Author Topic: Idea- Carb jetting database  (Read 5056 times)

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Offline Jonesy

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Idea- Carb jetting database
« on: January 10, 2006, 03:17:09 PM »
I saw this on another website and thought it might be a good idea. They had the members put down what kind of bike they had, along with all the jetting info and any mods that were done. This way someone could find a similar setup and have a good starting point for jetting based on what's worked for others. An example would be:

Bike: CB750K3
Year: 1973
Carb: Stock KeiHin
Main: 110
Idle (slow): 40
Needle clip position: 4
Plugs: NGK D8EA
Airbox: Stock
Air Filter: Stock
Exhaust: Stock HMC 341
Camshaft: Stock
Displacement: 736cc (stock)

Think something like this would be of value? We could keep it as a thread and when a good number of folks have filled it in, we could make it an FAQ.
« Last Edit: January 11, 2006, 05:26:01 AM by Jonesy »
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Offline SteveD CB500F

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Re: Idea- Carb jetting database
« Reply #1 on: January 11, 2006, 05:11:50 AM »
That's quite a good idea and may work alongside the FAQs we have on standard setups for the different carbs.

I have tried this with tyres (spellcheck says OK!) and oil filters.  After an initial rush (usual suspects) it fades away into the background and vanishes from view.

Worth a try though!

(Sorry, I can't tell you what's in my bikes - they are both stock and never been apart (not by me anyway)
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Offline Jonesy

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Re: Idea- Carb jetting database
« Reply #2 on: January 11, 2006, 05:24:34 AM »
I have tried this with tyres (spellcheck says OK!) and oil filters. After an initial rush (usual suspects) it fades away into the background and vanishes from view.

Hmmm... 45 looks and no responses (other than Steve). I hope those that looked are out looking at thier bikes to see what they have and report back...
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Offline Bob Wessner

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Re: Idea- Carb jetting database
« Reply #3 on: January 11, 2006, 06:07:49 AM »
I too think it would be a good idea.

Along these lines, this, in addition to cbjunkies thoughts about a standard maintenance table for new members/bike owners without a manual, is there anyway to set-up an updateable table for members to "fill in the blanks" on things like this?
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Offline Jonesy

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Re: Idea- Carb jetting database
« Reply #4 on: January 11, 2006, 07:08:15 AM »
Exactly what I was thinking of, Bob.
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Re: Idea- Carb jetting database
« Reply #5 on: January 11, 2006, 07:33:20 AM »
This would be good for those that want the to do the 836 or pods of if they are switching exhausts.

Offline 82CB650SC

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Re: Idea- Carb jetting database
« Reply #6 on: January 11, 2006, 12:27:08 PM »
Hello new here.  I did find this chart on the stock settings which would help if you didn't have manual.

http://www.motorcycleproject.com/motorcycle/text/specs.html

« Last Edit: January 11, 2006, 12:49:43 PM by 82CB650SC »
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Offline Jonesy

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Re: Idea- Carb jetting database
« Reply #7 on: January 11, 2006, 01:37:55 PM »
I think we have that chart on this site as well. I was thinking more for guys who have put in piston kits, cams, 4-to-1's, pods, etc. Sometimes just a change in sparkplugs can make a difference. I just threw my stock bike on there as an example of setup.
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Offline SteveD CB500F

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Re: Idea- Carb jetting database
« Reply #8 on: January 11, 2006, 02:26:27 PM »
Yep "82", we have that in the FAQs, together with a few others.  I agree that a chart of members actual setup for non-standard bikes may be useful to to anyone who has the question "If I fit pods/4-1/836cc etc will I have to rejet?"
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Offline Bob Wessner

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Re: Idea- Carb jetting database
« Reply #9 on: January 11, 2006, 02:28:33 PM »
Steve,

Any ideas how it could be done collaboratively?
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Offline mrbreeze

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Re: Idea- Carb jetting database
« Reply #10 on: January 11, 2006, 07:13:25 PM »
Someone could draw up a questionaire that you could add all of your info to. Besides year,make,model,performance add-ons,etc..... It would be good to know the altitude,average temp/climate and also a short comments section at the bottom. So what do you think? Is it a good FAQ candidate? Man,I know I could have used it last summer when I set mine up.
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Offline Bob Wessner

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Re: Idea- Carb jetting database
« Reply #11 on: January 11, 2006, 07:16:13 PM »
I think there's pretty solid agreement it would be a good FAQ topic. Trying to figure out, within the forum software's capability, how to allow folks to update (i.e., fill in the blanks) yet limit access say to members.
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Offline paulages

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Re: Idea- Carb jetting database
« Reply #12 on: January 11, 2006, 07:34:28 PM »
since i was one of those "lookers" and not a responder, i'll chime in. i will certainly contribute my own findings once i get my '76 cb550 on the road. "how to jet with pods and a 4 in 1" seems to be a really common question, so i'll be happy to share, if and once i figure out the perfect setup for my bike.

even if this is a slow moving thread, i reccomend someone keeping it alive and top of the list with stupid questions/posts or whatever, because it is a great idea and could certainly prove very helpful in the future.

lloyd, you could start with "you oughta be running a stock setup anyway..."  ;);D
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Offline paulages

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Re: Idea- Carb jetting database
« Reply #13 on: January 11, 2006, 07:35:36 PM »
bt the way, it just aint right that "cb" shows up as a spelling error on this website.  :D
paul
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Offline mrbreeze

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Re: Idea- Carb jetting database
« Reply #14 on: January 11, 2006, 08:52:56 PM »
Alright Jonesy! You're list of specs plus a few more....Altitude,Average temp,Location.One question before we start though.....needle clip location(VERY IMPORTANT!!) Notch 1-5 from top or bottom of needle? Mine is at second from top (lean side)-------------------OK! Heres mine-----------
BIKE- 750 K5
YEAR-1975
CARB-Stock Keihin
MAIN-138.5
SLOW-Stock 40
NEEDLE-Second From top
Plug-Stock-NGK D8EA
AIR FILTER-K&N Pods
EXHAUST-4to1 Kerker 2.5"--No Baffle
CAM-Stock
DISPLACEMENT-Stock
ALTITUDE-Under 100 ft.
AVERAGE TEMP. - 80 to 105 deg F in summer
LOCATION- Modesto, California
COMMENTS- Dyna 2000 ignition,Accel coils , Home synched with Morgan Carb-Tune
   OK......how is that? Now if everyone listed that way, would'nt it take up alot of space? Like Bob brings up.....How can it be formatted to the software on this forum to make it easier?
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Offline TwoTired

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Re: Idea- Carb jetting database
« Reply #15 on: January 12, 2006, 12:01:26 AM »
lloyd, you could start with "you oughta be running a stock setup anyway..."  ;);D

I'm so misunderstood. :'(   But, if you're going to pick on me, I'll share my thoughts.

So, far the only predictable jetting info is from Honda's extensive testing and jetting selection with the stock components.
Most questions seem to ask for the easy way out for carb jetting or to get the best operation from their modified bike.  I simply maintain that the fastest, simplest and surest way to get to that "best streetable performance" goal is to return to stock and use Honda's settings.  That formula pretty much guarantees success with a minimum of frustration, and minimizes a needed learning curve for the tuning art.

I'm thinking you guys are underestimating the amount of variables in the end chart.  To get an idea, just start making a list of all the SOHC4 Hondas (number A).  Then list all the header examples (number B), then list all the muffler examples (number C), then list all the air filter examples (number D). Your chart is going have a data entries for AxBxCxD. If we choose an arbitrary number of 10 for each entry, that's 10,000 entries.  Each time you add another variable or range of variables, you multiply times the previous number.

The chart gets pretty big and unmanageable rather quickly.  Note I have assumed that say the manufacturer of a muffler has a recipe that makes EXACTLY the same muffler in restriction and flow characteristic for each and every muffler they make.  Or, no variability between samples of product.  I can't believe a cheap muffler such as a Mac type has quality control measures to ensure each muffler flows exactly the same (another variable multiply by the range of variability).  Same is true for air filters.  Are they all packed with the same length size and density of filter material?  Each variability of example adds another range of multipliers to the chart.

Then there is the criteria for success. The variabilities of Temp, Baro pressure, and humidity all effect performance benchmarks.  Who's going to tabulate and normalize the performance data and how is it measured?  I don't want to be demeaning, but "it feels better" is a statistically insignificant attribute, sorry.  There are variations between Dyno machine calibrations.  How do you account for variations in seat of the pants feel?  And, how well does it have to run before it runs "well enough"?  Then there are jets that have been drilled or bored when cleaned which don't actually match what their stamped numbers indicate.  And, what do we know of slide needle profiles both stock and aftermarket? 

Even if every member contributed their setup with 100% accuracy, we would have about 1600 entries, which is probably much less than 10% of the possible variations of build setups and jetting.  Do you really think that the next custom build will be exactly the same as one of these entries?  Seems statistically unlikely.  Customs bikes are based on individualism, no?

 Without precision measurement tools, and standardized components of known dimensions that can make the chart a science, we'll have a tuning chart based on artistic interpretations, rather than engineering specification.   

I think custom bikes need custom jetting.   Specific tuning charts and specifications are for mass produced machinery.

Finally, in all my engineering days of lab experimentation a cardinal rule is that a working test case example of one, while promising, is not conclusive proof of concept or mass manufacture (worthy of copying).  Just because you've built an example of one machine that works perfectly (usually after many adjustments), does not mean all machines built similarly will behave the same (variations of components).  If my homemade recipe works 95 out of a hundred times.  Are you sure you didn't build 1 of the 5 out of that 100 that doesn't work the same?  And, when it doesn't, what will you say of my recipe?

I'll watch this thread with the greatest hope.  And, wish you all well with the endeavor.  Don't let me discourage you.  That's not my intent.  A project's success can be better predicted with good preparation.  I just think you are going to learn something you didn't expect to learn during the project.  And, that can be valuable, too.

Cheers,

Lloyd... (SOHC4 #11 Original Mail List)
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Offline paulages

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Re: Idea- Carb jetting database
« Reply #16 on: January 12, 2006, 12:00:15 PM »
i wasn't picking on you actually lloyd, because i agree with everything you just said...you just seem to be the resident reminder of these points. it's an unglamorous job, but somebody's gotta do it!

i do, however, think that such a database or at least a thread (which seems unlikely to even come close to approaching the data levels you were discussing...remember many members on here are just lurkers or at least not major modifiers) could be a helpful starting point. my stock 4 in 1 with uni pod filters and whatever silencer i end up running might not run exactly the same as the next guy's, but it would certainly be nice to have a closer starting point than stock when setting up something similar. for example, there are several jet sizes in between a stock 98 and a 120 or 125, and buying 4 at a time could add up. i'm willing to lose some money experimenting, but the next guy might like to know whether to jump up to a 110 or a 120 before he/she starts doing plug chops. doesn't eliminate the need for custom jetting, but it could cut out quite a bit of guesswork in the beginning.
paul
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Offline TwoTired

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Re: Idea- Carb jetting database
« Reply #17 on: January 12, 2006, 12:26:28 PM »
Hey Paulages,

I knew you weren't picking on me.  Somehow, the smiley I wanted at the end of that comment didn't get there in my prior post. Sorry.

But, that unglamourous comment hurt. (sniff).


Cheers, :D :D
Lloyd... (SOHC4 #11 Original Mail List)
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Those that learn from history are doomed to repeat it by those that don't learn from history.

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Re: Idea- Carb jetting database
« Reply #18 on: January 12, 2006, 12:53:05 PM »
I dont think everything would have to go into minute detail.

Year of bike does not really matter, just model.

Engine displacement if something other than stock.

current jets used.

Modifications done.

Would not need much more than that. Since every machine wears slightly different, you could not be exacting anyways. If you could then we could all set our bikes at the same setting and run all the same, we know this does NOT happen.

EXAMPLE

750K8

mains: 130  Lows: standard.

Mods: Pods and 4-1


Very simple and still gives a good base.

One other thing to add would be if carbs are stock or if a person switched to CV carbs or something.

Offline paulages

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Re: Idea- Carb jetting database
« Reply #19 on: January 12, 2006, 01:47:11 PM »
yeah, just add to that the carb # (e.g. 069A)
paul
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Offline Bob Wessner

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Re: Idea- Carb jetting database
« Reply #20 on: January 12, 2006, 03:13:45 PM »
How about clip position on the main?
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Offline mrbreeze

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Re: Idea- Carb jetting database
« Reply #21 on: January 12, 2006, 05:56:53 PM »
Like I said.....clip position is very important Bob. It should be noted in the specs questionaire. That was actually the final cure for my bike last summer after rebuilding carbs,switching to pods,4to1, dropping from 5000ft. to 100 ft. altitude,etc.,etc. I ended up trying 4 different size jets but only had to acually buy 3 sets (still costly though at $28 per set) Like Paulage says...it is a means to start in the right direction instead of $30 each time to buy a set of jets or the dreaded pull the carbs to change needle position(Huh Bob?) . This FAQ will be for a starting point in the right direction,,,,not to beat out the dyno or defie rocket science!!!
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Offline Jonesy

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Re: Idea- Carb jetting database
« Reply #22 on: January 12, 2006, 06:28:16 PM »
You guys hit the nail right on the head. I just hoped this would be a close starting point, not a "bang-on" tuning guide. All jetting setups will require a bit of finessing, but it's nice to start relatively close. We'll probably have to put this at the bottom: ::) :P

"The information contained herein is, to the best of our knowledge, accurate at the time of this writing. It is recommended that predicted results be verified by actual testing. We make no warranties, expressed or implied. Offer not valid in all countries. Void where prohibited. Yadda yadda yadda yadda...." ;D
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Offline Bob Wessner

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Re: Idea- Carb jetting database
« Reply #23 on: January 12, 2006, 06:40:59 PM »
Quote
NEEDLE-Second From top

Oops, you did include that didn't you. Missed it.  ::)
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Offline mrbreeze

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Re: Idea- Carb jetting database
« Reply #24 on: January 12, 2006, 07:59:29 PM »
VOID WHERE PROHIBITED----- Right on Jonesy!!!!!
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