Hi All.  

Looking for some input on this cylinder condition or the guy measuring it. 

In a world of micrometers, snap gauges and bore gauges,  one has to wonder if ones getting it right.  

Ive revisited snap gauges and have decided again that i hate them.. numbers all over the place by the time one
gets them set, out, measured and recorded. 

I took this cylinder I have, original bore and started looking at it to decide what shape its in. 

To hone or to bore is the next decision. 

Im looking for the resident pros to look at this folder where Ive added some shots and short video of my bore gauge in the hole after setting zero at 79.96mm first of 4 standard bores noted in my manual for the RT1 360

Thanks in advance for input on the numbers or the process i used.  

4 measurements Taper walls 
4 measurements Thrust walls

Drac

drive.google.com/drive/folders/1iwb-nGlw...GCJOlqMDjhu5ELuVh8uN







 

If in doubt, bore it out.

TK.. lol, never heard that one..  reminded me of one i heard years ago. Without doubt, there is no curiosity.. 

Cheers.  Thanks for the chuckle 

Drac

Your picture shows you "zeroing" the dial bore gauge at "79.6".  You lost me right there.  Especially after I re-read your post and there you say you zeroed at "97.6".  

I don't know what your piston measures, but likely just under 80mm?  

For max taper and out of round, you really don't need to "zero".  Just compare the difference between the biggest and smallest readings.

For clearance, I measure the piston diameter at the skirt precisely as described in the Yamaha manual.  Zero the dial bore gage there.  Then every measurement will tell you directly how much bigger bore is than the piston.  

Mark.. lol. Sorta blew that one.. at least the data input here in my post. 

After setting the mic, The piston was measured at 79.96 ish.. 3/8 of a inch above the base of the apron.. 

It wasnt one of the larger stock pistons in the manual .97 .98 .99.. 

My thought was to set the DBG at the base measurement, tightest point, zero it to 79.96 then determine how large the bore had become vs the piston and to see if it had exceeded the maximum allowed number. 

As you mentioned, determining the “out of round, taper vs thrust wall isn’t determined by the piston but the maximum allowed difference between the two walls. 

The picture of the cylinder wall seemed to be rather smooth to me but i wondered if was glazed with piston material and reached out here for input. 

I will learn to proof read.

Ive came to the conclusion .. bore .. 1st oversize.. 

i didn't want to if it wasn't needed.  TK hit the nail on the head.  

Again, thanks for your time, input .. its deeply appreciated. 

Drac