Topic: Is it possible to have a non leaking cb350F?

[JerryRice]

I hear so many stories about the cb350F leaking oil at the head gasket.

Many people say to "just Deal with it"...carry a rag.. etc.

But I really dont like that. Is it possible to get a CB350F to
not weap?

Thanks for the advice.

[mattcb350f]

Yup.

........just don't start it 


Actually, I think the notorious cylinder head leak could be solved by a better designed gasket, like those multi-layered metal ones.

 Matt.

[bryanj]

Yes, they didnt leak when new but it takes time, care and patience along with $

[pampadori]

Jerry, make sure the tach drive seal isn't leaking.  my last cb350F looked like it had a leak by the head seal but after i cleaned it off well and then checked again for a leak i found that the only leak was at the tach drive.  i used a small self tapping screw to remove the old seal, and pressed in the new oiled seal using a 12mm deep well socket.  Engine still dry.  just a recommendation to check that seal first cause its cheap and easy.

[Reverend66]

I have a 1973 350f, 15000 miles no leaks in sight other than the right fork seal (which I will hopefully remedy this weekend). As far as I know it has never been rebuilt or opened up. Guess I'm just lucky (knock on wood).

[jimscamera]

Take your CB350F head off.  Get a piece of 3/8" plate glass 3 feet square. Go buy
some very fine valve grinding compound from a machine shop supply. Do not
buy the stuff that the auto parts store sells it is not fine enough.  Take your CB350F
head and grind it on the glass with the valve grinding compound.  You'll see where
it is no longer flat. The ground spots will shine while the low spots will still
be dull colored.  Use a oval motion to do the grinding checking it fairly
often. Do it slowly as no matter what you do this takes a while.  When it
is really flat you will know.  Go to the Honda dealer buy a $55 head gasket.
Put it all back on.  You will not have leaks any more for at least the next
10,000 miles.  If you have other parts that leak this works perfectly well
to seal them up. I once used this on a giant alternator cover on a 1950
single cylinder 500CC Matchless in Southern Africa.  It fixed things great
but took me a week to grind.

[hs2k007]

sounds similar to lapping.  i have used this method in the aerospace industry for washers and the like.  we used a very fine sand paper sprayed with oil on a 3 inch granite block.  rotate the part in a figure 8 motion.  I have similar leaking issues with my 350f.  I am thinking of a full gasket replacement and a lapping of the block and head.

[JerryRice]

Thanks for the replies!
Tach drive is good. No leaking there.

jimscamera, wow very advanced. I am not 100% sure
I understand the process. I would love to have a non
leaking bike.

Just to clarify..my leak is on the lower part of the head.
Just under the exhust outets.

[ttr400]

This is what I do with my motors and so far do not have any leaks, these are also race motors so get ridden at the limit and beyond 100% of the time.
First after making sure that the cyl head and cyl block surfaces are super flat. I have mine skimmed, or by some of the methods already mentioned.
Make sure the surfaces are nice and clean, install new rubber seals on the 2 oil restrictors and on the 2 studs, use a very fine layer of Honda bond around those seals. Spray a new head gasket with head gasket copper coat, allow a couple of Min's before you fit the gasket. Fit the head and torque the nuts as per the workshop manual to 14.5-16.7 lbs-ft. Then I torque to 18 bls-ft. carry on and complete assembly. let it stand for a few days before starting the motor.
This has always worked for me.

Kevin

[JerryRice]

How do you have it skimmed? Does the engine have to be out and taken somewhere?

What exactly do you mean by skimmed?

[ttr400]

Skimmed, as in machined flat. you would need to take the cyl head and block if required to a cyl head shop. they will know what to do. It only needs to be skimmed/machined to make flat.
Note: this only needs to be done if the surfaces are no longer nice and flat. If you look in the service manual it describes how to check this with a steel ruler or straight edge.

Kevin

[JerryRice]

Ahh I see. Thanks for the clear up!

[dusterdude]

of course,its a honda,hondas dont leak

[mattcb350f]

...install new rubber seals on the 2 oil restrictors and on the 2 studs, use a very fine layer of Honda bond around those seals...

Kevin

AHHHHA! I thought that might work. I was thinking adding some Honda Bond on the outside of the rubber seals between the seal and the gasket, so that if the oil got around the seal it would have to fight its way through the bonded gasket to get out.

Thanks for posting how you do it Kevin. I think I'll be re-doing my head gasket this winter 

 Matt.

[JerryRice]

Where do I buy honda bond? Any other alternatives?