Pod filters, yes, I stepped in it on purpose.

Guys,

I’ve read so much on this forum about pod filters since I joined in November or December of last year that I decided a separate thread was in order to clear up the mysteries and let you guys know what we found to be true and what we learned. A lot of animosity and purely judgmental statements have been posted but I have failed to see anyone post what an owner needs to do to properly install pod filters on their bike. I see this get bantered about in almost every forum that I belong to, usually with the only result being that some people feel they have been “shot down” or stomped on and others to feel that they are preaching or being preached to. We all own our bikes for mostly the same reasons centered by the fact that we love to ride and the other feelings that go with it. I do not however enjoy seeing conflicts on a forum where most of us would be friends if we were closer in distance to one another. I have no issue joining or starting a fight since I’m old school and we used to get in three or four fights a year when I was a kid but we don't need to fight about this.

Also important to understand is that I’m not on either side of the “to mod or not to mod” argument. I have a couple of bikes that I wouldn’t dare destroy their value by modding them. On the other hand, I have a couple of highly modified bikes that I not only enjoyed modifying them, I enjoy riding the wheels off of them.

There is nothing wrong with installing pod filters on your bike. This is still America and you still have that choice. Then, your bike will look as cool as one of my triples does with pods! I love the look without that huge air filter box and intake snorkel gone and even that huge rubber boot from the filter box to each of the three carbs, all gone and man does it look clean with the three pods. BUT…and it’s a big BUT….you need to do it the right way! Us slide type guys have it simple, re-jet and go but we found something completely different when we tried to install pods on CV carbs. Don't do it right and you can expect to have a hard starting bike that takes even longer to warm up. It may run great at low rpm only to die at high rpm....or the other way around. Basically, if you don't do it right, what results will be your own fault. I can almost guarantee you that your bike will run worse and it will be slower if you just bolt on a set of pods.

A lot of guys here remember when the CV carbs came out so I challenge you…remember the first thing you noticed about the specs of the CV carbs over the slide Mikuni’s or Keihin's? No, not the “big chrome top” but the SIZE of the carbs!! Look at the bikes that were already in production that switched to CV’s because of the emission requirements. Every single one of them increased the size of the carbs to compensate for the signal loss that is inherent with CV’s. Some of them went up by 6mm when they switched from slide to CV’s!

There’s no great mystery to installing pod filters, you only need to upsize the carbs by 2 or more millimeters(within limits). The other thing to keep in mind with pure pods AKA- flat round back K&N’s, is the fact that at WFO, your engine WILL experience reversion caused by the air direction changing too fast at the rear of the pod for the mechanical device (the carb) to compensate for. The cone type will minimize this effect. If your bike if fuel injected, it will be taken care on in milliseconds but with mechanical carbs, it take a bit more time. It isn’t nearly as big a deal on four strokes as it is on my 750 two stroke engines but I’m trying to let you know all of the possible pitfalls and outcomes, not just the ones you want to hear.

TEST RESULTS;
We experimented with pods on a 750 two stroke triple fitted from the factory with CV carbs and a four stroke 750 IL4 with factory CV’s and the testing showed that no matter how we “re-jetted” them, if we used the same size carb and switched to pods, it made less power across the board. The dyno didn’t care that with the pods installed it SHOULD have flowed more air and with the larger jets it SHOULD have flowed more fuel. No BS, no arguments, less power period. BUT, when we switched from the factory 34’s to 36’s or 40’s to 42’s and installed pods, the engine enjoyed a small increase in power at all rpms with no apparent loss down low.

When we increased the size of the carbs from 34 CV to 38 CV carbs when we fitted the pods, the bike made much more power, almost across the board. BUT we lost some down low because the larger carbs required more air (higher rpm) before they would flow properly. Without getting into the balancing act that carbs have to do, we’d be much better off if we had variable throated carbs which opened up larger as RPM increased, but we don’t so the carb has to be balanced enough to operate cleanly down low and up high and it’s a tricky proposition. Our final outcomes dictated that if you are going to install pod filters on a CV carb equipped bike, to do it without losing power, you are going to need to upsize your carbs.

All I’m trying to do is to state the facts as WE found them to be. I won’t be suckered into an argument over this. If you feel that you can reinvent the wheel and do a simple re-jet and get more power, have at it….but before you come on and rant and rave about how much faster your bike is, have the dyno sheets because if you take the time and spend the money to get more then a “seat of the pants” opinion, you will find yourself surprised.

jeff

 

Alrite mods, a nice, clean post, now TIME TO STICKY AND MAKE EVERY NEW MEMBER READ

 

only problem is a lot of the people won't listen. The last Thread that was going around i tried to explain it Also tried to tell them it can be done but takes one heck of a lot of work. Heck i even posted a pic of my dyno sheet. With a 4-1 on my vmax took the guys from tnt performance 43 dyno runs to get it right they changed everything from air jets to pods needles. They ended up running a stk filter box with the small part of the lid removed with a K&N fitter in the box. I think i even posted the write up on it on their website. Granted it picked up 20 hp and 15 ft lbs torque when it was finished. It never carburated right at idle again. With pods and all the other work it made like 6 hp more peak hp then stock but under that peak made less then the stocker did by quite a bit. But people told me that the dyno did not mean anything so i gave up

 

curious, what did 43 dyno runs cost ya?

 

Jeff; good write-up. I highly doubt most "pod-modders" are up for replacing their carbs, so you HAVE done a valuable service.

However, getting people who already "know better" to listen to the simple science behind the situation is going to be much more difficult.

("Don't confuse me with facts when I've already made up my mind.")

I found this surprising myself:

I would have thought that there would have been a GAIN, somewhere, offset by losses elsewhere in the power band. But the dyno doesn't lie, and better yet, doesn't have an agenda or an opinion.

Good job.

 

There's a BIG Difference between a 750 Two-stroke Triple and a DOHC-4 Four Stroker.

The Mission of this site isn't to tell anybody what they can of cannot do.
We try to be fair and present both sides of the story regarding installing Air Pods.

We seek to help-out the Member who sees Pods for sale and thinks they'll be a great addition to his bike, with all the facts, before he makes the alteration and find-out that he's experiencing tuning problems.

The issue that needs to be disclosed to everyone who is thinking about installing Pods goes beyond the need to experimentally rejet and shim.

We should find a caveat to publish that is the truth about switching-over from stock to Pods.

Somewhere between: "It's a piece of cake", and ... "You'll never get it right" is what needs to be presented as fact to those who have the Pods decision to make.

 

I have often thought that a "Restrictive Baffle" inside the Pod which doubled as a Velocity Stack would get you closer to defeating "The Pod Dilemma".

I envisioned a Pod :::
> with an internal Velocity Stack ... that was OPEN ... only at the far end.

(Air enters the Pod and is drawn-in at the far end of the Pod.)

+ The Internal Column >> Removable
+ The COLUMN end fitted with Restriction Mesh Caps
(Screens and Perforated Caps of Variable Density >> Multiples fitting)

The Carb Horn "Drilled-out" at the Atmosphere Opening Orifice.
The HORN Side of the Atmosphere Orifice >> Sealed.
+ Atmosphere to allow Air Supply to the Main Air Jets would be drawn through the Drilled-Out Holes.

Getting the Picture???

_________________
Rick Massey
MODERATOR & Tech Writer

Rick has done a wonderful job of pointing the guys who are trying to solve this problem in the right direction this test didn't try to solve any of these problems just proved what we all ready know. And a dyno test can not address the turbulence problem unless it is in a wind tunnel. I have come up with a design I hope will solve this problem which looks good on a bench test but will not be able to test it in the real word until warmer weather. But if this does solve the problem it's not going to change some peoples minds about pods anyway. I agree that you will not make your bike run better by taking a set of pods out of the box and bolting them on this I will not debate. But I refuse to assume that you can not make your bike run as good or better with pods and slight modifications. Here are some pictures of what I'm working on.

http://i1177.photobucket.com/albums/x35 ... 1083-1.jpg

http://i1177.photobucket.com/albums/x35 ... 1082-2.jpg

http://i1177.photobucket.com/albums/x35 ... C01087.jpg

http://i1177.photobucket.com/albums/x35 ... C01088.jpg

http://i1177.photobucket.com/albums/x35 ... C01089.jpg

 

For those who missed seeing this the first time..."and a four stroke 750 IL4 with factory CV’s "


jeff
P.S...fwiw-dyno time didn't cost a dime and testing was done at 3 test max, per day per bike to maintain parity in results and to preserve the machines at the dyno owners' requirements. All testing was done at controlled temp and humidity and finally, the carbs nor jetting kits cost anything either since we shared our results with a couple of other teams that had very nice connections.

 

what was the exhaust on this bike? stock exhaust matched with pods is a definite loss of power.

aside from the loss of power, were you able to make the bike run with pods? this is usually the argument in pod threads.

another question; if you are changing your carbs...why would you put another set of CV's on?! i come from the dirt world, and a CV carb is the first thing to be tossed off a brand new machine. FCR is my carb of choice, and it is extremely tunable (open element or full airbox).

do you have the graphs to post up?

 

Very nice write up. The facts are facts of less power then, BUT a lot of people argue that it cannot be tuned to properly run. I am not looking to argue, but is it possible then to make a bike run correctly, with pods installed. Just with less horsepower? Idle, low end, mid range, and high rpm?

I have 2 750s 1 stock airbox and one podded. They both seem the same for power. Can I ask what the number of hosepower losses are across the board? Just for poops and grins.

 

QUOTE There's a BIG Difference between a 750 Two-stroke Triple and a DOHC-4 Four Stroker.

Here is DOHC 4 cyl Yamaha vmax I cant find the dyno sheet with pods and jetting but it made 4 peak hp over stk but from 3k up made a lot less till it made a spike at peak. and that was with jetting changes on a dyno runs. This sheet was with the airbox on with a k&n in the box with the little lid off the top. I have posted this before .
I am not saying pods wont work they will work fine just don't work as well as a stock airbox does especially if your running open pipes

 

Cool. I am satisfied. I hope that a sticky is made to show people with questions, some things about pod filter tuning. Instead of an argument a link could be posted.

 

I was never one to say they wouldn't work. They will work a lot of people don't care as long as it runs ok. There are people with stk jets and open pipes that comment on how well they work in their eyes it does. But me personally I won't make a mod like that unless i am sure its going to help performance.
My maxim x had pods on it when i got it it ran ok. I switched to pvc duel filter pods seems like it had better throttle response. I bought a stock airbox with a k&n in it which im going to try next. See if it resolves low rpm and throttle response

 

I had bad luck getting my pvc intake to work I never did try it with the stock jets, had 124s in it. I really swear by putting the rubber stacks on the pod. My bike runs really good. It ran better than my stock bike with an airbox, until I shimmed the needles. They both pull just as good as the other. I really don't feel any power losses, on my pod bike. I wouldn't settle for a poor running modification either. Any horsepower loss is not felt by my high tech seat of the pants. ;-) lol

 

bobberaha:

Don't forget that the AIR Jets get Atmosphere from the "Bean-shaped" orifice at 12 O'Clock on the Hitachi Intake Horn.
>> That AIR needs to reach the AIR Jet to supply the AIR surrounding the Emulsion Tube that gets drawn-up into the Intake Stream bringing atomized Fuel with it.

Performance:

I want the Bike to IDLE ... on its own ... at a Traffic Light ... and Accelerate IMMEDIATELY upon opening the Throttles ... without a hint of HESITATION.
When I crank her open ... I want POWER >> ON. Not an instants Hesitation or delay waiting for a Mixture that will accelerate the Bike.

I want the Engine to make FULL POWER and PULL without an overly RICH Mixture robbing me of HP because I need LOW-RPM Richness to compensate for a Main Fuel Supply NOT being siphoned-up from the Fuel Bowl because the Pressure above the Emulsion Tube isn't sufficiently lowered and Atmosphere needed at the Main Air connecting orifice is reduced causing the Fuel Supply to fail to move up the Emulsion Tube requiring what everyone thinks will be solved by installing a Larger Main Fuel Jet but actually requires a swift air current above the Tube and Main Air to feed the Vacuum.

 

I have ran my bike with streetbrawler's velocity pods and he is right it is pretty close to stock air box I'm just trying to see if I can make it a little better maybe I will maybe I won't but I have no problem running it with the velocity pods. They run like crap if you just bolt pods on and go.

 

Jeff,
Excellent write up. In your expertise, what carbs do you suggest (I know you mentioned the 36, 40, & 42) as other possibilities, but if you had your rathers, what would you install on a 1100 with Pods and 4-2 stock?

Second thought, what other bikes come with say the 36, 40, or 42 sized carbs and do they have a similar issue with running aftermarket pods? Very interesting reading, thanks.

 

All you really need to do, ...

IS

Put the PODS on the RIGHT KIND of Carbs.

Wanna go fast?
Put your Pods on Carbs MADE to run with Pod.
Simple as that!

http://store.starracing.com/servlet/Detail?no=368

 

yep, put $800 dollar carbs on an $800 bike...

 

Maybe less, ....

Sometimes you get lucky!

http://cgi.ebay.com/ebaymotors/MIKUNI-F ... ccessories

 

How does the oblong hole provide air for the air jet circuit, which lies on the periphery of the intake bell (green line), when it is connected to the blue spotted area in the picture, which is sealed from the rest of the carb by the diaphragm? The red spotted area is subject to vacuum through the hole in the slide piston, which is what raises the slide. The only air sent to the emulsion tube is through the air jet. If you want the slide to raise faster, drill the hole in the slide piston bigger. The only function I see for that oblong hole is to allow air in and out below the diaphragm to allow it to move.

 

That blue void area also contains 2 jets hidden by a little metal cover.

 

You're missing the point, it's not about the money, it's about having the bike run the best it possibly can with pods. I think that running larger carbs may just be the trick. We'll soon see. I think the pods (more air) along with the Wiseco 1196 piston kit and maybe a larger carb might be a nice mix.

 

The Drawing is a MIKUNI Carb.

Mikuni's Main AIR Jet is located on the Outside of the Intake Horn.

HITACHI Carbs have >>BOTH<< AIR Jets located below the Rubber Diaphragm, ... In the AIR Space where you have 4 Red Dots, on the Left Side, in the Diagram.

Sometimes hidden below a "Quarter-moon" shaped Cover ... The two Jets there NEED Air to supply to the Pilot Mixture and Main AIR space, surrounding the Emulsion Tube.

 

P.E.T.A. is going to get you guys

 

Polock,
I know, feel almost guilty for the exception that I am taking this to a different angle (larger carbs). It has been beaten to death, but this just might be the holy grail. LOL I hope so, then we won't have to discuss, read, see the topic any longer. Lol again.

 

I think that horse is still alive.

 

I hope this horse is at least on life support.

 

you guys happy now?

 

YES, larger carbs might help solve the problem, as long as they're NOT CV carbs. Larger CV carbs will still have the same problems running on an unrestricted air supply (pods) that smaller CV carbs do.

Good luck finding a set of 4 without spending a wad o'cash.

And if you do, good luck on those custom-made intake manifolds you'll need; once again without spending a wad of cash.

And since it's doubtful they'd bolt right up to the XJ's rack, you'll probably need a machinist to make up a couple of rack rails to mount them. $$$

Then there's re-jetting those larger carbs; they're not going to come pre-jetted for an XJ. Might be some experimentation involved so some more money will have to be spent on sets of jets until you get it right.

Now, how much are we spending on this again?

(I love my airbox.)

JeffK gave us the science behind the problem and one theoretical solution. Not necessarily a practical, easy or even feasible solution.

And NOT something you're going to pull off for under $500, or even under $1000.

 

I love how much time we spend on this.

why dont we just have a pods section?

 

The Carbs NEED:

A Non-turbulent and Swift Intake Air Stream passing over the top opening of the Emulsion Tube exit and below the Holle in the Bottom of the Diaphragm Piston.

Atmosphere to Feed the Main AIR Jets need for a supply to surround the Emulsion Tube which rushes through the Emulsion Tube's drilled Ports to promote efficient siphoning of Main Fuel Jet Supply and Atomize the Fuel on its upward movement.

Attaching a Pod to the Carb Horn NEGATES the above two essential elements.

The Pod allows the formation of a VORTEX at the Intake Horn.
The Vortex "Swirls" and the movement of the Intake Stream does not create the strong pressure reduction above the Emulsion Tube.

The Fuel that DOES get introduced into the Intake Stream is LESS than required AND drawn-up & out of the Emulsion Tube in an energy-wasting "Droplet Form" rather than an efficient-burning Atomized SPRAY. Lessening the Volume causing a Lean Mixture which enters the Intake Stream and Burns with less intensity.

The VORTEX is pulled across the Atmosphere Orifice:

Lessening the Volume of Air at the Orifice
Robbing Air away feeding the Main AIR Jet
Reducing Pressure is the Atmosphere Cavity making it more difficult for the Diaphragm Rubber to collapse and let the Piston rise further contributing to the LEAN Condition.

 

@Rick: Well said.

 

i just deleted a multi paragraph post because i realized;

sometimes you just wont win. no matter how much evidence, proven laws of physics, and real world experience you can show the debate...some people just wont accept it. religion, politics, and pods should be banned from the forums. :lol:

give that horse a flake of hay and fill its water bucket, its NOT going to die!
















oh yea....ITS SNOWING!

 

As long as pods and jet kits are made for the xj bike, people will put them on. FACT.

No sense ignoring it or debating it.

Maybe, just maybe, with thought and effort, a solution can be made to overcome problems encountered by affixing pods to a bike and having negative outcomes.

We all on this forum have read in great detail why pods will not properly function on a STOCK CV carb.

But I cannot belive that there is no way, you cannot modify, something, to get them to work. My bike is a testament. I invite you all to test ride, beat on, and try to get it to act out. It runs very well. Starts easily cold, warms up in no longer time than an airbox equipt bike, and will pull without hesitation or flat spots, throughout the entire rpm range. Albiet perhaps with less hp, on a dyno. I have never tried but would LOVE the opportunity.

If only there was an area to discuss pod filter tuning without constant posts of why they will not work. It would be glorious to share knowledge of tuning techniques, to achieve a well rounded, well performing pod filter motorcycle.

 

The fact IS that they do function properly or there would be NO ONE using them. I ran UNI Foam pods on my 400 tracker without a hiccup. I just shimmed the needle and increased the pilot one size and the main jets about 4-5. The plugs were perfect. This is only a debate by those who think it is blasphemy to install them on a XJ bike.

 

AMEN

 

a search on kzrider.com for pod filters brings up 1711 hits so i guess this horse still has life

 

bottom line is NO ONE EVER SAID THEY WOULDN'T WORK most people don't feel like pulling their carbs mutable times to get them to run decent. They just want to slap them on and drive away.Some people guess the first time on the jetting so it will run ok if you do your lucky. Granted I had professionals do 1 of my bikes on the dyno like i sad 43 times my carbs were on and off. The best they could muster was 4 hp with pods over stock even with changing all the flow characteristics of the carb. But thru out the rpm range it was less then stock it just made a 500 rpm bleep but at redline didn't drop as drastic as the stock did. The went back to the airbox with a k@n in the box with a modified air lid to give it a bit more air. Picked up 20 hp over stock there is your proof that carbs like airbox better. Even tho my vmax made over double the power of an air cooled 750. Pods will run ok if you get them pretty close. Most people that change to them don't miss the drop in power most air cooled xjs not including the 900-1100 make between 40-65hp range the lower the hp the more you will notice the drop in power for instance if you loose 2 hp on a 40 hp bike thats 5 percent 65 hp roughly 3 percent its hard to tell by the seat of the pants.
Best thing i can say is try them if you do not like fiddling with them to get them to run half way decent or if you get lucky and get everything right the first time. But if you do not like the results keep your air box. and put it back on either way then you will have your own opinion. There are pros and cons to everything pros on pods easy carb removal and they look bit-chin especially when they are on a bobber where a stock air box wouldn't look right. Cons hard to get tuned right,alters the stock power curve, And if you don't get it rich enough temps will make a more drastic change in the way it runs

 

When all gets said and done; there needs to be a Written Caveat to the newcomer who arrives here and asks about switching their bike from Stock to Pods.

I think we can all agree that making the switch is not done without complications.
The notion that you can un-box a set of Pods and slap them on the Bike without needing compensating measures is untrue. IF the warning was on the Box to inform the buyer it might save some aggravation.

I credit the Membership for all the experimentation that has been done in 2010.
The work done to find a solution outside of just jetting and shimming is likely to have someone actually discover a solution to putting Pods on the Bike and have the Performance equal the cosmetics and not need additional tinkering.

Life goes on.
We'll argue this like the debate for getting rid of the Penny.

 

Pipe and pods--Dynojet Stage 3 kit- Bob's yer uncle.

I'll second KZ rider.

There's plenty of expertise on this subject at the GS Resources. Guys there mods their bikes to ungodly power levels, and there's plenty of engine builders and racer's there who would be happy to help you out. And before anybody gets all shirty with me saying they ain't XJ's, they use mostly the same carbs, and are aircooled inline fours, many 8 valvers. I can guarantee you there's nothing you can do that someone there hasn't done before.

GS's and KZ's were the weapon of choice for serious hot-rodders for decades, so if it's power mods your after, there's gold in them thar hills.

 

Hey Mac!

KZ's ran Mikuni "Smooth Bore" type Carbs.

Way different from Constant Velocity Carbs.

The Smooth Bore Carbs are a favorite of Performance minded riders.
Mikuni 29mm smoothbore carbs

Once power-hungry riders realized the potential of the Z1 engine, a large array of performance parts appeared on the scene. One of the most important of these was the Mikuni 29mm smoothbore carbs.
The stock carbs did not adapt well to the increased fuel demands of high-lift cams and high-compression pistons, nor the back pressure changes of the barely flow restricted 4-1 exhaust systems.

The 29mm smoothbore carb was by-and-large a cure for many tuning problems. The top of the carb is identical to the 26mm (and later KZ1000 28mm) carbs.

The float bowl went back to using the 17mm drain plug directly under the main jet. Made rejetting a piece of cake.

Great for racers as it allowed for quick changes of the main jet.

 

I guess no one listens to me. I have been thru it Thats why it cost a grand on my vmax and 43 dyno runs. If someone is willing to pay for dyno time and i just dont mean 1 or to runs and is willing to buy all the necessary parts i can make your bike make a few extra horses. But most people don't want to spend that kind of money for a few horses. Pods will work even run ok if you get them pretty close just usually takes time. But are not going to out perform a stock air cleaner on a stock bike. Put a k&n in the stock air box you will get more flow and still keep all your velocity's correct.
Rick is right all the mega hp bikes use smooth bore carbs . Once you change cams overlap changes compression changes which really alters everything in the intake and exhaust side .
Best advice i have is try it pods and jets are cheap if you don't like it put your air box back on. I won't post anymore on this thread not worth the time to type it.

I guess my virago has is hi performance. Mikuni 40mm cv flat slides it has the big plug in the bottom of the float bowl so you can change jets lol

 

When I raced, the "hot lick" on the big Z's were 33mm smothbores. The 29's came out then the 33's a few months later I think and they really opened up the top end of the mighty Z engine, especially if it was bored to it's max 1075. Rule changes in Superbike rules made them use a 31mm restrictor plate but most of the guys found "inventive" ways around it. The 29's were mostly used on the 750's by the mid to late 70's.

Kinda funny but back then, I HATED the Z, it was powerful(would twist it's own swingarm), big and deadly fast....everything we DIDN'T want to see in the competitions hands! I was a diehard 2 stroke fan(GT750 heavily breathed on) and hated every good four stroke engine advance....I cringed at the original Z, nearly cried at the intro of the first GS750.....and finally gave up and accepted four strokes when the XS11 came out in late '77.

jeff


jeff

 

Smoothbores are good carbs, but with so many GSXR slingshot carbs going on Ebay for little money, there is very little incentive to use them anymore. Big bucks guys have the Mikuni RS competition carbs, the rest of us can slap on a set of 36mm gixxer cabrs and be done with it. Much better throttle response. They have perfect spacing for the old GS and KZ motors. I have a set of Bandit carbs for my GS1100 which will get installed...someday...cough cough....

Incidentally, those were Bandit/GSXR/Katana carbs in Rick's Ebay posting. If you had the time to get the spacing right for an XJ they would be a nice performance add-on. They have muuch quicker response than the older BS carbs. General consensus on the GS Resources is 36mm are the sweet spot for road work, with 38mm and 40mm being pretty breathless for anything less than race or very heavily modified (1400cc+) street motors.

 

Everyone seems to talk about a Stock Vs pods application.

If only life was that simple.

Someone buys an old XJ running rough, and then changes to pods.

It runs poor and they try to rejet, forgetting that there may be plugs/compression/valve clearance/blocked carb etc.

If you want to change the basics, please get it running smooth in a standard configuration.

Tuning for mods and fixing basic problems cloud each other.

(dig up stupid!)

 

Funny how some things just go on and on....seems to take on a life of its own. Personally I think its a good and healthy sign of a forum. I've watched plenty of times when subjects just get kind of left alone for the sake of keeping the peace as it were.

Have to say what has struck me from all the reading I've done is I don't really see anyone offering up info on what carbs from another bike might be a great solution. We talk about not spending x on a set of carbs, but the fact is you can easily spend some good hard earned cash on rebuilding or having them rebuilt...so I question if I was going to spend say 500 on a rebuild, why not consider 800 on a new setup, that would be workable.

I guess I also wonder about a lot of things, but the thing is when you add up your time to rebuilding a bike, you probably figured out in the end you could have just gone out and bought something almost new....but then the fun sometimes is in the getting there...don't think anyone who owns an older bike would say its the easy way to go.

 

lol long and hard have I said "@#$@ With all the $$ I've dropped into Maxine I coulda bought a new bike!!!" But yeah half the fun is doing it yourself.
Ohhhh how id love a brand new bike though

 

There are 2 things that are never mentioned in any of these discussions.

1. Engines are a positive displacement pump. They will move the same volume of air given any restriction. The difference is only in the speed of that change, and the velocity of the air as it goes through whatever restriction there is and into the cylinder. I'll elaborate my point below.

2. There seem to be different ideas of what pods are. When person A is saying that pods perform poorly because they don't maintain the correct velocity at the emulsion tube and person B says his velocity stacks work just fine, THAT IS AN AGREEMENT, not a disagreement.

Your velocity stacks work fine, yes, but you don't have pods!!! At least not in the sense that cause low velocity and that MOST people are referring to! Or maybe you do have pods, and SOME pods work just fine! I'm not Webster's dictionary when it comes to pods.

Now back to #1: Ever try to suck 15W-40 diesel oil through a syringe? It sucks, it's slow, but it always fills the syringe, and the pressure coming into it is very high. If the syringe had a bigger opening, but I pulled at the same speed, the pressure would be lower, and the speed of filling would be the same.

What I'm getting at is that the reason pods lose power, according to the dyno, is that you can't get more air by lowering the restriction. It's exactly the opposite (to a point, of course, and given a set amount of time). This is counter intuitive and exactly the opposite of what salesmen would have you believe. I calculated that some of our filters give dirty filter alarms at .2 psi of differential pressure. That's not much, and that's when we have to change it. A new filter is a lot less. So how do you lower nearly 0 restriction by installing a pod? You don't, but you do lower the velocity by giving a bigger opening. As it's said somewhere here, it's the opening in the airbox that restricts the airflow, not the filter itself. I don't think it has anything to do with turbulence, it's all velocity. The lower the velocity, the higher the pressure (or lower the vacuum, which is just a hard way to think about pressure differentials), the higher the pressure, the less pressure differential between the emulsion tube and the atmosphere, the lower the force acting on the fuel, the less fuel, the same VOLUME of air, therefore, a lean condition.

Granted, I don't race and never have and am not after that extra 3 hp that can give you the edge....but who is racing a xj650j anyways? I dunno, maybe they are...) I have no doubt that there are pod-like things that you can get that allow more air to get into the cylinder, and combined with the proper jetting you can get more hp at a certain rpm range.

Which might allow you to win a race that most of us will never see.