Topic: Bike running poorly after jet change??

[neurotoxin312]

So after my rebuilding my carb my bike runs a little sh*tty. The bike is a 76 CB550 with 4 to 1 Exhaust and pods. My jets are now 130 Mains & 42 Secondaries. Previously, there were 120 jets and 40 mains and the PO had a 2 to 2 Exhaust with pods. I thought that the bike was running a little on a lean side because it would easily overheat.

This is what I mean by poorly function: the bike starts climbs up the rpm range pretty ok but then studders around 6k RPM +. Maybe its running too rich up top? What do you guys think about my jet sizes?

[Deltarider]

130? 130?! That's not a jet, it's a manhole.

[neurotoxin312]

Ok. Found my issue then lol. I miscalculated what 1 jet size up is lol. So from my calculations I am suppose to go up around 3 jet sizes with Pods and a 4-1 Exhaust correct? This puts me at 115 no?

[ChopSticks]

Cal just curious why?

If someone else has the same exact bike and mods as his wouldn't the jetting be the same?

Figured by now most of the combos of mods has already been done and plug chopped for the correct jetting no?

Understand location is also a factor but let's say they're both in normal non Denver locations

[ChopSticks]

Meant why are "there no calculations" sure someone with a similar setup can at least give him a close starting point

[flybox1]

Meant why are "there no calculations" sure someone with a similar setup can at least give him a close starting point

This...

The explanation is simple: pods and WAY TOO BIG of carb jets. Also sounds as though you may have a vacuum leak, and poorly synched carbs. Impossible to determine all the factors.

Remove your carbs.
Replace your jets with 105 mains.
Put the needle clip in the 2nd slot from the top of the needle.
Put in 40 pilot jets.
Bench synch the carbs.
Install onto bike with new plugs.
Perform an idle chop.
New plugs.
Perform a WOT chop.
Commence tearing your hair out and fiddling with chops and tuning until you get the AF mixture right.

[TwoTired]

Honda jetted the carbs to match the stock Engine breathing characteristics, the stock air filter flow and pressure drop, and the stock exhaust flow and pressure characteristics.  This combination of components all had predictable behavior.  Honda made a lot of them with this typical behavior and controlled all the component specs.
Still there are no engineering charts that define what the stock flow and pressure characteristics are, which correspond to the stock carb jetting.

"PODs" has no predictable flow and pressure drop characteristic behavior, even from one manufacturer, let alone from 10 to 20 manufacturers.  No attempt has been made to mimic stock characteristics.  And no effort is made to make one example behave the same as another.

"4 into 1" also has no published dara regarding flow and pressure characteristics from the many manufacturers that make them.  No attempt has been made to mimic stock characteristics.  And no effort is made to make one example behave the same as another.

Still wonder why pie in the sky jetting formulas are fundamentally bogus?

Assume stock jet is 100.
100 = Estock + Filter stock + Exhaust stock.
Now solve the equation to find X with variable substitution.
X = Estock + F variable + E variable
The solution can only be imaginitive and variable.  ...with lots of different thumbs ruling.   

Cheers,