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Discussion Starter · #1 ·
ok so i have super hard low-end with no top-end. sounds like i'm running rich. before i make adjustments, it's right to go leaner, correct? or other way around?
 

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Does a leaner mixture means more or less gas. I have the same problem with my carb, great low but no high. How many turns out do you guys have, low and high settings? Sorry to go off topic a bit.
 

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Leaner means less fuel and oil and also less lubrication. I would ask what gas to oil mixture you guys are using. I use 40-1 with 92 octane and synthetic oil. I would look to the mixture before I would try adjusting around on the carb. I can tell you from experience that you can do more harm then good messing with the air /fuel mixture screw.
 

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Discussion Starter · #5 ·
the richer the mixture, the better the low-end you have. the leaner the mixture, the better top end you have, but be careful. too lean a mixture can really damage the engine. this is why you have to do some tuning. start rich, then work your way lean slowly... about 1/8th turns at a time.
 

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BoostedBoogie said:
the richer the mixture, the better the low-end you have. the leaner the mixture, the better top end you have, but be careful. too lean a mixture can really damage the engine. this is why you have to do some tuning. start rich, then work your way lean slowly... about 1/8th turns at a time.
So I should adjust my low setting "richer" (left turn) and my high setting "leaner" (right turn)?

IRT pocketbike71:

I'm using 25:1 on 91octane. wil be trying 32:1 after I drain/flush the old one.
 

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I'm going to interject here because it almost appears that it's different between stock carbs and aftermarket carbs. On stock carbs there is an idle screw and an air screw. Turning in the air screw (right) will decrease the air flow therefor increasing the fuel to air ratio, richer. This is what I gather from the Stock Carb Tune tip in the Tune Tips post. From what you guys are saying you must all be running aftermarket carbs where the adjustment screws control the fuel flow, making the adjustments opposite. This doesn't seem right but I'm just comparing notes knowing that I have to go home and hash it out tonight.
 

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Discussion Starter · #10 ·
actually, im not too sure with the dual-needle carbs. not sure if you want both needles to have perfect ratio of air and fuel, or if you want low end to be super rich and top end a little leaner.
 

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Discussion Starter · #11 ·
calvin71x said:
I'm going to interject here because it almost appears that it's different between stock carbs and aftermarket carbs. On stock carbs there is an idle screw and an air screw. Turning in the air screw (right) will decrease the air flow therefor increasing the fuel to air ratio, richer. This is what I gather from the Stock Carb Tune tip in the Tune Tips post. From what you guys are saying you must all be running aftermarket carbs where the adjustment screws control the fuel flow, making the adjustments opposite. This doesn't seem right but I'm just comparing notes knowing that I have to go home and hash it out tonight.
we aren't considering the idle here. just the air fuel ratio mix. before tuning the air fuel ratio, you need to set your idle first, because the a/f will change idle a bit. once you get the idle, set the a/f, then you'll have to adjust the idle again so its running smoothly.
 

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BoostedBoogie said:
we aren't considering the idle here. just the air fuel ratio mix. before tuning the air fuel ratio, you need to set your idle first, because the a/f will change idle a bit. once you get the idle, set the a/f, then you'll have to adjust the idle again so its running smoothly.
I wasn't really considering the idle screw yet either. Just trying to figure out if the a/f adjustment changes the airflow as indicated in the Tips post or if it leans out the fuel as you turn it in. Does turning the a/f screw in decrease air flow or decrease fuel flow?
 

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The experience I've had with ALL my bikes is that low speed is fixed or proportionate with the high speed mix needle. I like to slip a small piece of hose ove the adjustment screw so that I can turn it while driving. IN IS LEANER!! Ride the bike at top speed and turn the screw counterclockwise until the engine starts to double stroke. (sputter). Then turn it in slowly in small incriments until you achieve top speed. Then turn the screw back out 1/4 turn for safety.
 

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For whatever you are tuning, using your ears to do it is down right back-woods country. Get a digital Tach w/line clip - $60 from your local chainsaw shop. Although I am fairly new to this forum, I did notice that there is alot of SUBJECTIVE information included with some really good stuff.

Numbers dont lie but your head and heart will. Get a TACH and make your adjustment by the info it gives you. Then we can all compare solid numbers. We will get better faster that way.

Suggested Future PBP Goal: "No more I like this and that".
Sorry for the Rant, its late................

MOD: you may have to move this one.....LOL
 

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For the inexperienced, a tach is a good piece of equipment. But engines should be setup while under a load and riding down the street while looking at a tach AND tuning all at the same time is plain stupid. Someone is gonna get killed. Like I said before.....put a short piece of hose over your adjustment screws as an extension so you can turn them while driving. While under a load at full tilt you can reach down and tweak the adjustment screw without taking your eyes off the road.
 

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Q: guess you dont know squat about Tachs, cause if you did you'd know they can be used on the go as well as the bench. LOL

The only inexperience here is you knowledge of Tachs.
http://***************/accessories2.htm

I know you are not trying to imply that a FAT arzzz is as accurate as a Digital Tach.
Nuff said.
 
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