Topic: 1977 CB550 K cafe racer build

[Retro Rocket]

I have to disagree, K&N pod filters vastly out perform the stock air box when the Cabs are jetted properly.

I would love you to elaborate on that comment ....
Mick

It can be done Mick, but you and I both know its going to be a PITA.  Zaipai pointed out one alternative (actually more like $235 probably).  You and I have debated the pros & cons of the HA bread box, in the same filter thread.  Each to there own, but to me 'vastly out perform' means from idle up, and with clean transitions, not just 1/2 to WOT.  The stock system (550 & 750) was designed to use stacks, you loose those with Pods.

I was more after an explanation from Godffrey because blanket statements like that tend to make guys run out and get pods only to find out that they are inferior and a pain in the arse to set up properly. They are a compromise and won't run well through out the entire rev range because of the lack of a proper velocity stack and the lack of still air that the stock box provides, not to mention the problems with rain and even crosswinds. If pods were that good most  road bikes would have them, not airboxes...Why would the bike manufacturers spend millions on developing air boxes if pods were the answer, the pods may be common on older race bikes because of a lack of an alternative but modern racers use air boxes because they work better....simple as that....I am keen to see how your new system works with the stacks .....

Mick

[Zaipai]

but modern racers use air boxes because they work better....simple as that....I am keen to see how your new system works with the stacks .....

Mick

I beg to differ, a quick search showed every race bike I looked at had velocity stacks not air boxes. Any thing from Cafe racers to street fighters.. What race bikes do you see with air boxes? I would like to see that. I can't speak for every bike, all I know is mine runs 10 times better with pods then it ever did with the stock air box. I am not entirely sure it was ever on correctly however.

.: Scott :.

[BlindJoe]

http://forums.sohc4.net/index.php?topic=5410.msg741438#msg741438
http://forums.sohc4.net/index.php?topic=67991.0

[Zaipai]

Yea, I seen those threads. I am no expert far from it. I just think if the air boxes are so good why are they the first thing to go on the GP bikes?

.: Scott :.

[HalfFastMoto]

... if the air boxes are so good why are they the first thing to go on the GP bikes?

.: Scott :.

GP bikes are not tuned for slow speed low RPM tractability.  Velocity stacks provide optimum performance in the mid - high RPM range but sacrifice low end torque.

Street bikes are not tuned for high speed, high RPM performance.  An airbox provides good low - mid RPM performance with reasonable high RPM performance but sacrifices the ideal high RPM performance.

Essentially their two divergent target audiences. 

[BlindJoe]

Because they are run at consistently high rpms. The large amount of turbulence in the air box at such high rpm's negates its benefits. Air boxes can also become restrictive causing more fuel to be used than necessary.

[Retro Rocket]

Yea, I seen those threads. I am no expert far from it. I just think if the air boxes are so good why are they the first thing to go on the GP bikes?

.: Scott :.

You can't compare race bike especially GP bikes to real world application, there is only 1 speed for those bikes and that is flat out. You were talking pods and now you are talking Velocity stacks, 2 entirely different animals, pods do not have velocity stacks. If your bike runs better stock with pods then you never had it tuned properly with the airbox, i would say that you had more than one problem with it and that makes it a poor comparison. I am curious to know what race bikes you are looking at.? generally with modern frame design you can't even see that carbs let alone the airbox, it is usually buried beneath the tank because of the downdraught carbs {or injectors}used on most sports bikes since that late 80's....An airbox also functions as a plenum, a space where the air velocity is reduced so as to eliminate turbulent airflow prior to being smoothed and accelerated down the velocity stacks. In fact, if you just place your finger anywhere near the edge of the top of the velocity stack you'll see dyno power dropping off due to the disturbed air flow pattern.
This disturbed airflow is exactly what pods do and is not what is beneficial for an engine to run  consistently.. The easy way to tell that they are running airboxes in superbikes is to look for the inlet tracts in the fairing that go into the airbox to increase volume pressure at higher speeds for a rammed air effect similar to a turbo. We can all stuff as much fuel as possible into a bike but if it doesn't have the flow of clean constant air then it isn't running at its best.

Mick

[Zaipai]

Yea, I seen those threads. I am no expert far from it. I just think if the air boxes are so good why are they the first thing to go on the GP bikes?

.: Scott :.

You can't compare race bike especially GP bikes to real world application, there is only 1 speed for those bikes and that is flat out. You were talking pods and now you are talking Velocity stacks, 2 entirely different animals, pods do not have velocity stacks. If your bike runs better stock with pods then you never had it tuned properly with the airbox, i would say that you had more than one problem with it and that makes it a poor comparison. I am curious to know what race bikes you are looking at.? generally with modern frame design you can't even see that carbs let alone the airbox, it is usually buried beneath the tank because of the downdraught carbs {or injectors}used on most sports bikes since that late 80's....An airbox also functions as a plenum, a space where the air velocity is reduced so as to eliminate turbulent airflow prior to being smoothed and accelerated down the velocity stacks. In fact, if you just place your finger anywhere near the edge of the top of the velocity stack you'll see dyno power dropping off due to the disturbed air flow pattern.
This disturbed airflow is exactly what pods do and is not what is beneficial for an engine to run  consistently.. The easy way to tell that they are running airboxes in superbikes is to look for the inlet tracts in the fairing that go into the airbox to increase volume pressure at higher speeds for a rammed air effect similar to a turbo. We can all stuff as much fuel as possible into a bike but if it doesn't have the flow of clean constant air then it isn't running at its best.

Mick

Ah you are now talking superbikes, I thought you were talking race bikes. The images I was looking at had the tank off. They had pretty blue stacks. I agree my bike was not tuned correctly, still may not be my carb sync gauges seem to think they are, however it is a cheap carb sync gauge. All I  know is on my bike it runs really well with its current setup, no flat spots etc. They are stock carb's and maybe it would run that much better with the stock air box I just don't want to deal with trying to get it on. Honda could not have made it harder to put that box on..

.: Scott :.

[Tintop]

... if the air boxes are so good why are they the first thing to go on the GP bikes?

.: Scott :.

GP bikes are not tuned for slow speed low RPM tractability.  Velocity stacks provide optimum performance in the mid - high RPM range but sacrifice low end torque.
Street bikes are not tuned for high speed, high RPM performance.  An airbox provides good low - mid RPM performance with reasonable high RPM performance but sacrifices the ideal high RPM performance.

Essentially their two divergent target audiences. 

A stack can be used to tune all parts of the rpm range.  Depends on what your trying to achieve.  The reason most people suffer poor low end is they don't tune for it.  I agree with the second part but would add - '..is what you want in a strong street engine.'

[Zaipai]

I bow to the experts. I am not trying to convert anyone, really I am not. I fully admit that my bike may have issues, all I know is it runs better the way its setup now. I truly hate the stock air box on the 550's they are the worst design ever. The 750 I had was a pain but at least I could get it on with out wasting entire day.

And for what its worth, my brother a mechanic for Honda motorcycles for over 30years takes the stock air filters off as well. In fact he put stacks on his newly purchased 2006 Yamaha R6 (streetbike/daily rider). Why, because he knows how to tune it so it works best with them. I just wish he lived closer so he could work on my bike.

.: Scott :.

[Steve_K]

A reason factories put airboxes on is that they reduce intake noise and keep rain out. An other is that modern bikes use intakes that use ram air and the boxes need to be pressurised to let the carbs work.  Pressurised air may vary fuel level in carb.  (Maybe not so modern bikes ie; fuel injection).  I know that my Mikuni flatslides and K&N pods work very well on my 86 Gixxer.  I have seen alot of discussion on needle clip position, jet sizes and mixture screw adjustments, BUT, I do not recall any on slide cutaway.   I am talking about the angle of the bottom of the slide.   Granted there may not be any available for these stock carbs.  I know a cutaway is different on a 2 stroke vs a 4 stroke.  I suggest reading Kevin Cameron's book "Sportbike Performance Handbook".  He has a chapter on carbs.  Good reading and an other source of info.  I suppose  one could increase the cutaway by machining.
That approach make have some merit, but I say that without trying that myself.
BTW, this has been a most interesting thread.
Steve

[Flying J]

The question was is there an alternative that is par with the stock air box. The answer, until we get more results from tintop, is no, if your talking about street riding. Pods do not perform "Par". There is plenty of evidence and discussion and nerd calculations to explain it. Can you tune a bike to run pods well? yes. Do they look better? Yes! Are they Way easier to put on and take off or make any adjustment to the carb YES! For those reasons is why they are popular but they will not perform Par for street riding on a stock bike.

[Zaipai]

but they will not perform Par for street riding on a stock bike.

That depends, if you mean, take of the air box and put on pods with out any adjustments to the carbs, then yea probably. However with proper adjustments they can be par or even better. It all depends.

.: Scott :.

[Raef]

It also depends on riding style and preference if you like to putt around and have a obsessive compulsive disorder there is no reason to leave the stock air box. 

It's like arguing  which political party or oil is better.

[FunJimmy]

It's like arguing  which political party or oil is better.

These threads always degrade to the oil debate.
It's like sex and dinner. 

[Zaipai]

It's like arguing  which political party or oil is better.

These threads always degrade to the oil debate.
It's like sex and dinner. 

You mean you can have sex AND dinner??? Wow...

Pennzoil 10W40 is the best!

.: Scott :.

[HalfFastMoto]

It all depends on what the definition of "is" is   

[Retro Rocket]

To be honest, i like pennzoil as well, have used it in the older bikes for over 2o years with no problems.....

Mick

[Flying J]

That depends, if you mean, take of the air box and put on pods with out any adjustments to the carbs, then yea probably. However with proper adjustments they can be par or even better. It all depends.

.: Scott :.

Id find it hard to make an argument having never had a well running bike with stock filter.

[HalfFastMoto]

Id find it hard to make an argument having never had a well running bike with stock filter.

It would be nice to have some dyno runs.  Figure you'd want to have two set's of carbs, one tuned for stock config and one for pods.  Would eliminate a lot of the percieved  subjective/opinion bias that currently exists.

 

[Retro Rocket]

Id find it hard to make an argument having never had a well running bike with stock filter.

It would be nice to have some dyno runs.  Figure you'd want to have two set's of carbs, one tuned for stock config and one for pods.  Would eliminate a lot of the percieved  subjective/opinion bias that currently exists.

 

Thats where i think these comparisons are wrong, the dyno will probably show more peak power but the curve would be pretty crappy compared to the more linear curve of the airbox equipped bike....Still it would be interesting....  I am building {very slowly} a 1000cc monster, i couldn't give two hoots what it does at 11,000rpm because most of the riding i do is around town, torque is what i am looking for.....and maybe a sprinkling of fun.....

Mick

[Zaipai]

That depends, if you mean, take of the air box and put on pods with out any adjustments to the carbs, then yea probably. However with proper adjustments they can be par or even better. It all depends.

.: Scott :.

Id find it hard to make an argument having never had a well running bike with stock filter.

I agree, however I never said I never had one. I have, in fact my CB750 I had was all stock and ran like a champ, no thanks to me I had a friend doing the wrenching as I knew little about them. Also I have been on other 550's (3 to be exact) and 2 of them with stock air filters so I know about how they should run. If I were recommending to some one air box or pods (not sure who would ask me about it) I would most definitely with out hesitation say the stock air box as that is how the bikes came from the factory. However for me, its pods, just a personal preference.

.: Scott :.

[Flying J]

I understand that. I Have run pods then stock air box, then back to pods, then i tore the bike apart. My 750 started stock, went to pods and is now back to stock. It basically comes down to what you want to deal with. Looking clean and spending a lot of effort tunning. or running what honda already found out for you but having to fight with the air box to ever mess with the carbs and not to mention you have to ride the bike with that ugly contraption. My last post on that subject.

[FunJimmy]

My last post on that subject.

Promise?

[HalfFastMoto]

My last post on that subject.

Promise?

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