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Need a main jet size recommendation to start off with?


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Banshee, main jets required/recommended to start tuning? 

 

Altitude 300ft

K&N filter

Stock airbox with no lid

Stock Carbs, pilots never touched, currently 310 mains

Vforce 3's

Dyna FS ignition, ignition curve 1 setting

Boost bottle

Trinity pipes

Ported Jugs

Decked head 

Vertex pistons 10 over

Running VP C12 all the time

I was recommended to put 380's in and slot 4 on the needles.

 

What does everyone else see fit here?

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  • 4 weeks later...

So I'm having a jetting issue for quite a while now.

The Pilot jet is fine the low end is fine.

The problem is I can not give any throttle to the bike cause it just loads up and doesn't want to open up.  Trail riding the bike is in 2nd to 3rd gear mostly and the bike just struggles to get along and when I give it throttle it just dies out.  I haven't checked compression yet but I have the bike at almost original jetting when it ran great before the head gasket blew.  After I fixed the head gasket I worked from 340 mains all the way down to 310's and I have adjusted the needle to every slot on each different main jet.  This bike just won't clear up!!  I ohm checked the coil, stator coils and put the original CDI box back in and I'm getting no where.  The bike free revs just fine but any type of throttle over 1/4 it doesn't want to go.  Could I still be to big on the main jet?  I can't say i feel comfortable going down from the 310's that I've run in the bike for a good 5 years prior.     Please help

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30 pilot

Needle full rich (work up)

320-330ish main

^^^ trickedcarbine gave you an excellent staring point.

Are you still running 25 pilots?

If so, your pilot jet is your problem.

Look how jetting works with throttle.

carb_chart.gif

 

Put the needle clip full rich, so 5th groove from the blunt end and work your way up.

Also check the sync of your carbs and dial in idle.

Run the exact jetting tricked suggested and report back.

Eventually you'll need to do a quality plug chop.

Get a quality compression tester, pull both plugs out and move spark plug boots away the best you can.

Insert tester into a spark plug hole, hold WOT and kick the piss out of it until the needle stops climbing, write that number down.

Rinse and repeat for other hooe.

Finally, I'd do a leak down test for shits and giggles.

Yeah, it's some work, but it will say a lot about the condition of your motor.

http://bansheehq.com/forums/index.php?/topic/110585-leakdown-tester/

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What ^^^ said!!

 

Get rid of that boost bootle and replace it with an OE cross-over tube.

Do a search on here about boost bottles.

Boost bottles are gimmicks that offer no performance benefit, are always in the way and they can crack the intakes.

 

The sole purpose of a cross-over tube or boost bottle is to help equalize the volume the motor is drawing thru the carbs.

 

A properly modded, sync'd and tuned Banshee does not need a cross-over of any kind.

 

Read the following FAQ topic on Toomey's site.

There is a "rich spot" between 4000 and 5000 rpm on the Banshee.....

While it is true that it IS rich, the REASON it is rich needs more explaining.

http://www.toomey.com/index.php?option=com_jefaq&view=faq&Itemid=8

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Would this bike still have the T.O.R system on it? Parking brake switch, throttle switch, Black  box under gas tank? IF so try un-plugging the the box under the gas tank.

Tors was removed a while ago.  

I'll get ride of the boost bottle also.  

I'll try putting in a 27.5 pilot.

Thank you everyone for the help, just extremely frustrating and not having the area to play with the jetting over and over.

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Is it a ported bike what are the rest of mods

 

Altitude 300ft

K&N filter

Stock airbox with no lid

Stock Carbs, pilots never touched, currently 310 mains

Vforce 3's

Dyna FS ignition, ignition curve 1 setting

Boost bottle

Trinity pipes

Ported Jugs

Decked head

Vertex pistons 10 over

Running VP C12 all the time

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I'm pretty sure now that the bike has a different problem then jetting right now.  I have swapped enough jets and moved the needle countless times and it won't clear up it has the same symptoms everytime.  So I'm eliminating jetting at this point.  I've notice that the bike doesn't have a clean snappy free revving response that it use to.  It seems like its just choking up some how and any type of load on the engine and it just wants to die.  The plugs are not all loaded up with fuel and seem pretty good.  I can ride the bike in 1,2, and 3 gera on like 1/8th throttle anything more and its like the bike is breaking up/bogging, any hill or little incline the engine struggles and will only run on the idle to 1/8th throttle.  The bike starts and idles perfect it seems.  The TORS and the throttle rev limiter have been removed alone time ago.  Both systems were unplugged along time ago.  I finally did a compression test and both cylinders are 140PSI.  I'm at such a loss right now.  

 

Currently the bike has 27.5 pilots, 320 mains.  

Air screws were also adjusted from 1 to 2 turns a few times for tuning.  

Needle is currently on slot 3 from the bottom, but all slots were tested already.  

I ohmed the coil, stator circuit(s) all are good.

Cleaned contacts on flywheel and pick up sensor, gap is set to about a credit card thickness.  

Swapped a coil for the hell of it.  

Installed original CDI box and this thing still still has the same problem.  

The carbs are also in sync perfectly too.

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