Getting the !@#$%^& Airbox back in

[PlaneGuy]

I bought my Ninjette four days ago. The prior owner was not particularly well versed in tuning after making changes so I am in the process of returning the intake and exhaust to stock.

Changing back to the stock pipes produced a marked improvement. Now there is only a minor flat-spot between 7000 and 10000 RPM at partial throttle (1/4 to 1/2 throttle at cruise). So I figured I would put the stock air box back on. I figured it would be a piece of cake. I figured wrong.

Now before you tell me, let me tell you that I have found the ninja250.org website and its wiki instructing on removing the airbox. (http://faq.ninja250.org/wiki/Removing_the_airbox) What I am hoping to hear from someone here is which of the methods, rear-entry and side-entry, you have used and to what level of success. Also I would like to know if you have found any little things to help make it easier.

Please help me retain what little sanity I have left. Thank you.

[choneofakind]

From my experience, reinstalling it is either a real PITA, or a sinch. Kinda depends on the bike.

It sounds to me like the midrange is lean. If you can't figure out the airbox, try shimming the needles in order to get the midrange closer to right.

http://www.ninjette.org/forums/showt...ht=DIY+needles



whats the current setup on the intake right now? pod or airbox? You said you were putting the airbox back on, so does that mean it has pods? or that you took it off to play with the carbs? if it already has pods, it might just be easier to keep the pods and jet to make it work

[PlaneGuy]

Originally Posted by choneofakind

From my experience, reinstalling it is either a real PITA, or a sinch. Kinda depends on the bike.

Thanks.

It sounds to me like the midrange is lean. If you can't figure out the airbox, try shimming the needles in order to get the midrange closer to right.

http://www.ninjette.org/forums/showt...ht=DIY+needles

Yes, I suspected that and more below ...

whats the current setup on the intake right now? pod or airbox? You said you were putting the airbox back on, so does that mean it has pods? or that you took it off to play with the carbs? if it already has pods, it might just be easier to keep the pods and jet to make it work

It has K&N pods right now. And, yes, I am considering putting them back and not putting the airbox back in as an option. OTOH, I find the intake noise just pretty objectionable. (I find that sounds that I enjoyed in times past no longer hold the same attraction today.) I also assume that it has an effect on the mid-range tuning (needle), which others -- including you -- have suggested. I am on the fence because I have to come up with a filter for the oil breather (prior owner left it open) if I keep the pods, or drill the endplate in one of the pods, attach a fitting, and allow crankcase vapor to go back through the engine. Certainly dealing with maintenance and tuning of the carbs will be easier with the airbox out. <sigh>

The previous owner indicated that he changed the needle position up (richer) in order to accommodate the pods and the new open pipe, the latter of which I have removed. Since resorting to the stock pipes the flat spot is much better but still present, probably the result of the pods. I probably need to raise the needle another notch or two.

All my prior carb tuning experience is with Mikuni, Dellorto, Webber, and some Russian and Chinese pressure carbs used on radial engines. I have no experience tuning constant-velocity carbs but suspect they are not that far off from Mikunis, i.e. main jet controls full-throttle mixture, needle controls 1/4-3/4 throttle mixture (along with emulsion tube and air jet -- but not sure we have removable emulsion tubes and air jets in these carbs), and idle mixture is controlled by that idle-mixture screw/pilot-jet.

I suspect that my 1/4-3/4 throttle flat spot is from a too-lean condition on the needle. So I can raise the needle some more or I can put everything back to stock and see what happens then. In spite of all the problems getting the stock airbox back into the frame (and it is a gold-plated b---h), I think that I will be happier in the long run with the engine running 100% stock. It is the starting point I think I want to work from. I just don't think that making pipe and induction changes is likely to net the same overall balance desired for a general-purpose commuting/sport bike.

Thanks!

[PlaneGuy]

Ok, it is done. The K&N pods are off and the stock airbox is back installed in the bike. I have successfuly made the bike run again which I consider to be a major accomplishment. (Oh, and I have shed blood on it which means it really is mine now.)

It is much quieter.

There is no flat-spot at any throttle opening any more.

Top end seems just about the same.

But here is the thing that I suspect that many forget in their search for a bit more power. The airbox is a major source of mechanical support and vibration damping for the carbs. Unless you have constructed some kind of mounting bracket for the carbs, without the airbox they are suspended only by the rubber couplings to the head. Sure, the cables do provide some support but that is not what they are supposed to do and probably end up suffering from more fatigue failures because of the vibration.

[Racer x]

Congradulations on getting things back to proper running. The maniflods will hold the carbs witout any support. But running a long Zip tie to the tank support will hold them up .

It is amazing how much quieter the bike will run with an air box. You will also gain some bottom end power. Did the original owner rejet the carbs. You should have #98 jets (stock) but #100 are OK . You can shim the needles or up the pilot jets if the bike requiers a lot of choke during cold weather operation.

[PlaneGuy]

Originally Posted by Racer x

Congradulations on getting things back to proper running. The maniflods will hold the carbs witout any support. But running a long Zip tie to the tank support will hold them up.

Good idea.

It is amazing how much quieter the bike will run with an air box. You will also gain some bottom end power. Did the original owner rejet the carbs.

No. He did say that he had added a washer to the needle to richen the midrange. Could be I need to undo that. But I think I will ride it for a bit just to see how it is running now.

If one is going to mess with rejetting, one should start at the top end (wide open throttle) and do plug-cuts to set the main jet, then work backwards (partial throttle) to do plug-cuts to trim the needle setting. A good dyno and a wideband O2 sensor would be nice too.

You should have #98 jets (stock) but #100 are OK . You can shim the needles or up the pilot jets if the bike requiers a lot of choke during cold weather operation.

I probably should pull the carbs and check. OTOH, it seems to be running properly now with no obvious flat spots. While I need the choke to start the bike cold, I find I can turn it off pretty soon thereafter. Choke behavior doesn't seem unreasonable.

Still, I need to spend time running it at different RPMs and loads to make sure the whole mixture map is proper. EFI is SO much easier.

[Racer x]

Sounds good. Remember if you are going to do a plug chop tuning .Start with a new set of plugs. Once they turn dark they don't clean up enough to tell if you are lean. But it aounds like you are good.

EFI is great but the carbs work well and are easy to tune. I am a big fan of the dyno. It is safer and more accurate.

[choneofakind]

Originally Posted by Racer x

You should have #98 jets (stock) but #100 are OK.

OP has a pregen; those have a 105 main jet
http://faq.ninja250.org/wiki/Dynojet...zes_conversion
check the jet size; if the bike is completely stock intake/exhaust and stock jetting, there's really no need to worry about the mix being off; that's how it came from the factory. If you want to improve the midrange a little at the expense of 3-5mpg's, then put 1 or 2 washers on the needles while you're in there and call it a day and close it back up.


glad you got your bike running peachy again. Shedding blood for the bike is always a bonding experience with it

[Racer x]

Ooops. Sorry about that. Thanks.

[PlaneGuy]

Originally Posted by Racer x

Sounds good. Remember if you are going to do a plug chop tuning .Start with a new set of plugs. Once they turn dark they don't clean up enough to tell if you are lean. But it aounds like you are good.

Roger on the fresh plugs. I have four new plugs just waiting to do that.

EFI is great but the carbs work well and are easy to tune. I am a big fan of the dyno. It is safer and more accurate.

Dyno is the bomb. It is the only way to really do it right. Carbs have interaction between all the settings. A change to the main jet may (will) require a change to the needle. EFI is cake because you don't have any interaction at all. You just plug the injector duration numbers in for each box in the RPM/Load matrix. And you can do it on the fly without have to do any wrenching.

[choneofakind]

Originally Posted by PlaneGuy

EFI is cake because you don't have any interaction at all. You just plug the injector duration numbers in for each box in the RPM/Load matrix. And you can do it on the fly without have to do any wrenching.

and if you have a wideband O2 sensor hooked up, you can also check the mix on the fly and not even need to pay for the dyno time!

I'm just waiting for Kawi to finally come out with Fi the good ol US so I can trade in a buy new

[PlaneGuy]

Originally Posted by choneofakind

and if you have a wideband O2 sensor hooked up, you can also check the mix on the fly and not even need to pay for the dyno time!

Well, while a wideband O2 sensor is definitely great for getting the EFI dialed in initially, you do have to remember that best power mix is different best stoichiometric mix, and that is different from best economy mix. So you still need to get on the dyno to find the best power mix for the engine. Once you know that you can go back to it using the wideband O2 sensor later if you have made changes.

One nice thing about EFI is that I can change the fuel map to give me best economy mix at cruising RPM and load and still have best power mix under maximum load (full throttle). That is much more difficult to do with carburetors. Also, EFI can automatically correct for changes in air density (altitude and temperature). Carbs can't.

I'm just waiting for Kawi to finally come out with Fi the good ol US so I can trade in a buy new

Yeah, and then we can get a MicroSquirt and play with fuel maps until the cows come home!

http://www.diyautotune.com/catalog/m...f4503db4e7b9b3

[Racer x]

I don't think the stock fuel injection computer is programmable.

The microsquirt system is a bit expensive .I am going to the dyno today. just to break in the motor.

[PlaneGuy]

Originally Posted by Racer x

I don't think the stock fuel injection computer is programmable.

I would be surprised if it was. California (for one) doesn't want people dinking with the programming for emission reasons. Kawasaki probably doesn't either because they don't want people breaking their engines.

The microsquirt system is a bit expensive.

I suppose. Compared to other programmable ECUs it is dirt-cheap. But in absolute terms it does cost about $300. Right now the price on the Microsquirt is set high ($99,000 ) so that people won't buy the old version. They are releasing a new version that is completely sealed that will be more robust. But it will use the same internal module and you can still get that for about $250 so that sets the ballpark for the price.

I am going to the dyno today. just to break in the motor.

Huh. That seems a rather expensive way to break in the motor. I would probably just ride the bike. More fun. OTOH, I can see that, if you want to break it in under a higher-than normal load, the dyno would probably be the only way to do it. One of the nice thing about breaking-in aircraft engines is that we can run them at 100% power for extended periods of time. Good for making the rings seat really well.

[Alex]

Check out greg737's posts and setup, he went whole hog with the microsquirt if I remember his parts correctly. Neat setup.