Topic: Split - What is wrong with the stock Honda induction system?

[TwoTired]

I decided to go K&N for my 750s.  Mostly because you can clean them and reuse them.  It's a long term economy thing for me.
The caveate is that I have very few miles that I've put on the 750s.  So, no long term report on their usage.
I've been using the UNI NU-4055 foam filter in the 550's for years.  I know those work well in the stock air box.  It took 15 years for the foam to degrade and need replacement.  That's still economical, IMO.

I would go back to the paper stock type, if I lived in or operated in an area that was known dusty, though. (But, I wouldn't want to breathe there.   )

[BobbyR]

I decided to go K&N for my 750s.  Mostly because you can clean them and reuse them.  It's a long term economy thing for me.
The caveate is that I have very few miles that I've put on the 750s.  So, no long term report on their usage.
I've been using the UNI NU-4055 foam filter in the 550's for years.  I know those work well in the stock air box.  It took 15 years for the foam to degrade and need replacement.  That's still economical, IMO.

I would go back to the paper stock type, if I lived in or operated in an area that was known dusty, though. (But, I wouldn't want to breathe there.   )

Thanks, I will look into those as a long term and economical solution. I lived in Palo Alto for a couple of years, the conditions here are about the same. Except for the Snow and single digit temps.   

[edbikerii]

I had a UNI in-airbox foam washable filter in my airbox before I went to pods.  JCWhitney has 'em cheap.

I think the bike ran too lean, and too hot, but that might have been from the combination of the UNI filter and the MAC exhaust.

(that is a major part of the reason why I went with pods and re-jetted in the first place - see the thread in my sig for details).

[BobbyR]

I had a UNI in-airbox foam washable filter in my airbox before I went to pods.  JCWhitney has 'em cheap.

I think the bike ran too lean, and too hot, but that might have been from the combination of the UNI filter and the MAC exhaust.

(that is a major part of the reason why I went with pods and re-jetted in the first place - see the thread in my sig for details).

I bought bike for $100 and it was only ridden for 2 years. It has 120 mains which is not stock. I may be a bit rich so if the K&N or foam leans it a bit, it may not be a problem. The guy was a Mech Engineer and a Porsche Racer, so I have no idea what was done to the bike. He was laid off, left his wife and disappeared somewhere.

[kghost]

I had a UNI in-airbox foam washable filter in my airbox before I went to pods.  JCWhitney has 'em cheap.

I think the bike ran too lean, and too hot, but that might have been from the combination of the UNI filter and the MAC exhaust.

(that is a major part of the reason why I went with pods and re-jetted in the first place - see the thread in my sig for details).

I bought bike for $100 and it was only ridden for 2 years. It has 120 mains which is not stock. I may be a bit rich so if the K&N or foam leans it a bit, it may not be a problem. The guy was a Mech Engineer and a Porsche Racer, so I have no idea what was done to the bike. He was laid off, left his wife and disappeared somewhere.

We all feel the need to go out for a pack of smokes now and again .......

[BobbyR]

I had a UNI in-airbox foam washable filter in my airbox before I went to pods.  JCWhitney has 'em cheap.

I think the bike ran too lean, and too hot, but that might have been from the combination of the UNI filter and the MAC exhaust.

(that is a major part of the reason why I went with pods and re-jetted in the first place - see the thread in my sig for details).

I bought bike for $100 and it was only ridden for 2 years. It has 120 mains which is not stock. I may be a bit rich so if the K&N or foam leans it a bit, it may not be a problem. The guy was a Mech Engineer and a Porsche Racer, so I have no idea what was done to the bike. He was laid off, left his wife and disappeared somewhere.

We all feel the need to go out for a pack of smokes now and again .......

I thought they only did that in the Bronx. 

[TwoTired]

I should note that I still have the paper filter in my 78 550.  It still has the stock exhaust on it, too.  I'm going to try the Uni in it when it gets put back on the road in a couple months.

The 77-78 550K stock exhaust, has smaller outlets than prior years.  This increases exhaust system pressure and likely reduces scavenging of the cylinders.  With less oxygen getting into the cylinders (compared to earlier exhaust systems), the carbs can be set to provide less fuel for combustion.  The reduction in scavenging also leaves behind some unburned carbon (fuel) from the last cycle to be burned again.  This was probably Honda's reaction to EPA requirements/pressure, possibly noise import requirements, and the desire to extend the product line sales another couple years.
Simply changing the exhaust to a more open, scavenging type, would require carb compensation on those finely tuned carbs, requiring more fuel for the larger amount of oxygen getting into the chambers.  I wouldn't be surprised if the 77-78 k models made less HP than earlier models in stock trim.  I don't have any data, though.  I've no doubt the 77-78 K stock exhaust was heavier than the Mac.  My 78 550K certainly has a heavier bike feel while driving about, and probably contributes to my assessment that the 77 550F was the "best of breed" and certainly "sportier".  The 78 550K still cruises on the highway quite nicely and will easily break speed limits, even with two on board.  It is quite well mannered.

Cheers,

[BobbyR]

Like I said my 78 750K appears to be bone stock including exhausts. The only easily seen mod is the 120 mains. I put a Dyna in. Runs fine. If something was done internally I may never know. Pretty happy with it. Recent events make me more inclined to ride than wrench this year.

[Cormac]

Sorry, I'm not done yet. Sheesh, get back to work and find out you've been flamed as well as  *&^%$ by the white house, what a day.

In order:
Mlinder: Yes, less restrictive filters will increase performance. A very simple test here is to put the factory oil bath filter back on a bug, accelerate as fast as you can from zero to 40, time the results. Now repeat with a paper round filter, a foam round filter, and a K&N type round filter. Then come back and tell me that there is no difference. Or, you can just check any of a number of dyno tests that have been done over the years. Is it a huge difference? No. Except in the more extreme situations, like a dirty paper vs a clean oiled foam. And don't give me that "apples and oranges" bit. Internal combustion is internal combustion. Hell, they are both even air-cooled. What more do you want?

TT: So you are contradicting yourself now?
       Me "So then, the stock carb configuration is tuned around the fact that the stock filter media limits air flow, correct?"
       TT"No.  Unless, you clog the filter up with dust. The stock carb settings are tuned to the intact tract and the air filter pressure drop."
     That air filter pressure drop is caused by the limitation to flow. I.E. No filter, no pressure drop also no restriction to flow. Filter=restriction=pressure drop.
      

      Me"I know, the air box also smooths air flow, bonus... How can it possibly be a good thing to limit or restrict air flow?
      TT"It doesn't, for the stock engine, it's just a fictional point you made up."
      Actually, you stated that the filter created the necessary restriction for proper tuning, back in the "vintage motorcycle shop" thread.

I'll save some space and not copy everything for these:
      I stated that the air should be suitably clean, so I wasn't advocating no filter. Even drag-race guys typically use a filter.
      I've seen a great many hardtail bikes that have been ridden all over hell and gone for a great many years. So, yes, I expect one to last 100,000 miles. Don't really know what the engine life has to do with the bike life though. I've destroyed more than a couple vehicles and moved the engines into fresh rigs.
      I do not choose to go to a modern bike as A) I already own this one. B) Most modern bikes look like (IMHO) crap. C) I prefer to be able to build things to suit MY conditions and needs, instead of normal operating conditions.
      Oiled foam filters are considered to be the best flowing/filtering. AEM produces a dry filter that out flows and filters K&N, also Alexi filters. Petersons 4wheel and offroad did a write up a year or two back, unfortunately my magazine stash is still packed or I would cite the exact issue.
      I source my parts through Summit Racing, so by Cheap-o I mean their house brand filters. Two of which showed up with K&N stamped in the rubber. So I seriously doubt that there is a quality issue. Just like Wal-mart oil isn't going to be made by Wal-mart, same for Napa, Jegs, etc. etc.
      Me"Speaking of which, whether or not there is a honking big filter, if there is a pressure differential (which TT has time and again stated is necessary for proper tuning) created across the filter media then the filter is not flowing as much as the engine can ingest."
      TT"Science does not support that statement, I'm afraid.  It does consume more energy to maintain the same air flow.  But, the pressure drop alone does not freely equate to reduced flow."
       Ummm...Science does support that statement. A vaccum (aka pressure drop) only exists when there is a restriction to flow. When flow is in conjunction with a timed event (valve opening and closing) and there exists a pressure that is less than atmospheric, then that displacement has not been completely filled. Obviously the situation has more involved than just what filter is in use, otherwise we would all run around with no filter, get 100% VE and longevity be damned. But every little bit helps. This is also why turbulence is such a big deal, correct?

       And yes, I am looking to change things. For instance, I feel no need to feel like I'm straddling a barrel. Did you realize that the frame is nearly 7.5 inches wide at it's narrowest? The seat is 10.5" at the front, why? Oh yeah, there is a massive black box under it. The service jacked up my knees and hips, so I really don't feel like being uncomfortable on MY bike. Oh, and if it wasn't so much fun to screw with the HD guys, I would go get a normal cruiser.

       Now, why are you so resistant to change? You did great research, you obviously think about this a great deal, why the massive chip? I would think that you would be a the forefront of a quest to further improve these things, but anyone so much as says "what about" and you're giving the party line. "Engineers knew best". I ditched the points and factory coils as well, what about that? Put modern tires on too, any beef there? I may very well put in hardened seats and lighter valve retainers. Hell, I'll probably put in a cam as well.

       You asked what was wrong with the factory set up, well here it is. It is wide, ugly, restrictive, and in the way. Kinda like me I guess.

Cheers

[754]

FWIW, a few air cleaners I tried and no longer use..

 Way back in about 73 maybe I ran Uni socks in my CL 175, actually I think more of a pod shape maybe, might have had a spring in there.... Anyway they got crossed off the list the day it bacfkired and one caught fire.. and melted all over my gauntlet...

 Then one day I had a brainwave and just put some foam over a CV 350 carb with a hose clamp...... restriction lesson learned.

 Then i tried the first K&N round type on my 750, I liked them, no complaints..

 Around that time I started playing with the Webers and ended up with bugeye filters with the chrome mesh and the clips, also sold by Lynx, & i think another name. Heavy black foam, I was never ultra paranoid about dust, just want the big stuff out, they seemed to do that..

 Amyway the years rolled on I drag raced a bit and the now 836 did not see the street for many years, Around 89 or 99 I figured I would put it on the street and ride a bit.. Well I hauled out the bugeyes and blew them off and I saw fine black dust, then rubbed them and they started coming apart.. so I decided not to use them anymore..

 That is 2 aftermarket down and I already learned the WET paper filter lesson on my CL350..

 So I ran the 836 without anything, cept sometimes stacks.. in fact I ran it quite a while like that, even on the dirt track a few times with and without the sidehack.. and curiously and to the disappointment of a few, did not wear out immediately.. in fact I began to wonder why it still ran pretty good..

 The last trip it made was to Bonneville and back in 2007, still got better gas mileage than the 78 750K with stockbox & header I  rode with..  I had a few bad noises that trip, valve started sticking, I knew it was getting near the end...

 Anyway , that is what happened to me.. cuts down the choices a bit, for my setup..

[Frankenkit]

I'm sure Hondaman will post about K&N stock filter replacements and their virtues for the 550 and 750 rider, but I'd like to take this opportunity to parrot his thoughts on the use of K&N filters on cb650s.  

The cb650, having had its idle circuit leaned out to pass stringent EPA requirements, has been known to be rather cold blooded in regards to starting and torque below 4krpms.  

Some even attest to its being nearly impossible to start without full choke and/or without use of the accelerator pump as a "tickler".

This is where the K&N filter comes in.
(and this being my best understanding of our conversation, I hope this doesn't come off as a Tim Taylor recounting of a conversation with Wilson...)
Because the K&N filter is less restrictive to the incoming air flow, the carbs run slightly richer due to higher throat pressures.    This would, at least in theory, improve the torque below 4k on the über lean PD carbs.  550s and 750s might need to be leaned out a hair via the air screw,  but the cripplingly lean stock setup of the cb650 could actually benefit greatly from this.

Having had this discussion, I now wonder how this modification compares to the already-common mod of dispensing with the stock airbox cover and instead using large washers to hold the air filter in place, thus increasing the volume of air taken in and reducing the relative restrictiveness of the airbox.

[seaweb11]

754 is FWIW tween speak for

Find whatever I want?
Find what I will?
#$%* what? I'm wankin?
Fricken wow I win! ?

I'm lost.
signed pod squirrel killer
 

[mystic_1]

754 is FWIW tween speak for

Find whatever I want?
Find what I will?
#$%* what? I'm wankin?
Fricken wow I win! ?

I'm lost.
signed pod squirrel killer
 

"For What It's Worth".

mystic_1

[Laminar]

(and this being my best understanding of our conversation, I hope this doesn't come off as a Tim Taylor recounting of a conversation with Wilson...)

Haha...love it.

Because the K&N filter is less restrictive to the incoming air flow, the carbs run slightly richer due to higher throat pressures.    This would, at least in theory, improve the torque below 4k on the über lean PD carbs.  550s and 750s might need to be leaned out a hair via the air screw,  but the cripplingly lean stock setup of the cb650 could actually benefit greatly from this.

A less restrictive air filter reduces vacuum in the throat, causing less fuel to be draw through the jets. That's why when pods are installed, larger jets need to be installed.

[Simpson]

After reading the last pages of comments, I feel compelled to contribute a tad.

The points made by applying physics and sciences are extremely interesting. TT poses some thoughts and it is great topical items to bounce around. Kudos my most favorite "cantankerous" member. Most thoughts I agree with TT, not all but most.  I've learned a few neat details on fluids in motion, thanks. I agree in the sense, you have to balance and mix A/F with absolute precision for the best outcome in engine performance. This being the reasoning for the advent of fuel injection.

I'm confident there are no scientific studies, anecdotal evidence, or personal experiences I can contribute at this point that will change anyone's mind.

But... I can't help get a good chuckle reading some of these posts simply because of the day and age we live in now. You see, to me the year 2010 makes some thoughts obsolete.

Its pretty easy to buy a 100, 130, 150 plus HP bike in this day and age. Most of them will do 0-60 in around 3 seconds, blah blah blah, you get the point. I just don't understand what the expectation is for changing to Pods in terms of performance.

-If someone said "Hey, its a cheap solution to a missing air box", agreed!
-If someone said "Hey, they look better", okay, i understand!
-If someone said "Hey, I like the sound they give off", okay, i understand!

But when you talk performance, it just doesn't make sense unless we are living the the 70's to argue with long posts. Even if by some strange not understood undiscovered scientific reasoning they increase power, how much of a difference would you expect? 1-2 hp when we are talking about machines the average 30, 50 or 60 HP. Relative to today's machines the points have little weight as very best. How many people take their vintage bikes to track days? Does it even matter in this application or would a guy who focuses on better corner speed still school you?  

Personally, the most desirable vintage bike is a smooth, well mannered and reliable one. It's all about the smiles of abundance of miles. I put about 300 miles on my CB750 this weekend. How many miles have the performance guys put on your bike this year?

[754]

Simpson

None on the 836 this year, but I am sure you probably wont like what some of us did some years...

 And dont start asking how many times I have ridden this year...

[campbmic]

Personally, the most desirable vintage bike is a smooth, well mannered and reliable one. It's all about the smiles of abundance of miles. I put about 300 miles on my CB750 this weekend. How many miles have the performance guys put on your bike this year?

I've pushed mine about 20 miles this year

[scottly]

Personally, the most desirable vintage bike is a smooth, well mannered and reliable one. It's all about the smiles of abundance of miles. I put about 300 miles on my CB750 this weekend. How many miles have the performance guys put on your bike this year?

I've pushed mine about 20 miles this year

ROTFLOL! How many miles today, Mike?? (I love your attitude!! )

[BobbyR]

Personally, the most desirable vintage bike is a smooth, well mannered and reliable one. It's all about the smiles of abundance of miles. I put about 300 miles on my CB750 this weekend. How many miles have the performance guys put on your bike this year?

I've pushed mine about 20 miles this year

I would imagine this bike is very good for your Cardiovascular System. 

[Retro Rocket]

How many miles have the performance guys put on your bike this year?

None this year as mine is not complete yet but i have owned plenty of performance Honda/4's and have done thousands of miles on all of them, sometimes 2000 plus miles in a couple of days plenty of times. I plan on doing a 4000 mile round trip on my new one after it is run in and sorted and this one will be the most modded one i have ever owned, i am in no way expecting it to be less reliable, actually with all the quality parts i am using i expect it to be more reliable...

Mick

[GammaFlat]

Personally, the most desirable vintage bike is a smooth, well mannered and reliable one. It's all about the smiles of abundance of miles. I put about 300 miles on my CB750 this weekend.

You're really at the heart of the matter... at least for me.  I'm glad I have more than one because my favorite is down right now .  ... but hopefully not for long and like the 6 million dollar man it'll be faster, stronger, blah blah blah ... (my hopes anyway)

[Bob Wessner]

TwoTired's initial postings to this thread have been split off and moved to the FAQ area. Since it is not yet in its permanent place, and possibly form, I will return an insert a link to it later.

[BobbyR]

TwoTired's initial postings to this thread have been split off and moved to the FAQ area. Since it is not yet in its permanent place, and possibly form, I will return an insert a link to it later.

Great idea Bob1, info like that should not be lost.

[Bob Wessner]

It was Mark's (mlinder) idea.

[Retro Rocket]

Well done guys...

Mick