Rejet with pods?

Covering the pods to increase air flow restriction may no doubt help reduce the lean condition and help the engine run more like it would with an airbox, but it doesn't compensate for the loss of vacuum that the airbox provides. If you consider that with a multi cylinder engine there more or less is always one carb sucking air from the airbox the result is some level of vacuum in the airbox at all times. This has an affect on the carbs; particularly on the CV type carbs which use vacuum through the throttle vacuum passage to raise the slides. The vacuum available there is affected by the air passing through the main intake, so any change in the dynamics of the air passing through the main air intake has an affect on the raising of the slides. The link below shows how CV carbs work and helps show relationships between the various parts. Ed

650ed wrote: Simple - the exhaust system does not change the air/fuel ratio of the charge coming from the carbs into the cylinders, but changing the air flow restriction associated with the air filtration does.

Exhaust does affect it somewhat. Any change to the exhaust has always shown a change in AFR on the wideband.

The relevant parameter is air flow versus throttle position over a range of load to RPM.
If we eliminate the variable of accelerating RPM by assuming a steady speed (and RPM) at a constant throttle position (Let's say 1/, we can also assume a constant load on steady ground straight line etc. If we then change one parameter, that being opening up the exhaust, the engine will breathe more, and the RPM may increase slightly to a higher constant RPM, (as well as speed), the mixture will tend to be leaner at that same (1/ constant throttle position. So then you upjet to compensate (if it is deemed to be too lean). This will then result in a stronger mixture, which will cause the RPM to be at an even higher constant RPM at that same (1/ throttle position. If it goes higher enough to breathe more, you may find you will be slightly lean again (but far less lean than in the initial trial with the opened exhaust).

This cycle of jetting, then checking, and jetting again is a type of function known as "recursive". The first jetting change results in changes, not only to the final AFR, but to the initial conditions (RPM) and airflow. Those changes to the initial conditions then change the final AFR. So you have to make another change to the jetting. Each time, the required change becomes less and less until there is no required change. Recursion is sometimes the only method, and is often the fastest method at solving an equation.

This is why jetting from scratch takes so long.

As far as relevance to the bike at hand: KZ550 with TK22 carbs, ...
Pods will definitely liven up the motor. By that I mean on the highway it will have top end rush. But it requires rejetting. Actually it may get by with just a needle position change, which is good because aftermarket needles and jets are turning up defective lately.

But trying to do jetting on a motor with many condition issues is a waste of time. Everything else (motor, ignition, charging, intake tract condition, fuel tranfer and level) must be rock solid or you will pull your hair out trying to rejet.

I don't know about jets for TK carbs on a KZ550, but the one I had on a Yamaha XT200 had almost no options available for re-jetting. I had to search through Yamaha parts books for various vehicles until I found something like a Jetski or Snowmobile that used the same carb but had the smaller jet sizes I needed for altitude , , , they cost a fortune and I vowed never to buy a bike with TK carbs again, perhaps the Kawasaki's are a different story, but parts availability and price would be a consideration before messing about with anything that will require re-jetting.

I'd agree also that exhausts effect mixture, you can notice that when you get a hole in your muffler, but at the same time that does not mess with your tuning like Pods on CV carbs will. Normally for an exhaust it's just a straightforward change like one size up on the jets.

Don't let the nay sayers turn you off on Pod filters. They can be tuned to run perfectly, most people do not dedicate the time to do it correctly. I have dialed in pod filters and 4 into 1 exhausts on dozens of bikes and it really is not that hard. Dedicate some time to educating yourself on carb theory and what jetting effects what throttle positions. Once you have the theory down it's pretty easy.

loudhvx wrote:

650ed wrote: Simple - the exhaust system does not change the air/fuel ratio of the charge coming from the carbs into the cylinders, but changing the air flow restriction associated with the air filtration does.

The relevant parameter is air flow versus throttle position over a range of load to RPM.
If we eliminate the variable of accelerating RPM by assuming a steady speed (and RPM) at a constant throttle position (Let's say 1/, we can also assume a constant load on steady ground straight line etc. If we then change one parameter, that being opening up the exhaust, the engine will breathe more, and the RPM may increase slightly to a higher constant RPM, (as well as speed), the mixture will tend to be leaner at that same (1/ constant throttle position.

I'm no expert, but I'm not sure that's exactly true with CV carbs. Here's what I'm seeing. Take a look at the video I provided. As the RPM rises so does the vacuum applied through the vacuum passage, and that would then raise the diaphragm and the needle. Raising the needle would then enrichen the air/fuel mixture which would prevent the lean condition. Ed

I know Pods can be tuned to work well, but in my experience the vast majority of people are poor at dealing with carbs, so it's not something I would recommend to the inexperienced or faint-hearted. While I've owned bikes with Pods, I've still to be convinced they provide benefits to outweigh the negatives like wind, rain and tuning time. I don't feel they warrant ditching a functioning air box for them,. If more airflow is required, on the basis that the stock airbox has a restricted intake to reduce noise, I think looking at modifying the stock airbox would be a good first point for attention. There are numerous well documented modifications that include removing snorkels and putting extra holes in the air box case to get around this on different motorcycles and then a higher flowing filter can also be used.in the modified airbox.

Ed, possibly one of the problems with Pods and CV carbs is a reduction in the vacuum compared to stock, which means the needles are not rising as they did before relative to throttle openings and this causes a lean condition. On my XR650L I have a well known carb mod which involves shimming the needle and drilling out the opening in the vacuum passageway to speed up the throttle response for the CV carb with the other jet, airbox and airfilter mods - It works extremely well as a complete package. There are a lot of factors effecting what happens with these CV carbs, I'm sure a lot of thought, theory and testing goes into any stock setup so when we start altering things we can really create a rod for our own backs if we aren't careful.

redhawk4 wrote: I know Pods can be tuned to work well.

I'm definitely not an expert, but I pay attention when they speak. On the other Kaw forum, the tuners said there were a couple of bikes that couldn't be tuned right for pods. Most probably can be well enough to ride but as said, don't see the benefit compared to the grief.

redhawk4 wrote: reduction in the vacuum compared to stock, which means the needles are not rising as they did before relative to throttle openings and this causes a lean condition.

That hits the nail on the head. The length and taper of the specific needle was created to match the stock system. Change it and that means the taper is wrong. You can increase jet sizes and raise the needle to shotgun out the lean spots but that doesn't mean it will match the flow like the stock ones did.

650ed wrote:

loudhvx wrote:

650ed wrote: Simple - the exhaust system does not change the air/fuel ratio of the charge coming from the carbs into the cylinders, but changing the air flow restriction associated with the air filtration does.

The relevant parameter is air flow versus throttle position over a range of load to RPM.
If we eliminate the variable of accelerating RPM by assuming a steady speed (and RPM) at a constant throttle position (Let's say 1/, we can also assume a constant load on steady ground straight line etc. If we then change one parameter, that being opening up the exhaust, the engine will breathe more, and the RPM may increase slightly to a higher constant RPM, (as well as speed), the mixture will tend to be leaner at that same (1/ constant throttle position.

I'm no expert, but I'm not sure that's exactly true with CV carbs. Here's what I'm seeing. Take a look at the video I provided. As the RPM rises so does the vacuum applied through the vacuum passage, and that would then raise the diaphragm and the needle. Raising the needle would then enrichen the air/fuel mixture which would prevent the lean condition. Ed

I was really only talking about the carbs for his bike. (Manual slide TK). But in the CV scenario, raising the diaphragm increases the air flow and decreases vacuum being applied to pull up the fuel. There will still be more fuel flow, but not as much increase as there would have been if the vacuum was the same. But there are too many variables to predict the exact behavior with CV carbs because we don't know the needle profile.

With manual carbs, when we hold a constant throttle, we know the needle opening does not change because the needle is stationary. CV's are definitely another ball of wax.

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Regarding TK-22 jetting. Unfortunately, I still don't have a server for the website (lost the site host in October). I may be building a server and hosting it myself if I can get away with it.

But the last time I jetted a KZ550 TK-22 for pods, I found a setting that works pretty well for Pods, and it didn't require any new jets or needles. It only required very precise shimming of the stock needle. This came about as a result of the Chinese rebuild kits being basically defective. The needles were not usable at all. The jets may have been ok, but they were stock sizes.

This setup may not be ideal for ultimate fuel economy, but the bike ran great in all conditions. When I get the site back up, I'll have the details posted. I may have thread on KZrider with the details. It would have been back in July or August.

loudhvx wrote: I was really only talking about the carbs for his bike. (Manual slide TK).

OOOPS, my mistake. I was under the impression that the KZ550 had CV type carbs, but it does not. :blush: Ed

Slide carbs are a lot easier to tune for pods -my CV30 GPz550 I had the carbs off over 10 times...now I think I might be better at it but would still expect several attempts. People have told me the last 25 years that a bike will never run 'right' on pods but personally I like them, on ll of mine.

Downsides: bad in wet weather, lower quality of filtration ie increased rate on rings and valve guide wear , hassle to tune, lower mpg less bottom end tourque-particularly with a 4-1 pipe.

Upside look cool, sound ace -pure heavy metal. ease of maintenance, possible rpm power gains if done just right ? (this bit is controversial)

LOL wow