Topic: cb550 carb....jet HELP

[Pirateonjerseyshore]

So i have a 1977 cb550. I recently just got it back on the road from it's winter hibernation. I switched over to a 4 into 1 exhaust and pod filters. The exhaust has a baffle in it. I was told to go 2 jet sizes bigger, so i went from a main jet of 90 to 102's. It starts first kick every time and idles nice but runs terrible when you give it gas over 10 mph. Do i need to get them synced? I was told by 2 different sources to go up two jet sizes cause it wants more gas and told to go down two sizes because it's getting too much gas. I realize running with pods it will never be "perfect" but there has to be something i can do. Please help. Thanks in advance.

[LesterPiglet]

Do a search for pods on this forum. Arggghhhh. I can't be bothered. No offence.
Suffice to say I'm sticking with my airbox.

[dawdish]

Have you watched the "Two Guys Garage" video on youtube? Its about jetting a vintage Honda 4, cafe racer. They have some "relatively" easy tests to see if its lean.
I have to say, as a master technician (auto), and an old hot roder, I've had to deal with the same kind of "nay sayers" on modifying anything. I wish that they would just get over it, with the whole "air box" thing, and start being "helpful".

There are too many people out there that have done the exact same thing you and I have, whether for performance, the look, or, like me, missing parts, that have had success jetting their carbs.

So come on guys... start giving up some "good info" that help the rest of us not have to do SO much experimentation, and save some time and frustration.

[Pirateonjerseyshore]

Since i do use this bike to commute and the side covers are still in use, i decided to give up the look of the pods and put the stock air box back on. So now i have the 4 into 1 with the 102 jets and stock air box. Started right up and purred like a kitten. Throttle response was good in all rmp's and 2 min into the ride i couldn't keep it running. I took the air box cover off thinking it may need some more air and that did nothing. It also seems like the engine was running very hot.

[dawdish]

FROM; DO THE TON...

Quote
MAIN FUEL JET SIZE CHANGES NEEDED PER TYPICAL MODIFICATION:


Typical Exhaust Changes:

+2 main fuel jet size for custom 4-into-2 exhaust

or

+4 main fuel jet sizes for 4-into-1 exhaust

or

+4 main jet sizes for no muffler (open headers)


Typical Intake Changes:

+2 main fuel jet sizes for single K&N filter (inside a stock airbox)

or

+2 main fuel jet size for drilling holes in the airbox with stock filter

or

+4 main fuel jet sizes for individual pod filters (no airbox)



Additional changes:

- Add up all the main fuel jet size increases and subtract 2 sizes.

- Decrease main fuel jet size by 2 sizes per every 2000' above sea level.

- Under a mis-match condition, such as when using pod filters with a 100% stock exhaust, or 4-into-1 header with stock filter and air box, then subtract 2 main fuel jet sizes.


PILOT FUEL JET SIZES CHANGES NEEDED PER TYPICAL MODIFICATION:

Pilot fuel jet size changes are related only to the change in main fuel jet sizes according to the main fuel jet size formula described above. Note that this pilot fuel jet rule is for the main fuel jet size change BEFORE any main fuel jet altitude compensation is factored in:

Increase the pilot fuel jet size +1 for every +3 main fuel jet size increases.

Additional changes:

- Decrease pilot fuel jet size by 1 for every 6000' above sea level.



PRECAUTIONS:

- Make sure your carbs are in perfect working order before making jet changes....meaning fully cleaned internally and rebuilt, operating properly in their stock configuration, proper sized air jets and needles, etc. Otherwise, you'll like find that all of your efforts are going to be a HUGE waste of time.

- Check plug color often and adjust as needed, 2 main fuel jet sizes at a time and 1 pilot fuel jet size at a time. Bright white plug insulators are a sign of an overly lean fuel mixture condition and WILL cause damage to your engine over time, up to and including engine seizure!

- Synch the carbs after each jet change.

- Make sure the floats are set correctly

- Seriously consider purchasing a Colortune Plug Tuning kit.

- You may find it necessary to make changes to the size or shimming of the main jet needle. There are no guidelines on what or how to do these changes, this is true trial-and-error tuning!



EXAMPLE:

A 1982 XJ550RJ Seca using an aftermarket Supertrapp 4-into-1 exhaust and a single K&N air filter in the stock, unmodified airbox. Bike is primarily operated at an altitude of 2600 feet above sea level.

XJ550 Seca Stock Mikuni BS28-series Carb Jetting:

#112.5 Main Fuel Jet
#35 Pilot Fuel Jet
#70 Main Air Jet
#170 Pilot Air Jet
4GZ11 Needle


MAIN FUEL JET SIZE CALCULATIONS:

Changes made:

Exhaust:
4 into 1 with Supertrapp = +4 Sizes Main Fuel Jet

Intake:
K&N Pod Filters = +4 sizes Main Fuel Jet
----------------------------
Equals: +8 main fuel jet sizes above baseline
Subtract: -2 main fuel jet size per formula above
----------------------------
Equals: +6 main fuel jet sizes due to modifications, thus:

Stock main fuel jet size is: #112.5
+ 6 additional sizes
= a #118.5 main fuel jet size
---------------------------
Subtract: -2 main fuel jet sizes for Altitude of 2500' Average

= #118.5 calculated from above
-2 jet sizes for altitude adjustment

= a #116.5 main fuel jet size.


PILOT FUEL JET SIZE CALCULATIONS:

The formula is: +1 pilot jet size increase for every +3 main jet sizes increased.

Stock pilot fuel jet size is: #35
+ 2 additional jet sizes (since we went up +6 main fuel jet sizes before the altitude compensation was factored in):

= a #37 pilot fuel jet size.

Note that no altitude compensation is needed on the pilot fuel jet since our elevation is less than 6000' a-s-l.

[bollingball]

 Quote from dawfish There are too many people out there that have done the exact same thing you and I have, whether for performance, the look, or, like me, missing parts, that have had success jetting their carbs.

If this is true why not ask one of these many people. Maybe everyone with bikes with pods that run as good or better than those with the stock box should start a common thread on this site.
  To be sure a master tech and old hot roder could tell them what they need to do. I think there are just to many variables from bike to bike and altitudes to tell someone do this and put this in and your bike will run as good or better as a stock one.
Pirate If you have not done a synced then yes do it.

Ken

[crazypj]

550 F or 550K?
77 'F' isn't too bad to do, need to DROP needle, adjust fuel level, re-drill emulsion tubes with some extra holes (0.012"~0.016" drill, I forget exactly which)
 If it's a 'K', stock airbox works best
I had F1, F2 and K3 at the same time in 79 or 80
I gave up on the K and put it back stock (then sold it to my brother  )

[dawdish]

I agree, there should be a common thread. And yes there are huge variables. But there are some common directions to go to get started, and then others can add what worked for them. Rather than what seems to be the "default" reply, " go back to the stock air box", which for many of us, is not desirable.
Yea, I have huge experience with rods and sports cars, not so much with sohc4's, but setting up Webers or 6 packs on V8s, or multiples on sports cars, is no joy ride. I guess what I'm saying is, there is enough info out there on this forum, to be more helpful, and less discouraging.

[KC3]

Well, I hate to say it, but my bike runs the best it ever has with pods on it right now (according to my butt dyno). I have a '76 cb550 F with 4 into 1 exhaust, PD carbs with uni foam filters. Running #115 mains and the rest of the carb setup is stock config. I also sport Outerwears pre-filters in case of rain, but I keep them on all the time as they help with dust and sand.

That being said, I would recommend either staying with the stock airbox or taking the time to correctly re-jet for pods.

Too many people think they can just throw some pods on and step the jets up a few sizes and be done with it. That is never the case. If you aren't prepared to do it right and spend some serious man-hours tuning, then stick with the stock airbox. You will have more time to ride that way and less of a hassle whilst doing so!

In my case, I have nothing better to do, and I love tinkering; so I went with pods and loved every minute of tuning for them! In fact, I am now considering changing to velocity stacks just to give me something else to do with my copious amounts of free time.

[bollingball]

Well, I hate to say it, but my bike runs the best it ever has with pods on it right now (according to my butt dyno). I have a '76 cb550 F with 4 into 1 exhaust, PD carbs with uni foam filters. Running #115 mains and the rest of the carb setup is stock config. I also sport Outerwears pre-filters in case of rain, but I keep them on all the time as they help with dust and sand.

That being said, I would recommend either staying with the stock airbox or taking the time to correctly re-jet for pods.

Too many people think they can just throw some pods on and step the jets up a few sizes and be done with it. That is never the case. If you aren't prepared to do it right and spend some serious man-hours tuning, then stick with the stock airbox. You will have more time to ride that way and less of a hassle whilst doing so!

In my case, I have nothing better to do, and I love tinkering; so I went with pods and loved every minute of tuning for them! In fact, I am now considering changing to velocity stacks just to give me something else to do with my copious amounts of free time.

  This is the way it should be taken on lots of time and enjoy wrenching. Not for a newbie and your only means of transportation.
 I am not 100% against pods if I end up with a cheap second bike I would probably try it just for fun. The only common direction i see is changing jets. But what size? If you get it correct the first time I would call it luck close is not good enough for me. Best to take a pocket full of jets (and money) and buy some dyno time.
 I don't understand why this info can not be all together in one easy place to find all pod issues or maybe it has I have not looked for it because I have no need

Ken

[2manycbs]

Hi, I have a 75 cb550k with a mac 4 into 1 and pods.  I went with the dynatech electronic ignition.  The stock jet size is 100 main, and 38 low speed.  Make sure your ignition is working well and the plug gap is good.  Check the resistance on your plugs to make sure they are all equal.  If the bike has been setting and one of the plugs got a little fouled it will get more resistance and really weaken the plug.  You can't really clean them once they burn.  Double check the stock jetting sizes on your bike.  I would not go over one step on both initially.  The most important thing is to make sure everything else is right before adjusting your carbs.  Check for vacuum leaks by spraying wd-40 around the intake boots also.  The stock jets worked good in mine, but I am going one step up to 105 and 40.  Sounds like you have a vacuum leak and plug issues.  Good luck.

[LesterPiglet]

I have to say, as a master technician (auto), and an old hot roder, I've had to deal with the same kind of "nay sayers" on modifying anything. I wish that they would just get over it, with the whole "air box" thing, and start being "helpful".

So come on guys... start giving up some "good info" that help the rest of us not have to do SO much experimentation, and save some time and frustration.

I hope I didn't come across as a "nay sayer" as you say. I was trying to put across that I like an easy life and couldn't be bothered with the hassle of endless plug chops and re-jetting.

[dawdish]

I have to say, as a master technician (auto), and an old hot roder, I've had to deal with the same kind of "nay sayers" on modifying anything. I wish that they would just get over it, with the whole "air box" thing, and start being "helpful".

So come on guys... start giving up some "good info" that help the rest of us not have to do SO much experimentation, and save some time and frustration.

I hope I didn't come across as a "nay sayer" as you say. I was trying to put across that I like an easy life and couldn't be bothered with the hassle of endless plug chops and re-jetting.

Ah have mercy...It's just that I've read it over and over again. I hope the post I made of general changes needed for certain mods will be helpful. I know now I dont have to spend 50-75 bucks on jets.

[Pirateonjerseyshore]

Thank you all for the responses.  I appreciate it and will be in touch on my results in a few days.

[KC3]

Well, I hate to say it, but my bike runs the best it ever has with pods on it right now (according to my butt dyno). I have a '76 cb550 F with 4 into 1 exhaust, PD carbs with uni foam filters. Running #115 mains and the rest of the carb setup is stock config. I also sport Outerwears pre-filters in case of rain, but I keep them on all the time as they help with dust and sand.

That being said, I would recommend either staying with the stock airbox or taking the time to correctly re-jet for pods.

Too many people think they can just throw some pods on and step the jets up a few sizes and be done with it. That is never the case. If you aren't prepared to do it right and spend some serious man-hours tuning, then stick with the stock airbox. You will have more time to ride that way and less of a hassle whilst doing so!

In my case, I have nothing better to do, and I love tinkering; so I went with pods and loved every minute of tuning for them! In fact, I am now considering changing to velocity stacks just to give me something else to do with my copious amounts of free time.

  This is the way it should be taken on lots of time and enjoy wrenching. Not for a newbie and your only means of transportation.
 I am not 100% against pods if I end up with a cheap second bike I would probably try it just for fun. The only common direction i see is changing jets. But what size? If you get it correct the first time I would call it luck close is not good enough for me. Best to take a pocket full of jets (and money) and buy some dyno time.
I don't understand why this info can not be all together in one easy place to find all pod issues or maybe it has I have not looked for it because I have no need
Ken

I agree. Perhaps we should start a thread (or maybe I should) for people that have had good results with pods or velocity stacks. Then people considering the change could then find a bike that is set up fairly similar to theirs and have a good starting point for jet sizes in particular. It will obviously be just that; a starting point, but it would help get them closer to the right point than a complete shot in the dark. I know that I bought at least $75 of jets that I will never use... so hopefully someone else could save a few bucks and get some more time to ride...any thoughts??

[dawdish]

Well, I hate to say it, but my bike runs the best it ever has with pods on it right now (according to my butt dyno). I have a '76 cb550 F with 4 into 1 exhaust, PD carbs with uni foam filters. Running #115 mains and the rest of the carb setup is stock config. I also sport Outerwears pre-filters in case of rain, but I keep them on all the time as they help with dust and sand.

That being said, I would recommend either staying with the stock airbox or taking the time to correctly re-jet for pods.

Too many people think they can just throw some pods on and step the jets up a few sizes and be done with it. That is never the case. If you aren't prepared to do it right and spend some serious man-hours tuning, then stick with the stock airbox. You will have more time to ride that way and less of a hassle whilst doing so!

In my case, I have nothing better to do, and I love tinkering; so I went with pods and loved every minute of tuning for them! In fact, I am now considering changing to velocity stacks just to give me something else to do with my copious amounts of free time.

  This is the way it should be taken on lots of time and enjoy wrenching. Not for a newbie and your only means of transportation.
 I am not 100% against pods if I end up with a cheap second bike I would probably try it just for fun. The only common direction i see is changing jets. But what size? If you get it correct the first time I would call it luck close is not good enough for me. Best to take a pocket full of jets (and money) and buy some dyno time.
I don't understand why this info can not be all together in one easy place to find all pod issues or maybe it has I have not looked for it because I have no need
Ken

I agree. Perhaps we should start a thread (or maybe I should) for people that have had good results with pods or velocity stacks. Then people considering the change could then find a bike that is set up fairly similar to theirs and have a good starting point for jet sizes in particular. It will obviously be just that; a starting point, but it would help get them closer to the right point than a complete shot in the dark. I know that I bought at least $75 of jets that I will never use... so hopefully someone else could save a few bucks and get some more time to ride...any thoughts??

Yea, KC3, its a great idea. I'm using the info I posted here, and I just ordered jets for both my 400, and my 500, from Dime City. I'll keep you posted on my progress.

[dawdish]

Got my jets today, from DCC. I bumped the mains from 100 to 115, and lifted the needle from the top notch to the middle notch. Wow what a difference! Is it perfect probably not, but a great starting place. So right now I have to say the formula works well.

Some stats. 
CB500, pod filters, 4 into 2 with pea shooters, elevation 5800 ft +/-

[minimo]

dawdish, I was curious about your reference as it seems to be adopted from the one originally created by Denny Zander on the XS11 forum.
Your formula is a little different...

Using Zander's formula, the guidelines for my '77 CB550F would be to use the following:

+2 main jet, 4 into 1 exhaust
+3 main jet, individual pods
"Add up all the jet size increases and subtract one."
+1 pilot jet, for every 3 increase on main jet

Which further translates to, according to Zander's guidelines:

2 + 3 (-1) = 4 sizes up from stock main jet (98 for '77 550F)
MAIN JET: 115

Stock slow jet for the '77 550F is 38. One size up would make it 40.
SLOW JET: 40

Using the formula you referenced gives me slightly different results:

+4 main jet, 4 into 1 exhaust
+4 main jet, individual pods
"Add up all the main fuel jet size increases and subtract 2 sizes"
+1 pilot jet, for every 3 increase on main jet

4 + 4 (-2) = 6 sizes up from stock
MAIN JET: 125
SLOW JET: 42

Any success stories on which formula is the more adaptable one (specifically for a '77 550F - 'cos so far, the Zander one ain't working too well at the mo')?

FROM; DO THE TON...

Quote
MAIN FUEL JET SIZE CHANGES NEEDED PER TYPICAL MODIFICATION:

Typical Exhaust Changes:

+2 main fuel jet size for custom 4-into-2 exhaust

or

+4 main fuel jet sizes for 4-into-1 exhaust

or

+4 main jet sizes for no muffler (open headers)

Typical Intake Changes:

+2 main fuel jet sizes for single K&N filter (inside a stock airbox)

or

+2 main fuel jet size for drilling holes in the airbox with stock filter

or

+4 main fuel jet sizes for individual pod filters (no airbox)

Additional changes:

- Add up all the main fuel jet size increases and subtract 2 sizes.

- Decrease main fuel jet size by 2 sizes per every 2000' above sea level.

- Under a mis-match condition, such as when using pod filters with a 100% stock exhaust, or 4-into-1 header with stock filter and air box, then subtract 2 main fuel jet sizes.

PILOT FUEL JET SIZES CHANGES NEEDED PER TYPICAL MODIFICATION:

Pilot fuel jet size changes are related only to the change in main fuel jet sizes according to the main fuel jet size formula described above. Note that this pilot fuel jet rule is for the main fuel jet size change BEFORE any main fuel jet altitude compensation is factored in:

Increase the pilot fuel jet size +1 for every +3 main fuel jet size increases.

Additional changes:

- Decrease pilot fuel jet size by 1 for every 6000' above sea level.

PRECAUTIONS:

- Make sure your carbs are in perfect working order before making jet changes....meaning fully cleaned internally and rebuilt, operating properly in their stock configuration, proper sized air jets and needles, etc. Otherwise, you'll like find that all of your efforts are going to be a HUGE waste of time.

- Check plug color often and adjust as needed, 2 main fuel jet sizes at a time and 1 pilot fuel jet size at a time. Bright white plug insulators are a sign of an overly lean fuel mixture condition and WILL cause damage to your engine over time, up to and including engine seizure!

- Synch the carbs after each jet change.

- Make sure the floats are set correctly

- Seriously consider purchasing a Colortune Plug Tuning kit.

- You may find it necessary to make changes to the size or shimming of the main jet needle. There are no guidelines on what or how to do these changes, this is true trial-and-error tuning!

EXAMPLE:

A 1982 XJ550RJ Seca using an aftermarket Supertrapp 4-into-1 exhaust and a single K&N air filter in the stock, unmodified airbox. Bike is primarily operated at an altitude of 2600 feet above sea level.

XJ550 Seca Stock Mikuni BS28-series Carb Jetting:

#112.5 Main Fuel Jet
#35 Pilot Fuel Jet
#70 Main Air Jet
#170 Pilot Air Jet
4GZ11 Needle

MAIN FUEL JET SIZE CALCULATIONS:

Changes made:

Exhaust:
4 into 1 with Supertrapp = +4 Sizes Main Fuel Jet

Intake:
K&N Pod Filters = +4 sizes Main Fuel Jet
----------------------------
Equals: +8 main fuel jet sizes above baseline
Subtract: -2 main fuel jet size per formula above
----------------------------
Equals: +6 main fuel jet sizes due to modifications, thus:

Stock main fuel jet size is: #112.5
+ 6 additional sizes
= a #118.5 main fuel jet size
---------------------------
Subtract: -2 main fuel jet sizes for Altitude of 2500' Average

= #118.5 calculated from above
-2 jet sizes for altitude adjustment

= a #116.5 main fuel jet size.

PILOT FUEL JET SIZE CALCULATIONS:

The formula is: +1 pilot jet size increase for every +3 main jet sizes increased.

Stock pilot fuel jet size is: #35
+ 2 additional jet sizes (since we went up +6 main fuel jet sizes before the altitude compensation was factored in):

= a #37 pilot fuel jet size.

Note that no altitude compensation is needed on the pilot fuel jet since our elevation is less than 6000' a-s-l.