Topic: Pods Thread

[TwoTired]

Power production at less than full throttle is a moot point;

Sorry, I can't agree it is a moot point, unless you are making a pure race track only bike.  The vacuum loss from pod installation will lean both the pilot circuit and slide needle metering.  These have to get larger orifices/adjustments to keep the engine temps down, make correct cruise power mixtures at part throttle, allow proper throttle response off idle, and compensate for throttle position drop outs in some portions of slide needle operation.  I don't understand why you'd think this is without concern.

[scottly]

Power production at less than full throttle is a moot point;

Sorry, I can't agree it is a moot point, unless you are making a pure race track only bike. 

It's simple Lloyd: if you need more power for the riding conditions at hand, you open the throttle more, but that doesn't mean WFO. I have over 60 dyno runs on an FT500 after changing the stock airbox for a large K&N POD, and increasing the main jet alone was responsible for 90% of the tuning required to produce a well behaved bike under all conditions, and netted 58MPG in a combined 82 mile loop consisting of slow off-road as well as highway speeds up to 75 MPH.

[scottly]

Also, I used the stock carb to airbox rubber boot, so that rules out any conjecture about ducting and turbulence.

[Thamuz]

Now I have the 2 main pieces for the airbox and the carb boots.   I do not have the metal bits in the box.  Is this in any way bad?  I also do not have a lid for it.  Those are a tad hard to get around here.

[scottly]

Now I have the 2 main pieces for the airbox and the carb boots.   I do not have the metal bits in the box.  Is this in any way bad?  I also do not have a lid for it.  Those are a tad hard to get around here.

Sounds like a stock air box issue, rather than a pod issue?

[Retro Rocket]

Sorry to disappoint guys but you can put the refreshments away. That last response from RR summed up his character much better than I ever could.

Your doing well mate, get over yourself, you didn't understand my point in the first place , You chose to stick your nose in where it wasn't needed and decided to speak on behalf of someone completely capable of doing it himself and he did {notice you seem to care about it more than him?}, so stop whining when i comment on your petty sarcasm.   Anyway, you went on to say

I don't mind sacrificing a little function to achieve the form I want.

   
And therein lies the problem.
Thats great for you but the guy here is new to this, which means it will either cost him money or a lot of unnecessary screwing around to achieve his "sacrificed function", not to mention {which i already have} the fact the OP lives in the Philippines which is very hot, extremely humid, has monsoon rainfall, is very windy {especially at the moment} and salty air, not a great environment for pods.... You see, i was trying to help the guy asking the question, not the butt hurt pod people....

Scott, I don't know what carb is on the FT but some carbs work reasonably well with pods and plenty of early 4 cylinder bikes didn't have velocity stacks with their airboxes, A few only had tubes to connect the carb to the box, the Honda 4's really don't like pods as most pods have nothing resembling a proper stack not to mention the other obvious differences... and it just becomes a compromise, and  if we get back to the original guys question, a pain in the ass to tune, especially for a novice.  I have nothing against anyone using anything but when a noob asks for advice i'll stick to whats obvious .

[scottly]

Mick, which "OP" were you referring to? This thread was started in '07 by a guy in Texas. Also, to make the FT carb work properly with the low restriction pod, I had to increase the main jet from the stock 140 to a 185.

[Thamuz]

This is a ditching the pods issue.

So you can see where Im going.  Taking th K7N's off, so its a pods issue.

[Terry in Australia]

Yep, the original PO moved on years ago, but this thread is like "The Never Ending Story"...........

http://www.bing.com/videos/search?q=the+never+ending+story&qpvt=the+never+ending+story&FORM=VDRE#view=detail&mid=AC8EDD26AED1226A1257AC8EDD26AED1226A1257

[scottly]

Well, like I said on the other recently bumped Pod thread, every constructive post gets buried under 10 bull#$%* posts. Actually, over the long term it is more like 30 to 1.  

[Terry in Australia]

The trouble with diametrically opposed posts that may have some basis in fact, is that they only serve too confuse the average reader, so are of no more relevance to folks here than popcorn posts.

[scottly]

If the pro stock air-box contingent would stop posting on the pod threads, more usable information might be available for those forced to use pods, without having to dredge through years of popcorn.

[TwoTired]

It's simple Lloyd: if you need more power for the riding conditions at hand, you open the throttle more, but that doesn't mean WFO. I have over 60 dyno runs on an FT500 after changing the stock airbox for a large K&N POD,

Except... Most of the SOHC4s do not have CV carbs, or the same kind of induction set up as the FT500.

So, you modify a Ferrari and do a Dyno run.  And then say those same changes will apply to a Honda Civic? 

How many here will vote for an apples to oranges comparison?

Doesn't seem like sound science to me.

[Terry in Australia]

If the pro stock air-box contingent would stop posting on the pod threads, more usable information might be available for those forced to use pods, without having to dredge through years of popcorn.

Why does anyone need to be forced to use pods? Don't get me wrong Scott, I've used some old K&N pods as recently as last year on my much-modified CB750, straight after using Brian's anti-pod set up and didn't notice any difference at all in performance, (and didn't need to alter the jetting from the 130 mains I used with Brian's Anti-pod) but only went back to the stock airbox (with a K&N filter and no jet changes) because I was worried about water ingestion, so I'm not anti-pod myself, but OEM airboxes are still easily available, so I don't know why anyone would be forced to use one?

I've got a set of 31mm CR's that are going on shortly, and they came to me with foam unifilters, but I've no doubt they'll work fine also. Cheers, Terry.  

[Stoli]

P.abrera - If you have any more questions (for me) maybe it would be easier to send a PM. I'm no expert but I'd be more than happy to pass on my experience with the conversion process.

[TwoTired]

CV carbs position the slide relative the vacuum present in the carb throat.  If the induction changes impose a change in vacuum pressure, the CV carbs tend to adjust for that change.  So, it is not hard to see where changing just the mains would seem to be a complete cure for induction meddling on such designs.

Not so for the mechanical slide carbs, where slide position is totally set by the twist grip.  With an induction change, the vacuum at the venturi where the fuel jet supply exits changes, altering the fuel mix ratios.

Therefore, such offered "proofs" of only main jet changes being needed with pods on SOHC4s, fail... despite the nice pictures of dyno graphs.

Or, is the suggestion intended that pods should always be accompanied by a change to CV carbs as well?

[Retro Rocket]

Mick, which "OP" were you referring to? This thread was started in '07 by a guy in Texas. Also, to make the FT carb work properly with the low restriction pod, I had to increase the main jet from the stock 140 to a 185.

Sorry Scott, i meant P.abrera, the guy from the Philippines, thats who i have been referring to the whole time mate.. , he hasn't been back for a couple of days, probably due to the huge hurricane that has just hit the islands... 

[lucky]

just thought i would share this with you all , i have recently rebuilt one of my 750's with a f1 engine, i was running pods, 125 main jets & hm341 pipes , it would pull great to about 50/60 mph then it would start holding back and bog if you tried to give it more gas,    i tried messing with the air screws but it made no difference, so last night i pulled the carbs to see were the needle clip was set & if they were all the same,    they were on the fourth notch down so i moved them up one to the middle setting & i also bench set the carbs with a 1/8 th drill bit,   i refitted the standard air box without a filter as i don't have one at the moment & took the bike out for a ride,   what a difference it pulls like a train now and no bogging  , next things to do are order a air filter and do a plug chop or 2 and set the carbs up with the vacuum gauges .  I originally thought i would run pods on this bike as i already run pods on my other 750 f1 & that has 125 main jets but a 4 into 1 exhaust and that runs great set up that way  , i don't know if it's because the pod filters are different makes or if it to do with the exhausts that one is happy with pods and one is'nt ?.   I'm just happy that i'm finally getting all my issues sorted out and i will be able to ride it to death  ,   cheers mick.

There is NO WAY you are going to run pods by just changing the main jet.
Some pods are even sold with a new main jet and it leads the owner to believe that all they have to do is change that main jet. That is not correct. It will still be very lean and run very poorly.
1/4 throttle to 3/4 throttle is controlled by the slide needle and the clip position.
Different years of Honda CB750 carbs will need to be tuned differently.
The idle jet may need changing too. It depends on the intake and exhaust system that you are using.

[lucky]

CV carbs position the slide relative the vacuum present in the carb throat.  If the induction changes impose a change in vacuum pressure, the CV carbs tend to adjust for that change.  So, it is not hard to see where changing just the mains would seem to be a complete cure for induction meddling on such designs.

Not so for the mechanical slide carbs, where slide position is totally set by the twist grip.  With an induction change, the vacuum at the venturi where the fuel jet supply exits changes, altering the fuel mix ratios.

Therefore, such offered "proofs" of only main jet changes being needed with pods on SOHC4s, fail... despite the nice pictures of dyno graphs.

Or, is the suggestion intended that pods should always be accompanied by a change to CV carbs as well?

The main reason for the CV (constant velocity) carbs was so that as the bike experiences different altitudes and different barometric conditions that the vacuum operated slide make the necessary changes to deal with the changing conditions.

Honda used to have to re jet bikes going to Colorado and other high elevations,
With the CV carbs it was no longer necessary.

[scottly]

CV carbs position the slide relative the vacuum present in the carb throat.  If the induction changes impose a change in vacuum pressure, the CV carbs tend to adjust for that change.  So, it is not hard to see where changing just the mains would seem to be a complete cure for induction meddling on such designs.

Not so for the mechanical slide carbs, where slide position is totally set by the twist grip.  With an induction change, the vacuum at the venturi where the fuel jet supply exits changes, altering the fuel mix ratios.

Therefore, such offered "proofs" of only main jet changes being needed with pods on SOHC4s, fail... despite the nice pictures of dyno graphs.

Or, is the suggestion intended that pods should always be accompanied by a change to CV carbs as well?

Actually, I was trying to suggest that a change to pods should be accompanied by a dyno test, at least once for the model involved. The FT test was a very graphic (pun intended) example of the effects of a restrictive air box vs a free flowing intake. The idle jet was increased from a 52 to a 58, which is what the FT guys are running with a stock air box, and a 145 main. I went as large as a 62 idle, and found it wasn't helpful, so I returned to the 58. As far as the CV slide compensating, it doesn't, or I wouldn't have had to make such a radical change in the main jet. BTW, the blue lines in the pretty picture are with a 167 main, and the red lines are with a 185 main.

[scottly]

I've got a set of 31mm CR's that are going on shortly, and they came to me with foam unifilters, but I've no doubt they'll work fine also. Cheers, Terry.

G'day Terry. By forced, I was referring to the guys that bought a bike with the air box and boots missing.
As far as uni's, I also did a quick pull with the Seeley with uni's over the Weber velo stacks, and I was embarrassed at how rich it was at WFO. The foam filters I ran years ago were sewn into socks, from foam about 1/4-5/16" thick. The ones I have on now are about 5/8". It appears Webers are quite sensitive to even slight restrictions in air-flow? Only the dyno will tell.

[Terry in Australia]

No worries Scott, after I posted that I thought that I might attempt to make an aluminium airbox to go with the CR's this time around. To be honest after my previous attempts with a set of 29mm CR's I swore I'd never use them again, but I do miss the WOT thrill that the CR's provide, that just isn't there with the stock carbs. I've got a pair of new K&N twin dellorto filters here, I might see if I can use them in my airbox. Cheers, Terry.  

[TwoTired]

As far as the CV slide compensating, it doesn't, or I wouldn't have had to make such a radical change in the main jet. B

I don't understand why you don't see that when a vacuum operated slide is not full open it IS compensating for the vacuum changes.  It's why a main jet change is required but not slide needle position or profile (according to your posit).   There are still minute details of CV carbs I haven't yet explored.  But, they are very different in detail operation from mechanical slide carbs in the way they are able to compensate for engine demands and induction supply, as the slides are vacuum operated and control air supply (and fuel) based on those parameters.  In short, they "know" about vacuum changes and attempt to compensate for those imposed changes.  The predominate SOHC4 carb does not "know" about vacuum changes.  But, it still delivers fuel based on vacuum present in the carb throat, and NOT based on air volume beyond the venturi profile.

It is without doubt that vacuum levels change in the carb throat when induction drag and filter membrane pressure parameters change.  A carb that responds with both air and fuel metering changes may well adapt to at least some degree.  A carb with mechanically positioned carb slides has no chance of compensating either fuel or air volume with just a change to carb throat vacuum.

In this regard, posting evidence of CV carb tuning and suggesting its application to mechanical slide operation is a tangential distraction from what users of pods in this forum actually need to know.

[lucky]

+1

[scottly]

As far as the CV slide compensating, it doesn't, or I wouldn't have had to make such a radical change in the main jet. B

I don't understand why you don't see that when a vacuum operated slide is not full open it IS compensating for the vacuum changes.  It's why a main jet change is required but not slide needle position or profile (according to your posit).   There are still minute details of CV carbs I haven't yet explored.  But, they are very different in detail operation from mechanical slide carbs in the way they are able to compensate for engine demands and induction supply, as the slides are vacuum operated and control air supply (and fuel) based on those parameters.  In short, they "know" about vacuum changes and attempt to compensate for those imposed changes.  The predominate SOHC4 carb does not "know" about vacuum changes.  But, it still delivers fuel based on vacuum present in the carb throat, and NOT based on air volume beyond the venturi profile.

It is without doubt that vacuum levels change in the carb throat when induction drag and filter membrane pressure parameters change.  A carb that responds with both air and fuel metering changes may well adapt to at least some degree.  A carb with mechanically positioned carb slides has no chance of compensating either fuel or air volume with just a change to carb throat vacuum.

In this regard, posting evidence of CV carb tuning and suggesting its application to mechanical slide operation is a tangential distraction from what users of pods in this forum actually need to know.

The CV carb slide was fully open in the dyno tests. I did experiment with the needle height, but found it had no noticeable effect at WFO, just as would be expected with a mechanical slide.
As far as tangential distractions, have you EVER contributed ANYTHING of a positive or constructive nature on a Pod thread? You know, like what has worked for YOU?