Topic: CB350F - head gasket replacement

[johnzmg]

I have a low milage CB350F that was recently reborn after setting for 25+ years. It run great after cleaning the tank and rebuilding the carbs but after a couple of long rides an oil leak started at the cyclinder head gasket that has progressively worsened. Plus I'm seeing whitish color smoke from the two exhaust pipes on one side.

The Honda manual indicates replacement of the cylinder head gasket with the engine still in the bike... but it looks really tight.

Has anyone done this job that could offer a few pointers?

Thanks!
John

[Jay B]

It can be done easily with the motor in the frame. I use genuine Honda gaskets, more expensive but worth it, IMO. Take your time and make sure gasket surfaces are clean as can be before reassembly. You might want to do a compression check beforee you tear into it, if it needs more than gaskets, now would be the time to do it.

[Gordon]

When you have all the head bolts off and the head still won't budge, look again, because you missed a bolt.  And don't pry on the cooling fins to remove the head because they'll break easily. 

[Short Round]

I agree with gordon.  There is nothing that makes you feel more like an idiot than prying on the fins, breaking one and then realizing that you missed a nut or bolt.  Go slow, recheck everything you do and then proceed.  I have not taken the head off with the motor still in the frame but if your blowing white smoke you want to do a compression test, and also while you have the head off have the valves reseated.  Make sure you use a ton of ziplock bags and lable them as you go.  Good luck and keep us posted......................Chris.

[bill440cars]

        Glad you could make it John. There's a lot of great info, experience, great folks and awesome bikes here.

                                Later on, Bill  

[mattcb350f]

I have a low milage CB350F that was recently reborn after setting for 25+ years. It run great after cleaning the tank and rebuilding the carbs but after a couple of long rides an oil leak started at the cyclinder head gasket that has progressively worsened. Plus I'm seeing whitish color smoke from the two exhaust pipes on one side.

The Honda manual indicates replacement of the cylinder head gasket with the engine still in the bike... but it looks really tight.

Has anyone done this job that could offer a few pointers?

Thanks!
John

Hey John, Thats exactly what my 350F did when I got it running again two months ago.  Same thing, leaky head... getting worse and white smoke. Bet it runs fine until you wind up the rpm's too.
Anyway, If the head gasket is leaking, a compression check won't be very accurate but will give you an idea. There are also some O-rings you will need when you go to change the gasket and while you're in there, I'd replace the valve seals too. There likely adding to the smoke.
 Matt.

[johnzmg]

Guys, thanks for the information. I would really like this to be as painless as possible so it's good to know I may not need to remove the engine from the frame. I may try to re torque the head as Bill suggested in another post, however, I'm not usually that lucky. I'll probably replace headgasket and also change the valve seals while I'm in there... just cuz.

And Bill, thanks for directing me to this site. Lots of excellent info here.

John

[jas67]

I know this is an old topic, but, still relevant.
I've got a CB350F and CB400F that are both seeping oil at the head gasket.    I don't yet have a service manual (shame on me, I've got TWO each of CB350F and CB400F bikes).    Anyway, does anyone have the torque specs and torquing order handy that they can post?

[flybox1]

Its all in the HONDA manual you can download

http://www.honda4fun.com/materiale-documentazione-tecnica/shop-manual

[jas67]

Thank you!