Author Topic: Do I need sealant for a cooper gasket? (Read 6421 times)

camshaft1991 · « **on:** September 01, 2016, 05:01:22 AM »

Hi all,
I should of asked this awhile ago but I might as well ask now. On a CB350F, would I need to use some kind of sealant or adhesive on a copper gasket? Would it hurt not to have any? This is not a performance build.

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70CB750 · « **Reply #1 on:** September 01, 2016, 05:20:55 AM »

Head gasket? No.

camshaft1991 · « **Reply #2 on:** September 01, 2016, 06:48:16 AM »

Great, I found that a lot research points to use the of sealant for high performance engines but I never saw it being necessary for the 350f.

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flybox1 · « **Reply #3 on:** September 01, 2016, 07:30:42 AM »

It's not CC specific

More of a need if you will not be decking the mating surfaces. Helps to fill in the fine irregularities.
I used permatex copper spray on both my base and head gasket.

Duanob · « **Reply #4 on:** September 01, 2016, 10:13:40 AM »

Copper gasket? You mean copper washer? Or is there a copper head gasket for the 350F?

flybox1 · « **Reply #5 on:** September 01, 2016, 10:37:55 AM »

Quote from: Duanob on September 01, 2016, 10:13:40 AM

Copper gasket? You mean copper washer? Or is there a copper head gasket for the 350F?

some head gaskets have a copper layers for good squish.

Duanob · « **Reply #6 on:** September 01, 2016, 03:06:53 PM »

Makes sense. Is that for a CB350F HG? Never seen one for a 550.

bwaller · « **Reply #7 on:** September 01, 2016, 06:19:49 PM »

Copper is a rather poor head gasket choice for the street. They will ultimately weep oil. It's a good choice for a high comp. race engine. They can be annealed and re-used several times. I use Gasgacinch on both surfaces, found it seals better than copper spray.

I'd suggest MLS (multi layer steel) instead of copper, they seal better with a thin Viton layer. Surfaces have to be flat however, but the same is true for copper too. I'm not sure if there is an MLS choice for the 350/4 but ask Cometic.

Duanob · « **Reply #8 on:** September 01, 2016, 07:46:45 PM »

Quote from: bwaller on September 01, 2016, 06:19:49 PM

Copper is a rather poor head gasket choice for the street. They will ultimately weep oil. It's a good choice for a high comp. race engine. They can be annealed and re-used several times. I use Gasgacinch on both surfaces, found it seals better than copper spray.

I'd suggest MLS (multi layer steel) instead of copper, they seal better with a thin Viton layer. Surfaces have to be flat however, but the same is true for copper too. I'm not sure if there is an MLS choice for the 350/4 but ask Cometic.

I don't race but for these bikes my choice will always be OEM Honda.

camshaft1991 · « **Reply #9 on:** September 19, 2016, 08:23:09 AM »

I don't know why I didn't get notifications on this thread but I do believe I have oil leakage.
Pictures and videos
1. Oil leakage beneath cylinder head

6. Exhaust 3&4

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camshaft1991 · « **Reply #10 on:** September 19, 2016, 08:25:32 AM »

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camshaft1991 · « **Reply #11 on:** September 19, 2016, 08:28:04 AM »

1 Oil leakage beneath cylinder head
2. Leakage at
3&4 spark plugs pulled off and then cleaned
5 exhaust 3&4

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flybox1 · « **Reply #12 on:** September 19, 2016, 08:34:11 AM »

The spatter under your exhaust looks like condensation...supported by the presence of white exhaust vapor.
Do your exhaust have drain holes where they connect to the headers?
How long did you run it and did the vapor dissipate?

Your plugs look a bit lean. Turn all your idle mixture screws IN 1/3 turns.

Describe in detail your torque sequence.

camshaft1991 · « **Reply #13 on:** September 19, 2016, 10:03:41 AM »

30 minutes tops on run time. The white smoke goes away a little 15 minutes in but she's a puff daddy at 5k.
The exhaust system does not. I think that is a rust hole because it was only on the right side.

I'm still leaking oil do you think that's why my plugs are fowling? Here's a video of puff daddy

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flybox1 · « **Reply #14 on:** September 19, 2016, 10:24:50 AM »

Look again for an exhaust drain hole.
What was your torque sequence? What all did you do in the rebuild?
Those plugs are not fouled.
Did you reuse any copper washers when rebuilding the head? Reuse the valve stem seals?
Did you have the head decked? Did you also shorten your locating dowels if needed?

Too many unknowns you need to let us know about

camshaft1991 · « **Reply #15 on:** September 19, 2016, 12:49:20 PM »

I'll check this weekend for a matching hole on the other pair. I keep my bike in my dads shed 2 hours away. I only have weekends with work and school.

My torque sequence for my cylinder head was what I was told by my clymer manual. I did reuse the copper washers. They look fine to me. The valve stem seals I replaced even though they didn't need to be. They were replaced a year ago. The head and cylinders were mated together, however, there was no leaking from the gaskets prior just continuous white and more above 3k.

To give a recap on the bike from its last build.. It was rebuilt from the cylinders up by a former bike mechanic. He did a few things well with electrical and welding , but he did a couple of things that messed up the bike like a failed tank lining and tuning the carbs. The carbs were set so rich that the cylinders washed out. I never heard of that until a motorcycle shop diagnosed it and then I was told by an engine shop to hone them after I brought my cylinders to their shop. I ran the bike like this for 500 miles.

I had a motorcycle shop install the Pistons into my cylinders, fit my cylinder head cover on, and fix the timing and points gap. I had no way to safely compress my little Pistons. I couldn't figure out why my head cover wouldn't fit at TDC until they figured out that the crank had to be turned over a little for it to fit. I also had the entire engine vapor blasted 2 years ago along with the head and cylinders mated, and the rockers made new. I did everything else and lapped my own valves.

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camshaft1991 · « **Reply #16 on:** September 19, 2016, 12:51:11 PM »

Newer valve stem seals were put in two weeks ago

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flybox1 · « **Reply #17 on:** September 19, 2016, 01:01:52 PM »

Copper washers cannot be reused unless they are properly annealed. New ones are preferred.
Old ones do not crush and seal, especially with the heat/cold cycles an engine goes thru.
They can be a source of leaks, and you have quite a few (12) in the 350F head.
I'm not saying this is your issue, but reusing old ones definitely is suspect.

flybox1 · « **Reply #18 on:** September 19, 2016, 02:21:54 PM »

Did you torque the head in series, and re-torque the following day before buttoning it up?
After a few heat cycles, it might be a good idea.

camshaft1991 · « **Reply #19 on:** September 19, 2016, 07:24:01 PM »

I read that copper doesn't compress much but it expands outward when it does wear. It was stated that it should be re torqued after a heat cycle

http://scegaskets.com/wp_super_faq/given-the-choices-why-would-one-use-a-copper-head-gasket/

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camshaft1991 · « **Reply #20 on:** September 19, 2016, 07:27:15 PM »

I torqued them within 10 then 5lbs and so on down to 1lbs of each other. It was tedious and I used a digital torque wrench

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camshaft1991 · « **Reply #21 on:** September 20, 2016, 12:22:37 PM »

Should I run my engine a couple more times from cold to hot and then go about re torquing my cylinder head? Also can I take my copper gasket off and examine it and take pictures or will that cause me more problems sealing the engine together?

The reason why I wanted to use a copper gasket was because of how well copper transfers heat compared to graphite. I live in Louisiana, a hot state mostly year round, and I wanted to find a way to keep my engine cooler through efficient heat transfer. I know there are oil cooler kits out there for my bike but I don't want to look at a radiator on my bike.

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camshaft1991 · « **Reply #22 on:** September 20, 2016, 12:26:51 PM »

Like I mentioned before about sealant, what could I use for sealing a copper gasket? All I can find online is copper gasket adhesive or spray for graphite gaskets. None of which mention can be used on copper.

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flybox1 · « **Reply #23 on:** September 20, 2016, 12:41:36 PM »

Copper crushes. As I stated above, if you reused your 12 copper washers without annealing them, they are suspect.
I wouldnt worry about trying to remove the head gasket to apply a sealant to it.
You have the benefit of a bike where the valve cover can be removed without pulling the engine.
Get in there. Loosen all the head stud nuts in REVERSE order of the torque sequence by 1/2 turn, and then re-torque, or better yet, spend the $5 to get all new copper crush washers in there under the head nuts.
There are quite a few adequate torque methods.
I prefer in 3 stages, 50%, 75%, 100% several hours between each so the gasket compresses and the studs stretch. Let it sit overnight, loosen all by 1/2 turn in reverse sequence, then immediately re-torque to 100%.
No heat cycles needed. No re-torquing. No leaks (assuming mating surfaces are adequate)

bwaller · « **Reply #24 on:** September 20, 2016, 05:52:40 PM »

Not to be a pessimist but you'll never seal it simply by retorquing. I mentioned preferring Gasgacinch sealant for copper gaskets, but even with a good sealant copper will eventually leak. Just not the best gasket for a street bike that you want clean & neat.

That said, as flybox states you can retorque it easily and that way satisfy your curiosity.

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Author Topic: Do I need sealant for a cooper gasket? (Read 6421 times)