Topic: A Plug question

[FLo]

I'm in Vancouver, BC, right next to the water

[FLo]

So I was thinking, all these problems started when I changed to the uni foam filter (UNI-4055).  So out of curiosity, I put in the dirty OEM air filter.  Aside from the spuring at 6000rpms, the bike shifted through all gears evenly with good "balls", unlike when the uni foam filter was installed (which caused the bike to accelerate unevenly and poorly).  I'm concluding that either:

1) I don't need re-jetting with an OEM air filter

or

2) Installing the UNI foam filter will require re-jetting

or

3) I installed or oiled (with uni filter oil) the uni foam filter incorrectly.  I made sure that it was evenly and lightly oiled.  Do you need a lot of oil? because I didn't use a lot, though I applied it very evenly.  Also, I think maybe the hole in the bottom of the filter, is not quite fitting the tube sticking up from the bottom of the air box.  Will this cause my un-even and slow acceleration?  What other things could I of missed when installing the Uni filter, or is re-jetting a must when switching to a non OEM air filter such as the UNI Foam filter?

Thanks in advance.

[TwoTired]

The 77 and 78 CB550 were the first 550 models to fall under the perview of US EPA emissions requirements.  To achieve this using the same basic engine components, Honda decided to make the exhaust more restrictive and put more refined control of the idle mixture in the newly designed carbs.

A more restrictive exhaust had the effect of leaving more exhaust gases in the chamber to go through another combustion process.  This reduces unburned hydrocarbons released into the atmosphere.  The more refined control of idle mixture meant less hydrocarbons fed to the engine during idle.
The retained exhaust gases and hydrocarbons due to exhaust restriction meant less available oxygen for the next burn cycle and a need to reduce fuel delivery by the carburetors.  The carbs were then jetted to deliver a correct A/F ratio for the components as delivered by Honda.  The engine was happy as ran well.

Then owners changed things. 

The exhaust was replaced with one that has far less restriction, allowing more complete evacuation of the cylinders during the exhaust cycle.  Not only were there less hydrocarbons from the previous combustion cycle to burn, there was also more oxygen available in the chamber for combustion.  But, the carb still delivered fuel at the stingy rate that was required by the restricted exhaust, making the combustion mixture leaner.  The engine, while not exactly happy, still runs because there is a wide A/F ratio that still supports combustion, even if not ideal or one that makes best power.

The stock paper air filter has fibers interwoven to allow air passage, but traps tiny particles within the weavings.  As it traps these particles, air passageways are blocked, leaving less "tunnels" available for air passage within the filter mesh.
The fiber weavings when new, deflect the air inrush and cause it to turbulate.  And, the turbulation slows the air flow.  Most refer to this simply as air inlet restriction, which increases over time as the filter traps more particles.  In short, it become even more restrictive.  You can try to blow out the trapped particles of a paper air filter, But you just can't get all that are lodged within the fibers.  With each successive cleaning, the paper gets more and more clogged over time/use.  Eventually, you have to replace it with new, to reset the collection process.

Whatever the carb inlet restriction, it effects the depth of carb throat vacuum.  More restriction means deeper vacuum.  The choke plates (when closed) also cause deeper vacuum, as it represents a very high restriction.
The fuel jets in the carburetor, all deliver into the throat vacuum at one end and have a fuel supply at the other end of a tube type device.  And just like if you suck harder on a straw in your beverage, more vacuum means a greater amount of fuel drawn through the jets, making the A/F ratio richer.
A foam replacement air filter usually presents less restriction than even a clean paper air filter, resulting in even less carb throat vacuum than a clean paper air filter. Reiterating, less throat vacuum equates to leaner A/F ratios given the same sized metering orifices (jets).

Back to your bike. 
Your bike probably needed rejetting (ideally) when the exhaust was changed.  Perhaps an old dirty air filter made the mixture richer to compensate (in effect, acting as partial choke).
The UNI filter removed inlet restriction and made the carbs even leaner.  So lean, that coupled with the exhaust restriction change, the A/F ratio moved well away from ideal and to the point that power is lost.

The Honda engineers fine tuned, jetted, and set up the carbs to accommodate the exhaust and inlet restrictions of the bike as delivered.  Since you are no longer using the stock components, you now have to fine tune, jet, and set up the carbs for the changes made. or restore the stock components.

The stock exhaust is pretty much unobtainium these days.  I suppose you could modify your current exhaust to emulate the stock exhaust restriction.  I would.  But then, I like quieter bikes, too.
You will eventually have to replace the stock air filter.   So, before you assume that the stock air filter cures your ills, get a new one and try that out.  Honda states that you should change it every 6 Months/6000miles.  This approach is far more expensive long term than the UNI reusable filter.

If I assume that restoring the exhaust system is not a favored option, I think I would opt for rejetting, set up, and tunning of the carbs to deliver what the engine needs for both the exhaust and filter changes, particularly if a new paper air filter emulates the same power loss as the UNI installation does.  But, I still think that the 77-78 CB550Ks need a jet job with exhaust changes, and more so with air filter changes.

As far a filter oiling, it sounds like you did it right.  The oil should NOT be a factor to add inlet restriction.  It is only there make particles stick to the foam instead of being injested into the engine.  When you wash out the filter oil at service intervals, the collected dirt washes away with it.  Then the dirt collection cycle is effectively reset to "as new".

Cheers,

[FLo]

The 77 and 78 CB550 were the first 550 models to fall under the perview of US EPA emissions requirements.  To achieve this using the same basic engine components, Honda decided to make the exhaust more restrictive and put more refined control of the idle mixture in the newly designed carbs.

A more restrictive exhaust had the effect of leaving more exhaust gases in the chamber to go through another combustion process.  This reduces unburned hydrocarbons released into the atmosphere.  The more refined control of idle mixture meant less hydrocarbons fed to the engine during idle.
The retained exhaust gases and hydrocarbons due to exhaust restriction meant less available oxygen for the next burn cycle and a need to reduce fuel delivery by the carburetors.  The carbs were then jetted to deliver a correct A/F ratio for the components as delivered by Honda.  The engine was happy as ran well.

Then owners changed things. 

The exhaust was replaced with one that has far less restriction, allowing more complete evacuation of the cylinders during the exhaust cycle.  Not only were there less hydrocarbons from the previous combustion cycle to burn, there was also more oxygen available in the chamber for combustion.  But, the carb still delivered fuel at the stingy rate that was required by the restricted exhaust, making the combustion mixture leaner.  The engine, while not exactly happy, still runs because there is a wide A/F ratio that still supports combustion, even if not ideal or one that makes best power.

The stock paper air filter has fibers interwoven to allow air passage, but traps tiny particles within the weavings.  As it traps these particles, air passageways are blocked, leaving less "tunnels" available for air passage within the filter mesh.
The fiber weavings when new, deflect the air inrush and cause it to turbulate.  And, the turbulation slows the air flow.  Most refer to this simply as air inlet restriction, which increases over time as the filter traps more particles.  In short, it become even more restrictive.  You can try to blow out the trapped particles of a paper air filter, But you just can't get all that are lodged within the fibers.  With each successive cleaning, the paper gets more and more clogged over time/use.  Eventually, you have to replace it with new, to reset the collection process.

Whatever the carb inlet restriction, it effects the depth of carb throat vacuum.  More restriction means deeper vacuum.  The choke plates (when closed) also cause deeper vacuum, as it represents a very high restriction.
The fuel jets in the carburetor, all deliver into the throat vacuum at one end and have a fuel supply at the other end of a tube type device.  And just like if you suck harder on a straw in your beverage, more vacuum means a greater amount of fuel drawn through the jets, making the A/F ratio richer.
A foam replacement air filter usually presents less restriction than even a clean paper air filter, resulting in even less carb throat vacuum than a clean paper air filter. Reiterating, less throat vacuum equates to leaner A/F ratios given the same sized metering orifices (jets).

Back to your bike. 
Your bike probably needed rejetting (ideally) when the exhaust was changed.  Perhaps an old dirty air filter made the mixture richer to compensate (in effect, acting as partial choke).
The UNI filter removed inlet restriction and made the carbs even leaner.  So lean, that coupled with the exhaust restriction change, the A/F ratio moved well away from ideal and to the point that power is lost.

The Honda engineers fine tuned, jetted, and set up the carbs to accommodate the exhaust and inlet restrictions of the bike as delivered.  Since you are no longer using the stock components, you now have to fine tune, jet, and set up the carbs for the changes made. or restore the stock components.

The stock exhaust is pretty much unobtainium these days.  I suppose you could modify your current exhaust to emulate the stock exhaust restriction.  I would.  But then, I like quieter bikes, too.
You will eventually have to replace the stock air filter.   So, before you assume that the stock air filter cures your ills, get a new one and try that out.  Honda states that you should change it every 6 Months/6000miles.  This approach is far more expensive long term than the UNI reusable filter.

If I assume that restoring the exhaust system is not a favored option, I think I would opt for rejetting, set up, and tunning of the carbs to deliver what the engine needs for both the exhaust and filter changes, particularly if a new paper air filter emulates the same power loss as the UNI installation does.  But, I still think that the 77-78 CB550Ks need a jet job with exhaust changes, and more so with air filter changes.

As far a filter oiling, it sounds like you did it right.  The oil should NOT be a factor to add inlet restriction.  It is only there make particles stick to the foam instead of being injested into the engine.  When you wash out the filter oil at service intervals, the collected dirt washes away with it.  Then the dirt collection cycle is effectively reset to "as new".

Cheers,

Thanks TwoTired for the very informative reply.  Very much appreciated.  I think then it's best to do the following:

1 - get the stock coils on, because I have them, to cure my battery drain
2 - stick with the uni but re-jet, since as you stated that changing to my mac 4-1 exhaust would require it.  Add this with the air filter mod, then it seems that re-jetting is unavoidable.  Plus the uni will save me money over time.

I think with my limited knowledge and only 1 year riding experience, I'm going to suck it up and got to a shop with dyno. However, here in Vancouver, they charge $85 per ride on the dyno -eek!!!! I think this will alleviate some frustration and time for the re-jet process.  At least with all the information I have collected on this board, I'll be well prepared to understand/assess what the mechanics are doing.  I'll report back on the jet size changes I've made so other people on this board can use it as a reference.  Give me a week or so, and I'll have a report for y'alls.

Thanks again especially to TwoTired and Eldar, Master for all your insight.

Also, if anyone knows of a good shop/mechanic in WA state who can save me some cash on the dyno, please let me know.  The border is only 20mins away.  Is there a section on this board for adverts/services by region?

[mutt]

thanks, Ttired.... I got hip to this early 70's carb problems when I built a XS650 bober for a gal I knew. She had a 79 to start with, & I thought te carbs wee way too small.
Rummaging thru a vast parts pile, & some shop books, I determined that 72  was the last year you wanted carbs for California imported machines as the screwball Ca emmissions really affected sound mechanical practice after that.
In order to limit what came out of the tailpipe, they limit what goes into the combustion chamber. And keep some of the burnt, previous charge in there as well.
Those old carbs woke that bike right up. much bigger venturis. Of course, I just had 2 to deal with, & not 4. But you chaps should take that into consideration, moreso if your bike was a California import....as sold, it designed to pass an arbitrary standard set by politicians. If you want it to run well, you have to undo the rube goldberg add-ons, restrictions, & limiters.....

[FLo]

Or, you could seek out a 750 guy that wants 3 ohm, have him get the 5 ohm versions and swap. 

I found the stock coils in a box the PO gave me with the bike.  Out of curiosity, I'm wondering how much I can sell these 3ohm coils for?

[Hush]

This has been good reading.
Flo my 650 has had "no balls" problems and I just fitted a new air filter and boy does she light up now so might be on the right track with your old air filter and when your problems started.....Hush.

[FLo]

This has been good reading.
Flo my 650 has had "no balls" problems and I just fitted a new air filter and boy does she light up now so might be on the right track with your old air filter and when your problems started.....Hush.

I miss my balls.  what kind of air filter? OEM, pod, uni or k&n?  I'll report on my progress as I get things rolling.

[Hush]

OEM and just fitting it changed my plugs from black carbon to light brown. Never imagined an air filter could make such a difference but these bikes do have sealed air boxes so guess unless the filter is breathing then the motor isn't.

[Deltarider]

The engine was happy as ran well.

I have test reviews here (Dutch and German) where these later model 550’s were critisised for not offering the same driveability as the former models with old-style carbs. New owners experienced this too. Then some owners changed things.
 
OK, below I pass on the information I gathered from filterspecialists. Years ago in a motorcycle magazine I read an interview with the director of a company that imports filters for motorcycles. The man concluded by the volumes he sold that the average rider took extreme care of his bike. He demonstrated this by calculating that he sold far more airfilters than necessary and he doubted whether people knew that by renewing their filters all the time ‘just to be sure and have the best’ wasted not only money but perfect filters too. It was in that interview I learned for the first time that contrary to popular belief a paper airfilter actually filters better when it gets older and is at its best, just before it clogs up.

The stock paper air filter has fibers interwoven to allow air passage, but traps tiny particles within the weavings.  As it traps these particles, air passageways are blocked, leaving less "tunnels" available for air passage within the filter mesh.The fiber weavings when new, deflect the air inrush and cause it to turbulate.  And, the turbulation slows the air flow.

A paper filter filters in three ways. Firstly by inertia. The air flows around a fiber. The heaviest particles cannot follow this track. Because of their inertia they collide with the filterfiber. The second way is the blocking effect. The somewhat lighter particles manage to follow the track of the airflow but hit the fiber sideways and so get blocked. The third way is by diffusion. The smallest particles can follow the airstream but by all kinds of accidental movements (turbulence) deviate nevertheless. When they contact a fiber, they get stuck. Diffusion is quite accidental. Enough filtermaterial and many thin fibers offer the ‘accident’ a helping hand.
In a filter not ony the fibers filter but also the already trapped particles. That’s why a new filter filters not as good as an used one. Although the filter during its lifetime traps more and more dirt, pressureloss-over-the-filter hardly increases if at all. It’s not before the filter is almost full of dirt, that pressureloss increases all of a sudden. Have a look at the picture below. It’s a scheme for a typical paper air filter’s lifetime and demonstrates that there’s no loss of pressure over the filter until… the very end of the filters lifetime. Then pressure loss over the filter increases dramatically. t1 actually is the ideal moment to replace the filter by a new one. BTW, on the horizontal axis it says trapped particles and on the vertical axis it says pressureloss.

You can try to blow out the trapped particles of a paper air filter, But you just can't get all that are lodged within the fibers.

But you don’t have to. Leave the trapped particles where they are, as they help your filter filter. 

Honda states that you should change it every 6 Months/6000miles.  This approach is far more expensive long term than the UNI reusable filter.Well those six months we have discussed before.

Well, those six months we have discussed before. I will not go into that again now, but it is nonsense. If you want to believe that, it’s fine with me. When Honda states that the filter should be renewed at the 6000 miles interval, it does not mean the filter has reached the end of its lifetime, it means that under average conditions Honda cannot guarantee the next complete 6000 miles. Honda didn’t have people like us in mind, that do maintanance themselves, but the average customer that goes to a dealer and after collecting his bike doesn’t want to go there again, that is not in the next 6000 miles. Where I live, I can do easily 12000 miles with a paper airfilter and it is still good. At David Silver Spares the filter for my CB500 will cost me US$ 23,97 (€ 19,04) for genuine and US$ 15,51 (€ 12,32)for a good imitation. I can change my paper airfilter in 10 seconds and that includes opening the seat, removing the tooltray, the cover etc. Why would I mess with a foam filter that can tear, is from new already inferior in it’s filtering performance and then have to mess with oil that makes me uncertain about how much or how little, where I can have the pleasure at acceptable cost to have the genuine thing that will give me 12000 miles of riding pleasure without ever having to think about it? I don’t know about prices in the US, but here are some current prices at David Silver Spares: CB 550K/F for a Genuine Honda US$ 24,68 or € 19,60. That's € 3,35 cheaper than Louis asks for an imitation! All genuine filters are available though Honda BTW and you'll find imitations in mailordershops like Louis.

[FLo]

Thanks Deltarider for the informative response.  I just ordered a paper OEM filter.  I'll report on it's performance once installed.  Thanks all for your insight.

FLo from Vancouver

[TwoTired]

I'm working on a response to DRs well written post.  Naturally, I can't agree with his inferred suppositions/conclusions.  And, the graph posted, while looking quite officious, completely ignores air velocity, which has a great deal of influence over pressure drop vs restriction, and is prominently featured in our SOHC4s

It's complex, and not easy to explain.  But, it is far more likely that his Dutch model air filter snorkel/restrictor interacts with his air filter longevity.  I'm still searching to find data on filter media permeability.  It simply has to change as it collects airborne debris.  Just when, during debris collection, that it becomes the most restrictive part of the entire inlet path, depends upon where the most restrictive element in the path resides and the velocities demanded.  (doesn't matter how big you make your throat, if you are breathing through a smaller diameter straw.)

More later...

Cheers,

[Deltarider]

Maybe this is an idea. When the maid was hoovering around the legs of my deskchair, I couldn't help noticing a tiny window on top of her vacuum cleaner. Whenever one of my papers would block her nozzle an orange coloured piece of plastic appeared in that window. Activated by underpressure, it's in fact an indicator that tells her when to replace the dustbag inside by a new one. Wouldn't it be nice if we had a similar indicator that informs us whether an airfilter element is still good or has reached the end of it's lifetime. I believe the type of plenum that's on my CB 500 offers a possibility for just that. Have a look at the picture of that plenum, if you will. At the bottom there's a small tube attached ment to drain any fluids from the plenum. What if I - temporary - extend that tube and attach a simple vacuummeter at it's end. I could go for a testride and check at various speeds and RPM's if there's any significant change in underpressure in the plenum. I could compare the values of a new element with those of the old ones I still have and proof they're still 'open' enough. Now I myself will not ride shortly (it's still too cold here) but if anybody wants to perform this experiment, I will be very interested in testresults. Just a tube and a simple manometer. If you have a set of manometers (to sync carbs), you could use one of those. Or am I talking crap and will differences be to small to notice?

[eldar]

I wont worry about the air filter debate much. Honda filters work just fine. I had an emgo style and while it filtered good, it restricted air too much. I dumped it with probably less than 3000 miles on it. It was like always having a choke on.
I decided after seeing a dealer want $35 for a paper filter, that I would spend less than double that for a k&n with oil and cleaner. So far the k&n has done great. yes I know that they have been shown in some instances to filter fewer small particles but I think I would rather have a nice running bike than a poor running one even if the change or dirt may be slightly higher. Maybe I will just stay off gravel roads.

I also know the whole "you will need to rebuild your engine sooner" thought but really, is there any actual road proof on this? Some here have been using a k&n for years and have thousands of miles and have not had to rebuild.
everyone has to go with what they think works best, even if there is no proof either way other than what you might think.

For the time being, I am going to the k&n camp and it has been good so far.