Topic: **Need help with POD filters install** Bike shuts off at high rev's

[crazypj]

Restricting 'pods' has been done and is the dumbest thing I've ever heard of as a 'performance' modification
Carbs work on air pressure, ambient is around 14.7psi @sea level.
With the airbox in place, there is almost always lower pressure at carb throat (except maybe at idle?)
 When you remove airbox your not getting 'more' air, your getting more pressure.
 The breathers, if vented to atmosphere, are designed to work at ambient pressure with lower pressure in carb, lowering fuel level about 2mm compensates a little for 'pods' but isn't the entire story. There is a hell of a lot more to things that first assumed, I've been working on bikes most of my life and a lot of the stuff 'old timers' taught was relevant in 1940's~50's but already obsolete by late 1960's (even though much of it is still thrown around as 'fact' today)

[vonvendetta]

Restricting 'pods' has been done and is the dumbest thing I've ever heard of as a 'performance' modification
Carbs work on air pressure, ambient is around 14.7psi @sea level.
With the airbox in place, there is almost always lower pressure at carb throat (except maybe at idle?)
 When you remove airbox your not getting 'more' air, your getting more pressure.
 The breathers, if vented to atmosphere, are designed to work at ambient pressure with lower pressure in carb, lowering fuel level about 2mm compensates a little for 'pods' but isn't the entire story. There is a hell of a lot more to things that first assumed, I've been working on bikes most of my life and a lot of the stuff 'old timers' taught was relevant in 1940's~50's but already obsolete by late 1960's (even though much of it is still thrown around as 'fact' today)

I have to admit, I did get pods. Not to replace the airbox, because the bike came with nothing. I am doing a triangle delete and really wanted a clean look, I also didn't read this forum before buying them. 
Would you have other suggestions that would work well besides the big airbox?

[Stev-o]

Tin tops anti pod - search for it

[crazypj]

Hi Jacksonville, I'm near Orlando
Re-set float height +2mm for starters

[jamesbekman]

Maybe I should rephrase...  What besides stock or pods would work.  Air horns if designed right should take care of at least the turbulence problem...  Smaller velocity stacks have been made for other carb applications to solve inherit turbulence problems.

I know a lot of people would like a sleeker functional option for the cafe/brat bike looks etc...  So they can relocate the battery and airbox and keep a very clean minimal look (Sorry purists, but hey those bikes are normally bought in horrible shape anyway).  If I knew how to do plastic molds etc Id love to mess around with a design...  I for one have one bike that came with the stock airbox and filter.  It actually has the filters last service date written on it in 1974!  The other bike came with airhorns.  But I just have the carb on and nothing else for the time being as Im doing work. 

Maybe have a shorty airbox that sucks in from the top of the airbox from just under the gas tank.  That should at least solve the turbulence problem but Im guessing itmight hinder the amount of air flowing through the box due to its design? 

[Retro Rocket]

Maybe I should rephrase...  What besides stock or pods would work.  Air horns if designed right should take care of at least the turbulence problem...  Smaller velocity stacks have been made for other carb applications to solve inherit turbulence problems.

I know a lot of people would like a sleeker functional option for the cafe/brat bike looks etc...  So they can relocate the battery and airbox and keep a very clean minimal look (Sorry purists, but hey those bikes are normally bought in horrible shape anyway).  If I knew how to do plastic molds etc Id love to mess around with a design...  I for one have one bike that came with the stock airbox and filter.  It actually has the filters last service date written on it in 1974!  The other bike came with airhorns.  But I just have the carb on and nothing else for the time being as Im doing work. 

Maybe have a shorty airbox that sucks in from the top of the airbox from just under the gas tank.  That should at least solve the turbulence problem but Im guessing itmight hinder the amount of air flowing through the box due to its design?

Tin tops anti pod - search for it

http://forums.sohc4.net/index.php?topic=79491.0

Better than stock velocity stacks, designed with modern tech...   An airbox is still ideal but this has been the best solution to date...

[vonvendetta]

Hi Jacksonville, I'm near Orlando
Re-set float height +2mm for starters

You should come up and fix my bike, I'll even throw in a case of intuition.

[lucky]

Bunch of pods haters are we?!

Well, I was too, but my "Black Beauty" runs fantastic on the pods! Now I'm a believer.
She sure pops on decel though!!

Could you tell me what jets (idle and main) and needle position are?
Popping on decel could be fixed with making the mixture screws richer.

[lucky]

I have a 1978 550k with PD46C carbs.  They have 104 mains, 42 pilots and a 4-1 MAC exhaust, runs pretty well, still needs a little tuning but is definitely in the ball park.

It must hesitate when given quick throttle .
You need to address the needle position. One step richer for that set up.
#42 pilot sounds right.

Are you running pods?

[dave500]

i still tinker with and run qjets on cars,,id sooner fool around with qjets than fool around with pods on honda fours,,and most guys think qjets are akward complex finicky things?

[NewOldSchool]

Mixture = fuel to AIR ratio at ANY given instance.  Ive never seen a forum so scared to tune a carb. 

I fully understand that its a lot easier to just put the correct stock jets etc in and run the air box and just go.

One drawback to that and its something we should all be looking into is its really rare to get stock pipes.  All I see are 4 into 1 pipes nowadays. 

I also see a million posts of just put the stock filters on and not a whole lot of hey I have pods this is what works for me, these are the drawbacks, these are the gains...

You don't see a lot of posts about what works with pods because they truly don't. You will get it to idle ok, then the midrange will be off. Or they will run great at WOT and then they are fat and ruin plugs. You may be able to get them to run within an acceptable ballpark range, but there will always be a trade off. TL;DR.

You don't see a ton of posts talking about how people got their pods to run great because they don't.

[dave500]

they are a race item full stop,,you dont care about idle and cruise,,just wide open and jet the slow speed for the odd dip into the lower end of the scale and live with it,,for traffic and tractiblity they aint good,,,,but who cares,,ive "cleaned up"my triangle and these are what every one else in the cafe crew use?as far as being a good filter thats a joke,,also dont forget an ounce of handling is worth a pound of horspower!

[NewOldSchool]

they are a race item full stop,,you dont care about idle and cruise,,just wide open and jet the slow speed for the odd dip into the lower end of the scale and live with it,,for traffic and tractiblity they aint good,,,,but who cares,,ive "cleaned up"my triangle and these are what every one else in the cafe crew use?as far as being a good filter thats a joke,,also dont forget an ounce of handling is worth a pound of horspower!

Great info, but with the half informed "cafe" crowd looks farrrrrrr outweigh (actual) performance enhancing mods and those with basic mechanical understanding are few and far between. Glittery helmets look great with mustaches though amirite? If it's louder it means it's faster too!

[dave500]

ha,,now let me get this straight?is it form over function or style over practibility?or some other #$%*?how come where ever we stop im the one with the greasy jeans and shirt(truely) and filthy finger nails?lately ive been considering how the public might concieve me so have decided ive looked #$%* for so long im going to clean up my act,and will stay as i am,,if i try and clean up ill look like im trying to look like some crowd?no one wants to look like me man!this is just another three page pods thread?so im keen to go off into a tangent.

[crazypj]

I have a 1978 550k with PD46C carbs.  They have 104 mains, 42 pilots and a 4-1 MAC exhaust, runs pretty well, still needs a little tuning but is definitely in the ball park.

It must hesitate when given quick throttle .
You need to address the needle position. One step richer for that set up.
#42 pilot sounds right.

Are you running pods?

Personally I found dropping the needle 1 clip worked better
Raising it may improve acceleration but it really sucked at fixed throttle cruising (30~60 mph, depending on traffic)
I never got around to modifying slides, but they need a smaller cutaway to improve off idle transition
Also, I didn't like the 23~26mpg I was getting from a stock 550F1, with modifications and K&N filters I was getting  consistent 41mpg at same (or higher) speeds

[750K]

ha,,now let me get this straight?is it form over function or style over practibility?or some other #$%*?how come where ever we stop im the one with the greasy jeans and shirt(truely) and filthy finger nails?lately ive been considering how the public might concieve me so have decided ive looked #$%* for so long im going to clean up my act,and will stay as i am,,if i try and clean up ill look like im trying to look like some crowd?no one wants to look like me man!this is just another three page pods thread?so im keen to go off into a tangent.

Why the hell would you want to clean yourself up, haha. No way, if I cleaned up and say shaved I think my wife would kick me out. She like a man to look like a man, haha. Not all clean cut and smelling fresh...

[Stev-o]

Bunch of pods haters are we?!Well, I was too, but my "Black Beauty" runs fantastic on the pods! Now I'm a believer.She sure pops on decel though!!

Could you tell me what jets (idle and main) and needle position are?
Popping on decel could be fixed with making the mixture screws richer.

No, sorry. She is sold and gone. 

[Rookster]

I know a lot of people would like a sleeker functional option for the cafe/brat bike looks etc...  So they can relocate the battery and airbox and keep a very clean minimal look

Sure lots of people want that but it doesn't work out with stock carbs on the 750.  It is more than just the stacks that make the stock air box work.  Stacks alone will give you idle problems and the flat spot as well.

I tried a breadbox with stock stacks and then shortened stock stacks along with jetting changes and restricting the intake opening.  All it did was result in a huge flat spot when the throttle was opened quickly.  Sold the breadbox and went back to the stock  air box.

I suggest you try it out.  Jets are cheap and the pods can always be resold when you're done with them.

Scott

[NewOldSchool]

ha,,now let me get this straight?is it form over function or style over practibility?or some other #$%*?how come where ever we stop im the one with the greasy jeans and shirt(truely) and filthy finger nails?lately ive been considering how the public might concieve me so have decided ive looked #$%* for so long im going to clean up my act,and will stay as i am,,if i try and clean up ill look like im trying to look like some crowd?no one wants to look like me man!this is just another three page pods thread?so im keen to go off into a tangent.

I like you

[lucky]

Mixture = fuel to AIR ratio at ANY given instance.  Ive never seen a forum so scared to tune a carb. 

I fully understand that its a lot easier to just put the correct stock jets etc in and run the air box and just go.

One drawback to that and its something we should all be looking into is its really rare to get stock pipes.  All I see are 4 into 1 pipes nowadays. 

I also see a million posts of just put the stock filters on and not a whole lot of hey I have pods this is what works for me, these are the drawbacks, these are the gains...

You don't see a lot of posts about what works with pods because they truly don't. You will get it to idle ok, then the midrange will be off. Or they will run great at WOT and then they are fat and ruin plugs. You may be able to get them to run within an acceptable ballpark range, but there will always be a trade off. TL;DR.

You don't see a ton of posts talking about how people got their pods to run great because they don't.

Sorry but what you think is just not true.
I agree there is not much posted on how to make bikes with pods run right
but racing bikes do it all the time.
Velocity stacks or pods.

I even posted a video of a 1978 CB750 with 1978 carbs and velocity stacks that ran perfect.
No hesitation at all and even when the throttle was turned as quickly as possible. No hesitation.

The problem is many owners just change the main jet and idle jet and think they are done.

This idea will not work.
The slide needle position MUST be set correctly too.
But because setting the slide needle on the post 1970 carbs is so time consuming many owners just want to avoid it at any cost.

[crazypj]

Not just needle but slide cutaway, if it isn't right you will still get hesitation as the air moves faster than the fuel can so motor runs lean before it picks up (or just jet transition real rich - may be OK for racing but sucks on the street)

[jamesbekman]

For the SU carbs that I was talking about, there is a company that will make you custom needles to suit your needs. 

The needle is what is allowing a metered amount of fuel to be sucked into the carb via the venturi effect dependent on the position the throttle is at.  The needle accounts for the fuel metering from 15% to 60% open throttle correct?  (For SU's its dependent on engine vacuum pulling up a piston and accounts for fuel metering 100% percent of the time...)

When you open up the throttle on your bike that raises the needle which makes its diameter smaller (its a tapered needle) which allows more gas come out of the hole...  When you are at WOT that should be what that main jet should be set for.  Same with the secondary idle jet for idle correct?  Im used to the SU's which just have one jet and the needle doing all of the work.  Correct me if Im wrong.  The air valve controls the mixture correct?  But that can also be controlled from Needle height correct?

If you can get custom needles made like you can for SU carbs this seems like a problem that could be solved quite easly.  That company is apple hydraulics for SU's...  What company are guys using for all the race bikes for custom needles?  Ive even heard of guys sanding certain areas on their needles to make their own custom set. 

[crazypj]

I've worked on SU carbs (had 1965 Rover P6) they also have adjustable needle jet block.
Your correct in your assumption about needle taper but a mechanical slide carb is different to a CV carb.
The cutaway determines how much air flows over the needle jet as throttle is opened, smaller cutaway gives higher air velocity so lower pressure drop (therefor, more fuel)
The needle tapers really only have an effect when motor is spinning around 4,000 rpm on most bikes

[jamesbekman]

Just came across this link.

http://web.archive.org/web/20090201085544/http://keihin-us.com/tune2.htm

This is the main link with more info:

http://web.archive.org/web/20090301055044/http://keihin-us.com/tune.htm

It looks like the CR26 carb would be good as they have all various needles, jets etc in stock but it would be a little hard to get a baseline setting first.

Im guessing no one is messing with custom needles for our old carbs nowadays are they?

[NewOldSchool]

Mixture = fuel to AIR ratio at ANY given instance.  Ive never seen a forum so scared to tune a carb. 

I fully understand that its a lot easier to just put the correct stock jets etc in and run the air box and just go.

One drawback to that and its something we should all be looking into is its really rare to get stock pipes.  All I see are 4 into 1 pipes nowadays. 

I also see a million posts of just put the stock filters on and not a whole lot of hey I have pods this is what works for me, these are the drawbacks, these are the gains...

You don't see a lot of posts about what works with pods because they truly don't. You will get it to idle ok, then the midrange will be off. Or they will run great at WOT and then they are fat and ruin plugs. You may be able to get them to run within an acceptable ballpark range, but there will always be a trade off. TL;DR.

You don't see a ton of posts talking about how people got their pods to run great because they don't.

Sorry but what you think is just not true.
I agree there is not much posted on how to make bikes with pods run right
but racing bikes do it all the time.
Velocity stacks or pods.

I even posted a video of a 1978 CB750 with 1978 carbs and velocity stacks that ran perfect.
No hesitation at all and even when the throttle was turned as quickly as possible. No hesitation.

The problem is many owners just change the main jet and idle jet and think they are done.

This idea will not work.
The slide needle position MUST be set correctly too.
But because setting the slide needle on the post 1970 carbs is so time consuming many owners just want to avoid it at any cost.

Lucky, you just proved what I was saying right there with "race bikes." Pods may work ok at WOT, but around town there are major trade offs. Also, velocity stacks are different than pods. Of course those would work,  that's how the stock air box works, but then you have no filtration or very little if there is a screen or something involved and a lot more buffeting and uneven airflow at speed than with an air box.