I just put a pair of FMF's on my banshee. I jetted the carbs to the FMF specs....260 main and 30 pilot. Now i am backfiring. Sometimes it's actual flame comming from the silencer, other times it's just a sputter/missing sound. Once i rev it to the powerband this stops. Any ideas??? I thought backfiring was a timing issue??? Is this electrical or fuel related??

 

I have been doing searches in the tech section of this website, and have come to the conclusion that the problem is in my pilot circuit, and i need to richen it up by turning out the adjustment screw.....I have stock carbs with the TORS tops. Is the screw on the of the TORS the air/fuel adj. screw that i need to turn?? What are the tiny screws on the side of the carb for??

Also i read about (electrically) diconnecting the TORS system. If i do this, and leave the units still on the carbs, how will this benifit performance??

thanks

 

The screws on the top of the TORS is what you need to adjust. The screws on the side of the carbs are the air screws and should be at the stock setting which is 2 turns out from seated.

 

Before you go adjusting, is it only backfiring when first started? and once you get it in the powerband does it run good? Im just thinking that it is too rich of the bottom, mabe drop the needle one notch and see if that helps.

 

SMW, the big screws on top of the TORS IS NOT TO ADJUST YOUR IDLE MIXTURE> DO NOT ADJUST THEM!!!
They will adjust your idle SPEED. If you turn them tou have to turn them both the same amount or you will mess up the syncronization between your carbs.

Before you do ANYTHING, read and head.

Adding pipes will not have that big of an effect on your bottom end settings. If it is backfiring/sputtering it's probably something you did wrong when you dis/re-assembled the carbs. Make sure that the little rubber tube between the carbs is on. This is commonly missed and may have fallen on the crankcase when you took the carbs off without you even noticing it. Make sure the cross-over "pipe" is still on between the reed cages in front of the carbs. You shold not have taken this off but let's just be sure.

Did you do both carbs at the same time??? If so, it is possible you got the slides reversed. Look in from your air cleaner opening and make sure you see the cut-out on the BACK of the slides. Easier still is to look through the little glass windows on the carbs near the top and on the out side to see the indentenation in the slides when it is at full throttle.

Do these things and report back and we'll take it from there. We need to know at what throttle positions it is doing what to be able to help you.

 

Well, I know i put the little rubber tube back on that connects the carbs. And i have a boost bottle and didn't take that off. And i am almost 100% positive i kept the assemblies on thier correct sides.

What is the "the cut-out on the BACK of the slides" look like if i look up the airbox?? And i never saw a little glass window when i had the carbs out?? I'll look again for the glass when i get home.

Wouldn't moving the needle height affect more of my fuel delivery when I'm above the 1/4 throttle position.

thanks for the support....please keep it comming

 

Look at the carbs while they are mounted normally on your Banshee from either the left or right side. Near the top of the carb, below the cap you will see a small (1/8" or less) glass window in the round part of the carb where the slide goes up and down... I'm sure there's a name for this part but I don't know what it is. Anyway, when you pull the throttle all the way to full you will see a little drilled out indent in the slide that will line up with that little window. Make sure you see this. This shows that your carbs are both going up at about the same time.

Actually, thinking about this I don't think that's a good way to make sure you have the slides in right because no matter what you will still see the little indent... Ok, just look in from the airbox. and make sure you see the cut-out in the slides.

This is probably not your problem anyway as you sound pretty sure you did this correctly.

If it is running poorly below 1/4 throttle you have a problem with your idle circuit. From 1/4 to 3/4 it is with your needle height and above 3/4 throttle it's your main jet. Of course, you have to get the correct main jet first then work your way back from there.

Backfiring, especially upon deceleration is indicitave of a lean condition in the idle circuit but sputtering seems to be more related to being rich so I am a little confuesd. Try opening the choke a litlte once it is warmed up and runing and see what happens. If it runs better you are lean on the low end. If it runs even worse you are rich on the low end.

 

ok i put the choke in half way and the motor ran better, but started to load up a bit....so i would say i'm lean in the idle circuit. I put the recommended 30 pilot jet in. How can i be lean?? I took it for a blast and it ran fine through the gears (1/2 - full throttle). Maybe some dirt in the pilot jet(s)??

 

Also, what cut-out am i looking for on the slide when i look up the airbox?? The only cut-out i remember was the one "slot" that i had to align with the set screw in the carb...i thought this was pointing sideways(therefore i wouldn't be able to see it from back??) or is there a different cut-out i'm missing.

I looked up the air intake and just saw the round OD of the slides NO CUTOUTS. Do you mean the half-moon radius on the bottom of the slide (that you would be able to see when you are in full throttle position)??

 

One of my friends did this....

He put the slide backward into the carbs. It is easy to get the slides mixed up ....and if you do that is what happens. His bike would sputter like crazy...we tried switching carbs and everything just to find out the slides were put in backwards.