Author Topic: 76 550 top gear rev problem  (Read 6732 times)

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Offline FIREBLADE74

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Re: 76 550 top gear rev problem
« Reply #50 on: May 02, 2017, 04:50:16 PM »
Ok, now we're cooking with fire. Runs exceptionally well, can get 5th gear to 80 mph and it slowly climbs, I guess this is normal.

RAF, my petcock was fvcked, tube broke and was floating around in the tank. Drained the tank and noticed one side stopped before the other. I think the spark plug caps contributed to most of the problems.

Also, I have those cheap pods that is like running with nothing on the carbs. I got some unis coming in.

Overall, Id like to thank you guys for all the help and I will be posting a video of how she runs as of now.

Stay tuned...
06 CBR1000RR, 76 CB550

Offline FIREBLADE74

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Re: 76 550 top gear rev problem
« Reply #51 on: May 02, 2017, 05:02:53 PM »
Check the video and let me know if something sounds funny.


06 CBR1000RR, 76 CB550

Offline DaveBarbier

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Re: 76 550 top gear rev problem
« Reply #52 on: May 02, 2017, 06:40:26 PM »
Given that I'm listening on a phone, your bike doesn't sound bad at all.

One thing to consider is that with pods you may experience some issues at high speeds due to turbulent air. One thing the airbox does is protect the carbs from cross winds and such. But even with velocity stacks with no filter material I didn't have any noticeable issue going 90+

Offline BomberMann650

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Re: 76 550 top gear rev problem
« Reply #53 on: May 02, 2017, 07:24:29 PM »
The fifth gear is a long one.  Rolling on from 65/70 won't have much wow factor.
But 4th gear will go the distance with some added torque.  Take fourth up to 80/85, then shift for 5th and you'll get to the hundred from there.

The 550's will cruise at 75/80 in 5th all day.  And they'll do it smooth so long as everything is in tune. 

Glad ya got it all sorted, enjoy the summer!

Offline TwoTired

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Re: 76 550 top gear rev problem
« Reply #54 on: May 02, 2017, 07:30:17 PM »
Ok, now we're cooking with fire. Runs exceptionally well, can get 5th gear to 80 mph and it slowly climbs, I guess this is normal.

80 is routine.  It shouldn't show any signs of slow acceleration until about 90.

Also, I have those cheap pods that is like running with nothing on the carbs. I got some unis coming in.

You have the stock exhaust.  Why oh why do you not use the stock air box and filter?
The carbs are tuned for that air box and exhaust and runs famously with that combination.

With pods you are now looking at a carb rejet.  Pods alter the carb throat pressure, raising it closer to atmospheric.  The difference in pressure between the outside atmosphere and the carb throat is what pushes fuel through the carb's fuel orifices.

Picture a tube where vacuum is presented at one end.   At the tubes inlet end, the pressure is normal outside atmospheric.  Half way down the tube there is half the vacuum as what is presented.  Even while there is airflow there, is still a pressure drop within the tube.   This is called pressure equalization.  Low pressure at one end is equalized by the higher pressure at the other end.  Block the tube's inlet and the whole tube experiences source vacuum all along it's length.  Alternately, shut off the source vacuum end and the whole tube will experience the pressure presented at it's inlet.

The bike's intake was made with a length of tube.  Vacuum is presented by the falling piston at the intake valve seat end of the tube.   Air is sourced at the inlet of the air box and that length is about a foot and a half-ish.  The carb throat is also part of the tube and located about 1/3 the distance between the intake valve seat and the filter box inlet.

For simplicity, lets say the carb fuel jets are being pushed by 2/3 (66%) of what the falling piston develops, since it is 2/3rds the distance between the vacuum source and the inlet supply. ( It is closer to the vacuum source.)

Now take off the air box and put pods directly onto the carb inlets.  The inlet supply tube has now been shortened by nearly 2/3rds.  The carb throat is now about 2 inches away from atmospheric pressure air supply and about 8 inches away from the source vacuum presented.  The carb throat fuel jets now sees about 2/8th of the supplied vacuum or about 25% of what it saw with the stock air box arrangement.  From 66% of source vacuum to 25% of source vacuum is a loss of fuel flow push force of 41%.  All the carbs fuel jet orifices will experience a reduced flow fuel.  Pods do not present any less air volume than the stock air box for upwards of 3/4 or more of the engine's RPM range.  But, all pods shorten the inlet duct and alter the pressures by which the factory set the jet sizes in the carbs.  A 41% drop in available fuel pressure flow force necessitates increasing all the fuel orifice sizes to compensate for the loss of throat pressure differential induced by pod's intake runner length shortening.  In other words, pod conversion routinely demands a carb re-jett and re-tune.

Pods MAY allow more air flow volume than the stock airbox at RPMs hovering around Red line.  At all RPM ranges below7/8 of redline, the stock filter and box arrangement supply equal volumes of air compared to any pod filter.  The engine only demands just so much.

There are also other issues of turbulent air reaching into the carb throat upsetting the fuel orifice exit ports.  This is what the velocity stack portion of the stock air box address. 


Looked at your video.
FYI: The tank color is original for that year model.  Looks like a pretty nice survivor of the era.  I have the same model in orange.  Stock exhaust and air box.  It gets to 95 mph pretty easily even with a Vetter Quicksilver fairing fitted to it.  But, then the air drag resistance starts to demand more HP than the motor can produce.
... and it get 50 MPG.  I've never heard of any pod altered 550 getting close 50 MPG.  This speaks the power plant's overall efficiency of the model.

When new, the prices for the F and K model were nearly the same.  The difference is in the styling. Motors are the same for each model.  But, I think the F models were a bit lighter, due to the exhaust system difference.

Best of luck with your 550.
Don't see why you are unhappy with the stock airbox. Lots of engineering dollars and work went into that design.  Shame to throw it away.  But, if it's for sale, do let me know.  I think I have a project bike that can use it.

Do count the sprocket teeth for the drive chain.  Many cases where taller sprocket ratios were used, when the owner didn't like the higher cruise RPM compare to other bikes.   This actually diminishes the top speed capability, since there is no extra power provided to compensate and the ratio's mechanical advantage is diminished.

Cheers,
Lloyd
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline flatlander

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Re: 76 550 top gear rev problem
« Reply #55 on: May 03, 2017, 03:18:04 AM »
your video sounds fine.
listen to TT, he really knows what he's talking about. to add to his recommendation towards the stock airbox: with your stock 4-1 exhaust, that one is your limiting factor in terms of flow. you won't have any benefit from the pods so why bother faffing around with them?
in the stock airbox, the stock paper filter beats the aftermarket foam replacements (uni) in terms of flow. i tested them against each other on the dyno.

Offline 754

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Re: 76 550 top gear rev problem
« Reply #56 on: May 03, 2017, 04:45:19 AM »
Sounds a lot like low compression...
Maker of the WELDLESS 750 Frame Kit
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Lost quite a few CB 750's along the way

Offline flatlander

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Re: 76 550 top gear rev problem
« Reply #57 on: May 03, 2017, 05:09:57 AM »
how can you tell, from the video sound that may not be super realistic?
not questioning, genuinely interested.

Offline flybox1

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Re: 76 550 top gear rev problem
« Reply #58 on: May 03, 2017, 07:02:17 AM »
Checked out your vid.  Its good to see another bike resurrected.  Good work Fireblade.  8)
Pods certainly make getting the carbs off an easier task, but consider the airbox.  Its not all that bad for a sweet running bike.
TT is correct, if you stick with pods, a rejet will be needed.
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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Offline 754

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Re: 76 550 top gear rev problem
« Reply #59 on: May 03, 2017, 10:00:50 AM »
Flatlander , were you asking me ?
 I am/was riding one with low compression.. No tuning will restore lowered compression.. If it only has 75 percent if the compression it should have, it cant hit normal top speed...its worn.
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline flatlander

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Re: 76 550 top gear rev problem
« Reply #60 on: May 03, 2017, 10:30:26 AM »
yes, was asking you ;)

Offline FIREBLADE74

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Re: 76 550 top gear rev problem
« Reply #61 on: May 03, 2017, 12:39:43 PM »
With 6k miles I figured compression would be good but I don't know how those miles were acquired, damn.

I did rejet to 110 mains. I think these unis will help if not I'm thinking of a 2 piece stock airbox, much like most cars. I'm anal about dirt in bowls so I like to pull them to inspect but with that stock airbox... forget it lol
06 CBR1000RR, 76 CB550

Offline flatlander

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Re: 76 550 top gear rev problem
« Reply #62 on: May 03, 2017, 01:28:24 PM »
you can remove the bowls with the carb rack in place.

Offline RAFster122s

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Re: 76 550 top gear rev problem
« Reply #63 on: May 03, 2017, 01:49:28 PM »
There is an FAQ on the 550 that tells you how to pull the carb rack.  New boots to the intake manifold are worth the investment, makes the job much easier.

Replace your carb float bowl screws with button head socket screws and you can drop the float bowls much easier.  Even on the side of the road if so inclined, provided that you packed that wrench in your tool kit.

Another downside of pods will be in rain, they can ingest water and when they get wet their draw of fuel changes drastically.  They can strand you.

You will lightly oil the Uni-s, but don't oil them too heavily...  I think you have Emgo pods.  They are merely decorative as you say.  Sell them on ebay or throw them away or give them to an enemy, someone you don't like.

Far less work and classic looks to stay with stock airbox.  For a stock motor you will not see any improvement in anyway using the pods.  They can be a real bear to tune and jet with pods on a stock motor.  A modified motor presents different requirements as well as having higher fuel needs...there are experienced folks who have jetted for pods on modified motors...

Very pretty Candy Sapphire Blue bike.  A very nice survivor that will clean up and polish up nicely.  You picked it up in Charlotte, so where are you located?  Is that NC or VA...from your accent and southern drawl I think it is likely you are from NC or maybe SC.
TwoTired is really one of the most knowledgeable 550 guys on this forum.  It is good to have him back with us, I have missed him.

A PO has painted the front headlight ears black, they were chrome.

If removing the side covers is stiff, do yourself a favor and buy some new grommets for the side covers, they will go on without any struggle and you will not risk breaking them getting them on or off.

Take care Riley...until your next update...
David- back in the desert SW!

Offline FIREBLADE74

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Re: 76 550 top gear rev problem
« Reply #64 on: May 03, 2017, 02:13:09 PM »
Raf, I'm definitely a Carolina boy South, can't get rid of that drawl for hell.

TT, I appreciate your wisdom and I still have the stock stuff. If these unis doesn't work I'm going back to stock everything.

Stay tuned... I will update so that someone else struggling may find the answers they seek.
06 CBR1000RR, 76 CB550

Offline evinrude7

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Re: 76 550 top gear rev problem
« Reply #65 on: May 04, 2017, 06:16:37 AM »
a little silicone spray on the side cover grommets helps with installing/removing side covers. 
cb750 k6 - ugly

Offline FIREBLADE74

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Re: 76 550 top gear rev problem
« Reply #66 on: May 06, 2017, 10:03:31 AM »
Ok, got the unis on and wow! Now I can feel 5th pulling away from 80, winds were gusting to 20mph so I couldn't really run it like wanted to and record.

So to anybody going with pods don't skimp out, get quality brands!!!

Also does that tacky oil fvck with the carbs?
I only oiled the outside, I figured the sucking would pull in the oil.

Either way I'm happy, I'll post a video as soon as these windy days die down. Thanks again fellas for all your help!!!

06 CBR1000RR, 76 CB550

Offline TwoTired

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Re: 76 550 top gear rev problem
« Reply #67 on: May 06, 2017, 11:52:47 AM »
A foam filter functions on the principle of the "tortured path".  Yeah kinda made up that term.  But it applies pretty well.

The filter's base filtering rating is related to the size of the cell bubbles that comprise the foam membrane.  Generally nothing can get past unless it fits through tiny holes.  Most bugs, plant, and dirt flakes will pile up on the outside.  This, of course, is better than having the engine ingest them.

On to the next level of particulate matter; finer abrasive dust/sand, etc.
You'll note that seeing through the filter membrane is difficult at best.  This is because the open cell foam structure does not reveal line of sight pathways.  And this is the reliant principle by which all foam filters operate.  Air cannot take a straight through pathway through the filter membrane.  It has to twist and turn to get to the other side.  The mass of the dirt particles is heavier than air molecules, and so have a difficult time changing direction of travel.  The particles then collide with the foam cell structure and hopefully stick.  This is where the oil comes in.  Particles are more readily trapped by an oil whetted adhesive surface.

Of note, is that foam filters are what is termed "statistical" filters rather than absolute filters.  The foam pathways are bigger than almost all dust particles.  But, they statistically trap most particles due to oil's adhesive properties, and the "tortured path" they are forced to take through the membrane.  Since the oil is a functional part of the foam filter system, a thin but pervasive coat throughout the membrane is desired.  But, note, there is no guarantee that it will trap ALL particles which are smaller than the size of the cells in the structure.

Also, they are not install and forget.  The dirt and oil must be cleaned out periodically in relation to whatever dusty environments you operate within.  Dirty foam can dislodge the trapped particles with shock and/or oil's adhesive fatigue.  Then it dumps the oiled globs of dirt into the intake for ingestion.  Not a good thing.  So, it is best to stay on top of the cleaning cycles.

In the environment I'm used to (CA bay area), we have low particulate laden air.  So, I've been using the UNI foam filter inside the stock air box now for decades.  I've noted that summer use requires more frequent filter cleaning cycles than in winter months.

With my move to Arizona, I will have to revisit my foam cleaning schedule and perhaps return to the more expensive Paper filters, which guarantee finer particle collection at the expense of more frequent replacement schedules, due to not being able to effectively clean them after some use.

Lastly,  the foam DOES deteriorate with age, at which point bits of foam, clean or dirty, pass through the engine cylinder on it's way to the exhaust with varying degrees of abrasiveness.   This occurs with UNI foam whether its a POD type or the air box element.  This is best found during a clean/re-oil process.  Rather than years of in situ use.  In my experience, 10-15 years is the service life, with proper cleaning solvents and correct oil use.

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline turboed13b

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Re: 76 550 top gear rev problem
« Reply #68 on: May 06, 2017, 02:26:05 PM »
It doesn't really matter what kind of intake you run once you jet it correctly they will all run the same. A lot of people on here are hardcore antipod and I am not sure why because they work perfectly fine.

With that said you can't run the unis in the rain you will have a bad time.

Offline FIREBLADE74

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Re: 76 550 top gear rev problem
« Reply #69 on: May 06, 2017, 03:26:55 PM »
TT, wonderful explanation, thanks!!

Turboed, I almost never get caught in the rain knock on wood. As for anypods working I have to disagree even with proper jetting I was having problems with the regular pods and based on TT explanations I think it's the tortured air path that put me in the game!!!
06 CBR1000RR, 76 CB550

Offline turboed13b

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Re: 76 550 top gear rev problem
« Reply #70 on: May 06, 2017, 09:08:05 PM »
I have plenty of bikes working on pods and run just as smooth as stock. It takes a while to learn how to tune and many people give up way too quickly.

Offline FIREBLADE74

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Re: 76 550 top gear rev problem
« Reply #71 on: May 07, 2017, 03:13:57 PM »
Geezus! Only getting 80 miles to reserve.

Is this normal?
06 CBR1000RR, 76 CB550

Offline TwoTired

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Re: 76 550 top gear rev problem
« Reply #72 on: May 07, 2017, 04:07:17 PM »
How tall is your stand pipe?

How much fuel did you put in for a fill up?

Didn't you say you found problems with something floating inside the tank?

Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline FIREBLADE74

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Re: 76 550 top gear rev problem
« Reply #73 on: May 07, 2017, 06:33:06 PM »
How tall is your stand pipe?

How much fuel did you put in for a fill up?

Didn't you say you found problems with something floating inside the tank?

New stand pipe, it appeared to be the same as the one that was broken.

I put in about 3.76 gallons.

The problem was the stand pipe broke off from the petcock and was floating in the tank, it has been fixed.

I will say that I am pretty aggressive towards the throttle, lol. I filled up today and not even 2 miles from the gas station I get a nail in my tire, smh! I will ride more civilized once I get the tire replaced and see if I can get at least 100 miles to reserve.

What is the average to reserve? Also I run 89.
06 CBR1000RR, 76 CB550

Offline BomberMann650

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Re: 76 550 top gear rev problem
« Reply #74 on: May 07, 2017, 07:28:43 PM »
80 miles on reserve is ~2 gallons - that's nothing to scoff at!

2.5 gallon fill up for bloo.  ~100 miles on main fuel