C72, CA72, CB72 & CL72 piston differences?

Alan F.

Alan F.

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In the 77/305 piston thread Mr.Honda had stated that there were 3 types of pistons for the 72/250 models.
After a look at CMSNL I find these four part numbers for standard bore. Are two of them the same compression ratio and the other two are other ratios?

PISTON
13101-259-000
from serial number: C72E-010001
upto serial number: C72E-313267


PISTON
13101-259-010
from serial number: C72E-313268


PISTON
13101-268-010
from serial number: CB72E-010001
upto serial number: CB72E-104081


PISTON
13101-268-030
from serial number: CB72E-104082
 
Did you ever find an answer to this? I am helping a guy with his CL72 Engine number: CL72E-1107626 I am assuming his pistons are wrong from how they look. No direction arrow, stamped standard, very narrow across the top. I will post pics
 
jsikes22 said:
The middle photo is of the piston my friend put on his bike.
Click to expand...
Since there are 3 total pictures and 2 of them side by side, not sure what you mean by "middle". If you had captioned the picture you're referring to it would have made things easier to understand. If you mean this piston below, it would appear to be an aftermarket (possibly higher compression ratio) piston and with only that view of it, it's hard to be sure of any possible marks it might have to indicate which side is intake, but it's rare that a piston is not marked accordingly.

1750598162615.png
 
ancientdad said:
Since there are 3 total pictures and 2 of them side by side, not sure what you mean by "middle". If you had captioned the picture you're referring to it would have made things easier to understand. If you mean this piston below, it would appear to be an aftermarket (possibly higher compression ratio) piston and with only that view of it, it's hard to be sure of any possible marks it might have to indicate which side is intake, but it's rare that a piston is not marked accordingly.

View attachment 46745
Click to expand...
From mobile it looked like they were posted in succession. I will post a better photo this afternoon.
 
ancientdad said:
Since there are 3 total pictures and 2 of them side by side, not sure what you mean by "middle". If you had captioned the picture you're referring to it would have made things easier to understand. If you mean this piston below, it would appear to be an aftermarket (possibly higher compression ratio) piston and with only that view of it, it's hard to be sure of any possible marks it might have to indicate which side is intake, but it's rare that a piston is not marked accordingly.

View attachment 46745
Click to expand...
jsikes22 said:
From mobile it looked like they were posted in succession. I will post a better photo this afternoon.
Click to expand...
ancientdad said:
Since there are 3 total pictures and 2 of them side by side, not sure what you mean by "middle". If you had captioned the picture you're referring to it would have made things easier to understand. If you mean this piston below, it would appear to be an aftermarket (possibly higher compression ratio) piston and with only that view of it, it's hard to be sure of any possible marks it might have to indicate which side is intake, but it's rare that a piston is not marked accordingly.

View attachment 46745
Click to expand...
Here is a picture of the piston he used off the bike. I also measure the opening on the piston that the arm goes into it was 22mm and the top of the arm is 17mm. Everything I am seeing is point to wrong piston. Your thoughts?IMG_1220.jpeg
 
If the wristpin hole is 5mm larger than the small end of the rod, then the dome and valve cutout discussions are moot.
 
What year is the engine ? / What is the engine number ?

Did you ever find an answer to this? I am helping a guy with his CL72 Engine number: CL72E-1107626 I am assuming his pistons are wrong from how they look. No direction arrow, stamped standard, very narrow across the top. I will post pics
Click to expand...

found it :ROFLMAO:

CB72 pistons sets and liners.jpg

I'm pretty sure I have all versions, even the high domed pistons, (you see one at the right, second row from below), in an original Honda box including the part number.
 
IndianRob said:
From Bill Silver (MrHonda):

“One must choose the piston setup carefully, as Honda lowered the compression in order to reduce the number of piston seizures that occurred due to overheating. Lugging the little 250cc engine on a 300 lb motorcycle with low torque values causes the pistons to work very hard in a space of only about .001” to .002” clearances. With the known issues of erratic spark timing and today’s questionable fuel qualities that didn’t exist when the bikes were built, these engines can and will seize their little cast pistons to the cylinder walls.”

original pistons - 13101-268-010
lower compression - 13101-268-030
Click to expand...
Thanks, but please recheck your PMs (private messages).
 
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