After cleaning what seems to be about a million carbs, I can tell you that it is very rare that the float level is a culprit. Generally speaking, I have only had to mess with the float when someone else prior to me felt like they needed to mess with the float. Then I had to go back and correct it. Usually when there is a float problem one of two things happens:
1.) The float closes off the fuel supply too early and it will run out of fuel on a wide open throttle run (starve).
2.) The float doesn't close it off soon enough which results in fuel pissing out of the overflow tube. Usually when it is coming out the over flow tube it is more likely the needs and seat are bad and it is unable to close off the fuel supply. I have had to deal with this a few times.
Point being, I wouldn't worry about the float just yet. When you do mess with it, it is done with the carb off of the machine and upside down. I do inspect each one to make sure the needs is not stuck. I will gently raise and lower the float and physically watch the operation of the needle to make sure that it does in fact move easily.
Your problem is most certainly going to be in that main jet if in fact the passages are clean.
The factory one that had in there is very lean but this is what these guys are being required to do now a days to get through emissions testing in order to sell to the U.S.A.
All 150cc carbs are not created equal and in fact the vary widely from manufacturer to manufacturer. As an example, in an American Sportworks machine, right off the bat I put them at about a 128 or so main jet, up from a factory 114, and they like it there in stock form. On the other hand, on a Baja Motorsports machine, it came with a 108 and I bumped it to a 112 and it would flat out fall on it's face due to over jetting. It has to do with how the individual manufacturers deal with the fuel passages (best I can tell).
That said, in your case, you have to find out how sensitive it is to jetting. The proper way to do it is all trial and error and you inspect a brand new spark plug after a wide open run. (you may find you go through many plugs until you find the sweet spot...a plug cleaner is a good investment). I actually used a wide band controller on our Helix to find the optimal jet size at one time and somewhere (on this site) I have a picture of a perfect plug.
So, in your case, I would first try a 105 (or 108) and see how it does then read the plug. If it runs on that but the plug is still white, bump to a 114 and see what it does. You have to find what's too much and then start backing off from there. Tom at SYC powersports should have the jets you need. Click the banner above and contact him.
Going with an open element is a very effective, yet cheap, easy power gain and will in fact require a re-jet again. How big you go depends on how sensitive the machine is to your initial jetting experiments.
If you mod the exhaust, you will need to jet again. CDI may or may not require a rejet depending on how extreme you get. Same plug across the board as far as I am concered.
The screw on the bottom of the bowl is used to drain the float bowl for servicing.
There are two tubes on the carb that go to nowhere. One is the vent for the fuel bowl and the other is an overflow tube. What you described appears normal.
There is another tube that (in your case) goes to the intake manifold. This provides the vacuum that is needed to raise the slide during operation.
There are manuals in the tech section.
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Originally Posted by JDbuggyman
Guys, Thanks for the great info. Studman, I'm gonna check out those manuals and diagrams as soon as I'm done with this.
Justlooking...Great info on 'how to jet', but after reading that I have a couple questions. The writer talks about "checking and adjusting the float level" and also the "slide".
*How do I check and adjust the float level?
*Should this be done with the carb off the machine or when its up and running?
*Is the "slide" the black cylinder shaped diaphram in the middle of the carb with the needle sticking out of it?
I did not check or adjust the float level when I inspected my carb and looks like it could be one source of problems. Two of my local shops did not have the main jets in stock, so I'm still on the hunt for them. In the mean time, I'd like to rule out all other causes. Thanks again for the info and advice guys!
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