Topic: Cylinder 1 issues.

[750K5]

 So I'm in the depths of the K5 currently.  I was planning to hone and re ring. After I measured the cylinder bore, taper and out of round which were in spec I found that the number 1 cylinder isn't as happy as I hoped. I entered this with plans to keep it low cost (I see others here are wise to how that goes). If I run this cylinder what issues could I be facing? I've already purchased all gaskets, seals and o rings.  Cam chain , primary chain's and all associated guides and rubber parts. The primary cush gear is ordered.  Should I just bite the bullet and ship it off to cycle X for machine work and oversize 0.25? All thoughts are appreciated! The other pic is number 2. I have more photos of the project I'm finding I cannot load many pics with my phone.  I'll try with my computer and resize to share the progress.
Thanks

[bryanj]

Looking at the pictures it seems that the markings are lower than lowest ring travel and if they are, considering cost of boring plus pistons i would run it

[Tracksnblades1]

K5,

Did you take picture after using a "stiff" precision hone?

Or was it a glaze buster type?

If your planning to bore, just sayin, Bore it.....😎
There are some economical kits available if your planning to bore and purchase oversized pistons anyway...

Without knowing your measured cylinder specs, especially cylinder taper, it would be a Hail Mary to make recommendations. I personally don't like rerings. New piston rings tend to be square. While old piston ring grooves are not. The vertical score marks are an issue for me, but I've seen worse ran again.

A lot would depend on your preferences and planned usage.

P.S. Is that by chance an old Yamaha 360MX....

[750K5]

Thanks for the reply!
This is what I've got.

I used a flex hone. 2.5in. 240grit.
The cylinder measures: #1
Y1-2.401 in. Y2-2.401 in. Y3-2.402 in.
X1-2.401 in. X2-2.401 in. X3-2.402 in.
Based on the book this should meet serviceable spec?

This a a 75' CB750k

[Tracksnblades1]

Thanks for the reply!
This is what I've got.

I used a flex hone. 2.5in. 240grit.
The cylinder measures: #1
Y1-2.401 in. Y2-2.401 in. Y3-2.402 in.
X1-2.401 in. X2-2.401 in. X3-2.402 in.
Based on the book this should meet serviceable spec?

This a a 75' CB750k

What are your pistons measuring?
Your x-y measurements don't show much taper...

P.S. I know the cylinder is k5. What's in your picture doing a wheelie? 360mx....

[750K5]

That's just a random old school pic I grabbed. It reminded me of my first bike when I was kid. Which was a 1981 Yamaha YZ80. Although the YZ had a mono shock which I believe was the first year for that tech.

I'll confirm piston measurements tonight. The way I understood the specs was if the bore is in spec the standard pistons are good as long as the taper/out round is 0.002 or less?

This is off memory as I dont have the specs with me currently.

[Tracksnblades1]

That's just a random old school pic I grabbed. It reminded me of my first bike when I was kid. Which was a 1981 Yamaha YZ80. Although the YZ had a mono shock which I believe was the first year for that tech.

I'll confirm piston measurements tonight. The way I understood the specs was if the bore is in spec the standard pistons are good as long as the taper/out round is 0.002 or less?

This is off memory as I dont have the specs with me currently.

The piston will have a service limit also...
Above the standard piston size and service limit are indicated.

With the scores in the cylinder, the same may be on the pistons.
If you do the math, you'll find the maximum allowed piston to cylinder wall clearance Honda recommends.

[750K5]

Thanks for the info.  I'll take a closer look at the piston sizes tonight. I don't see similar scoring on the piston skirts though.

[HondaMan]

That's a nasty scratch! Ow...
I'd suggest at least the 0.5mm step-bore size for a scratch like that one. Otherwise you might not get the uneven, hard-line surface that will border both sides of that scratch.

[Jerry Rxman Griffin aka MuthaF'er]

Or have another stock cylinder installed by CycleX land use your current pistons?