Carburetor Float Level - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

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post #1 of 24 Old 03-28-2010, 01:50 AM Thread Starter
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Carburetor Float Level

This is something I need to understand though I have never read a post about the carburetor float level and setting. I have read the Clymer manual but...
-how does the float level effect the engine?
-the float level is 17.5 mm or .69 in
-have you ever measured the float level height?
-have you ever adjusted the float level height?
-is there a maximum the float level can be adjusted?

Thanks for your input.

Tim

2005 KLR 685
2015 Yamaha Super Tenere ES, 5/23/2015
2012 Yamaha Super Tenere; Purchased 7/30/2011; Sold 5/23/2015
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post #2 of 24 Old 03-28-2010, 10:20 AM
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Quote:
Originally Posted by tomatocity View Post
This is something I need to understand though I have never read a post about the carburetor float level and setting. I have read the Clymer manual but...
-how does the float level effect the engine?
-the float level is 17.5 mm or .69 in
-have you ever measured the float level height?
-have you ever adjusted the float level height?
-is there a maximum the float level can be adjusted?

Thanks for your input.
The float level keeps enough fuel in the bowl to feed the engine. So, the only way for it to impact the engine is if the level is too low, which could serve to starve the engine of fuel in conditions where the engine is demanding lots of it. That would be pretty much WOT at high loads, like when you're trying to maintain 100mph, or up hill into a huge headwind.

I did measure the float level once, using a clear piece of plastic tubing attached to the drain and curled up towards the top of the carb. It was spot-on and didn't need to be adjusted.The fuel level should be sitting a bit higher that the joint between the carb body and the bowl.

There was a time when floats would leak (brass) or would soak up fuel and sink (plastic), but I haven't run into an issue like that in ages.

A more likely cause of incorrect level in the bowl, on the KLR, is a failure of the vacuum petcock - it won't flow fully and can't keep the bowl full. Unfortunately, you can't see that with a float level inspection, as the bowl will fill to the correct level by the time the engine is off.

A maximum? There is usually a tolerance on the setting, but there's nothing to be gained by setting the float level higher.

Tom

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Last edited by Tom Schmitz; 03-28-2010 at 03:11 PM.
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post #3 of 24 Old 03-28-2010, 11:55 AM
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The float level is actually pretty important. If the float is set to high it can make the engine rich as there is less ground the fuel has to cover to get up through the emulsion tube, through the carb body and into your engine. A high float level can fill your air bleeds causing you to be on the incorrect fuel circuit for engine demands. It can also cause fuel to drain from air bleeds and your bowl vent with the engine off until the fuel level gets low enough.
A cool expirement to help understand this is to fill a glass with water. punch holes into the bottom quarter of a straw simulating an emulsion tube. The more holes you punch in the straw the more suction or vacuum is required to suck the water to your mouth, but if you put the end of the straw in the water enough to cover the holes it will do just the opposite and allow more water to your engine (mouth) with less suction resulting in a rich condition.
Mr. Smitz was right on about the low float!
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post #4 of 24 Old 03-28-2010, 12:12 PM Thread Starter
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Quote:
Originally Posted by Tom Schmitz View Post
The float level keeps enough fuel in the bowl to feed the engine. So, the only way for it to impact the engine is if the level is too low, which could serve to starve the engine of fuel in conditions where the engine is demanding lots of it. That would be pretty much WOT at high loads, like when you're trying to maintain 100mph, or up hill into a huge headwind.

I did measure the float level once, using a clear piece of plastic tubing attached to the drain and curled up towards the top of the carb. It was spot-on and didn't need to be adjusted.The fuel level should be sitting a bit higher that the joint between the carb body and the bowl.

There was a time when floats would leak (brass) or would soak up fuel and sink (plastic), but I haven't run into an issue like that in ages.

A more likely cause of incorrect level in the bowl, on the KLR, is a failure of the vacuum petcock - it won't flow fully and can't keep the bowl full. unfortunately, you can't see that with a float level inspection, as the bowl will fill to the correct level when the engine is off.

A maximum? There is usually a tolerance on the setting, but there's nothing to be gained by setting the float level higher.

Tom
I like your method of checking the float level. The manual shows to have the carburetor off the engine, bowl removed, and turned upside down. The measurement should be 17.5 mm. The adjustment is made my bending a tab that rests on the float valve. This is what I attempted a couple of months ago.
-The carburetor was removed from the engine.
-Measured the float height at 15.5 mm.
-Removed and bent the float adjustment tab (many times) until it was close to 17.5 mm.
-End result was the static float level was correct though the tab put enough pressure on the float valve that it closed the flow of fuel.

Is this the correct method to set the float level. If so, why did I run into the float valve problem?

I like your method of measuring the float level. What fitting did you use to replace the drain screw? What exterior mark on the carburetor did you use to check the float level?

"vacuum petcock" I can't find this in the Clymers manual.

Tim

2005 KLR 685
2015 Yamaha Super Tenere ES, 5/23/2015
2012 Yamaha Super Tenere; Purchased 7/30/2011; Sold 5/23/2015
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post #5 of 24 Old 03-28-2010, 12:28 PM
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Run a clear piece of tubing off the float bowl drain and loop it up along side the carb and tape it in place. Your reference mark for measurement will be where the bowl joins the carb body. Open the bowl drain screw and the fuel will flow into the tube showing you where the fuel level is at. It should be right at the the top of the bowl. No need to remove the drain screw.
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post #6 of 24 Old 03-28-2010, 12:29 PM
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Quote:
Originally Posted by tomatocity View Post
I like your method of checking the float level. The manual shows to have the carburetor off the engine, bowl removed, and turned upside down. The measurement should be 17.5 mm. The adjustment is made my bending a tab that rests on the float valve. This is what I attempted a couple of months ago.
-The carburetor was removed from the engine.
-Measured the float height at 15.5 mm.
-Removed and bent the float adjustment tab (many times) until it was close to 17.5 mm.
-End result was the static float level was correct though the tab put enough pressure on the float valve that it closed the flow of fuel.

Is this the correct method to set the float level. If so, why did I run into the float valve problem?

I like your method of measuring the float level. What fitting did you use to replace the drain screw? What exterior mark on the carburetor did you use to check the float level?

"vacuum petcock" I can't find this in the Clymers manual.
When checking the float the carb can not be completely upside down. The float needle has a spring loaded rod in it that can't be depressed when making your adjustment. when you flip the carb upside down start to tilt it slowly with the needle at the top and the float towards the ground until the float stops. once it stops if you keep tilting you will see the float move a little more depressing the spring in the needle. If you adjust the float with this spring depressed it will be inaccurate.
Hope this helps solve your problem.
Also in my Kawasaki manual the petcock is called the fuel tap. I've also heard it called a cockpipe, and fuel valve. It has a vacuum line that attaches to the carb or intake so that even with the fuel valve in the "on" position it will stop flow with the engine off.
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post #7 of 24 Old 03-28-2010, 12:40 PM Thread Starter
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Quote:
Originally Posted by rickybobbywebb View Post
When checking the float the carb can not be completely upside down. The float needle has a spring loaded rod in it that can't be depressed when making your adjustment. when you flip the carb upside down start to tilt it slowly with the needle at the top and the float towards the ground until the float stops. once it stops if you keep tilting you will see the float move a little more depressing the spring in the needle. If you adjust the float with this spring depressed it will be inaccurate.
Hope this helps solve your problem.
Also in my Kawasaki manual the petcock is called the fuel tap. I've also heard it called a cockpipe, and fuel valve. It has a vacuum line that attaches to the carb or intake so that even with the fuel valve in the "on" position it will stop flow with the engine off.
Thanks RBW. Good explanation of how to adjust the static float level . Now I understand.

Thanks SLO. Good method. Can the float level be set too high or can the gasoline be seen higher (in the tube) than the float bowl line?

Tim

2005 KLR 685
2015 Yamaha Super Tenere ES, 5/23/2015
2012 Yamaha Super Tenere; Purchased 7/30/2011; Sold 5/23/2015
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post #8 of 24 Old 03-28-2010, 12:44 PM
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post #9 of 24 Old 03-28-2010, 12:46 PM
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No problem Tim. In all actuallity your float was probably good, that spring could be the difference of 2mm! It very rarely comes out of adjustment without another issue happening.
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post #10 of 24 Old 03-28-2010, 01:09 PM Thread Starter
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Originally Posted by SLO-KLR View Post
Here's some pics from when I did my carb. See post #13
http://klrworld.com/forums/index.php/topic,4106.0/
Thanks SLO. I copied the information as a Word document. Good to take to the garage.

Tim

2005 KLR 685
2015 Yamaha Super Tenere ES, 5/23/2015
2012 Yamaha Super Tenere; Purchased 7/30/2011; Sold 5/23/2015
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