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Old October 21st, 2019, 10:31 AM   #1
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2007 250ZZR Carb cleaning - any mods should I do while the carb is apart?

Good afternoon, everyone!

I have finally got my first bike - 2007 Canadian ZZR 250 (EX250H) with 11k miles on it and now going through the overall maintenance, cleaning.

I am working on the carb now and took everything apart and am currently soaking the body in Pinesol.
I am going to do the cleaning on the weekend and will start putting it back together.

I am planning to shim the needle with a couple of washers to make it running richer. At the moment the bike slightly hesitates when I open the throttle quickly and the plugs are a bit white/grayish which suggests me it's running on the lean side.

Now I am thinking should I go with a slightly bigger pilot jet (current is 38 , I was thinking 40) before I assemble it back ? The bike was idling OK. My mixture screws were out 2 1/4R and 2 3/4L turns from the factory (the plugs were still in). They are close to what I read a tigger of going a bit higher (3 turns).

I am also planning to replace the stock (in the fitting) fuel filter with an external filter from a lawn mower tractor which is a bit bigger and more convenient to change and it provides better filtering.

Are there any other mods that could be done to the carb while it is still parted out ?

Thank you in advance.
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Old October 21st, 2019, 02:06 PM   #2
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No need to change anything in carbs other than thorough cleaning. Meaning more than just soaking. Use ultrasonic cleaner if you can. Alternate between polar and non-polar solvents. Floss out all jets, bleed holes and all hidden fuel-circuits in body. Final clean-up with micro soda-blasting.

Measure and set float height with final wet-test.

Set pilot-screws for best-idle with warmed up engine. That's setting that gives highest idle with prompt & crisp throttle response.

Last futzed with by DannoXYZ; October 21st, 2019 at 05:24 PM.
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Old October 21st, 2019, 03:48 PM   #3
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Thanks !

I am using Pine-sol approach posted on ninja250.org. Followed by a carb cleaner cleaning of the passages. I do have an ultrasonic cleaner but it is not big enough to put the body in. I will clean the jets in there however.
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Old October 21st, 2019, 04:56 PM   #4
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Cut the battery tray off the back of the airbox while you're at it. Makes future airbox/carb removal much quicker.
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Old October 21st, 2019, 05:23 PM   #5
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Quote:
Originally Posted by choneofakind View Post
Cut the battery tray off the back of the airbox while you're at it. Makes future airbox/carb removal much quicker.
Chris, my tray is a separate item, may be it's a feature of Canadian EX250H ? While looking at the service manuals I did notice that the air box for EX250F is different.
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Old October 23rd, 2019, 08:46 AM   #6
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Originally Posted by choneofakind View Post
Cut the battery tray off the back of the airbox while you're at it. Makes future airbox/carb removal much quicker.
Chris,

I was mistaken. You were correct. I checked the air box today and it does indeed have that second tray connected to it , bolted to the rear fender bracket.

I thought you were referring to the rubber tray that the battery is sitting in.

Thanks for the advice , I do see a value in separating those two. I will need to fabricate some brackets, however, to hold the airbox firmly in place.
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Old October 23rd, 2019, 04:23 PM   #7
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Does your ZZR have an aftermarket exhaust on it? I ask because the OEM Keihin carbs are very well matched to the volumetric efficiency of EX250's 125cc pistons (when the bike's original equipment airbox and exhaust is in place).

My advice, don't rich-it-up unless you've done mods that have increased the pumping efficiency of the engine (aftermarket exhaust and airbox modification for better flow).

The smaller the piston the more delicate the balance is between rich and lean (or too rich and too lean), just a little extra gas in a small displacement cylinder can take things too far. I've seen the bad results with guys working on Suzuki GSF400s, which have 100cc cylinders. They rich-up the mixture to the absolute limit in search of extra horsepower and end up in a constant struggle for usability everywhere in the rev-range except for high-rpm wide-open-throttle.
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Old October 23rd, 2019, 04:52 PM   #8
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Thank you Greg, I have the stock exhaust and the air box. I read about it in few other places and made a decision to keep the jets stock. Just like you are recommending.
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Old October 23rd, 2019, 06:18 PM   #9
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I recommend tuning with wideband O2-sensor using datalogging. They are dirt-cheap nowadays and much, much more precise than staring at tiny gauge while flying down road at WOT!
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Old October 24th, 2019, 10:01 AM   #10
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Quote:
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I recommend tuning with wideband O2-sensor using datalogging. They are dirt-cheap nowadays and much, much more precise than staring at tiny gauge while flying down road at WOT!
Thank you , I will have to look into that. Do you remember any names of the top of your head ?

Do they require me to drill anything in the downpipes, or it's just a tail end clip on sort of thing?
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Old October 24th, 2019, 10:11 AM   #11
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I really like all-digital units from http://techedge.com.au . Most widebands use analogue display with analogue voltage signal to drive gauge. Even though gauge looks digital with numerals, it’s really displaying an analogue feed. And lots of these gauges do not have a regulated reference voltage, so their accuracy varies with alternator output. Turn on lights and you see AFR change by 20%. Most notorious is Innovate LM line, avoid those.

TechEdge wideband also have on-board memory for datalogging, so no need to carry laptop along. To install, you weld on O2-sensor bung like used on autos. There should be flat spot on factory exhaust at 2-1 merge for O2-sensor bung.


Last futzed with by DannoXYZ; October 24th, 2019 at 12:46 PM.
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Old October 24th, 2019, 12:16 PM   #12
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Quote:
Originally Posted by DannoXYZ View Post
I really like all-digital units from http://techedge.com.au . Most widebands use analogue display with analogue voltage signal to drive gauge. Even though gauge looks digital with numerals, itís really displaying an analogue feed. And lots of these gauges do not have a regulated reference voltage, so their accuracy varies with alternator output. Turn on lights and you see AFR change by 20%. Most notorious is Innovate LM line, avoid those.

TechEdge wideband also have on-board memory for datalogging, so no need to carry laptop along. To install, you weld on O2-sensor bung like used on autos. There should be flat spot on factory exhaust at 2-1 merge for O2-sensor bung.

Thanks a lot ! I understand what you mean re. accuracy.
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Old October 24th, 2019, 02:01 PM   #13
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The ZZR250 doesn't have a 2-into-1 exhaust, right? Correct me if I'm wrong but the ZZR250 has the same exhaust configuration as the Pre-Gen bikes.

If you want to monitor a Pre-Gen bike's exhaust gas air/fuel ratio with one wideband O2 sensor (which is the usual configuration) you would have to install a 2-into-1 exhaust system and the O2 sensor would have to be installed downstream of the merge point for the individual cylinder headers.

But... if you do have a 2-into-1 exhaust system installed on your EX250 here's a picture of what I think is the perfect location to install a Bosch 5-wire Wideband O2 sensor.



This is a picture of the bottom of my EX250 which has an Area P full stainless steel 2-into-1 exhaust system installed. In the picture you can see that there's a gap of about 2.5 inches between the rear end of the engine oil sump and the forward pivot point for the rear suspension. That 2.5 inch gap is the perfect place to locate the O2 sensor.

I use a Bosch 5-wire sensor and Innovate Motorsports LC-1 wideband sensor controller.

If you have sharp eyes and really know what the bottom of an EX250 looks like you will notice that my Pre-Gen's oil sump looks like a Next-Gen oil sump because I retrofitted the large capacity Next-Gen oil-screen cover, which includes its own drain plug. This is an easy mod to do to a Pre-Gen engine and it has two advantages: it increases the EX250 engine's oil capacity and it makes draining the oil easier.

And you can also see that, as with all EX250 2-into-1 exhaust systems, I had to remove the bike's center stand because it (the center stand) cannot clear the 2-into-1 exhaust.
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Old October 24th, 2019, 06:08 PM   #14
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Quote:
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The ZZR250 doesn't have a 2-into-1 exhaust, right? Correct me if I'm wrong but the ZZR250 has the same exhaust configuration as the Pre-Gen bikes.
...
.
Greg, I really appreciate the picture ! Nice looking bottom of the bike, looks really like it's receiving some TLC

ZZR does have the same exhausts configuration.

Thanks for all the information. That's something to think about possibly next winter. I have got my hands full for this winter - the bike was kind taken care of from the simple maintenance prospective - the guys was following oil changes, chain lubes and cleaning the exterior. But mechanically it was a bit neglected and I now have to fix all that first so I can pass the Ontario safety inspection. Some of the crazy stuff I caught: original 12 years old tires - cracking already, the front engine bracket was holding just on one bolt on one side - and that bolt had the nut half way loose (he is lucky as he could literally lose the engine on a big bump). other missing bolts and nuts here and there .

Started with the valves and fixing the intake issues - carb, airbox, etc..
I actually found few reasons why my rpm sometimes were funky , already recovered a what looked like a mosquito leg from one of the needle jets. Breather connector was loose, one boot from the carb to the head was loose. I guess I had quite some vacuum leaks there. It's great you talked me our of changing the jets. Looks like the reason for lean running lies elsewhere.

I did notice you have that oil cover from the new gen, at first I actually thought yours is the new gen.

I have already purchased a cover from a 2008 new gen. Should be here in a couple of weeks.
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Old October 24th, 2019, 09:07 PM   #15
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the front engine bracket was holding just on one bolt on one side - and that bolt had the nut half way loose (he is lucky as he could literally lose the engine on a big bump). other missing bolts and nuts here and there .
Loose nuts and fasteners are very common on the EX250. I've always attributed this to the vibrations produced by the EX250 engine (a particular vibration that only a high-revving parallel twin with a 180 degree crankshaft can make, my Suzuki GSF400, a 100cc per-cylinder inline 4, is also a "shift at 12,000 RPM kind of bike and its fasteners don't come loose like they do on my EX250).

And the nuts on the Engine Mounting Bolts are especially bad about coming loose (all three of them: the Front Engine Mounting Bolt and the Upper and Lower Rear Engine Mounting Bolts).

I put a dab of Loctite "Blue" 243 on just about every fastener on the bike when I work on it. Loctite Blue is their medium strength product and it "permits disassembly with hand tools".
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Old October 25th, 2019, 04:21 AM   #16
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Thanks for the advice , I do see a value in separating those two. I will need to fabricate some brackets, however, to hold the airbox firmly in place.
No need Between the battery wedged in behind it and it being attached to the back of the carbs, it won't go anywhere.
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Old October 25th, 2019, 07:10 AM   #17
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I took the airbox out yesterday and what I found interesting is that areas that are located close to the tank bracket have provisions (extra plastic) that could accommodate a screw. Almost like they we planning to add brackets there by design. They do not look like re-enforcements for rigidity.
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Old October 25th, 2019, 07:40 AM   #18
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I put a dab of Loctite "Blue" 243 on just about every fastener on the bike when I work on it. Loctite Blue is their medium strength product and it "permits disassembly with hand tools".
I hear you. I use the blue one pretty much on 80% of fasteners on my bicycles and cars. Especially in places exposed to elements. It keeps the moisture and what's worse , salt, which we have tonnes in Ontario out.
If there are no special conditions or instructions regarding the joint and it's on the exterior side the loctite goes in

I go through a 30ml bottle in a year.
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Old October 25th, 2019, 12:05 PM   #19
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Yeah, my friend with airplane repair biz says no bolt ever goes on plane dry. It either has lube or locking-compound on it.
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Old October 26th, 2019, 10:50 AM   #20
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Yeah, my friend with airplane repair biz says no bolt ever goes on plane dry. It either has lube or locking-compound on it.
Makes sense to me...
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Old October 26th, 2019, 10:58 AM   #21
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Ok the carbs are back together...
I installed them on the heads and connected the choke cable only. The airbox is off still - waiting for the gaskets to come and complete the airbox mod.

I decided to do a quick check realizing the mixture would be lean still. No synchronizing the carbs yet and no pilot mixture tuning has yet been completed either (screws at 2 1/2 turnes out). To my surprize the bike ran well even with no tunning. better than before I did the cleaning. It could even run at 500 rpm without stalling - never hapened before (quickly raised it back shortly after confirming).
Throttle response was great - no percieved lag. Given the box was off I could see the gates openning and they were openning together.
I guess 1.5 mm of washers under the jet needle helped.

Thanks for all your help folks.
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Old October 26th, 2019, 11:59 AM   #22
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Good job!

Clean factory-fresh carbs work best. It's always difficult to resist temptation to use larger jets to make up for lean mixtures from dirtymand clogged carbs.
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Old November 10th, 2019, 06:59 PM   #23
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No need Between the battery wedged in behind it and it being attached to the back of the carbs, it won't go anywhere.
You we correct Chris. I have completed the modification today and the box stays put. Jammed by the battery tray and held my the rubber band it's not moving. I will keep it this way for a bit and will see how it goes once I start riding it.
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Old November 10th, 2019, 07:05 PM   #24
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I have finally assembled everything today and rode it a bit on the driveway. The response to the throttle is good. No lag or hesitation.

Not until I received the new parts has I realized how shot all the rubber was. The new airbox gasket is puffy and seals the box well. The old breather tube was barely staying put, the new one was hard to slide on but it stays solid.

I suspect that breather tube alone was a huge leak

My new fuel filter routing did not go well , the hose tends to kink. I will have to add a 90degre elbow.

Next stop is the synchronization and mixture screw tuning.
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Old November 10th, 2019, 08:08 PM   #25
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Originally Posted by SibSerge View Post
You we correct Chris. I have completed the modification today and the box stays put. Jammed by the battery tray and held my the rubber band it's not moving. I will keep it this way for a bit and will see how it goes once I start riding it.
I won't go anywhere. A lot of Ninja 250 owners have ridden a lot of miles with their battery boxes cut off their air boxes, or with the air box removed completely for pod filters.
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Old November 24th, 2019, 09:39 PM   #26
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Originally Posted by DannoXYZ View Post
No need to change anything in carbs other than thorough cleaning. Meaning more than just soaking. Use ultrasonic cleaner if you can. Alternate between polar and non-polar solvents. Floss out all jets, bleed holes and all hidden fuel-circuits in body. Final clean-up with micro soda-blasting.

Measure and set float height with final wet-test.

Set pilot-screws for best-idle with warmed up engine. That's setting that gives highest idle with prompt & crisp throttle response.
The carb saga is now complete

I synchronized the carb today and set the pilot mixture screws. I had to actually screw the pilot screws back in by about half a turn. They are at around 2 turns. The rpms now settle straight into the idle without hanging or dipping after the throttle is released.
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