What is the proper way to adjust the air screws on stock Banshee carbs? I run 92 octane gas, FMF Fatties, K&N with no lid, 300 mains, 32.5 pilots. Also, how do know if your pilots are the right size? Do you just let it idle for awhile and then check the plugs?

Thanks,
Mark

 

For stock carbs you are supposed to have the air screws 2 turns out. You may have to plug and play with them since you have some mods to your carbs. They really make a big difference in how it runs throughout the rev range. I installed new Boyesen Power Reeds yesterday and tried running it with the air screws 1 and a half turns out and it ran awful no matter how high it was revving and wouldn't reach full rev. Took them back to 2 turns out and it ran great like usual. Hope this helps. If you have any ideas on where to start to jet stock carbs on stock banshee for K&N filter I would appreciate it. I think I could use some bigger jets since I've had the K&N on for 6 months. You can just E-mail me through the atving link. Thanks.

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Jeremiah Lucas

1989 Yamaha Banshee

 

VENOMOUS,

Thanks for the reply. Mine seems to run best at 2 turns out too. I just wasn't sure if there was a better method. Greg Hall says "hot idle" but I'm quite sure what that means. As for the jets with K&N filter, I had to bump the mains up to 260. Then, after I added the pipes I had to go to 300's
Boysen reeds are my next purchase since they are a fairly inexpensive. Are there
different styles of Boysen reeds? Which are the best?

Thanks,
Mark

 

You're basically duplicating what me and several friends have done (FMF's or Toomey's, Pro-Flow Filter w/o air box lid, boyesen reeds not the rad valve, it's a waste of cash). Most everyone has settled on 300 to 320 mains (for the dunes, we'd rather be a bit on the rich side) some of us stayed with the stock pilots and needles, but raised the needles one notch. Others went with the Toomey jet kit (which I haven't been convinced to be worth the money). Air screws on just about everyone are 1 1/2 turns out. I don't quite understand what was posted above about air screws affecting the top end. That doesn't make sense to me. The air screws only affect idle to 1/4 throttle, from 1/4 to 3/4 throttle it's the needle and pilot jets that make the difference, and from 3/4 to full throttle the mains are really all that matters. As a rule for air screws, let the engine idle and adjust them in 1/2 turn increments until you find the smoothest idle. That's all that's really necessary. I usually set my carbs up a bit on the rich side. It's a lot better to be slightly down on power than to sieze or melt the pistons. Another issue is where the quad is ridden most of the time. Dune riding is pretty hard on the motor. There's a lot of time when you're at full throttle and loading the engine for extended periods. You'd be best to run rich so the motor runs a bit cooler. For woods riding and even mx, you can get away with leaner jetting because the engine isn't held at full throttle for very long, so it doesn't create the same amount of heat.

It is possible that there is another jetting problem that could cause the motor to run like crud if the air screws are richened up. If the needles/pilots are too rich, then the air screws or mains would need to be leaned out to compensate somewhat. It's pretty important to set each circuit (air screws, pilots/needles, mains) individually, but if there is a situation where one circuit is WAY off, you'll have a hard time getting the other circuits dialed in without first getting the problem circuit closer to where it should be.

I could go on, but I won't unless you really want to know more.

 

I have a new Banshee with Toomey's and their jet kit. I also went to 32.5 pilots and running 300 mains, I ride in the dunes. It really runs well and seems to stay pretty cool, even running it hard.

I really like the effect the Boyesen reeds had on my CR500 and am thinking I'll put them in my Banshee as well. Is everyone happy with them, notice a difference? Also, I had to drop a couple sizes in my main on my CR when I put them in, has anyone needed to go a little leaner with the Boyesen's? Thanks!

 

Well, I answered my last post and installed some Boyesens today. Made a big difference and much more responsive, especially at lower RPM's. Thought it might make it run too rich, but doesn't seem to be the case, I'm dialed in now!

 

I made a mistake in my reply to VENOMOUS. I meant to say I'm NOT quite sure what Greg Hall means by hot idle.
I remember reading in my old YZ250 manual to adjust the air screw to achieve the highest idle speed. Then adjust your idle speed to where you want it.

 

I have a 96 banshee with pro flow/ K&N Filter, Boyseen carbon fiber dual stage reeds in stock cages, toomey t5 pipes with the dyno jet kit. I am running 1 1/2 turns out on air screw, dyno jet kit needle with the clip on the 4th groove from top. 280 main jet. Running a little (not to bad safer) phat on the plug. At low rmp's the low end seems little rough like it is loading up a bit maybe still may need a little tweaking. stock pilot jets.

Brian 96 banshee

 

98 Banshee I have no idea what "hot idle" means nor have I ever heard it used before. All I know is that it's best to set the idling after it has been warmed up or even run a while. Could this be it?

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Jeremiah Lucas

1989 Yamaha Banshee