Topic: Huge Crack in Crankcase Cover... HELP!

[bsrunner829]

Well, yesterday I changed the oil and oil filter in my 1975 Honda CB400F. Everything went fine. I put a little over 3 quarts in, then started it up and let it idle for a couple minutes. I then added a little more oil which put it to full on the dipstick. I drove it up the street and back and then parked it. I went out to dinner, came back, and tried to start up the bike to move it. It was making a really funny whistling noise and wouldn't stay started. I turned on the choke and then it stayed stared but it still had the weird whistling sound so I shut it right off. I saw some oil on the ground and then noticed the huge crack in my crankcase. I have no idea what could have happened. Can anyone help me out? It's the clutch that's right inside where the crack is right?

Any help would be greatly appreciated.

Brent

[bwaller]

Looks like something on the inside wants out! Not sure why the whole side of the bike isn't covered with oil, but that's definitely where you need to start, pull the clutch cover and catch what falls out.

I would suggest you remove the oil pan after you survey the damage to see what may have ended up there.

[bsrunner829]

yeah, i'm also wondering why so little oil came out of the crack.

[Bodi]

That's the primary shaft under there, and it indeed looks to want to drive right out. I don't know why it would do that... there's a nut thing that holds the gear on, but I would hope Honda has it threaded so it doesn't want to unscrew whilst running.
The oil level isn't much above the sump top so not much should come out with the bike level.

[bsrunner829]

Thanks for the replies. I'll take the cover off, take a look, and then go from there.

Anyone think that the crack can be fixed or would it be wise to try to find a new cover?

[fixahonda]

I would think finding a new cover would be easier than fixing that one.

Foremost though, you really need to find out what was trying to escape in there before thinking about covering it back up. You are likely going to need a bit more than a new cover.

[Johnie]

I agree...don't try to fix it or you will be wondering during every ride, "is the fix holding?"  And if you are on a nice ride and the fix gives, then you are stranded.  Hey, let us know what you find?  Never saw something like that one before...at least not on a Honda.

[bryanj]

Has it falen over onto the gearchange (opossite side) which may have pushed the gearchange shaft through and caused the crack?

Dont try a fix it wont work, get another case

[bunghole]

JB Weld it!

Wheeeeeeeeee!

[oldbiker]

Get a new cover but after finding the cause you could also repair the old one. See thread
 http://forums.sohc4.net/index.php?topic=36600.0

[Hush]

Ask your neighbours kids which one kicked the football over the fence, are you sure something is trying to get out or did your bike get knocked over and then guiltily put back on it's stand?
I've seen crankcases mended with araldite and they worked fine for years, they were british bikes.
Not sure I'd risk a beautiful classic like a CB750 when there are many spare cases around to be had for cheap.

[crazypj]

Get a new cover but after finding the cause you could also repair the old one. See thread
 http://forums.sohc4.net/index.php?topic=36600.0

 Thanks for the link, very informative. I'm going to try it out on a clutch cover
PJ

[ttr400]

As bodi has pointed out this is the location of the primary shaft. I have a couple of clutch covers with holes in the same place, normally caused by the bolt that holds the primary gear on has come loose and backed into the cover.

Remove the clutch cover and use some blue locktite on that bolt and make sure you torque to 36.5-43.8 Lbs-Ft. also make sure the lockwasher is in place, it is marked "OUTSIDE".

Kevin

[kghost]

Looks like it ate the cover not the case.

[mattcb350f]

...normally caused by the bolt that holds the primary gear on has come loose and backed into the cover.

Remove the clutch cover and use some blue locktite on that bolt and make sure you torque to 36.5-43.8 Lbs-Ft. also make sure the lockwasher is in place, it is marked "OUTSIDE".

Kevin

That's exactly what I think happened. the oil change and the bolt comming loose are likely unrelated, just a coincidence.

If it's just the bolt that's come loose, than there likely isn't any other bits inside the engine. But like bwaller said, you should pull the pan just in case; to make sure no parts ended up down there.

 Matt.

[bsrunner829]

You guys are awesome... thanks for all the informative replies.

To you guys who asked if the bike was knocked over:

I completely forgot that three days before I noticed the crack, I accidentally dropped the bike down on the left side while in the driveway. I was about to leave the house but then realized I had forgotten something inside. I thought that the kickstand was still down (but it wasn't), and as I went to lean it over, it just kept going all the way to the ground... DOH! However, like I said, that was THREE days before I saw the crack. It ran completely normal up until I first heard that funny noise. Could the drop have created a hairline crack in the case and knocked that bolt loose from the primary shaft? Maybe it took three days to completely spin itself free and then decided to pay a visit to the outside world.

Anyway. I won't have a chance to take the cover and oil pan off until next week as I'm really busy getting moved out of my apartment and into a new one.

I'll let everyone know what I discover.

-Brent

[bsrunner829]

Well, I'll go ahead and ask here...

Does anyone have a clutch cover, without cracks, that they'd like to sell me?

Thanks,
Brent

[bsrunner829]

well, i finally got around to pulling the clutch cover and the pan. luckily, there were no surprises in the pan. the only thing i saw was the bolt that had come loose off of the primary shaft. the bolt didn't seem to want to thread back in properly as the treads must have gotten messed up when it tried to push through the cover. i got a tap and die though, so it should be all good.

i ordered a clutch cover from SS 2 Wheel which is supposed to arrive tomorrow. i'm not sure if it's going to come with a gasket though. has anyone made their own gaskets before? i think they sell gasket material that you can use to cut out your own gasket.

hopefully i'll have it back on the road by next week!

[crazypj]

I pretty much always make my own gaskets. get 1/32" gasket Paper,wet it down then lay it flat to dry.( don't soak it, just surface wetting)
 Don't use paper towels, use old T shirt or rags.
 If you have the old gasket it makes life a lot easier, even if it is in pieces
PJ

[bsrunner829]

well, luckily the clutch cover i got came with the gasket still attached, and it was in pretty decent condition. i put some blue locktite on the bolt threads and torqued it down. i let it settle over night and then filled the bike with oil the next day. i had a lot of trouble starting the bike, but that must be because it was sitting for about a month. i think i flooded it and then i ran down the battery. i cleaned the plugs, charged the battery, and kept trying. after a while it started right up.

it ran like new from Saturday until yesterday when (hopefully) my battery decided to go. the bike kept shutting off during my ride, and there wasn't enough juice to use the electric starter. by the time i got home the battery was so gone that i couldn't even kick start it. i'm hoping it's just the battery as that will be the easiest/cheapest fix.

again, thanks for the help everyone!

Brent

[UnCrash]

Hey Brent,

Sure does sound like your battery.  If it were me and the battery were a few years old I would spring for a new one.