philr54
Non-Com
fuel system apprentice
Posts: 118
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Post by philr54 on Dec 22, 2009 11:17:10 GMT -5
Had to do an oil change this morning and as long as the weather wasn't bad (sunny, no wind, 34 degrees F) I decided to do a little tweaking. After the oil change, I took a 40 minute spin up to 45mph to get warmed up good and adjusted the A/F screw. To this point it was out 2-1/4 turns. I seated the screw and started backing it out - I got 3-1/4 turns out with increasing rpm and I feel like it could go more but was leary of going any further - something about that little screw and spring shooting out . From reading several articles on carb tuning if the adjustment is less than 1 turn you're low speed jet is too rich and if it's over 2 turns it's too lean. I know I'll need to get several low speed jets but I could use some advice on how many and what increments to get. The scooter is a stock Carino LE (ZN150T-F). I don't plan any HP mods but I would like to tweak it a little here and there. First the carb and then the CVT. Appreciate any advice Phil
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Post by Rebel on Dec 22, 2009 13:06:28 GMT -5
I'm not a carb expert, but this comes to my mind when I try to dust off the cobwebs from the stored memories on adjusting the carb. Screw it out until you get an increase in the RPMs then back it in just a hair, one quarter of a turn. You can run it and check the plug to see if you have it too rich and if you want to use an instrument to get it close there is a thread here on making your own sensor to check it with. I'll look for it and post a link here. This was posted in our help resources area; scooterrebels.proboards.com/index.cgi?action=display&board=otherreadonly&thread=491&page=1I did read a suggestion once that said to screw the mixture screw in until it stumbles then back it out until it stumbles, then set it halfway between the two. The question also might be, why did you feel the need to adjust the mixture. Was it not running well? You say you want to tweak it a little, well increasing the fuel going through the carb is one way, but you need to also increase the ability for it to blow exhaust out. Routinely the way to just tweak these GY6 scooters is to start with a new air cleaner or by drilling holes in the air box, a pod filter (Uni) is popular, looks like a bag made of foam and it goes directly to the carb. Then you take the exhaust off and replace it with an after market performance exhaust, or modify the one you have to reduce the air flow restriction. This all will make you run on the lean side and you wll need to install a larger jet or raise the needle jet to richen your air fuel mixture.
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Post by Rebel on Dec 22, 2009 13:59:56 GMT -5
Oh, another way to get some more performance is to change your rollers/sliders in your variator to tune it to the way you ride and your physical weight.
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philr54
Non-Com
fuel system apprentice
Posts: 118
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Post by philr54 on Dec 22, 2009 14:13:54 GMT -5
The info I have is the scooters are jetted lean to meet emission requirements. One method I read for setting the A/F is to seat the screw, turn out 2-1/4 turns, turn in until there is a change then turn out till there's a change (counting the turns) and split the difference. Another method is to turn out the screw until You get the highest rpms, then turn in 1/8 or 1/4 turn. I'm out 3-1/4 turns and I don't think the rpms have peaked yet. The scooter is running better and smoother at this point but 3-1/4 turns seems a bit much to me so unless there is something else involved I think I need to increase the pilot jet. I'm just not sure if I need to buy 1,2 and 3 sizes larger or 2,4 and 6 (no experience with how much effect 1 size larger will have). I hope I'm being clear on this, I have good mechanical apptitude but not much mechanical experience.
Phil
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Post by Rebel on Dec 22, 2009 14:23:29 GMT -5
OK, sounds like you have a pretty good handle on this to begin with, I'd first see if the needle jet is on the bottom adjustment, if not move the clip down a notch and see what that does. moving it down raises the needle up and makes it run richer, it opens the valve a bit. If you have it on the bottom grove, you can check out Leos thread where he modified his by cutting another couple grooves in it, again I'll look for it and post a link here. Once you have maxxed out on the needle valve, well it becomes trial and error, go up a jet size and see what it does.
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Post by Rebel on Dec 22, 2009 14:34:41 GMT -5
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philr54
Non-Com
fuel system apprentice
Posts: 118
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Post by philr54 on Dec 22, 2009 14:59:54 GMT -5
Appreciate your efforts, Rebel. Will the needle position have an effect on the idle/low speed performance. My understanding is the needle diameter, taper and position were more for midrange. Of course all those jets overlap so it's difficult for a newbie to comprehend sometimes. I figure if I go at this one step at a time, I'll know where to look if there's a problem. I've seen too many people make a bunch of changes and then try to figure out what went wrong . Phil
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Post by Rebel on Dec 22, 2009 15:09:18 GMT -5
Well, like i said before, move the needle and see how it goes, if you see an improvement great, it was free and no money lost. If not then think about changing jet out. If you have the right drill bit set you can drill your jet to a larger size, if you go out too far you can solder the hole back up and drill it smaller. The cost of the drill bit set will be the same as buying several jets though. Regarding the needle, like I said in my first post, I'm not a carb expert, seems to me that it can only make a difference up to the point where it is just too high. Before you buy any jets you will want to pull out the one you have to see what size it is, they vary in these things.
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Post by Rebel on Dec 22, 2009 19:20:53 GMT -5
I was just over at dawgland and saw that you posted the same thread over there. You also got very similar advice. JR said to raise the needle one notch, in reality it is actually lowering the clip that you do, lowering the clip does raise the needle. Things get a little confusing at times. I'd suggest that when posting over there you have to pick a person to follow the advice from, there are so many that post there it can become a plethora of ideas and doing more than one thing at a time can just lead to more problems to fix.
My suggestions stands at lowering the clip, then if you need go to a bigger jet.
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Post by Rocketdog on Dec 22, 2009 20:01:04 GMT -5
I have a suggestion. If you have to turn your pilot screw out that far, you might very well need a bigger pilot jet. Before you buy one, try lowering your float a mm. Just one mm and see if things don't improve. If it still needs more that 2 and a 1/2 turns out get the next larger pilot jet.
RD
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philr54
Non-Com
fuel system apprentice
Posts: 118
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Post by philr54 on Dec 22, 2009 20:05:53 GMT -5
If you pay attention to who posts what, you get a feeling for who knows what they're talking about and who's blowing smoke. I had already decided to take your advice and JR just added confirmation. This scooter is my only transportation for now so I consider any info I get carefully before doing anything. I appreciate all your help and the links you posted.
Phil
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philr54
Non-Com
fuel system apprentice
Posts: 118
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Post by philr54 on Dec 22, 2009 20:15:25 GMT -5
I have a suggestion. If you have to turn your pilot screw out that far, you might very well need a bigger pilot jet. Before you buy one, try lowering your float a mm. Just one mm and see if things don't improve. If it still needs more that 2 and a 1/2 turns out get the next larger pilot jet. RD Thanks RD, a larger pilot jet was what I thought originally. In the mean time I'll try Rebel and JRs suggestion, like Rebel said it's free and if it doesn't work I can change it back. I'm not sure I'm ready to play around with the float yet. For my continuing education, what would lowering the float do exactly? Phil
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Post by Rebel on Dec 22, 2009 20:37:34 GMT -5
The float is just like the one in your toilet, it keeps fuel in the bowl of the carb. I'm not sure how lowering it will effect the operation of the carb except that making the adjustment lowering the tab the needle valve rests against would let more fuel come into the bowl, perhaps giving you a reserve so to speak and keep it from running dry.
Like I said from the start, I'm not a carb expert, RD may have an experience that could prove valuable. Also it is another no cost thing to try, you can always put it back if it does not help or if it makes things worse. Still I would try one change at a time so you know just what that change does by itself.
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Post by Rocketdog on Dec 23, 2009 5:26:43 GMT -5
The float is just like the one in your toilet, it keeps fuel in the bowl of the carb. I'm not sure how lowering it will effect the operation of the carb except that making the adjustment lowering the tab the needle valve rests against would let more fuel come into the bowl, perhaps giving you a reserve so to speak and keep it from running dry. Like I said from the start, I'm not a carb expert, RD may have an experience that could prove valuable. Also it is another no cost thing to try, you can always put it back if it does not help or if it makes things worse. Still I would try one change at a time so you know just what that change does by itself. I know a little about it and have learned what I know from trial and error. Not to mention advise from experts. Definitely change one thing at a time and be patient. Here's my explanation. I'm also not the guy who writes the service manuals, so bare with me. hehe Raising and lowering the float decreases and increases the fuel lvl in the bowl, respectively. Raising the float, which actually lowers it down into the bowl, makes the fuel lvl lower. The theory is that this makes it just a little harder for atmospheric pressure to push fuel into the venturi of the carb and makes it run just a but leaner. Lowering the float is just the opposite. It does work, but it's really more of a fine adjustment. If you were close on your jet sizes it might make the difference. I did it to a 150cc that I was having trouble with. A 38 pilot was just too large and the 35 wasn't enough. I lowered the float a little and it made the difference. RD
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Post by Rebel on Dec 23, 2009 13:15:25 GMT -5
RD, so what you want him to do is make it easier for the venturi to suck up some gas thereby enriching the a/f mixture? You want more fuel in the carb bowl?
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