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Discussion Starter · #1 ·
I have a 2002 Honda shadow vt750 ace and recently put cobra 2" drag pipes on with no baffles and K&N spiked air filter with dyno jet kit but had to put stock filter back on because it would not run properly with the aftermarket... anyone know what size jets I should start with
Tire Land vehicle Wheel Fuel tank Vehicle
Tire Land vehicle Wheel Fuel tank Vehicle
 

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2001 Valkyrie I/S
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Are you wanting new jets so you can go back to the spike air cone or are you still having problems with the bike running with the original air intake?
 
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Rule #1: Get the concept down as a 'speed event change.' Who enters faster, has less drag, friction, is the leader.
1. Air Cleaner box - Is more or less closed around the intake of the carb. There is your friction speed. Takes time to start at the intake opening of the box, the filter and screen-big friction factor, then into the open chamber of the box. Lots of drag at those entry and exit points.
2. Madonna Titty Thing - Simply less restrictive shows the air enters sooner, or easier to pass, or nature acts like electricity and finds the shortest path. Of course it still pulls heavy, friction like drag out of a hole, but you are up against formula like it's amazing how a neighbor retires and moves away, leaving me with a couple of books on thermodynamics. Math, no; the abstract written, kind of. Once I saw 'formula' for every fuking thing on earth, you be fuking wit air speed.
Formula says box needs this square per pull, I mean, I can make up this kind of sheet up, and sure asshit a formula will be in that fatass book.
3. Cover that woman up - Hose me nylon over and over till speed tiits, equally meets; speed [of the] box. That says two flavors out of both. (1)Engine- the layer will block more microns, keep the pleats cleaner, being dead open in the air, and aimed in that direction. (2)Throttle- the point of the whole speed event is to throw layer over it not jet.

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Laymen as close as I get
 

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2003 VT1100C Spirit
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From the Cobra USA website regarding baffles being removed...

"Performance. It will suffer. It may sound like a rip-snortin', fire-breathin' race bike, but it will perform more like an overloaded, high-mileage rental car at altitude. This is because the exhaust system has been designed to create a bit of back pressure in order to scavenge more spent exhaust gasses from the combustion chamber. Remove the baffle and you remove this feature, which helps the engine produce more power."

"Warranty. Remove the baffles from a Cobra system and you've just voided the lifetime warranty that came with your system."
 

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2007 VT750DC Spirit “chopper”
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Discussion Starter · #7 ·
Are you wanting new jets so you can go back to the spike air cone or are you still having problems with the bike running with the original air intake?
It runs really well with the stock filter but I I wanting to put the spiked on..
I running 42 pilot 110 and 112 main with my needle shimed half way up
 

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Discussion Starter · #8 ·
I have a 2002 Honda shadow vt750 ace and recently put cobra 2" drag pipes on with no baffles and K&N spiked air filter with dyno jet kit but had to put stock filter back on because it would not run properly with the aftermarket... anyone know what size jets I should start with View attachment 302082 View attachment 302082
Bike is running good with stock filter and I have 42 pilot and 110 and 112 main with a shim able needle but would like to get it to run with the spiked filter
 

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'83 VT750C
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If those are the DynoJet main jets, they’re equivalent to 115 and 118 Keihins. More clearer info about what is installed, please! HOW was it running poorly with the spiked filter on?

One other thing I’ve always wondered about is if the turbulence of the airflow disrupts the CV piston in the carb throat. The ‘nylons’ example is an extreme one, but if someone had ever put an aluminum honeycomb into the intake pipe, like the kind you get in Mass Airflow sensors to ‘smooth’ the airflow, I’m wondering if that would help… 🤔
 

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1999 Shadow 750 ACE VT750CD3 Modified
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You are probably going to need Keihin sized main jets of larger size I'm guessing a 132 front and 135 rear just to get it to run at all so you can start the tuning procedure that @Froth indicates.
Follow it!!
142 pilots are going to work OK I think as will the Dynojet needles.

There are a couple of things to consider forward facing intakes such as the "Spike" create an unstable variable "ram air" effect that is impossible to get right for all conditions with carbs and also in rain conditions they will vacuum up a lot of water.
 

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1999 Shadow 750 ACE VT750CD3 Modified
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One other thing I’ve always wondered about is if the turbulence of the airflow disrupts the CV piston in the carb throat. The ‘nylons’ example is an extreme one, but if someone had ever put an aluminum honeycomb into the intake pipe, like the kind you get in Mass Airflow sensors to ‘smooth’ the airflow, I’m wondering if that would help… 🤔
The spike air filter maintains the OEM air box and intake runners to the carbs and "just" replaces the filter box, so it is not as bad as sticking pods directly on the carb air horns, which does cause turbulence and fluttering of the slides and fuel stand off. On my bike I increased the length of the slide springs and retempered following dyno proven success of folks on the Hawk GT forum. This gives the slide more seat pressure and avoids flutter, the throttle response remains OK-ish.

Ideally the Intakes would have long runners between the carbs and filters, this can't fit due to everything being stuffed in the limited space of the V of the cylinders.
This also affects the available space for any honeycombs, slats or grilles or other gizmos and with the limited available space they end up stuffed in the air steam restricting the net flow though the carburetor(s). Such stuff has been used successfully with various engines with decent size airboxes/plenums to calm down the air entering the plenum and the engine sees stable unrestricted air from plenum and as long the intake to the plenum is sufficiently sized.

The more you look at it Honda did a pretty good job, within the compromised space with the design of the OEM intake system, given the physical space and noise constrains they have to deal with, it does the job.

Personally I'm a big fan of the "Bean box mod" of the 750 ACE and Spirit, with appropriate rejetting, the only drawbacks are increased intake noise (sounds cool though) and the thing is still in the way of your knee. (-;
 
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