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Discussion Starter #1
Hello everyone! I'm a fairly new member of the site and also a fairly new motorcycle owner. I love to learn so this is going to be a fun experience and I would love any feedback.

I just recently acquired a '81 CM400T from a friend. It's in pretty good shape from what it looks like due to the fact it has been sitting in his garage whenever he wasn't riding it. I think he hasn't really done much with it for a year or so though. Anyways, I've been doing the usual things to do after getting a new vehicle recently to get it into riding shape... and I think this issue could be partly my own doing because of this.

As part of the clean-up, I changed the oil and oil filter. I've been reading about the whole debate between different oils and just decided to go with what the Clymer manual that I have said to use. So I used 10W30 (auto oil, Clymer didn't specify between auto or motorcycle). I ran it for a few miles afterwards and it seemed to run okay except for a little trouble going from 1st - 2nd gear. I left it for the weekend because I went out of town. I started it up yesterday for a quick run and it wouldnt' shift from 1st - 2nd at all. Every time I tried up-shifting out of 1st it went into neutral. When I got back I noticed a little oil seepage (not excessive but enough to notice) coming from the crankcase and dripping onto my exhaust, dang it smelled. I've been thinking about it and have a few ideas about what to do but could use input.

Could it just be that the clutch cable needs some major adjustment? I don't have much experience with clutches so I honestly would't know if this could be the problem
Or more likely, could it be that the oil is running too thin and causing the clutch to slip? Or running thin and seeping into the crankcase? Would the seepage and the shifting issue even be related?

I can give more info if needed, I'd appreciate any ideas or advice!
 

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First off welcome to the group. Pictures of your bike would be most welcome!:p

Clymer is not totally worthless but I don't have any tables with one short leg right now so mine doesn't get much attention. I just sent you a PM about the factory service manual. I think it will be sufficient to guide you through the clutch adjustment but if you need more help just let us know.

Your research into oils must have missed the part about not using modern auto oil since much of it contains friction reducers that don't play well with our wet clutches. There are other options but the simple answer is to use a motorcycle specific oil in the weight recommended for your bike.

It's helpful to thoroughly clean the engine so you can tell exactly where the leak is at. It's unlikely that changing oil will help that problem. Again, pictures are helpful.
 

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+1 for everything J-T says.
Correct oil for you is JASO MA rated 10-40W oil. Unlikely you'll be riding in 85+ degree temps so stick with the 10-40. 20-50W is for ambient riding temps of 85 plus
 

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Discussion Starter #4
Thanks for the resource! I hear Clymer's aren't the best so it will definitely help. I'll definitely be tweaking the clutch cable because the bike tends to creep in 1st gear.

As for the oil, I just changed it out for 15W40 oil as I read it may work better (I just so happened to have some because I use the same stuff in my diesel car). Unfortunately it didn't seem to make a difference.
Looks like I'll be on the hunt for some Motorcycle specific oil.

What do you mean by thoroughly cleaning the engine? Take the case off and check things out in there?
 

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You can find engine degreaser at AutoZone, O'Reilly, Advance Auto parts stores. Use that on the exterior of the engine following the specific instructions on the can. Then after it's dry throw some baby powder on the suspect area for the leak. It'll turn into a gooey mess wherever the leak is.
You can also find MC oil in the same stores, usually located in the "small engine" section. I use Castrol 4T 10-40W
 

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Discussion Starter #6
So it's been a few days and I just now figured out my problem. I was taking off the left crankcase cover because the gasket is pretty much non-existent which leaked in a little water the other day. Of course to take off the cover you also must remove the shift lever. As I was placing the shift lever back on the bike I decided to turn the shift lever on more of a downward angle than it had been at before. I started the bike up and it shifts fine. Turns out the last time I placed the shift lever I had put it on at too much of an upward angle preventing it from shifting higher than neutral.

I feel pretty dumb but it was a rookie mistake, shows that I'm learning every day haha
 

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Discussion Starter #8
Yeah that case. I'll upload a pic tomorrow of what it looks like at the moment.
That is the same case that the oil is coming from. There isnt any oil on the alternator rotor though. Its not a whole lot but I'm presuming there shouldn't be oil in that case?
 

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That's a dry area or at least it's supposed to be. However you have 4 seals in that area, crankshaft, shifter, countershaft/output and the starter pinion shaft O-ring. Pop the cover, clean it and run it, you should be able to spot the leak after a few minutes
 

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Discussion Starter #11
IMAG0308.jpg IMAG0309.jpg IMAG0310.jpg IMAG0321.jpg IMAG0322.jpg IMAG0323.jpg IMAG0324.jpg

Here is what the inner case looked like. The first time it was just some oil. I cleaned it out and put it back on. The other day after a little ride I took the cover off and there was some whitish stuff with the oil as you can see in the pics... no idea what the heck that is.
I replaced the gasket on the case since I took these pics, although that has nothing to do with the leak.
Looks like the oil is coming from below/behind the alternator rotor.
 

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Normally the shift lever is parallel to the ground but that isn't a fixed rule since everyone has different size feet and riding styles.
The white stuff is oil and water mix, no big deal since the cover sort of seals water out. Leaking behind the stator means the crankshaft seal is leaking.
The correct way to replace it is remove the engine, split the cases after releasing the cam chain from it's gear, turn upside down, unbolt the rods and crankshaft carrier and lift the crank up to slide the old seal off and new on. Reassemble.
Since Honda designed this seal with a fixing lip on the inside that fits into a groove cut in the case it's a real booger to just pop the seal out on the bike. Also the new seal will not go in unless you grind the fixing lip completely off. It can be done but you have to be careful not to mar the sealing surface of the crankshaft and getting the new seal in far enough evenly is a booger. One shot deal per seal so if you screw up it's another new seal. Don't ask and I won't tell how I know this
 

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Discussion Starter #13
Oh okay so it's not a huge deal having the shift lever positioned like that, good to know.

The water/oil mix makes sense because some water did get in the case before I replaced the gasket.

Now on the topic of replacing the crankshaft seal. How urgent is this matter? I already plan to pull the carbs right after my skills test, hopefully in a week or so. Is this something I can do at the same time?
Also, thank you for the description of how to replace the seal, it will definitely help!
 

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Sure, which way are you thinking of doing it. If the incorrect way then order 2 seals in case you bugger the first one. Doing it the correct way I'd suggest replacing all of the seals on that side at the same time since the out put seal is easier with the case split and the starter drive pinion gear shaft O-ring is only accessible from inside the lower case.
 
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