Gentlemen, Is there a way in which the float level ('99 Roadstar OEM carb)can be accurately set by the method I used to use on Dell'orto carbs (a la Ducati.) That is to say, taking off the bowl, turning the bugger upside down and taking a fixed measurement from some reference point on the carb body to the top of the floats as they rest on the needle. If the answer is yes, what is that measurement

No.

The needle is loosely attached to float arm so there is a poor correlation between the point at which the needle stops the flow of gas and the position of the float.

A more accurate method is to measure the distance from the top of the float to the carb float bowl mating surface just as the flow of gas is interrupted (just when the needle seats).

Using this method, a measurement of 14.5 mm = 3.5 mm by the OEM float measurement method.

Doc

IMHO, I don't think there's are right or wrong way for this one. There are variables in any method.

I personally like your method and use 16mm, measured from the left side (float tang in front), at the midpoint on the carb seam.

Thanks.

06MidnightStar wrote:
I personally like your method and use 16mm, measured from the left side (float tang in front), at the midpoint on the carb seam.

That's correct, there are variables in any method but the aim is to minimize those variables in order to improve precision and accuracy. I believe the two most accurate methods are the OEM and (for lack of a better name) the valve seating methods. The precision of these methods can, however, be improved by taking multiple readings.

The OEM method is the 'real' reading under actual working conditions and accounts for all possible varibables. I believe this to be the best, although most labor intensive, method.

The valve seating method indicates the position of the float when it's pressing directly on valve as the gas flow is stopped. It's also a real-time test.

The float fully compressed method is a static method. In this case, the float tab may be in contact with the valve but it does not bear any relationship to when the gas flow it stopped. But it is the simplest method to do.

But here's the rub, using the upside down float fully compressed method, I did not get 16 mmm for a measurement; I believe it was somewhere in the 5 - 10 mm range (Post Edit: the 24 mm refers to the height when the carb is right side up and the floats just hang)(getting ahead of myself here). This method can be standardized to obtain good precision but the accuracy is questionable.

These are my opinions based on testing out the various float adjustement methods. In the end, you will need to make your own decisions on how you wish to set the float level.

Doc<br><br>Post edited by: DocShadow, at: 2007/06/08 11:35

the two most accurate methods are the OEM and (for lack of a better name) the valve seating methods.

This statement has the best chance of being true: 1) if you are trying to reset the float level in a stock carb to the OEM settings, AND 2) if you didn't already have the corresponding &quot;number&quot; using a different method.

No one method is any more &quot;accurate&quot; than another; it's simply another method.


But here's the rub, using the upside down float fully compressed method, I did not get 16 mmm for a measurement; I believe it was somewhere in the 5 - 10 mm range. This method can be standardized to obtain good precision but the accuracy is questionable.

This is a completely different issue that has nothing to do with &quot;accuracy&quot; or measuring. This is about the measurement.

IMHO, it makes perfect sense that we got different numbers. You are trying to mimic the OEM setup. I am trying to mimic a recommended aftermarket setup.

&quot;Carb tuning&quot; is affected by every component in every fuel circuit; therefore, I still do not understand why one would want to duplicate OEM float level in a carb that is anything but OEM. Changing the float level is really no different than changing the pilot jet, PMS, needle, main jet, accel pump, and on and on. Even same model carbs, set up identically, will not function exactly alike.


These are my opinions... In the end, you will need to make your own decisions on how you wish to set the float level.

No truer words have ever been spoken!

06MidnightStar wrote:
No one method is any more &quot;accurate&quot; than another; it's simply another method.

I disagree. Accuracy is a reflection of the sum of the errors within the system. When the carb is upside down, there is no constant relationship between the needle, the seat, the tab and the floats between different carbs. Each carb has its own systematic error. Consequently, the accuracy of this method is questionable. On the other hand, these variables are constant within a carb and that's why I believe the precision is good (I have not tested this assumption). The precision of this method only relies on the ability of the person to take the measurement the same way each time.

The accuracy of the other methods is better as there are less variables that can contribute to errors of measurement. On the other hand, the precision is not as good as there is more reliance on the operator to make the same adjustments each time. For example, can one position the float at the same spot each time to shut off the flow of gas? Is your eye in the same spot each time to read the meniscus? Some of these errors in measurement can be minimized but at what cost.

But here's the rub, using the upside down float fully compressed method, I did not get 16 mmm for a measurement; I believe it was somewhere in the 5 - 10 mm range. This method can be standardized to obtain good precision but the accuracy is questionable.

This is a completely different issue that has nothing to do with &quot;accuracy&quot; or measuring. This is about the measurement.

It's unfortunate the I linked two thoughts in one paragraph. I was just illustrating that our values are substantially different but I suspect we may be measuring the float height at different areas. BTW .... looking at my pic there is no point on the edge of the float that is more than 10 mm from mating surface.

But yes, in a way it has to do with accuracy as accuracy defines whose value is closest to the 'real' value. In other words if you measured 16 mm and I measured 7 mm (check my notes) which value is closest to the value it should be?

&quot;Carb tuning&quot; is affected by every component in every fuel circuit; therefore, I still do not understand why one would want to duplicate OEM float level in a carb that is anything but OEM. Changing the float level is really no different than changing the pilot jet, PMS, needle, main jet, accel pump, and on and on.

Even same model carbs, set up identically, will not function exactly alike.

I think this has been discussed previously (by erizo). But at any rate, all jet settings are provided a starting point from which to move on. If you look at the article that you cited you'll notice that he does not stipulate that X mm is the float height or x main is the one to use. Everything is base on performance. Thus you start with the 170 main and then test to see if you need to change it, etc.

It's starting to storm heavily here so I need to get off the computer. We'll have to continue this stimulating discussion later.

Doc

Each carb has its own systematic error. Consequently, the accuracy of this method is
questionable. On the other hand, these variables are constant within

this sounds like engineer talk... are you an engineer? If so I can no longer believe anything you say ~Guido

davehrn wrote:
this sounds like engineer talk... are you an engineer? If so I can no longer believe anything you say ~Guido

I'm a scientist.

Can you still respect me in the morning.

Doc

Can you still respect me in the morning.

scientist... ok.. but as long as your not irish (to understand watch blazing saddles) ... My brother is now an engineer... and everytime he starts getting into areas he doesn't know the answer to .. he just uses bigger words.. last time I asked him if they had a class that taught him that... ~Guido

I adjust mine till she squeals with delight ....then like any smart man I leave it alone and just ride her ......Coug <br><br>Post edited by: Cougar, at: 2007/06/11 16:50