Topic: 590cc Big Bore Kit

[WeirdTim]

Hello, I've got a 1971 CB500K with a 590cc big bore kit.  The only problem is that this kit was installed in the mid 70's.  I'm in need of rings and a head gasket.

Would anyone have any information on where these can be acquired?

Appreciate any information.

[bwaller]

There is a guy (Classic Cycle I think) on e-bay still selling what he calls a 605cc kit. They are 61mm pistons. If yours are Henry Abe or Hainstd 61mm pistons you can try to sweet talk him into selling you those rings, that include one piece oil rings which are in this case junk.

OR, as a better alternative, you can use early std. CB750 rings. The top two compression rings fit, but the piston oil ring groove needs to be machined wider to accept the good quality Honda three piece oil rings.

For a head gasket, try www.cometic.com. Part number H0516SP2059F.

[A Grove]

So, bwaller, is this 605cc kit really junky?  Because I really really want to bore my 550 out without getting too crazy like machining pistons, etc.

[bwaller]

A well respected person here has stated that "old #$%* is still old #$%*." 

 I agree with that logic most of the time, but I do have a set of these pistons in a 550. I found this low mileage set in an engine I acquired, otherwise I'd have gone the modified 750 piston route. Since they didn't cost me much I opted to have a skirt and dome thermal coating applied. However I didn't risk using these rings and decided instead to make 750 rings work instead.

There are at least two others here that have had bad experiences with these kits. However we rarely hear the positive side, so no way of knowing how many people run them and are happy.