How is engine CC measured?

[desperate]

I'm coming from the UK for 2014. There are a few of us coming & I'm bringing my blown Indian 741B, & my team-mate has a blown Kawasaki 650. There are a few more Brits coming too. I keep reading about "Impound" and if any of us are lucky enough to end up there, how are the engines measured?

I've also read about having motors sealed as opposed to being stripped so we can carry on. We're hoping to try & get a record, & if it's approved, ride our bikes until they blow to bits. How would we stand then?

Our bikes have been built so the heads can "just" be removed with the enginesd still in the frame, but removing the Kawasaki one would be no fun.

[Seldom Seen Slim]

It's an oft-repeated story -- but it still is worthy of another telling.

Before you are awarded with a record your engine size must be verified as within the min/max limits for your chosen class.  Measurement using dial indicator and micrometer/ruler is the basic and a very accurate way to measure.  There are other ways, though -- for instance, if the sparking plug (hey - he lives in Britain ) is dead center in the head the measuring official can use a measuring stick -- graduated length for depth, and with a ruler that's on a center pivot so it can swing from vertical (to get into the cylinder) to horizontal (to measure the bore).  That's a pretty accurate way to go.

There are a couple of hydraulic methods of measurement -- one using air and one with a fluid such as brake fluid.  There the valve train is disconnected so all valves are closed and oil is introduced into the cylinder from a graduated column.  When the cylinder is 100% full the crank is rotated 180 degrees, and the oil/fluid that comes out is measured.  that gives you the displacement.  Air can be used as well -- but since I've never seen it done and only heard about it -- I won't try to describe how it's used.

The fluid volume methods are not a precise as the physical measurements, and are therefore more commonly used when there's little chance the the displacement is very close to the edge of the class.  That is -- if you're in a 500 - 750 cc class and your engine is (according to you, who built it, about 745 cc, more or less, you'll probably be asked to allow the officials to do a direct measurement.  If you've got a motor in the same class and it's a 685 cc -- pumping it with oil will likely be all that's required.

Remember, of course, that I'm giving you the story as one who's been measured a good few times.  I'm not the guy doing the measuring, and if he wants you to tear it apart - you don't have lots of choices  remaining.  You could, I suppose, whine and moan and try to have the chief inspector tell the not-so-chief that he doesn't need to be that precise.  Remember, of course, that the inspector is the guy that's holding you at arm's length from your record - don't be too snippy

[salt27]

Once your engine has been measured, you can ask to have it sealed.

You will need to have holes drilled in the head fasteners for the seal wire.

I think the seal is good for 1 year.

Don't forget your log books.

See you there, Don

[Richard 2]

I think you also have the option of sealing the engine, unmeasured in impound after a return run, and running the rest of the meet then tear the engine down for measurement and certification of a record, if someone else has not had a faster run during that time. I only heard of this never done it.
           (but best you check with Dan W. or his motorcycle impound equivalent.)

Also the rule book shows displacement computed by the following formula; bore x bore x .7854 x stroke x number of cylinders.

The cubic inch to liter conversion shall be computed by formula; cid/61.024= liter. That's per the 2013 rule book section 2A page 15.

Richard 2

[mbuk]

I read a tech on hear saying they are not keen on sealing and checking later as if you seize your motor they can't then check it and they don't want loads of people coming along at the end of the meeting to get their motors checked.

Kinda makes sence.

Andrew

[overdue]

Having disassembled many dozens of seized / broken engines during my early years in an automotive machine shop, I never found it impossible to determine the bore nor the stroke, given enough time with common tools. Usually it is a simple matter of sacrificing pistons, but usually there are at least 2 of those already beyond saving, anyway.

[Old Scrambler]

Assuming all of the above is for SCTA...............if you compete at BUB its basically the same but they seal the motor (potential record) with paint. I've had it done twice and upped my own speed on a later run. I then measured on the second to last day to avoid the crowd. 

[osti]

I've been lucky enough to set a few SCTA motorcycle records at bonnevile the last couple years. Every single time I have been to impound the process has been to measure the motor as soon as you set the record right then and there. BEFORE you go out and run anymore. Then they will seal your motor if you want to keep racing. I once asked if I could seal and then measure at the end of the week after I was done racing instead of right then and there when I made it to impound. I was told no.

YMMV.

[dw230]

Come over to the car side of impound, we are much nicer.

DW

[MRK]

Come over to the car side of impound, we are much nicer.

DW

And better looking!