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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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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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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
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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
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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
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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
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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, I’m about sick of carburetors.
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Old April 20th, 2019, 05:42 PM   #14
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Quote:
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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
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Yeah, I’m 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 April 21st, 2019, 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 April 21st, 2019, 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 April 21st, 2019, 07:11 PM   #19
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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 April 21st, 2019, 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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Old April 22nd, 2019, 06:23 AM   #21
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Auto manufacturers were forced into FI because of emissions laws. I'm not knocking FI!
You don't see MotoGP, F1, or any any other top racing leagues running carburetors. They aren't bound by any emissions rules that I am aware of. Even NASCAR who is slow to adapt new technology has ditched carburetors.
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Old April 22nd, 2019, 06:51 AM   #22
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You don't see MotoGP, F1, or any any other top racing leagues running carburetors. They aren't bound by any emissions rules that I am aware of. Even NASCAR who is slow to adapt new technology has ditched carburetors.
You're right of course, but I was talking about fuel injection becoming common on consumer vehicles as a result of emissions and fuel economy rules.
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Old April 23rd, 2019, 05:26 AM   #23
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OK FI is great because you run different fuel maps with a computer. Makes tuning easy, just push a couple buttons.
Something electrical lets go or one of the many sensors and you are out of the race or parked along th road. I have both high performance bikes with FI an a bunch of carbureted bikes. They all run very nicely because I have taken the time to learn how to tune carbs or FI.

I have four carb rebuilds coming up and a spark plug change of the FI and then a couple of dyno pulls. New mufflers.
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Old April 23rd, 2019, 12:24 PM   #24
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Even the last bastion hold-outs for carbs have adopted EFI... namely NASCAR. The year after EFI was adopted, the cars went faster than ever. Smaller restrictors were introduced to lower speeds back to previous levels.

Daytona 24-hr all-time lap-record was set in 1993 by Dan Gurney’s AAR Eagle MKIII-GTP car. It had smallest displacement of entire field at 2.1L, yet made +800bhp. Simply not possible to tune such boosted monsters with carbs to get easy sub-freezing cold-starts, along with friendly partial-throttle mid-range in addition to that kind of peak-power. Daytona 24-hr lap-record finally broken this year, 26-yrs later by Mazda.
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Old April 23rd, 2019, 12:28 PM   #25
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Robert, you need to send your carbs to ducatiman for full refurb job. Idea is to restore carbs back to factory-fresh clean condition. It takes tonnes of experience, specialized machines and some sprinkles of black magic. I don’t think it’s best use of your time spending next couple decades to acquire that kind of expertise.
https://www.ninjette.org/forums/showthread.php?t=226815

Some related threads:

https://www.ninjette.org/forums/showthread.php?t=330960
https://www.ninjette.org/forums/showthread.php?t=322846
https://www.ninjette.org/forums/showthread.php?t=321223
https://www.ninjette.org/forums/showthread.php?t=317977
https://www.ninjette.org/forums/showthread.php?t=317810
https://www.ninjette.org/forums/showthread.php?t=316395
https://www.ninjette.org/forums/showthread.php?t=315193
https://www.ninjette.org/forums/showthread.php?t=280658
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Old April 23rd, 2019, 04:35 PM   #26
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What's so special about these carbs that only the most seasoned of carb gurus can rebuild these? I've gathered that ducatiman is the respected carb guy in these parts, but can the average home mechanic empowered by YouTube, Google, and internet forums not tackle these? I mean, I learned to rebuild all 12 (2 boats, both twin engine, 3 carbs per engine) of my Mikuni carbs by following a write up posted to a popular jet ski forum.

Besides I'm not keeping the bike. Now that my wife and I have kids, we're selling our motorcycles. I just need it to run so I can sell it.
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Old April 23rd, 2019, 05:57 PM   #27
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They're not special, they just have a lot of teeny internal passages that are difficult to clean properly. On top of that the diaphragms are delicate and expensive. I do all the work on my vehicles myself with rare exceptions, but chose to send my 250 carbs to Gordon recently because I've been very busy and wanted them done right the first time.

You know what it takes to clean them yourself, just don't overlook anything or you'll be doing the job multiple times.
@DannoXYZ has some labeled photos that show all the parts that need cleaning, maybe he'll be kind enough to post them for you.
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Old April 23rd, 2019, 08:04 PM   #28
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Thing you have to keep in mind is modern non-chlorinated carb “cleaners” are worthless at cleaning carbs. They no longer have any carbon-tetrachloride nor trichloro-ethane is what does cutting of poly-vinyl bonds in dried-out petrol. Liquid solvents are just carriers for these compounds. Unfortunately, that’s all that’s left in carb “cleaners”, carrier solvents.

I used to use carb-cleaners to clean my sprockets covers and it would drip off thick and black like tar with chunks of grime rolling off. Nowadays, the carb-cleaner drips off clear, maybe slightly grey and i have to attack the sprocket cover with screwdrivers, toothbrushes and gasoline. Such extreme measures are also needed for effective cleaning of carbs. Need to disassemble carbs down to individual components for thorough cleaning of each part:



Take apart emulsion tube into constituent parts: main jet, holder, needle jet collar. Note how needle-jet collar is oriented so you can re-assemble later same way. Unscrew pilot jet being careful to not lose spring, washer and O-ring. Might as well replace O-ring, float-bowl seals and float-valves.



Then use soft copper wire of various diameters to poke through all tiny bleed holes in all parts. Some people use guitar string to floss out secret passages in carburetor body. Then soda blast these fuel circuits at 100000 psi to remove difficult stuck on bits wire didn’t remove. Also soak in ultrasonic cleaner for several days. Then blow compressed air through all circuits and verify you've got air coming out other end.

These real cleaning steps restores carbs back to factory-fresh condition and bike runs exactly as it did when rolling off dealer floor with zero miles. If bike doesn't run like that, then carbs are not factory-fresh clean.

Here's good site for working on these carbs: http://www.vulcangadgets.com/files/keihin_carb.html

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Old April 23rd, 2019, 08:49 PM   #29
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Also be sure to clean out secret fuel passages. Does not matter how clean your jets are if circuit supplying them petrol is clogged.

Quote:
Originally Posted by n4mwd View Post
Here are the secret passages in the carbs. They are kind of hard to figure out sometimes and this picture guide will show where they are for cleaning purposes.

Carb Pilot jet Circuit


Carb Main Jet Circuit


Carb Fuel and Overflow Drain


Carb Diaphragm Intake, upper choke and vacuum ports


Carb Choke Circuit


Last futzed with by DannoXYZ; April 24th, 2019 at 07:57 AM.
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Old April 24th, 2019, 06:11 AM   #30
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My first carb rebuild was a 1955 Chevy. The year was 1965. No google, no ultrasonic cleaner, no manual, just had to wing it. No big deal.

I collect old motorcycles and WWII stuff. Working on a rebuild of a Cushman 53 airborne scooter. It’s fun working on 75 year old carbs. Amazing how that old antiquated carp still works.

Arguing with is better is stupid. If your bike has carbs you can’t call the magic fairy to sprinkle magic dust and wave a magic wand and turn them into FI.
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Old April 24th, 2019, 07:08 AM   #31
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What's so special about these carbs that only the most seasoned of carb gurus can rebuild these? I've gathered that ducatiman is the respected carb guy in these parts, but can the average home mechanic empowered by YouTube, Google, and internet forums not tackle these? I mean, I learned to rebuild all 12 (2 boats, both twin engine, 3 carbs per engine) of my Mikuni carbs by following a write up posted to a popular jet ski forum.

Besides I'm not keeping the bike. Now that my wife and I have kids, we're selling our motorcycles. I just need it to run so I can sell it.
Details...details...details...a lot of people don't get the details right - at least the first time.

Depending on the severity of the issues, it can take more than just a can of carb cleaner and a screwdriver to do the job right. Sometimes that's all people have to work with.

For those that want it done completely, absolutely, positively correct the first time, and don't have all the tools and skills required, ducatiman is The Man.

Sounds like you have it figured out.
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Old April 30th, 2019, 08:22 PM   #32
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Sounds like you have it figured out.
No, I don't have it figured out. Like I said before, carburetors are archaic and crude, and have no business on a street bike manufactured in 2007.

Now my problem is in the high speed fuel circuit. The bike now starts and idles fine, but falls on its face when under load.

This problem was not present before. Previously once I coaxed the motor into the higher RPMs, it would ride normally. Now it has now power at all. Not sure what changed.

So how much does ducatiman charge for a set of carbs?
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Old April 30th, 2019, 09:27 PM   #33
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I would recommend contacting him directly. He has a basic charge for a restoration, and of course if they need parts like diaphragms the price will be higher. For the time he puts in, his prices are very reasonable.
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Old May 1st, 2019, 08:30 PM   #34
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Think I found my problem.
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Old May 2nd, 2019, 05:31 AM   #35
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Yep!

On another note, Auto Zone used to carry carb cleaner with methylene chloride.
Stopped yesterday to get me some. Oh boy no carb cleaner with methylene chloride any more. So I did some research. It is a “Green” initiative. OK, so I went to Lowe’s to get some methylene chloride. They no longer sell it. Yes, guessed it a “Green” initiative. I think that is just the excuse. Anyone heard of round up? Some folks say round up causes cancer. With all the lawsuits you can imagine. Well it has long been known methylene chloride causes all kinds of medical problems.

Being a chemist I have used methylene chloride for all kinds of extractions in the lab.
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Old May 2nd, 2019, 06:22 AM   #36
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I agree that methylene chloride is a very aggressive and useful solvent. I stay away from it as much as I can, since it caused me to have a low platelet count and a very concerned doctor when I was younger. Knowing that, if I were a manufacturer I would not put it out to the general public in products like carb cleaner.
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Old May 2nd, 2019, 07:25 AM   #37
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I'm looking for a replacement diaphragm locally.

Harley-Davidson's use CV 40mm Keihin carbs. Does anyone know if those diaphragms fit the CVK 30mm? None of the local Kawasaki dealers have the diaphragms in stock, but the Harley dealer has it for the CV 40.

Not sure if they're the same size or not, and I didn't think to bring the old torn diaphragm with me to work this morning, it's still sitting on my work bench at home.
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Old May 2nd, 2019, 08:00 AM   #38
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i think you'll find HD diaphragms dimensionally incompatible , the HD a much larger body, and utilizes wider metal slides.
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Old May 2nd, 2019, 08:25 AM   #39
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i think you'll find HD diaphragms dimensionally incompatible , the HD a much larger body, and utilizes wider metal slides.
Gotcha, not surprised.

Am I able to replace the rubber diaphragm and without replacing the slide? Or is it one piece?

I see this ebay link here has the rubber but no slide for $35. Is it possible to replace the rubber on the slide, or will I just end up ripping it?

https://www.ebay.com/itm/KAWASAKI-Ni...kAAOSwBUVZ24Ra
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Old May 2nd, 2019, 08:32 AM   #40
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a member recently posted he used the $35 diaphragm with success via stretching, using hot soapy water, IIRC.

Hey give it a shot.
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