carb question

[bowhunter007]

I can't find a thread, doing a search, that explains the carb slide(i.e. it's exact function). I'm confident that I understand pj, mj, needles, etc. I just don't understand how the slide affects the lean or rich condition, of the carb. Yes, I'm tinkering...again. Thanks

[bowhunter007]

bump! Anyone?

[Jakobi]

The slides role is to meter the airflow into the carb. Obviously with throttle closed the slide is only allowing a very little air to pass under it. The idle screw actually manually lifts the slide to set the idle. Its basically the slide stop. As the needle and slide are both connected lifting the slide by opening the throttle allows more air to pass and also lifts the needle to add more fuel to the mix. The slide cutaway/number is the angle at which the slide base is cut. It affects the velocity of the air as it passed under the slide. Once you begin opening the slide up a certain distance the effect is less noticable as your working on other circuits more so. The little notch in some slides to to assist in air flow at idle by allowing the slide to be closed further.

[twowheels]

Originally Posted by bowhunter007

bump! Anyone?

You knew you had to wait for Jake right?
Basically what he said ...

PlusOnePerformance

[Jakobi]

So what tinkering has occurred and what did you find out?

[bowhunter007]

Originally Posted by Jakobi

So what tinkering has occurred and what did you find out?

Aside from swapping needles in & out, I've just been studying the effects of changes in clip position with different needles. I've found with my riding style, I like to run a smidge on the lean side. I lug the bike pretty good in very slow technical sections. Since I don't multi-task very well, constant clutching is a pain, so I'm "gas on, gas off" with it. The JDRed needle is working very well for this, untill I relearn a few things. Part of the problem is I'm standing, and I'm not comfortable loosening my grip enough to smoothly use the clutch lever under power. I'll work on it at a later time. I'm still worrying over my endurance for long rides. Since I'm predominently standing, I find when I'm tired, sitting down actually screws up my focus & balance. So far I'm only really good for about 4 hrs of hard riding(hard riding for me). I've kept track of my changes, so I know what I've done and I don't repeat. Thank you for explaining the slide. Now the picture is complete. Now I have to resist the urge to play with different combos of needles & slides. It is an interesting theory "Leaner slide w/richer needle" and so on. I need to start using the clutch properly so I richen the mix a bit, and ride a little harder on the pipe.

[Jakobi]

I hear you. A needle diameter change is somewhat similar to the slide in that they both overlap also with the pilot.

It never ceases to amaze me how much the power delivery can change even with just one minor adjustment. For instance I went to try Glenns theory of richer = more torque and more power. I went a half a clip richer on the needle and that was all. I did pick up a bit more torque off idle, but I also had a rich to right transition in the lower. More of a hit right off the bottom you could say, but it wasn't a crisp clean hit. Just an annoying burble and then brap. The mid range response was noticably smoother and tractored well gear high half throttle. The top end the same. After lunch I went half a clip leaner again. The grunt off idle was still there but there was very little burble. As soon as I opened the throttle the bike pulled clean, building revs to the mid range. From here the bike snaps hard to life into the top end where it peaks out hard. The mid range hit either lights up the rear end or puts the front end skyward. It wouldn't do this as well with the richer setting. Further to that. The half clip leaner last week, same conditions, same loop, I stopped on the trail and donated a litre of fuel from my tank to a mate and still made it to the servo. It took 8L neat to fill the tank. This week I hit reserve on my own and took over 8L to fill the tank. I know which setting I'm sticking with.

As for the clutch I use it just about all the time. The leaner jetting usually responds better to clutch work as it'll lack some of the torque of a richer set up, and also be snappier once its revving hard. Its just another skill that you dial down, the same as braking or giving throttle. Practice practice practice!

[bowhunter007]

My bike is turning into a portable laboratory

[GMP]

I'm convinced that these newer ASII carbs are more of a PIA. If the slide is correct (a #7 in a 250 at low to mid altitudes), the needle should not be such a big problem, and you can acheive good torque and runnout without a blubbering mess. Beleive me, I raced this bike a lot this year and you don't holeshot on a bike jetted like a pig. What fouled me up on the '12 was the notched slide, it wanted a RICHER, not leaner pilot. bowhunter, you shouldn't have to screw around with your older carb 250 much, if all is well it should jet pretty easy and you just ride it.

[bowhunter007]

Originally Posted by GMP

bowhunter, you shouldn't have to screw around with your older carb 250 much, if all is well it should jet pretty easy and you just ride it.

You're absolutely correct. I mess around with it, because I can. When it's time to ride, I set things to what works. My biggest problem, I'm fascinated by silly things like carbs, EFI, etc. I took apart a perfectly good carb, on my first car...to study it. I managed to figure it out, reassemble it, and tune it. First time...Lucky