2019, 06:31 AM   #3
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Quote:
Originally Posted by Robb235 View Post
I am supposed to be able to see straight through the pilot jet, right??
Yes, and for a stock 250 Ninj #38 Keihin pilot jet use a .014" guitar string (steel, not nylon, duh) its rigid enough to allow some penetration power to "poke" while also sized correctly to prevent reaming or mauling. I cringe when I read folks blindly reaming jets, not knowing ID of jet nor the OD of the "wire" they have chosen.

Once you have provided a "pathway", hit it with cab cleaner again to assure no peripheral deposits remain above or below or around the actual metering orifice.

Be careful, the string will deeply pierce flesh, ask any geetar player!
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Old April 15th, 2019, 04:44 PM   #4
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That size 0.014” corresponds to light 2nd position A string.
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Old April 15th, 2019, 04:54 PM   #5
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a B (2nd) string, D'addario EXP link

http://daddario.com/resources/jdcdad...g23_main_1.jpg

If you know a guitar player, or hit your local Guitar Center (ask for cut-offs)
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Old April 15th, 2019, 05:53 PM   #6
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Quote:
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That size 0.014” corresponds to light 2nd position A string.
It's only a (octave higher than A) if you tune down a whole step like Trower.
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Old April 15th, 2019, 06:09 PM   #7
Robb235
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I don't play guitar so I have no idea what you guys are talking about lol
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Old April 15th, 2019, 06:19 PM   #8
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diameter of guitar stings in thousandths of an inch, useful for "poking" pilot jets to clean and return them to factory spec opening size.

Just realized you are the OP....this was all done just for you. See post #3. Any more questions, comments, just fire away.
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Old April 20th, 2019, 01:14 PM   #9
Robb235
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This carb is going to be the death of me.

I couldn’t clear the second pilot jet, so I just bought new ones.

Now when I put the carbs on and crank the bike, carb keeps leaking gas. One cylinder fires, and I think it’s the carb for the other cylinder is leaking. It’s just a slow drip while cranking, can’t really see where it’s coming from. Took the carbs back off, opened them back up and retightened all the screws and recleaned all the mating surfaces. Still leaks gas when I crank the engine??
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Old April 20th, 2019, 01:31 PM   #10
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If your float levels are set halfway near correct and it's doing that, your float valves are not sealing so the carbs are overfilling. They could be dirty or worn, or hanging up on something.
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Old April 20th, 2019, 03:08 PM   #11
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On older, disused carbs EVERY pathway and system, both visible and not should be considered suspect (clogged) until proven not to be. Sitting for years with rotted fuel, it invades all.

Getting it all dealt with in one shot can be frustrating and difficult, where coupling aggressive methods and knowing "what to do where" become important. Different parts and differing systems require various methods, within both the cleaning and setup process.

Whatever you do...remove the slides and keep them safely away from chemicals or mayhem! Soap and water only, if cleaning them! The actual rubbers can be safely "rubbed down" with Armor All.

And don't lose the needle jets! (very common)
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Old April 20th, 2019, 04:06 PM   #12
Robb235
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Quote:
Originally Posted by Triple Jim View Post
If your float levels are set halfway near correct and it's doing that, your float valves are not sealing so the carbs are overfilling. They could be dirty or worn, or hanging up on something.
I didn’t mess with the floats when I cleaned the carbs. Just shot carb cleaner through the passages and cleaned (or replaced) the jets.

What are the float valves? Is that the needle valve?
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Old April 20th, 2019, 05:03 PM   #13
Robb235
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Also, what size are these CVK carbs?

Between these Keihins on this bike, and the two sets of triple Mikuni carbs on my boat, Iím about sick of carburetors.
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Old April 20th, 2019, 05:42 PM   #14
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Quote:
Originally Posted by Robb235 View Post
I didn’t mess with the floats when I cleaned the carbs. Just shot carb cleaner through the passages and cleaned (or replaced) the jets.

What are the float valves? Is that the needle valve?
Shooting carb cleaner through the passages is often not enough to get them clean, so beware of that.

I suppose you shouldn't have been working on carbs without knowing what the float valves are, but they are the combination of floats, float needles, and seats that regulate the level of fuel in the float bowls. The floats raise the needles as fuel flows into the bowls, and when the level reaches the set height, the needles are pushed into the seats to block incoming flow. If that isn't working, fuel keeps coming in and ends up coming out the overflow tubes.

"Needle valve" is a generic term for a type of valve. Our 250 carbs have needle valves in multiple places including the float valves, the idle mixture valves (often called "idle mixture screws"), and the midrange metering system that uses needles and needle jets.
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Old April 20th, 2019, 05:49 PM   #15
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250 Ninj carb sizes:

'86-'87 used 32mm Keihin CVK with metal slides

'88-'12 are 30mm Keihin CVK with the all familiar black plastic slides
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Old April 20th, 2019, 08:15 PM   #16
Robb235
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Yeah, Iím not all that familiar with carbs. Much more familiar with fuel injected applications. My only prior experience has been with the Mikuni carbs on my Yamaha jetboat, which are the float-less kind. Personally I think that carburetors are an antiquated piece of equipment that have no business being on a street bike manufactured in 2007. But I digress...

Believe I located the leak. I only opened the lower part of the carbs to access the jets, since I was hunting a specific problem (and found it with my plugged pilot jets). The gasket on the lower section of the carb is leaking at one of the corners. Looks like I need a new gasket. Any recommendations on where to order from?
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Old Yesterday, 06:04 AM   #17
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Rob
Hate to say it, but you have been your worst enemy.
When you approach old fashion carbs you need all the parts to repair and replace. Plus the knowledge to do the job correctly. After rebuilding carbs for 50 years they are no big deal.
When you solve all the carb problems, and get your bike running, you will be an expert on carburetors.
Live and learn. Fuel injection is not all it is cracked up to be. Electrical gremlins can ruin your day.

Or just send them to ducatiman.
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Old Yesterday, 08:35 AM   #18
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Rob
Hate to say it, but you have been your worst enemy.
When you approach old fashion carbs you need all the parts to repair and replace. Plus the knowledge to do the job correctly. After rebuilding carbs for 50 years they are no big deal.
When you solve all the carb problems, and get your bike running, you will be an expert on carburetors.
Live and learn. Fuel injection is not all it is cracked up to be. Electrical gremlins can ruin your day.

Or just send them to ducatiman.
So true. Various forums filled with complex FI diagnostic difficulties...when tracing issues back to ECU related ...can get highly technical, time consuming, needed replacement can get super $$$. Old fashioned carbs, OTOH usually cheap and simple, totally eliminating the complexity of ECU from diagnostics.

I'm generalizing, of course, exceptions (simple FI fixes) do exist and can be cited...but not always, FI "non-starts" can be bitchy.

Faced with a "non-start".....in a diagnostic/repair perspective...I'd prefer a carbed bike to FI anytime.
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Old Yesterday, 07:11 PM   #19
Robb235
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In the grand scheme of things, my opinion is that fuel injection is overall superior to carburetors in terms of reliability and performance. There's a reason auto manufacturers use FI and not carbs anymore. The reliability of FI beats carbs. My fuel injected R6 sat for just as long as the 250, and when I hit that starter it fires right up. No pilot jets to plug up. No choke to screw around with. In all of the fuel injected vehicles I've owned, I've only ever had one fuel delivery issue, and that's when a MAP sensor went out on an old POS car that I drove in high school. Carburetors are a different story. I've owned two carb'd boats, and every couple years you gotta rebuild those carbs. Doesn't matter that I used ethanol free gas. Still gotta rip those carbs off and redo them. I haven't had that maintenance issue with FI.

Fine tuning FI runs circles around carbs. To change the fuel maps on my R6, literally all I have to do is plug my laptop in to the Power Commandder and I can make fine tune adjustments to the fuel tables. Good luck doing that with a carb.

Anyways, now that I've completely derailed this thread with a healthy FI vs carb debate, time to get back on topic. I've ordered a new float bowl gasket. The old gasket seems slightly chewed up in one of the corners when I look closer. I'll replace and see what happens.
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Old Yesterday, 08:12 PM   #20
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There's a reason auto manufacturers use FI and not carbs anymore. The reliability of FI beats carbs.
Auto manufacturers were forced into FI because of emissions laws. I'm not knocking FI!
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