Most anyone that builds their own kart engines probably uses a burette to check the combustion chamber volume for legality .... however, have you ever checked the burette itself for accuracy?
There is a simple way to check the accuracy .... it is as follows:;
You need to make a small rod (I used steel) that displaces exactly 9cc's (or 11cc's, or whatever you want to check for).
The idea behind this system of checking is that it's fairly easy (for most of us) to make something out of a solid material that has a volume of an exact amount, because we can use a micrometer and vernier to check it. Fluid volume is something that is quite a bit more difficult to verify for the average person (who does not have laboratory equipment laying around .... which is most of us).
Measure the ID of your burette, and obtain some barstock that is slightly smaller so you can drop it inside. I used some GROUND DRILLROD to make mine ...... because it is VERY accurate as far as being of consistent size (diameter) over its length. (available at most tool supply companies in 1/16" or 1/32 increments)
I'd recommend using something that is around 1/16 to 1/8" smaller than the inside diameter of your burette. If you use something that is too small, the test rod you make will be too long, and something too big (too close to the ID) will be difficult to drop in and out.
Now, here's how to calculate the size of a bar that displaces exactly a given amount:
The length of your bar should be:
DESIRED DISPLACEMENT (volume) IN CUBIC INCHES / (RADIUS² x PI)
.... or in plain English: the length of the bar will be:
[The desired volume], DIVIDED by [the "area" of the cross-section].
I'll give you some numbers here where I've already converted the metric volume to cubic inches, but you can calculate them for yourself if you want:
11cc's = .67126125 in³ (cubic inches)..... or 9cc's = .54921040 in³ (cubic inches)
Now we'll calculate an imaginary bar for 11cc's
Measure the diameter of your barstock EXACTLY........ to the tenth if possible... and by "tenth", I mean to the ten thousandths of an inch, NOT to the "tenth of an inch". (I'll show you later WHY it's so important to measure the diameter accurately.)
Let's say the diameter of your ground bar is .3752 (not uncommon for standard fractional sizes of drillrod to be a couple of tenths oversize)
(.1876)² x 3.14159265 = .11056446
..... or in English: the RADIUS of your bar [squared], times PI will equal the cross-section.
..... so the length of a bar that diameter (.3752) that displaces EXACTLY 11cc's will be:
(.67126125 divided by .11056446) which equals 6.0712 inches long
.....or in English: the volume we want [divided by] the cross sectional area of the bar = 6.0712 inches of length
Cut your barstock to that length........ DO NOT CHAMFER THE ENDS, JUST REMOVE BURRS!
Ideally, your bar should have dead sharp corners with no burrs, because chamfering the ends will reduce the volume of the bar ..... so try your best to face the ends dead flat without any chamfers or burrs.
Now, all you have to do is fill your burette up to 11cc's below the top, and carefully drop in the bar you just made, and see how high the fluid comes up. If the burette is accurate, you'll be right on the zero mark.
As I mentioned earlier in this article, it's very important to be extremely precise when measuring your material (especially the diameter), because just a small error in diameter can cause the length to be quite a bit off. If you re-run the above example for a diameter of .3750 (a difference of ONLY 2 tenths ..... that's .0002 of an inch) you'll see that the bar would need to be about .0065 longer !
In other words, mis-measuring the DIAMETER of your bar by only .0002 would make the length of your bar be off by .0065.
So............ try to measure the diameter within .0001 if possible, and try to cut your bar to length within about .001 or .002. You'll be assured of having a "gauge" that is virtually perfect !