Topic: CB550 valve cover on CB650 cylinder head

[reverb]

I am customizing a CB650 from 1982.
I'm looking for the power from the 650 engine combined with the good looks from the 500/550   
I can get an engine from 1979 with the smooth flange on the head where the valve cover rest.
Will it be a close fit or will it be necessary to thicken the head casting to make a wide enough surface for a good seal ?
Will the 550 rockers be a one on one match with the 650 rockers ?
Are there other problems to deal with ?

[bwaller]

550/650 rockers will interchange. They may not be identical looking as the 650 uses a spring on one side of the rocker, but ratio is the same. I believe the 650 head needs some welding in spots to allow a 550 cover to seal. You're not the first so maybe search around here for better info on the head and cover.

[SOHC4 Cafe Racer Fan]

Unless retaining a kick start is a requirement, you may simply transplant the entire 650 motor into the 500/550 frame.  The only glitch is that you will need to remove the valve covers, oil pan and filter before installing the motor.

[reverb]

Thanks bwaller,
So if I understand it well you can change the valve covers but keep the rockers from the 650.
it is good to hear that it can be done.

[bwaller]

Thanks bwaller,
So if I understand it well you can change the valve covers but keep the rockers from the 650.
it is good to hear that it can be done.

Yes....but not without some work.

Here's a link to someone who made it work. Beautiful job too.

http://forums.sohc4.net/index.php/topic,63938.0.html

[turboguzzi]

yes, seen at least two, seemingly with the up to 80' head (better flow), so doable

your best bet is getting a cheap one from ebay and see where's the welding needed