Topic: too much air from pods?cheap fix

[bikerbart]

I am running an old Alphabet 4-1 header,pod filters,rejet carbs(130 main)Still the pods let in way too much air so after trying different jets I was still lean.So,I tried putting a 7 ounce tin can(beans I think,maybe tomato sauce)over the pods,and they cover them just enough,and restrict the flow perfectly,my 73 750 is running almost perfect now,no more backfiring,starts 1st kick,and looks kinda cool in a rat bike sort of way.best of all it only cost about 2 bucks.I will put up some pics in a few days.

[kghost]

It only costs 2 bucks and you get to eat the contents.....what a tip. 

Wow...thats all I'm gonna say....

[bikerbart]

Yep,It was me that was backfiring after 4 cans of beans.phfffft bbrraaaap!

[kghost]

Did ya at least polish the cans? 

Notice I did not ask nor do I wanna know about your can after the beans......

[hopterfixer]

I just don't want to hear about your can "running rich"......

[bikerbart]

yeah,I polished the cans,pics tomorrow.if I can get off my can.

[heffay]

please remember the proper cans to photo ... unless you have a hotty wife 

[754]

Too much air, yeah right!!

 I think you have unequal air to draw from is the problem. I bet if you took 2 cans and only left the outer sides on each, mounted on the outer filter (1/2 can to outside) it would solve the problem..

[heffay]

Too much air, yeah right!!

 I think you have unequal air to draw from is the problem. I bet if you took 2 cans and only left the outer sides on each, mounted on the outer filter (1/2 can to outside) it would solve the problem..

agreed.  most airbox inlets are not in direct airflow.  basic problem w/ pods 

[bikerbart]

Thanks,I will try that.I am doing all this off the cuff,I have no formal expertise,and all the books and tuning manuals just seem to confuse me.I have just moved to the other side of the country and have not got in good with any local mechanics.And,as we all know,most newbies dont know *&%?@# about old bikes.They just plug into a computer and it does all their work for em.

[cafe750]

You can cover half of the pod with some duct tape, and then turn the pod so the faces the center of the bike....you barely see it, and until you have it jetted properly, it works!

[Gregorymoto]

Hi, did you oil your pod before trying to run the motor?

[heffay]

You can cover half of the pod with some duct tape, and then turn the pod so the faces the center of the bike....you barely see it, and until you have it jetted properly, it works!

why?  the airflow is coming from the outside edge... not the inside.

i can see what you're getting at... you want to hide the duct tape.  but half covering a pod toward the inside of the motor... will do very little if anything at all to performance.

what he did to fix his problem was to direct airflow away from his pods and essentially made 4 airboxes (aircans  )  what you suggest would be to open up the pods to the detrimental airflow again.

[cafe750]

I'm not knocking how Bart did it, in fact I think its a good idea. It was a quick, temporary fix on my brothers 550 cafe, until we could jet it properly.  He had put aftermarket pipes on it, and  pods, and it was running incredibly lean. The purpose of the tape was simply to restrict the pod's capability of flowing air, and in turn, temporarily solve the problem. It worked until the jets came in, and we were able to jet properly for the pods and pipes.

[754]

The inner carbs are not getting the air the outer 2 are, the duct tape though reduces filter area. It needs a shield about a 1/4 inch away from the filter surface on the outer edge.

 Try this, rige about 60mph with legs against the tank, then move the knees outward and you can usually feel the difference.. Then when you get a wind from one side it also changes.....unless maybe you are WFO or going thru the gears..

[winnipeg550guy]

That can idea has me intrigued, Brain not working good now need pics please

[rbmgf7]

i tried rolling a little felt into the pod to help restrict the air flow into a more ambient state. i haven't prefected it. too little, and it doesn't make a difference. too much and you choke it.

i was running 130 mains and it seemed to do the trick but it an noticably rich (but man did it sound nice opening it up on the highway)

how do people running on velocity stacks solve this problem? i heard it's a fluid dymanics problem. the air flow around the sides of the engine causes a pressure drop in the center. the two center carbs experience a different pressure then the two outside carbs causing an uneven pull of air into the cylinders.

[bikerbart]

For some reason the pics are not uploading,not sure if its this server or I am just an Idiot,I will keep trying

[edbikerii]

I've never experienced this problem with my pods after proper oiling and jetting.  Has anyone who has jetted and oiled properly actually had this problem first-hand or is this a theoretical discussion?

In my experience, after removal of the airbox, all four pods have access to much more air above, below and to either side, with no shortage to any of the pods.

Of course, if you actually discover that the inner two carbs are getting less (or more) air than the outer two carbs, you can always jet them a little different than the others.

[754]

Ed please try this. get up to 60 mph in top gear on hwy. Mow ride knees tight to tank and accelerate, then repeat and move legs away from the tank and see if it changes..
If not you are lucky.

Here is the difference pods and stacks have over stock airbox. When you are at low throttle at say hiway speed and give er the air the motor is trying to grab, is rushing past at say 60 mph. You are now trying to grab some of that and make it turn 180 degrees (with stacks) into the carb. Once the  air starts to move into the carbs it gets easier..its the transition that is tough and suffers.  Now on a race bike with stacks, it is usually not a problem, if you are always revving, or going thru the gears.

The airbox however is drawing air from a more an area more neutral from the speed of air flowing past the bike and draws in air easier and smoother. I dont think the WARMED air though is helping horsepower..

[edbikerii]

Ok, I tried this tonight.  There is a perceptible difference in the sound produced, probably due to deflection off my legs, but little, if any perceptible difference in performance.  Honestly, if there was any performance difference at all, it was so small that I couldn't tell you which way would have been better.

I have learned, however, that I tend to ride with my legs pretty tight up against the tank, pretty much all the time.  I guess that makes any difference basically irrelevant anyway.

Most important of all, it is a beautiful night, and I had a really nice ride!

Ed please try this. get up to 60 mph in top gear on hwy. Mow ride knees tight to tank and accelerate, then repeat and move legs away from the tank and see if it changes..
If not you are lucky.

Here is the difference pods and stacks have over stock airbox. When you are at low throttle at say hiway speed and give er the air the motor is trying to grab, is rushing past at say 60 mph. You are now trying to grab some of that and make it turn 180 degrees (with stacks) into the carb. Once the  air starts to move into the carbs it gets easier..its the transition that is tough and suffers.  Now on a race bike with stacks, it is usually not a problem, if you are always revving, or going thru the gears.

The airbox however is drawing air from a more an area more neutral from the speed of air flowing past the bike and draws in air easier and smoother. I dont think the WARMED air though is helping horsepower..

[tbpmusic]

I'll just throw in my two cents worth here.

Especially after major changes to both intake and exhaust, it is easily possible that a bike with those type of carbs can be running rich at low/medium speed/rpm, yet also run lean at high speed/rpm. Or even opposite of that.
I've been through it myself.
I had a Honda with similar carbs (a twin, though) on which I'd installed Uni filters and much more free-flowing exhaust. The bike's plug readings indicated rich, but it idled great, with snappy throttle response. However, when pulling hard at high revs/speed, it would tend to crap out. This was confusing to me.
When it displayed that behavior, I tried using the choke a bit (at speed, now), and it ran better. Aha - a clue !!
Clearly, this bike was rich at low and mid, lean at high. The changes were getting responses that were not "linear" like I expected.
The solution, which was sort of counter-intuitive at first, was to go to larger main jets and drop the needle down all the way. This leaned it out at the low end, and made it richer on the top end.
Problem solved, good running at all rpm and loads.


bill

[edbikerii]

Yes Bill, I agree.  Re-jetting when installing pods is a definite must.  I've gone through this, too.  I'm pretty sure this is why I'm not seeing the problems that others are reporting with their pods.

I'll just throw in my two cents worth here.

Especially after major changes to both intake and exhaust, it is easily possible that a bike with those type of carbs can be running rich at low/medium speed/rpm, yet also run lean at high speed/rpm. Or even opposite of that.
I've been through it myself.
I had a Honda with similar carbs (a twin, though) on which I'd installed Uni filters and much more free-flowing exhaust. The bike's plug readings indicated rich, but it idled great, with snappy throttle response. However, when pulling hard at high revs/speed, it would tend to crap out. This was confusing to me.
When it displayed that behavior, I tried using the choke a bit (at speed, now), and it ran better. Aha - a clue !!
Clearly, this bike was rich at low and mid, lean at high. The changes were getting responses that were not "linear" like I expected.
The solution, which was sort of counter-intuitive at first, was to go to larger main jets and drop the needle down all the way. This leaned it out at the low end, and made it richer on the top end.
Problem solved, good running at all rpm and loads.


bill

[tbpmusic]

Yes Bill, I agree.  Re-jetting when installing pods is a definite must. 

[/i]

Well, I guess I could have piped in sooner, didn't occur to me.
I spend most of my time working on 450's, which are fairly immune to these problems, due to the nature of their carbs.

But with these  "cable pulls up the slide" type carbs, jetting changes are generally indicated after mods to intake particularly (but also exhaust changes many times). And since there are several "circuits" (different jet systems) involved, several different effects can be observed - none of them may be what you expect, and they're rarely "linear".
In the absence of sophisticated equipment (oh, you've seen my shop), everything has to be worked out emperically (get on it and ride).

Fiddle with the choke a bit when it's running weird - if it runs better, you're lean in that range.
If you want a good plug "reading", go somewhere that you can immediately start the bike and take off like a bat outa' hell. Go to this place, and install fresh clean plugs. Take off like the aforementioned bat, get on it hard for 4-5 miles. Keep the rpm up, but use a lower gear if it if it causes you to go 120mph.  Hit the kill switch, pull over and look at the plugs. That will tell if you're rich or lean on the top of the range.
Reading the plugs after extended normal driving is really only indicative of the lower parts of the power range, since you spend a bunch of time idling and at low rpm.

Since the  slide needle is tapered, a combination of jet sizing and needle placement can generally "linearize" your response and give even performance.

bill

[subkulture]

great info. thank u