Topic: 750F rings

[fastback321]

Hi all,

I wonder if anyone knows of a source for getting piston rings for a 1978 cb750F Supersport.

I've looked at previous posts on here and they confirm what I found out by searching the web .... they're very hard to find.

I'm not sure where else to look, hopefully someone can help cause I don't really want to machine the pistons to get the older rings to fit.  I believe the correct part number is 13011-410-610.

Thanks

[SD750F]

I have the same model and had the same problem. And with a little research I found that they are next to impossible to find and you might get a chance a couple times a year to grab a couple (even rarer for a set of 4). But I did something else. I had my top ring groove cut out to fit a standard K series ring set that you can get easy. This cost me only $30 a piston...

Scott

[fastback321]

Thanks for the reply Scott.  Might end up having to do that.

Is it just the width that needs to increase?, no depth change?

[SD750F]

Depth was fine, the machinist checked out everything and did the research. And after all the homework was done the width was the only thing he had to change because the 77-78 F series top ring was thinner than the K series. I would have the pistons checked as well as the bore first to see where you stand there. My bike had 30,000 on it and the pistons were fine and still in spec. But I did have my top end cleaned and checked. And the exhaust valve guides needed replacement. Common issue with the 78 super sport engine. I found that one of my oil restrictors wasn't installed so I had some issues there also. New restrictor, new valve guides, new rings. Flatten (machined) cylinder top and head bottom. And I am back in business.

[TwoTired]

Just wondering why you couldn't grind a standard ring to thickness of the F ring?  Is this more expensive than re-grooving pistons?

Cheers,

[SD750F]

TwoTired,

I thought the same thing. The machinist could have done that, but would have cost more per ring than re-grooving ($50-80 per ring). And then I also considered the outside chance that the rings would have to be replaced again sometime. Or I break one when I install the pistons... So I thought this would be the best way and couldn't find any reason that would hurt.

Scott

[Flying J]

my honda shop said the cold get the piston rings for me. was going to be 190 for a set of 4.
i got a set on ebay for 50. Some people hate ebay, but i hate my honda dealer more.

[MRieck]

If I remember correctly the 77 and 78K rings are the same as the F2. Honda gave them different parts numbers. I know I bought a new set of OEM rings that fit the F2 a while back.

[fastback321]

So, I measured the grooves and diameter of my pistons and both grooves are the same width at 0.045" and same depth at 0.105" and the piston diameter is 2.380".

I wonder if someone has already machined the top groove on these pistons.  Does anyone know what the factory specs are for 1978 F pistons from a serial number 3026041 engine?  Do these specs line up with the specs for K rings?

[jtb]

If I remember correctly the 77 and 78K rings are the same as the F2. Honda gave them different parts numbers. I know I bought a new set of OEM rings that fit the F2 a while back.

You got a set for me, Mike, and they were 410 (F2) rings.