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Discussion Starter · #1 ·
Hello everyone,

I am a new owner of 1980 CM400E. I have pick it up just yesterday and since then I have been finding a few things about the motorcycle.

First, I think the gaskets are old and leaky as shown here.
IMAG0030.jpg
I will address this by doing gasket job later this summer. But what gaskets do I need to replace? Do I need to pull the cylinders out as well? I would like to know what is a good guide to follow. I am very inclined to do the work myself as I have some tools I use for my own car.

Second, I do not know what this hose/line is supposed to do. One end of it starts from the engine and the other doesn't seem to be connected to anywhere.
IMAG0026.jpg
It is the hose right between the fuel tank and the carburetor.

Third, I have this green switch on the left handle bar. Is this supposed to be another light? Is this OEM or after market?
IMAG0018.jpg

There are some pieces missing as of now, but I plan on taking some time during weekends to fix her up. I will probably come here often for some advice from you guys!

Thanks a lot.
 

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Welcome aboard
You'll want the FSM, factory service manual, for reliable information on the bike. PM sent on that
I don't see any oil leaks other than the valve cover gasket has heavy seepage. Head gasket and base gasket look good. You'll want #8 and 2 of #17 in this fiche 1980 Honda CM400E A CYLINDER HEAD COVER / CAMSHAFT HOLDER | PartsFish.com Note that the valve cover bolts are shouldered, when they bottom on the shoulder they are tight. If you try tightening them more they snap off.
The hose in question goes from the right side of the valve cover to the left side of the airbox, that's the breather hose.
That Green switch is an aftermarket piece. Possibly a headlight flash to pass switch? May interfere with the clutch lever getting fully pulled.
Loose that fuel filter. There's a fine mesh screen in the tank that strains the fuel of contaminants. The filter can cause the float bowls to run low or empty at times.
A good power wash using and engine degreaser will get rid of a lot of old oil on the engine.
In this section you'll find the sticky "New to you old bike checklist"
 

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Discussion Starter · #4 ·
Welcome aboard
You'll want the FSM, factory service manual, for reliable information on the bike. PM sent on that
I don't see any oil leaks other than the valve cover gasket has heavy seepage. Head gasket and base gasket look good. You'll want #8 and 2 of #17 in this fiche 1980 Honda CM400E A CYLINDER HEAD COVER / CAMSHAFT HOLDER | PartsFish.com Note that the valve cover bolts are shouldered, when they bottom on the shoulder they are tight. If you try tightening them more they snap off.
The hose in question goes from the right side of the valve cover to the left side of the airbox, that's the breather hose.
That Green switch is an aftermarket piece. Possibly a headlight flash to pass switch? May interfere with the clutch lever getting fully pulled.
Loose that fuel filter. There's a fine mesh screen in the tank that strains the fuel of contaminants. The filter can cause the float bowls to run low or empty at times.
A good power wash using and engine degreaser will get rid of a lot of old oil on the engine.
In this section you'll find the sticky "New to you old bike checklist"
Thanks for the reply and welcome message!

I will definitely take your advice and replace the valve cover gasket. By the way, it makes me think how you were able to infer that the head gasket and the lower gasket are fine? I am sure an expert like you have some reasons and I would happy to hear some about it.

Just to make sure, the breather hose doesn't have to connect to anything, is that correct? I could not locate any hole in the air box that would accommodate the hose.

I will definitely look into removing the fuel filter. I am sure the previous owner put it there. If there is no advantage in using one, I don't see why I can't get rid of it.

I certainly will take a look at the checklist and make those suggestions in the very near future. I would like to again thank you for your help! I am glad to be a part of this forum.
 

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Discussion Starter · #5 ·
Thanks for the reply!

I am going to replace the gasket, at the minimum, in order to make sure the leak doesn't appear anytime soon. I just got to get some :). I have worked with car valve cover gaskets and the solutions often were to replace the old gaskets with new ones. I guess the same logic may apply here. Plus, I don't think I want to strip the screw for the valve cover.

How exactly does the hose connect to the air box? I looked around the air box but I couldn't find any hole that would allow the hose to go into.

Thanks again.
 

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The base gasket if it's leaking will show on the sides and rear corners since that's where oil pressure is present. The head gasket will show at the rear corners where there's an oil passage. The only other place for a head gasket to leak is the front center at the cam chain case are which isn't in the picture but due to the lack of serious oil I'd say it's fine.
The breather hose connects to a nipple above the left carb. Pop the left side cover off and you should see it. Sorry, no pictures of that area to share.
In regards to gaskets, there is no sealer added to the valve cover gasket. Sealer is only used on the case halves and sometimes on the right engine case cover if needed. The only sealer to use is HondaBond or YamaBond, SuzukiBond. They're all made by Three Bond with different labels. You only apply a thin smear of sealant when used. NEVER use RTV or any other automotive sealant.
Read through the FSM, it's got all sorts of info like the oiling system, explanation of the balancers and the CDI ignition system
 

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Welcome to the forum. Great to see another 400 series here.
 

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Discussion Starter · #8 ·
The base gasket if it's leaking will show on the sides and rear corners since that's where oil pressure is present. The head gasket will show at the rear corners where there's an oil passage. The only other place for a head gasket to leak is the front center at the cam chain case are which isn't in the picture but due to the lack of serious oil I'd say it's fine.
The breather hose connects to a nipple above the left carb. Pop the left side cover off and you should see it. Sorry, no pictures of that area to share.
In regards to gaskets, there is no sealer added to the valve cover gasket. Sealer is only used on the case halves and sometimes on the right engine case cover if needed. The only sealer to use is HondaBond or YamaBond, SuzukiBond. They're all made by Three Bond with different labels. You only apply a thin smear of sealant when used. NEVER use RTV or any other automotive sealant.
Read through the FSM, it's got all sorts of info like the oiling system, explanation of the balancers and the CDI ignition system
I had a chance to inspect the front of the engine where the can chain runs along, and attached the photo of it. It's staring to show some hint of oil leak. It doesn't seem to be in a bad shape but if I am going to replace the valve cover gasket I might as well do the other gaskets and be worry free I guess.



Sent from my 831C using Tapatalk
 

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OK, then you're going to do a top end overhaul. Rings, hone cylinders, valve job with new valve seals, etc.
If it were me I'd give it a good power wash and ride it awhile to evaluate if this is years of accumulated seepage or if there actually is a problem. Most of these bikes have never seen a power washer or in some cases a garden hose.
Valve cover gasket and grommets are a good idea.
 

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Welcome, got good advice already...
 
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