Cafe Racer Forum banner

41 - 59 of 59 Posts

·
Registered
Joined
·
1,610 Posts
Discussion Starter #41
....don't say laminar flow just because it sounds cool
I think that is the first time, in 25 years as an engineer, that I can remember a mechanical engineering term accused of being cool. I guess we can thank Sheldon Cooper for "Bringin' Nerdy Back".....

If you don't understand the term...I can probably 'splain it to ya.
 

·
Registered
Joined
·
30 Posts
I recently picked up a '69 Yamaha R3 which didn't come with an air filter. I've been looking for a few weeks now, and I haven't been able to locate one nor does it look at all promising. So, what's the recommendation here - is it OK to run pod filters in this situation, or should they be avoided at all cost? What other alternatives are there?

It looks like I'll have to get an exhaust system made for the bike, and it will be re-jetted at that time. Will this also compensate for pod filters if I have to go that route?
 

·
Registered
Joined
·
23,303 Posts
I don't think two strokes are as sensitive to the airbox as some of the other 4 strokes. I've run individual filters on my 2 strokes for years and this is my take:

Try not to run any filter with a metal top. AS it was explained to me, on piston port two strokes without reeds there is a chance some of the wave that comes back to push the charge into the cylinder can push through the carbs, hit the filter top, and come back again throwing off the fueling at certain RPMs. Whether it is true or not I can't say but it sounds plausible.

buy a high quality filter. On my '71 T500, it ran best with Uni-foam individual filters. It ran the absolute worst when DiamondJ bought me a set of emgos at mid ohio one year because my airbox boot ripped. I had K&Ns on one of my H1s years ago and it was fine. I tend to lean toward the uni-filters because I see a lot of dirt bike guys use them on their two strokes.
 

·
Registered
Joined
·
1,231 Posts
Many years ago I had good success with K&N Pods that had rubber tops on a chamber equipped Kawasaki S2. I've also had success running the offset pods from MikesXS on several XS650s and my XS proddy racer ran well with Uni-filter pods. My 350 Aermacchi runs well with a small K&N pod on it's 27mm Dellorto VHB and it ran really good with a 30mm VHB sporting a long open velocity stack. At no time have I have run a tapered, cone type pod on anything.
On a similar note, a friend of mine has an old H1 dirt drag bike he traded for. I rode it around his neighborhood and it never seem to run on more than two cylinders at any one time, always felt like it was about to come on the pipes but always fell flat. Interestingly it has three different pod filters attached to it's trio of carburetors, all a little different size and shape.
 

·
Registered
Joined
·
129 Posts
so if pods make less pwer, would velocity stacks be better?
 

·
Registered
Joined
·
23,303 Posts
so if pods make less pwer, would velocity stacks be better?

Ah....but they don't always make less power, well the emgo ones always do because they have that restrictor ring inside that chokes down the size of your carb, but for the most part it depends on the carbs, intake tract, number of cylinders, size of engine, etc.... big Harley twins run just fine with a pod filter or open air element, the bigger the piston and intake tact, the less sensitive the engine is to minute changes in airflow, barometric pressure, etc.. even if your airflow has to make a 90 degree bend :p

but you are starting to think about this the right way - if you look inside the airbox of almost all the 1970's to now Japanese fours you'll see velocity stacks shaped to the engine's airflow needs. That's part of what makes it work. There are some racers who just use those stacks outside the airbox and they worked pretty good for that limited application.

Where people get the most out of the airbox is part throttle operation in day to day traffic. Having a plenum of non turbulent filtered air makes transitions smoother and the fuel mixture easier to manage consistently.
 

·
Registered
Joined
·
129 Posts
aight, I've got a nice £40 pod for my single but im thinking of switching to a velocity stack
 

·
Registered
Joined
·
23,303 Posts
aight, I've got a nice £40 pod for my single but im thinking of switching to a velocity stack
well the question then becomes...if it is a street bike how do you keep the engine clean inside? The answer is you keep the individual filter and forget the velocity stack.
 

·
Registered
Joined
·
1,610 Posts
Discussion Starter #50
There. I fixed my pictures. I can't fix those from other posters, though.
 

·
Registered
Joined
·
2 Posts
posted from another thread at Marc's request:

Pods aren't the work of the devil, they aren't nearly frustrating enough. However, there is a lot of misinformation and just general stupid logic that goes through a newbie's head when it comes to this area that the job is actually a lot harder than it is. Most newbies don't have the patience for it either or the methodical approach to develop the necessary skills to properly dial in carbs. I probably shouldn't have to say this but all carb tuning and evaluation should be done at operating temp. You would not believe how many people I know that complain about rough running on an aircooled engine while it is still on the choke and warming up.

common misconceptions:
- They are a performance upgrade: This is just flat wrong and it is derived from the worst place of all....working on cars. Back in the 1950's-1970's carb'ed cars usually ran restrictive air filters assemblies. Why? it as cheap to do so, it was easy to tune for regular partial throttle use, it helped make torque....who knows. All I know is that you took the air cleaner off your 440 siz pack superbee and the car made slightly more horsepower. So people think this applies to all mechanical things. However, most performance motorcycles starting in the mid 1960's were the result of Grand Prix racing technology (esp the japanese) and you saw things there that hadn't trickled down to stock performance cars yet - OHCs, multiple carbs, velocity stacks, etc. In most cases, esp amoung the japanese bikes, the engineers put a lot of thought and design into the intake tract to maximize performance, reliability, and part throttle fueling. Often if you delete this engineering one of those things suffers (usually partial throttle fueling). I have never seen a stock multiple carb setup benefit from individual filters, often I see them lose power. Why do you see them in high performance applications? well, in racing smooth partial throttle is less of an issue, plus once you upgrade the carbs the airbox rarely fits and if you went with a larger carb size and changed the flow characteristics of the head, then the plenum size of the airbox may not be properly sized for the airflow needed and you end up with a restriction.

- All filters are created equal: This is just bunk. When it comes to filters in motorcycles, you get what you pay for. If you buy cheap EMGO pods (often rebranded as other mfg or reseller's parts like Dime City Cycles or Dixie) you usually get a filter material that doesn't filter, is more restrictive (if the paper is intact) and the inlet will have a blockage in it that may obstruct vacumm passages that otherwise are needed to remain open. But they are usually $10 and price is more attractive when you have no fucking clue what you are doing. Filters from name brands like K&N and UNI are generally better, and for a "universial" filter they are going to be as good as it is going to get but they are oftern $20-$50 a filter and often require more maintenance than a stock filter (perodic oiling) and suffer shorter lives (esp if you ride in the rain). At the end of the day you are still getting a lowest common denominatior velocity stack shape vs the designed specifically for your application velocity stack shape of the stock airbox connecting rubbers.

- If you have pods and an exhaust you have to rejet one size up: This is just stupid logic perpertrated by idiots looking for an easy answer who don't understand carb tuning. Will you have to rejet? you might. It is a guarantee that you will have to do it....no. Carb jetting depends on a lot of factors like density altitude, actual altitude, barometric pressure, tempreature, humidity, etc. Getting jetting advice on the internet, specifically jet size numbers, is like asking getting masturbation advice from a eunic. In order to properly tune a carb you must first need to know how the carb works through out all it's throttle positions. Plus you must know how to evaluate an engine and it's fueling conditions. Than means plug reads, test rides, lots of time. When you open the throttle in your hand you have to have in your head what is actually going on in the carb as the slide lifts - if you can't picture that, you have no business poking your pecker at carb internals. Getting optimal fueling isn't a one shot process - if yu aren't tuining with a dyno and an o2 sensor then there is a lot of trial and error in getting the fueling spot on. And there are instances where certain carb just won't be receptive to the filter's airflow characteristics. Case in point - I have a GTO with a 400 ci pontiac mill running a 1969 GTO HO Quadrajet. At one point I ran one of those K&N filter tops where it was able to suck air directly from the top of the filter. Every time I stepped on the gas to open the secondaries the carb would backfire. I put a normal air filter top back in place the car ran fine. I used that filter top on any non Quadrajet carb car it ran fine. Every single quadrajet equipped GM car I put it on (a friend's chevelle, A camaro, a 350 chevy powered firebird, my GTO, A friends 442) had a carb backfire when the secondaries open. That carb design just didn't like that filter design. Sometimes it happens - often with parts that weren't specifically designed to work with each other but rather generally work of a large variety of applications - like pod filters.

- I'm never going to learn unless I do it: Bullshit. This is the mantra of the uninitated right before they get in over their heads. While I do agree experience is the best teacher, Carb tuning is a science and like any science it takes more than a set of screw drivers and a positive attitude to get good results. Mostly it takes reseach and a measured scientific approach. Again know your carb and know how it works in both theory and practice. Know the signs of how an engine responds to different fueling conditions and how to recognize them. Change only one thing at a time and evaulate the response. Test, Test, Test and collect data as you do it. Pay attention to variables like weather conditions. Use proper tools - can't tell when an engine is running slightly lean? use an o2 sensor or a dyno. Use your head. Are there guys who can pop open a set of carbs, do a bunch of changes, and have it be almost spot on? yes those people do exist and they got there through thousands of hours of trial and error and being methodical and through.

- "There is no point in being in this hobby unless I can't get exactly what I want and what I want is the look of pod filters because they are sooooo cool": Do I even need to point out how dumb this is? Sadly this is the attitude of most (but not all) new riders or newbies to old motorcycles. I call this the spoiled hipster newbie attitude. Honestly, motorcycling is a rich and rewarding hobby and if all the satisfaction you are getting out of it is in the value of how cool your bike looks to you then clearly you aren't getting the full measure of enjoyment from the hobby. But don't despair - motorcycling may just not be for you. There are plenty of other pursuits out there. Plus you can always pay an expert to just work on your stuff for you. There are other options.

* I am going to add one thing here at the bottom. Pod filters tend to be a typical newbie trap. It sounds like a job that is easy enough, after all it is just changing a filter, and has a high yeild of job satisfaction based solely on looks. However, most noobs who buy old motorcycles and don't have a clue what they are doing have usually already bought a collection of little projects that the application if individual filters plus a lack of tuning knowledge would already exacerbate. It is for this reason that I highly recommend that if you are considering doing this job you make sure that all these other tasks are done first:
  • points oiled and serviced (gap and dwell set)
  • Timing set and advance mechanisim checked and oiled
  • new plugs
  • new wires
  • Coils tested and showing excellent spark (or replaced)
  • Carbs rebuilt and cleaned with all new rubber parts
  • Carbs set to factory tuning specs and properly synched with stock airbox in place
  • All fuses in good working order
  • No shorts in electrical system
  • Charging system in good condition and charging according to factory specs
  • Battery new or tested good.
  • Exhaust gaskets replaced and heat cycled.
  • Intake manifold rubbers replaced.
  • Compression tested (hot) and shown to be with in spec.

Once all these tasks are done then you will have eliminated 99% of the issues that can mask themselves as carb tuning problems or be made worse by a filter change. At this point you should have an excellent running machine and a perfect baseline to get optimal fueling. Kind of a long list isn't it? How many newbies do you think just assumed that since the bike was running ok (without knowing what an ok running bike was really like) they could tune carbs? If you answered all of them you are probably right.
 

·
Registered
Joined
·
2 Posts
posted from another thread at Marc's request:

Pods aren't the work of the devil, they aren't nearly frustrating enough. However, there is a lot of misinformation and just general stupid logic that goes through a newbie's head when it comes to this area that the job is actually a lot harder than it is. Most newbies don't have the patience for it either or the methodical approach to develop the necessary skills to properly dial in carbs. I probably shouldn't have to say this but all carb tuning and evaluation should be done at operating temp. You would not believe how many people I know that complain about rough running on an aircooled engine while it is still on the choke and warming up.

common misconceptions:
- They are a performance upgrade: This is just flat wrong and it is derived from the worst place of all....working on cars. Back in the 1950's-1970's carb'ed cars usually ran restrictive air filters assemblies. Why? it as cheap to do so, it was easy to tune for regular partial throttle use, it helped make torque....who knows. All I know is that you took the air cleaner off your 440 siz pack superbee and the car made slightly more horsepower. So people think this applies to all mechanical things. However, most performance motorcycles starting in the mid 1960's were the result of Grand Prix racing technology (esp the japanese) and you saw things there that hadn't trickled down to stock performance cars yet - OHCs, multiple carbs, velocity stacks, etc. In most cases, esp amoung the japanese bikes, the engineers put a lot of thought and design into the intake tract to maximize performance, reliability, and part throttle fueling. Often if you delete this engineering one of those things suffers (usually partial throttle fueling). I have never seen a stock multiple carb setup benefit from individual filters, often I see them lose power. Why do you see them in high performance applications? well, in racing smooth partial throttle is less of an issue, plus once you upgrade the carbs the airbox rarely fits and if you went with a larger carb size and changed the flow characteristics of the head, then the plenum size of the airbox may not be properly sized for the airflow needed and you end up with a restriction.

- All filters are created equal: This is just bunk. When it comes to filters in motorcycles, you get what you pay for. If you buy cheap EMGO pods (often rebranded as other mfg or reseller's parts like Dime City Cycles or Dixie) you usually get a filter material that doesn't filter, is more restrictive (if the paper is intact) and the inlet will have a blockage in it that may obstruct vacumm passages that otherwise are needed to remain open. But they are usually $10 and price is more attractive when you have no fucking clue what you are doing. Filters from name brands like K&N and UNI are generally better, and for a "universial" filter they are going to be as good as it is going to get but they are oftern $20-$50 a filter and often require more maintenance than a stock filter (perodic oiling) and suffer shorter lives (esp if you ride in the rain). At the end of the day you are still getting a lowest common denominatior velocity stack shape vs the designed specifically for your application velocity stack shape of the stock airbox connecting rubbers.

- If you have pods and an exhaust you have to rejet one size up: This is just stupid logic perpertrated by idiots looking for an easy answer who don't understand carb tuning. Will you have to rejet? you might. It is a guarantee that you will have to do it....no. Carb jetting depends on a lot of factors like density altitude, actual altitude, barometric pressure, tempreature, humidity, etc. Getting jetting advice on the internet, specifically jet size numbers, is like asking getting masturbation advice from a eunic. In order to properly tune a carb you must first need to know how the carb works through out all it's throttle positions. Plus you must know how to evaluate an engine and it's fueling conditions. Than means plug reads, test rides, lots of time. When you open the throttle in your hand you have to have in your head what is actually going on in the carb as the slide lifts - if you can't picture that, you have no business poking your pecker at carb internals. Getting optimal fueling isn't a one shot process - if yu aren't tuining with a dyno and an o2 sensor then there is a lot of trial and error in getting the fueling spot on. And there are instances where certain carb just won't be receptive to the filter's airflow characteristics. Case in point - I have a GTO with a 400 ci pontiac mill running a 1969 GTO HO Quadrajet. At one point I ran one of those K&N filter tops where it was able to suck air directly from the top of the filter. Every time I stepped on the gas to open the secondaries the carb would backfire. I put a normal air filter top back in place the car ran fine. I used that filter top on any non Quadrajet carb car it ran fine. Every single quadrajet equipped GM car I put it on (a friend's chevelle, A camaro, a 350 chevy powered firebird, my GTO, A friends 442) had a carb backfire when the secondaries open. That carb design just didn't like that filter design. Sometimes it happens - often with parts that weren't specifically designed to work with each other but rather generally work of a large variety of applications - like pod filters.

- I'm never going to learn unless I do it: Bullshit. This is the mantra of the uninitated right before they get in over their heads. While I do agree experience is the best teacher, Carb tuning is a science and like any science it takes more than a set of screw drivers and a positive attitude to get good results. Mostly it takes reseach and a measured scientific approach. Again know your carb and know how it works in both theory and practice. Know the signs of how an engine responds to different fueling conditions and how to recognize them. Change only one thing at a time and evaulate the response. Test, Test, Test and collect data as you do it. Pay attention to variables like weather conditions. Use proper tools - can't tell when an engine is running slightly lean? use an o2 sensor or a dyno. Use your head. Are there guys who can pop open a set of carbs, do a bunch of changes, and have it be almost spot on? yes those people do exist and they got there through thousands of hours of trial and error and being methodical and through.

- "There is no point in being in this hobby unless I can't get exactly what I want and what I want is the look of pod filters because they are sooooo cool": Do I even need to point out how dumb this is? Sadly this is the attitude of most (but not all) new riders or newbies to old motorcycles. I call this the spoiled hipster newbie attitude. Honestly, motorcycling is a rich and rewarding hobby and if all the satisfaction you are getting out of it is in the value of how cool your bike looks to you then clearly you aren't getting the full measure of enjoyment from the hobby. But don't despair - motorcycling may just not be for you. There are plenty of other pursuits out there. Plus you can always pay an expert to just work on your stuff for you. There are other options.

* I am going to add one thing here at the bottom. Pod filters tend to be a typical newbie trap. It sounds like a job that is easy enough, after all it is just changing a filter, and has a high yeild of job satisfaction based solely on looks. However, most noobs who buy old motorcycles and don't have a clue what they are doing have usually already bought a collection of little projects that the application if individual filters plus a lack of tuning knowledge would already exacerbate. It is for this reason that I highly recommend that if you are considering doing this job you make sure that all these other tasks are done first:
  • points oiled and serviced (gap and dwell set)
  • Timing set and advance mechanisim checked and oiled
  • new plugs
  • new wires
  • Coils tested and showing excellent spark (or replaced)
  • Carbs rebuilt and cleaned with all new rubber parts
  • Carbs set to factory tuning specs and properly synched with stock airbox in place
  • All fuses in good working order
  • No shorts in electrical system
  • Charging system in good condition and charging according to factory specs
  • Battery new or tested good.
  • Exhaust gaskets replaced and heat cycled.
  • Intake manifold rubbers replaced.
  • Compression tested (hot) and shown to be with in spec.

Once all these tasks are done then you will have eliminated 99% of the issues that can mask themselves as carb tuning problems or be made worse by a filter change. At this point you should have an excellent running machine and a perfect baseline to get optimal fueling. Kind of a long list isn't it? How many newbies do you think just assumed that since the bike was running ok (without knowing what an ok running bike was really like) they could tune carbs? If you answered all of them you are probably right.
this was grate or the best im going to salder my air jets closed and drill them smaller to create more restrition becase i have no air box .i put 4 peaces of 3inch salder to restrict air in the jets and it ran beter some one call me 562 if 489 your as 5412 good as the guy that posted this thank you
 

·
Registered
Joined
·
6,468 Posts
This ** site is so awesome, where else can you read something like this:
"going to salder my air jets closed and drill them smaller to create more restrition becase i have no air box"
 

·
Registered
Joined
·
1,069 Posts
this was grate or the best im going to salder my air jets closed and drill them smaller to create more restrition becase i have no air box .i put 4 peaces of 3inch salder to restrict air in the jets and it ran beter some one call me 562 if 489 your as 5412 good as the guy that posted this thank you
wouldnt you want "bigger" jets with no air box? more air and more gas i thought. why not buy a selection of jets? what kind of carbs? cv or rounds slide etc? and as far as someone calling you to help you. how about offering up something in return/ like payment. maybe take it to a service pro and pay for the job.
 

·
Registered
Joined
·
6,468 Posts
:unsure: air box or not there is no reason anything has changed unless the air box was restricting the intake to begin with.
If you are running a felt pod they are suppose to be oiled and in reality they are no more or less restrictive then a brand new paper filter, until you fill everything with dirt.
If you are running a treated paper pod filter out in the elements, you might want to rethink that because water destroys treated paper filter material, thats' why oiled foam and felt filters exist.

Why do pod filters exist? because they are cheap as **** and sell like hot cakes.

... and if you run a paper pod filter on your crankcase breather vent, well that's just plain old stupid.
 

·
Registered
Joined
·
3,475 Posts
Until the mid-late 90's, stock airbox will generally give best performance until it reaches flow limit somewhere below red-line.
From late 90's on, you are pretty much guaranteed a big performance drop if stock intake system is removed. (around 20~30bhp)
Some bikes are more trouble than it's worth to remove stock system (1979~84 Honda 4's with 3 jet CV carbs, CBX-6, etc)
It's possible to fix them but never easy to get 'stock' low-mid range performance back
 
41 - 59 of 59 Posts
Top