Topic: CB650 C Head Gasket Replacement

[650HELPER]

I'm a newbie to the site. A friend (non-mechanical) owns a CB650 Custom which he has asked me to get back to running order. I noticed that oil is leaking out of the #1 head. Is it possible to replace the head gasket without removing the engine from the frame. I already have the carbs off to clean them up.

Thanks, Ron

[bryanj]

Yes but its best to do the base gasket as well and you will need all the O rings and seals

[Ibsen]

The answer to your question is yes, you can overhaul the 650 top end with the engine in the frame.
And I would recommend that you replace the o-rings for the oil ways between the cylinder and the cylinder head, the rubber pad seals between the cylinder head and the rocker arm cover, and the o-ring gasket for the rocker arm cover as well.

One other thing, make sure you clean the area around the head for the two middle front cylinder bolts before you loosen them. Usually dirt will collect around the bolt heads and when you screw them out the dirt will fall into the threaded hole in the crankcase and you run the risk of stripping the threads.

[650HELPER]

I'm looking at a gasket set on Ebay. #120180476264. Will this contain all the necessary item?

Thanks, Ron

[Ibsen]

No, it doesn't contain all the seals you need. David Silver in UK are selling a complete kit, and I also think the kit from Partsnmore might be a complete kit:

https://www.partsnmore.com/cat_index.php?model=cb650_sohc&category=engine

[tomkimberly]

If you only want to do this job once then use OEM (Honda) parts. They are all still avalible from your local dealer. Make sure you relplace every "O" ring and those pucks!

BTW, ask me how I know.

Tom

[mkramer1121]

I believe Honda used Vesrah and Athena as thier gasket manufacturers.

[Pinhead]

Are the gaskets different thicknesses? Do they make thinner gaskets for the 650's to raise the compression a bit?

[Ibsen]

Are the gaskets different thicknesses? Do they make thinner gaskets for the 650's to raise the compression a bit?

You really need to address that question to David Silver Spares. I used the complete set they are selling, and I didn't ask for an option, or if there are any differences at all. I can't say I noticed any difference before and after though.

[tomkimberly]

I believe Honda used Vesrah and Athena as thier gasket manufacturers.

The first set I used was from Athena. It leaked just as bad or worse before I used it. I then used OEM and no leaks.

BTW, be careful, some of the Ebay sellers sell very old kits, all dried out and missing one or two pieces.

Tom

[Ibsen]

The gasket set I bought from David Silver are made by Sankar NP in Japan. And the top end has been completely oil tight for 2 years now.

http://www.npgaskets.com/

I also have a complete top end gasket set bought from Bitzforbikes in England that are made by Centauro in Italy, but I haven't used it yet.

Centauro was founded in 1958 to produce gasket sets for motorcycles, mopeds, scooters, tractors, agricultural machinery, stationary engines, chain saws, and marine engines. Centauro  is the oldest company in Europe producing gasket sets for motor-cycles.