What ring size do I need?

[razooki]

I just had the head measured by my local shop and these are the measurements:

CYLINDERTOPMIDDLEBOTTOM x-axisy-axisx-axisy-axisx-axisy-axis #168.35668.36968.36468.36668.36468.364#268.35668.35668.35668.35968.35668.359#368.35668.36168.35968.37468.35668.374#468.34868.36168.35968.36468.36668.359

I'm pretty sure that the cylinders were bored .5mm over but I would like a second opinion. Also, the rings that I currently have have an "N" stamped on them. I was wondering if anyone knew if the tolerances for the oversize pistons are the same as for stock ones with respect to end gaps, etc.

Thanks,

Raz

 

[Guest]

The N just needs to be facing up when installing. That's all that means.
You need a manual with spes.
If you don't have a .5 over you may have to with the difference in numbers. That's a guess because I don't kinow the max wear. I'm not sure if a home would even those numbers out or not.

 

[razooki]

The N just needs to be facing up when installing. That's all that means.
You need a manual with spes.
If you don't have a .5 over you may have to with the difference in numbers. That's a guess because I don't kinow the max wear. I'm not sure if a home would even those numbers out or not.

Do you mean a manual specific for the oversize rings? I already have the 850 manual downloaded from BassCliff's site.

 

[Guest]

If you have a manual than you have the numbers to compare an overize to stock.

Ring gap will be the same.

 

[Nessism]

Okay, I fixed those numbers which were hard to read...

TOP MIDDLE BOTTOM x-axis y-axis x-axis y-axis x-axis y-axis

#1 68.356 68.369 68.364 68.366 68.364 68.364
#2 68.356 68.356 68.356 68.359 68.356 68.359
#3 68.356 68.361 68.359 68.374 68.356 68.374
#4 68.348 68.361 68.359 68.364 68.366 68.359

The GS850 has an 69 mm bore so something wrong with these numbers.

 

[razooki]

sorry about the numbers. I tried pasting the Exel spreadsheet but that's how it came out and photobucket was not help because it's not a pic. I sse what you mean about the bore measurements. I converted all of them from inches. What the heck kind of basket case motor do I have?

 

[Nessism]

Post the english measurements and please take the time to make it legible...like my post. Maybe you had a conversion error.

 

[Guest]

Post the english measurements and please take the time to make it legible...like my post. Maybe you had a conversion error.

What da ya mean "like my post"?
I don't understand much of anything you say.

I bet he got those numbers from a document. Maybe a bored 750 cylinder? Take a caliper and measure the pistons.

 

[Nessism]

What da ya mean "like my post"?
I don't understand much of anything you say.

I bet he got those numbers from a document. Maybe a bored 750 cylinder? Take a caliper and measure the pistons.

Hey Bill,

I took the original post and made the numbers readable...only it was listed in the Quote so it was hard to tell what I did. Fixed my post so check again...

 

[Guest]

Hey Bill,

I took the original post and made the numbers readable...only it was listed in the Quote so it was hard to tell what I did. Fixed my post so check again...

C'mon guy
I saw what you did and it made a big difference in the "readability" AKA legibility of the post.
I was talking about the big picture. :-\\\

 

[razooki]

Post the english measurements and please take the time to make it legible...like my post. Maybe you had a conversion error.

Here you go:

TOP MIDDLE BOTTOM

#1 2.6912 2.6915 2.6915
#2 2.6912 2.6912 2.6912
#3 2.6912 2.6913 2.6912
#4 2.6909 2.6913 2.6916

 

[Nessism]

Here you go:

TOP MIDDLE BOTTOM

#1 2.6912 2.6915 2.6915
#2 2.6912 2.6912 2.6912
#3 2.6912 2.6913 2.6912
#4 2.6909 2.6913 2.6916

Good job posting the numbers, thanks. Unfortunately, those bore sizes are undersize for an 850 so not sure what to suggest.

 

[razooki]

Good job posting the numbers, thanks. Unfortunately, those bore sizes are undersize for an 850 so not sure what to suggest.

Is it possible the PO fitted 750 pistons and cylinders to this bike? Would that be possible? My other option is to take the head back and have it re-measured.

 

[razooki]

Is it possible the PO fitted 750 pistons and cylinders to this bike? Would that be possible? My other option is to take the head back and have it re-measured.

Silly question. I just checked the 750 manual and the bores for that are in the 65mm range so I'm leaning toward the mechanic having measured it wrong. I dropped the head off on Saturday and I heard them mention something about having just gotten an new bore gauge.....

 

[Nessism]

Silly question. I just checked the 750 manual and the bores for that are in the 65mm range so I'm leaning toward the mechanic having measured it wrong. I dropped the head off on Saturday and I heard them mention something about having just gotten an new bore gauge.....

Yea, I'd take it back. BTW, its a cylinder, not a head. The head has the valves in it.

 

[razooki]

I got the cylinders back from the dealer's and they apprently are in perfect condition. The numbers are well within spec. So I removed the rings so that I can check the free end length as well as the gap when inside the cylinder. All rings end gaps were well within specs however there were a couple that had a free end gap that was a bit bigger than spec ( 9.5mm vs. 9mm). Is this cause for concern?

 

[gearhead13]

I got the cylinders back from the dealer's and they apprently are in perfect condition. The numbers are well within spec. So I removed the rings so that I can check the free end length as well as the gap when inside the cylinder. All rings end gaps were well within specs however there were a couple that had a free end gap that was a bit bigger than spec ( 9.5mm vs. 9mm). Is this cause for concern?

Having larger free end gap is ok (having numbers smaller than spec is the problem there) AFAIK, The most important is the ring end gap as measured when in the cylinder.