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  #16  
Old 07-02-2004, 11:19 PM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

Quote:
Originally posted by TexasDirtNap393
Great writeup and I now know how to set the float level but what exactly does the float do.
Sorry for the confussion, maybe I should have clarified. The "floats" as the name implys are meant to float in the gas that is filling the bowl. As the fuel enters the float bowl it causes the floats to rise which push against the fuel inlet needle. Once there is enough fuel in the float bowl to raise the floats to the specified "float level" the the fuel inlet needle makes a seal with the fuel inlet valve seat cutting off the fuel supply. As the carb uses fuel and reduces the ammount in the float bowl, the floats are lowered and the seal is broken, allowing more fuel into the float bowl until the desired level is reached and the needle contacts the seat and shuts off the fuel supply.

Whew, I hope you can understand that.

Also, there is a small air pocket that resides on top of the fuel, that is why the carb is vented, and this is where atomospheric pressure comes into play. The atmospheric pressure is helping the force the fuel through the jets in order to equalize the pressure difference between the float bowl and the low pressure zone in the venturi of the carb. Atmospheric pressure, plus the weight of the fuel equals the amount of fuel pressure acting on the jets.

These questions are great, if you have more keep them coming! Let's help everyone understand.
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  #17  
Old 07-03-2004, 01:20 AM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

Faded, if you already haven't, I think you better open a bike shop!! I'm sure you will have a lot of customers because you're mechanical skills seem SO GOOD to me, really!!! great job you've done here!!!
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  #18  
Old 03-22-2007, 09:12 AM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

This is probably one of the best "how to" articles I have ever read!
thanks Faded!
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  #19  
Old 05-15-2007, 12:38 PM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

I have a question. I just tried to adjust my floats, which are shaped just like the ones in your pics, to 16mm. The previous adjustment was so far from 16mm when aiming for the very tip top of the float, that I began wondering if the very top of the float was the spot you were supposed to measure at. Just for the heck of it, I adjusted the float , setting the very top of it to 16mm, and it was quiet a huge change /adjustment to get it there! Something didnt seem right, -even with the carb completely upside down the fuel needle didnt seem like it was seated at all after this major float adjustment. I verified this by hooking a vacuum gauge to the fuel inlet and verified indeed the needle was not seating.

So I thought to myself, there's no way you measure at the very top of this float, but maybe closer to the linear line about 2/3 up, where its a normal "shape". I ended up adjusting my 16mm to line up with where the metal arms mold into the plastic float, and doing it this way gave me a sealed needle as judged by my vacuum gauge.

Im not questioning your writeup, Im questioning why did setting my float to 16mm the way you say cause some weird things to happen and actually hang my fuel pin up from seating?

Note= the bike spits whitish exhaust smoke at all times when reving from idle to full throttle in neutral (87 cr125)

Now i will go back to the garage and try this adjustment again.
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  #20  
Old 05-21-2007, 01:24 PM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

Two things come to mind...and I'm not saying it's either of these but definitely something to check. First verify that the floats are installed correctly and not upside down (it could happen). Second, especially on a bike that old, how sure are you that someone didn't do you a favor and use a set of floats from a different carb?

It is also a commonly accepted practice to set the float level by having those 'mold lines' parallel to the gasket surface. Usually this is used in a pinch or if you can't obtain the factory spec. With your current setting how far off from parallel are you?
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  #21  
Old 05-26-2007, 08:09 PM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

hey faded awesome explanation
but i have a question? is that a pwk keihin and if so what is the float measurement for this carby and also does jetting have anything to do wit float level adjustment
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  #22  
Old 05-28-2007, 11:41 AM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

Quote:
Originally Posted by RMer98 View Post
is that a pwk keihin
Yes, 38mm AirStriker.


Quote:
Originally Posted by RMer98 View Post
if so what is the float measurement for this carby
16mm.


Quote:
Originally Posted by RMer98 View Post
does jetting have anything to do wit float level adjustment
The float level has everything to do with jetting. The first post of this thread explains how it affects all jetting circuits and the importance of setting the float level first.
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  #23  
Old 05-28-2007, 12:48 PM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

The float level has so much to do with the overall fuel air mix (jetting if you wish to call it that), that it is the way lots of dyno tuners experiment with different fuel air mixes. They do it by simply varying the float level by having the vents hooked up to a vacuum source. It is used on various things such as snow machines to compensate for temperature and altitude, again by varying the pressure in the float bowl itself.

But I still love it when someone who feels they know better look at me and just say "the size of the jet determines how much fuel gets into the air stream". To rip off Paul Harvey, now you know the rest of the story.
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  #24  
Old 06-16-2007, 05:21 PM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

So whats the measure ment for a 93 kx 250 i would look it up but i dont have a manual yet
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  #25  
Old 06-25-2007, 03:13 PM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

Wow this is awesome. It doesnt seem all that hard any more. I kinda know what floats do but what do like the float assembly tang and the fuel inlet needle do?? AWESOME write-up Faded
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  #26  
Old 08-28-2007, 06:56 PM
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Usflag Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

do now how to do the same to a 82'yz100 cause its way diffrent.thanks
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  #27  
Old 10-04-2007, 09:33 AM
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Cool Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

Quote:
Originally Posted by Faded View Post
T,

This one is free.
Lmao of course its free f it wasnt he wouldnt have put it up lol..but thanks man for it helped me out alot
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  #28  
Old 11-27-2007, 10:14 AM
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Icon3 Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

ok faded.. I'm brand new to fixing bikes. Took the carb off a 95 cr 250 to "grasp an understanding" of it.. Wish I would have been pointed in your direction sooner. The bike was running fine and when we put it back together... It will only start if you clean the plug every time and it only stays started for about 3-8 seconds before it "boggs out". The spark plug is wet and has unburnt fuel on it. The main question is, if you take the float and everything off the carb.. when you put it back on do you have to reset it. Could the float be causing this "flooding/ bogging out" problem. Thanks For the sick breakdown of the carb and float adjustment. I seriously was looking for a "dirtbikes for dummies" at the store. If you know that much about the rest of the bike you could write a sick "general knowledge" book. I personally would pay good money for one. If you know of one already out there .. let me know
craig
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  #29  
Old 01-08-2008, 09:39 AM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

Wow,what can i say great write up faded, now i have a better understanding of the float level, but would you know by chance the float level measurment for a 2002 CR250R, dont have a manual and by the way i would buy a book as cddj77 was saying of general knowledge +2
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  #30  
Old 01-11-2008, 08:15 AM
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Default Re: How To Set Your Motorcycle Carburetor Float Level (more commentary).

I don't know for a 2002. you could call your local dealer and they might give you the specs. If not.. you could always go "peak" at a clymers manual at a shop or bookstore. you could get a manual off ebay for 15-30$$ It was a great help to me.
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