do lettered cylinders have certaon rings?

[wornknobby]

my 90' cr 125 has 2 types of cylinders made for it,, an "A" and a "B" cylinder. now if i didn't order a piston but just wanted rings, do they still need to know what letter i have sonce the pistons are different sizes, or are the rings the same?

 

[i_955]

Same...

 

[BigRedAF]

not sure about the CR but the YZ rings are the same for all A,B,C,D cylinders. After market pistons are sized to the B size piston on the YZ's as well.

Go to the Service Honda web site and check the oem parts on the site. They will have a break down of rings and pistons for your CR, good luck.

 

[CR3999]

Yes They take different rings and piston, when you order a top=end tell the parts guy you have a A or a B jug.

 

[jmossbarger]

The rings are the same, just the pistons are different.

Joe

 

[motometal]

The pistons are so close that the difference is almost negligible, as stated above that's how the aftermarket piston companies can make just one piston. The guy at the shop said that most folks run the biggest piston regarless of the cylinder on the Hondas, when running Honda pistons.

Disclaimer: I'm not inferring that "the guy at the shop" always knows what he is talking about.

 

[ellandoh]

i ran a Vertex (B) piston in an (A) cylinder.......it tightened the clearance just enough to stop the CR deathrattle

 

[BigRedAF]

Just as a point of referance!

If you run a "D" piston in a "A" YZ cylinder and both are speced as advertised you will have less than .001 clearance and that is to tight!

If you measure your bore with a dial bore indicator and it is worn you can tighten things up a bit with a larger letter piston. However, this is a band-aid since the bore doesn't wear evenly and certain areas will be tighter than others.

 

[motometal]

looking at my Honda manual on this, their call outs are confusing. There's .00028" difference between service limits on the pistons A and B, which is actually somewhat significant considering the tight piston clearance on this type of engine. However, there's only .000079" difference in the service limit of the cylinder, which is negligible. Why wouldn't the difference be the same on both? Considering piston clearance should be the same between A and B as a goal. I got these figures doing my own conversion from their metric. If you look at their inch conversion, there actually is no difference between A and B because of their poor conversion accuracy, rounding to the nearest .001". This is why I had it in my head that the difference in pistons was negligible. To do your own conversions, multiply the mm by .0394.