Good news about "pods"

There's a bazillion threads on pods. Let's get back to the duct tape.

 

http://www.lowridersbysummers.com/twt/13/index.html


This is what schooter is talking about with the duct tape on a breadbox air filter.

 

Actually, I looked at the part number he gave, and I think it's actually 2 filters, each one taking care of two carbs a piece. Somewhere in the middle of the argument, I'd say. :wink:

 

if anyone gets tired of reading these airbox/pod threads, here's some more
http://kzrider.com/index.php?option=com_kunena&Itemid=116&func=view&catid=3&id=433056

 

Update on "pods", which are actually 2 into 1s

Hey, still screwing with the jetting. Running lean. Was perfect, but got leaner and leaner. It was driving me crazy, but then I realised the temps going up were effecting it dynamically. Running lean will destroy the engine, so just jetting and test riding. That's one thing I love about Rt 50 near my house. I've basically created a race bike with open exhaust and intake. The down side is race bikes have to be jetted for each event according to the environment, elevation, weather, etc. When you get into that level of tuning required for a street bike it is a hinderance. When I get it set for the summer, I'm leaving it and just let it run rich in the cooler weather. Thank goodness I'm not in the hills where I would have to deal with that with every hill and valley. I've learned that the factory engineers have put A LOT into finding the sweet spot that carries over different circumstances. Stock air box design in particular. I think it is much more profound in a highly tuned 550, than say a larger cc engine with a broader tuning band. I thank Fitz for suggesting I keep my eye on the plugs. These carbs are extremely sensitive when you set it to race. As said it's damn near tune it per ride like a racebike. I enjoy working on it and think of it as a hobby and found a site that has OEM equivalent jets for $2 and change each, (jetsrus.com) so I'm not breaking the bank and learned A LOT about my bike with research and hands on. If I wanted a fast bike for the sake of speed and convenience, I would have just bought a newer sport bike. It's more fun when you earn it. That said if I get another bike it will be a sufficiently fast bike stock, and I'm not screwing with the engine. No lay person can ever dream of eclipsing multiple engineers. Not giving up on this bike's home tune, but I'm not opening that Pandora's box with another bike. :lol:

 

Moshumi13, Hey, how did you fasten that one air cleaner on all 4 carburetors? I see the center wingnut but what did the stud thread into? grunt007, 81'XJ750SecaR, Mi.

 

K&N RC-2372
The filters are 2 carbs to 1 filter, so two filter housings. The filters attach directly to the carbs with a hose clamp.

 

Re: Update on "pods", which are actually 2 into 1s

That isn't a race track....it's my gateway to the Ocean!! <LOL> I got a warning on Rt 13...two miles South of Salisbury a couple weeks ago...state Trooper, got me by pulling in front of me with rear facing radar...my detector went off but it was too late...while he pulled off to get behind me I stashed the detector in the console and was REAL nice to him....warning only.....

jeff

 

There are those among us who are interested in pod filters for reasons other than performance. For example, the 900 I have is missing the air box and they are not a common item out here. Also if you have chopped your frame and no longer have room for an air box then pod filters are the next logical choice.

From what I can see the main problem with pods is that they flow a lot more air than the standard air box and filter. The logical thing to do is to jet up to match all that air, but how about modifying the pods to make them present to the engine the same restriction as a standard air box?

I propose putting some instrumentation on a stock engine/airbox and measuring the air flow at a number of rev points then working out a pod system that will flow the same mass of air, such that standard jetting will work.

Has anyone tried something like this, in a properly controlled engineering manner?

And to pre-empt the obvious, there is a cross-flow effect in the airbox and the interaction of the individual inlets is no doubt highly complex but at the very least it is a plenum chamber with a restrictive filter so it should be possible to duplicate it with something like the breadbox filter referred to here, suitably modified.

The last issue to address would be noise. Aftermarket filters are notoriously noisy. The bell mouth on the rubber inlets inside the air box reduce the turbulent flow around the hard corners thereby reducing the noise. Or just run a louder exhaust to drown out the hiss

Any thoughts?

 

The reason Pods don't provide the Engine with the correct Air~Fuel Mixture has much LESS to do with the SIZE if the JETS, ... and much MORE to do with the SHAPE and SPEED of the Intake Air PLUS the PRESSURE and AVAILABILITY of MAIN AIR Supply.

A problem MUCH easier to address with the MIKUNI Carbs on the 900 which have an EXTERNAL Main AIR JET right on the Intake Horn.

Pods and Pod related issues have been the subject of many discussions, here, in the XJ Bikes Forums, ... to the point of ad nauseum.

 

Point being, altering the air flow on a 550 is a Pandora's Box. If you want to open it go ahead.

Haha. Yeah, you're right JeffK, you have to watch out for smoky bear on Rt. 50 and Rt. 13 around here.

 

I hear ya "bobberaha"... I also find it strange to read negative comments within the "XJ Modifications" forum. Whether or not someone is being attacked, very often there seems to be a negative connotation involved with something other than what the engineers at Yamaha designed in the 80s (AKA a modification). If you haven't been to, you should check out http://www.thechopperunderground.com It's a great site dedicated to chopping/modifying bikes.

 

Update: The nature of the airbox

Rick said something about the air actually being an issue in this post and other posts I believe, and after reading it I decided to research it and found out a few things.

Apparently, an inherent design feature of the airbox is to regulate the positive/negative air pressure ratio within the carbs. The CV carbs are also said to stand for Constant Vacuum.

A set amount of vacuum is required for the slide to actuate as designed. When the airbox is removed the negative atmospheric pressure becomes so close to the high pressure within the carb, the differential is no longer great enough to actuate the slide at WOT and to a lesser degree at mid range. This creates the bogging at WOT that Fitz has mentioned.

Carbs stages are activated at throttle positions not tach positions.

The solution that is safest is to either purchase weaker springs (Dynojet includes one in their jet kit for Harley CVs) or clip stock springs to find the rebound/compression needed to allow the slide to actuate with the diminished vacuum. I'm currently clipping my springs little by little and testing. As of this posting I have up to 3/4 throttle, where I had only half throttle before. This is where you will have to only clip a little at a time. If you clip too much the slide will "bounce" because the resistance in the spring is too weak and it will shoot up and then come back down trying to find the sweet spot in vacuum. This will repeat rapidly until it settles or you back off the throttle.

I would not advocate drilling out the slide! If you go too far with the springs, they're cheap to replace and you can then back off from where it started "bouncing" with the new one. The slides are rare and expensive.

Here are a few links about CV carbs in general:

ttp://www.rhinoforums.net/hunterworks/2 ... -mods.html

http://forums.sohc4.net/index.php?topic=5410.0

http://www.hondanighthawks.net/carb14.htm

http://www.bikerenews.com/Stories_Archi ... etors.html

 

But why clip the springs when you can use bread wrapper ties to "coil bind" them (partially) which is reversible if you go too far??

 

A person can approach it in whatever manner they see fit. The end game is to create the adequate +/- pressure ratio. Also, you would have to apply the ties to the upper spring to avoid friction, mechanical interference and binding.

In my case the springs are already down to 3/5 their original length and it is just stating to actuate the slides. The +/- ratio is slim and the vacuum is very weak, so the spring has to be just as weak or slightly weaker. That would be a lot of tying up.

 

You will still have to deal with eliminating Negative Pressure at the Atmosphere Vent at the top of the Intake Horn.

Net Negative Pressure at that Atmosphere Orifice:

Lowers the Pressure beneath the Rubber Diaphragm making it more difficult for it to collapse against the Intake-caused Low Pressure variant upon the hole at the bottom of the Piston.

Atmosphere needed there, to supply Air to the MAIN AIR JET which supplies Air to surround the Emulsion Tube, ... necessary to effect an Up-draft Siphoning and Atomization of the Main FUEL Supply is deminished, ... causing:

The Fuel Supply to be diminished -- ( The Lean Condition )

Because:

The Diaphragm cannot evacuate and fails to fully rise.
The Needle fails to fully withdraw from the Tube.
Any Fuel which does enter the Intake Stream isn't atomized for efficient combustion.

You need to do more than just put-in weaker Springs.

 

You're "Because:" section states why the springs need to be weaker than the vacuum. I.E. the spring is too strong to allow the slide to compress with the +/- ratio as it stands sans airbox.

The other method is to enlarge the vacuum port, which is dicey.

You have a lot of critiques, but no solutions, Rick. I'm in the process of figuring this out and relating my findings. I am seeing real world results. I'll take results over theory.

People that spend all their time humming, hawing and pontificating never get anything done.

 

Every so often, another crusader comes-along and says they are going to be the guy who figures-out how to afix Air Cleaner Pods to Constant Velocity, ... (Constant VELOCITY --- Not --- Constant VACUUM) Carbs.

They look so cool.
They must be easy to install and run.

Here it is. 2011.
And your the guy; this time.

Good luck.
The process began 31 Years ago.
You'll take results over theory.
There's the rub.

Until you thoroughly understand the theory; how do you expect to get results?
Experimentation?

Please read this article.
Your attention is directed to the Paragraph near the end titled:
"Carb Venting".

http://www.drpiston.com/Cvcarbs.html

No.
I don't have a solution.
Nor, am I aware of anyone who actually does.

 

You drill another port, incrementally, that is fillable with JB-Weld (just trying to help) This gives a quicker reaction time.

 

This thread was started to share my experiences with putting open exhaust and intakes on my bike. Information to use or not use for people doing, or thinking of doing the same thing. Nothing more and nothing less.

The same thing some of us are doing, or trying to do, is done thousands of times to Harley CVs, and I got a hunch they aren't being hounded by other members of their forum.

If you're going to stand up against something, stand up and spread the word about something that will make a difference in the world. The anti pod argument has been beaten over the head of the naive that stray from the path of "righteousness" enough already. We get it! Now, if you please, pipe down and leave us to our toys.