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I bought a highly modified R75/5 long block awhile back and it's time to jet carbs for it. How do I determine the actual cc of the cylinders without (hopefully) removing the heads? I've seen video of the Bonnieville Salt Flats where they poured some liquid in the spark plug hole and measured it. Any tips on how to do this correctly? What are the actual volumes I'm looking for? Also, in an earlier thread on this block, someone mentioned determining if it has a 336 cam by measuring lift and a link to the "moragafalconer" website for more info, but the website is no more. Any actual numbers I can use?

Graduated cylinder with a petcock and hose into an empty bdc cylinder should do it. Or fill a container to a mark, test, make a new mark and calculate the volume. Or convert ccs to ozs and use a meauring cup. Use vegetable oil, you can blow it out after, and you might have a convienent source.

Native /5 wrote:Graduated cylinder with a petcock and hose into an empty bdc cylinder should do it. Or fill a container to a mark, test, make a new mark and calculate the volume. Or convert ccs to ozs and use a meauring cup. Use vegetable oil, you can blow it out after, and you might have a convienent source.

If you are filling with the head on, you have to subtract the head volume, so you have to know that ahead of time, or do the process you describe twice, TDC and BDC, and subtract the TDC volume from the BDC volume.

I did it once, but the heads were removed.
A plexiglass plate was bolted to the head mating surface and had 2 small holes in it near the chamber perimeter. One to put fluid in, one to let air out.
Measurement was done by using a burrette - http://en.wikipedia.org/wiki/Burette.
How many cc's for your bike I don't know.
It is beneficial for engine balace that the 2 heads have the same capacity. Bear in mind that evening them up requires making one BIGGER. More than a tiny bit and your compression ratio drops. That is usually compensated for by head and/or barrel milling as this process is usually part of building a high performance engine.

dougie wrote:I did it once, but the heads were removed.
A plexiglass plate was bolted to the head mating surface and had 2 small holes in it near the chamber perimeter. One to put fluid in, one to let air out.
Measurement was done by using a burrette - http://en.wikipedia.org/wiki/Burette.
How many cc's for your bike I don't know.
It is beneficial for engine balace that the 2 heads have the same capacity. Bear in mind that evening them up requires making one BIGGER. More than a tiny bit and your compression ratio drops. That is usually compensated for by head and/or barrel milling as this process is usually part of building a high performance engine.

That method is for determining the volume of the combustion chamber in the head, is it not? I don't think it would work for the cylinders because the piston sticks up higher than the gasket surface, correct?

Tim Shepherd wrote:That method is for determining the volume of the combustion chamber in the head, is it not? I don't think it would work for the cylinders because the piston sticks up higher than the gasket surface, correct?

CYLINDERS!!! YIKES!!!
I was thinking cylinder heads, probably 'cause that's what I did.
(Note to self - listen.)

Tim,
The 336 sport cam has a vakve lift of 10.67mm.

On measuring the cylinder volumnes, Why do you want to? Are you trying to determine whether the engine is a 750, or 800, or 900 or 1000. Do you need to be accurate enough to tell if the 750 cylinders have been bored?

Major Softie wrote:

Native /5 wrote:Graduated cylinder with a petcock and hose into an empty bdc cylinder should do it. Or fill a container to a mark, test, make a new mark and calculate the volume. Or convert ccs to ozs and use a meauring cup. Use vegetable oil, you can blow it out after, and you might have a convienent source.

If you are filling with the head on, you have to subtract the head volume, so you have to know that ahead of time, or do the process you describe twice, TDC and BDC, and subtract the TDC volume from the BDC volume.

All true. I was just thinking of getting a very rough figure, then deducing which size the bore was. The volume in the head would likely not put the disp. into the next ballpark.

Native /5 wrote: All true. I was just thinking of getting a very rough figure, then deducing which size the bore was. The volume in the head would likely not put the disp. into the next ballpark.

Yeah, I only made the point because the OP implied with the "highly modified" comment that he could not trust that the bore was anything standard.

Major Softie wrote:

Native /5 wrote: All true. I was just thinking of getting a very rough figure, then deducing which size the bore was. The volume in the head would likely not put the disp. into the next ballpark.

Yeah, I only made the point because the OP implied with the "highly modified" comment that he could not trust that the bore was anything standard.

How about a comparison with a known standard? Such as Tim's R75/5 that he's been trying to crash.