Idle Question

[THE BIG SITT]

So I'm currently in the last process of tuning my carbs. I have already re-jetted, as well as shimmed the needles with three washers. My bike has a slip on can, as well as the airbox removed (replaced with K&N 0990).

When I start my bike, the choke MUST be fully engaged for it to start. Also, even once it's fully warmed up, I can't take the choke more than half-off. This would lead me to believe I need to adjust the idle screw, so that more fuel is put into the carbs.

Now what has me confused is this: When I blip the throttle, the engine revs up, goes way bellow idle, pauses, then returns to idle, which, according to Vex, means the bike is running too rich…

What the heck does all this mean?

[cliff0529]

What size jets did you rejet too? Did you change the needles too or just shim the stockers?

[gt_turbo]

you need to read this: Factory Pro Carb Tuning Procedure

[THE BIG SITT]

I rejeted to 110, and yes just the factory needle… I'm sensing that I've missed something...

[HKr1]

Missed changing the needles.

[THE BIG SITT]

Hmmm… thought that what the washers were basically doing… I'm an idiot

So is there a thread that gives some guidance on the whole needle thing?

[cliff0529]

It does sound a little odd...the fact that you're having to keep the choke on to keep it running, indicates a lean condition. All "choking" a motorcycle does is richen the mixture slightly. However, when you rev it and it falls below idle before coming back up, that indicates a rich situation. But since you can't run the bike without the choke, that might explain why it's doing that.

I'd suggest installing the next size up pilot jet and see how that affects the idle. You're not going to be able to really dial in your jetting until you can get it running without the choke anyways.

Honestly, I'd go ahead and just order a jet kit. As you'll probably wind up needing the needle too to get a good mixture across the board.

[THE BIG SITT]

Ok so what exactly does "clip position" mean? I see this but have never seen it explained...

[cliff0529]

The stock needles do not have a clip position adjustments, that's why we shim them. However, aftermarket needles do have them. The needle in the jet kit should have 5 or 6 grooves already cut into it and there's a C Clip that goes on it. The 3rd groove is where you normally start and then you move the clip up a groove to lean bike out and move it down a groove to richen it up.



The needle on the bottom is what the stock needles look like and the needle on the top will be what you get in the kit.

Here's a diagram of the adjustments:

[THE BIG SITT]

Ahh it makes sense now… but how is that different from just adding washers?

[gt_turbo]

aftermarket needles are designed for performance. they are designed slightly different than stock: the length, taper, and of course the head. these differences help you get more performance over stock needles.

[THE BIG SITT]

Hmmm… well I actually have a stage 2 jet kit, but since the jets were too small for my application, I was gonna just sell it. Should I just use the needles from the kit?

And do you guys think this change will let my bike run without the choked?

[cliff0529]

I'd probably put in bigger pilot jets too, they're probably in the jet kit too. Put 40's in the pilots and then the needles from the Stage 2 kit. Start in the 3rd clip position and see what you get. Since you got the pod filter on there, it shouldn't be that big of a hassle to pull the carbs again.

I think the Stage 2 is designed to be run with the airbox, so you might wind up having to go down to the 4th clip position to richen it up a little more. Either way, that needle will probably work better than the stock one with shims.

Remember, the bike will run briefly from the gas that's in the float bowls and fuel line, so after you put the pilots in and the needle in, start her up and see what you get. If it warms up, runs without the choke and revs cleanly, then you're at least in the ballpark.

[gt_turbo]

Originally Posted by THE BIG SITT

Hmmm… well I actually have a stage 2 jet kit, but since the jets were too small for my application, I was gonna just sell it. Should I just use the needles from the kit?

And do you guys think this change will let my bike run without the choked?

wouldn't hurt to try the needles that came with the kit. i installed a stage 3 in mine with 3 washers and 3rd clip position, and i still have to use the choke every time to start up. once warmed up it runs like a champ tho. so i am not too worried about having to use choke. also i am using stock pilot jets. i have read various posts on here where others have said upgrading to 40 pilot jets doesn't really do anything. so i didn't bother. do a search, read the comments and see if that's what you really want to do. but imo, your problem is not with the pilot jets. try playing with your mixture screws to make it run more rich. also it could be possible your carb ports are clogged up, read up on how to clean them out.

[THE BIG SITT]

So today I got around to working on the bike for a while. In review, my bike wouldn't run without the choke on (if I took the choke off more than 25%, it would die), and the bike had nearly no power from idle to ~5000 RPMs.

What I did today was, after removing the carbs, I swapped out the stock needles and replaced them with the needles I had in my stage 2 DynoJet kit. I placed the "e-clip" thing in the 3rd position, and put 2 washers on top of the "e-clip" as described in the DynoJet instructions.Then I screwed in the mixture screws all the way, and screwed them back out ~2 3/4 turns.

Then I put everything back together and started her up. After she should have been warmed up, I tried taking the choke off a little bit, but it would still die at a certain point. Reluctantly, I put the seat on and took it for a ride. surprisingly, the bike felt better when accelerating. There is still a slight loss of power at very low RPMs (idle-2000), but the rest of the powerband felt a better.

Here are a few side notes: When I screwed the idle screws in, I noticed I had them out way more than I should. I probably had them out close to five turns. I don't know what happened, I'm just retarded I guess. Secondly, on one of the carbs, when I took the black cover off of where the needles go, the spring on that side looked like it had come unseated.

So with all of you expert opinions, what the heck should I do to make my bike run right? I'm so frustrated with this whole thing.

[THE BIG SITT]

Are you guys as stumped as I am? Sorry just a little impatient

[THE BIG SITT]

Would the idle adjustment knob have anything to do with this? Or maybe my carbs are out of sync?

[THE BIG SITT]

I think I figured it out. The guy who cleaned my carbs aparently adjusted the idle adjustment knob thing (the thing that goes on the throttle body) so the the butterflies were completely closed at idle. So I messed with the knob a bit and got the idle going right. I just need the rain to stop so I can ride it to see if the slight acceleration issue I was having is fixed as well...

[gt_turbo]

the idle adjustment knob is not on the carb directly, it's on the left side of the bike - large plastic knob that you can turn by hand. if you messed with something directly on the carb, you will have to sync your carbs. see vex's guide on syncing your carbs. also plenty of different diy manometers out on the interwebs if you don't want to use bottles.

[THE BIG SITT]

Yeah that's the knob I adjusted. The cord the knob is attached to basically just unscrews something on the throttle body so that it can't fully close, which affects the idle speed. Mine was adjusted so that the throttle body was completely closed at idle, so the only way the bike would stay on at idle was to have the choke cranked way up, which would force enough fuel into the engine to keep it running.

[greatwhiteninja]

have you adjusted the idle mixture screws? sorry i tried glancing through all the threads but didnt see were it said you did.. if not thats your problem, from reading your first post. once you change the jets they need to be adjusted. they are the very small needles coming up in the center opening of the inlet of the carb, the screws themselves are covered with a cap that you need to drill out to access. on mine with 110 mains, pod filters and shimmed needles i had to turn them ruffly 3 full turns out. before the idle was right. meaning revving the throttle and it falling quickly were it should, not hanging up or dropping below its set idle speed.

[gt_turbo]

Originally Posted by THE BIG SITT

Yeah that's the knob I adjusted. The cord the knob is attached to basically just unscrews something on the throttle body so that it can't fully close, which affects the idle speed. Mine was adjusted so that the throttle body was completely closed at idle, so the only way the bike would stay on at idle was to have the choke cranked way up, which would force enough fuel into the engine to keep it running.

in that case you did not mess with the carb sync adjustment, that is a screw directly on the carb. set idle to about 1500 when fully warmed up. take her out for a ride and see what happens. gl!

[THE BIG SITT]

So I've pretty much got my bike all back together and I'm having a slight issue. I'm still noticing a slight hesitation or loss of power when accelerating from a dead stop. Would this be and idle mixture screw issue, or do I need to put another washer on the needles? Fwiw, it is pretty cold out (40 degrees or so).