Author Topic: jetting.... the evil monster, a collective guide to be filled over time  (Read 1715 times)

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Offline Gurp

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So ive noticed all the questiond about jetting on the forum. So i decided to start a thread where we will all post the basic bike info pipes intake known jet sizes and so forth and if it is a good combo or bad and what the results and or problems are.

I'll start with my cb550 the last time it was running

74 cb550
Open headers
Ermgo pods
Stock jetting.
Other issues: plugs gapped to wide points a bit too wide also.

Vertict: fail.
It hardly idled uneless the idle was set high and bogged under load topped out about 60 mph like this.

Hope more ppl share their jetting stories to help build a base of knowledge for us all to use.

Thx ron
slow Progress 74 cb550.

Poor boy chop 73 CB500 chop

Future project 77 Cb750 Amen Savior

Offline dave500

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im sure there is a couple of  threads already along these lines,it sort of proved that what works for some dosent for others even with the same pods/airbox,open pipes or mac 4-1 etc,altitude and ambient temp plays a combined role aswell,im running stock airbox and genuine filter,4-1 exhaust,boyer micro power ignition and run 38/100 jets in type one carbs,mine flies.

heres one.
http://forums.sohc4.net/index.php?topic=6566.0;all
« Last Edit: July 30, 2012, 01:50:50 AM by dave500 »

Offline TwoTired

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There is only one known configuration that works every time; the stock one with stock components.
Honda controlled the exhaust design and induction characteristics and tuned the carb to expect these.

Pods is not a spec.  It's a style.  Pod characteristic behavior is not controlled, merely assembled.  Pod characteristics vary with manufacturer and even within manufacturer offereings, because people buy them for how they look rather than how they work.  The engine/carbs don't care how they look, they care how they work.

Exhaust has a similar story.  Many are made for how they look rather than how they work.  Which means 4 into one behavior varies between manufacturers as well as within manufacturers.  Building anything to a tight specification, costs more than building to a loose specification, and many people buy on price point rather than a specs or performance characteristic point.

Even "success" story reports are unreliable, as what "works" has a different standard depending on the reporters standards which vary from,  "it is good enough to sell", to "I can now drive it around the block", to "it stopped sooting plugs", to "look at my dyno HP chart" (rare).  Even better, "I've never driven one of these to know how it is supposed to perform so anything described as running is a success".


As Dave mentioned there are 4 or 5 threads that attempted to gather a database of jetting successes.  None are substantiated, and even if you used the exact same components that were reported, there is no guarantee because of component variability, and the reporter's judgement.

All you need to do get a feeling of how hopeless the goal becomes, is to make a matrix of each bike (350, 400, 460, 500, 550, 592, 750 836, 650), each pod brand or filter brand (are there 5 or more?) each exhaust type/ brand, each muffler type, with and without baffles.  Each variable is a line entry, and the line is then segmented with each and every other line item variable.

Then you can add line entries for pilot jet, Needle position, and main jet.  Then you have to arrive at how to judge if the combination "works" and how accurate the report is, while knowing that internet post have the distinct possibility for being made up and based on no fact at all.

Custom bikes are seldom duplicated exactly, even if they sorta look similar.  The stock recipe is pretty refined and reproducible and quite a lot of work went into making it so.

Good luck!
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 fastbroshi

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There is only one known configuration that allows the engine to run within Honda's design parameters every time; the stock one with stock components.


I think that's what you were trying to say, as we can alter the balance of the components subtly in many ways and improve power, and probably not affect longevity too adversely.    I won't say performance because mileage and measured sound ouput can be balled in there and depending on your goals (race? or frugal commuter?) you'd say it affects it one way or the other. 
Just call me Timmaaaaay!!!

Offline TwoTired

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I think I said what I meant.  There is only one identified configuration that is well known and tested for its tuning parameters and is available to all.  The rest are custom one-off configurations with unproven and unreliable tuning parameters.

No offense intended, but you simply don't know and have no data for a power vs. longevity trade off statement.  Those are pretty hard to do with one-off machines.  'Cause when it breaks, the root cause in rarely investigated to a firm conclusion, and the repair process is uncharacterized, uncontrolled, and often changes are made (while you are in there) to create yet another one-off example. Ever seen a data base that shows, say, a bearing brand change vs. endurance expectancy?
Besides, most of us only operate the engine at 1/3 or less capacity for 95% of the time.   If we used more than that routinely, Johnny Law would intervene.  It only takes about 15HP to cruise at 70 MPH, and 25hp at 80 MPH.

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.