Author Topic: 75 CB400F Splitting Cases loose but not apart (Read 5893 times)

r6100mph · « **on:** April 09, 2009, 07:33:44 AM »

I'm in the process of splitting the cases to remove a broken cam chain adjuster bolt.....

So i have the cases split, they are loose,but they are not coming apart. It apears to be the cam chain adjuster pivot arm is some how attatched to the upper case and goes below the main crankshaft.

I have the engine sitting upright with oil pan down, and trying to remove the upper case from the lower case, while leaving the guts, crankshaft, etc in the lower case.

How is the actual pivot arm attached to the cases?
Anyone else run into this problem?
Anyone with some helpful hints would be much appreciated!

Industrial Rat400f Killer · « **Reply #1 on:** April 09, 2009, 08:04:02 AM »

Do you have a picture of the current state of it? Are both the cam chain blades out?

MADCB400F · « **Reply #2 on:** April 09, 2009, 08:10:24 AM »

Hi there, get the book so yop can see the main crank drive chain shaft has to come out before the cases will come appart.

bryanj · « **Reply #3 on:** April 09, 2009, 08:12:48 AM »

You have to lift the bottom case off the top off as the aduster horseshoe bolts to the top case and goes arround the crank.

HINT:-

locktight the horseshoe retaining bolts in and make sure you use the right torque

r6100mph · « **Reply #4 on:** April 09, 2009, 08:19:57 AM »

thanks for the replies!

SO i need to flip the engine upside down, and remove the bottom case from the top case...

in theory the crank shaft will remain sitting on the upper case, along with all the gears?

once the bottom case is removed from the top, i'll be able to get to the cam chain horseshoe and unbolt it from the case...

I have the clymer manual but it's not very detailed...."remove bolts, and split cases" sort of thing.

I'll give it a shot tonight and keep the forum updated on the progess.

Thank you!

mattcb350f · « **Reply #5 on:** April 09, 2009, 08:46:32 AM »

Should look like this...

You'll need to pull out the main shaft (the one driven by the big chain) in order to spit the cases appart. The U shaped thing stays attached to the top case, and the crankshaft will have to stay in there as well. If you try to do this upside down (right side up in the bike), the crank will want to fall out and it will be caught up by the U shaped thing.

Matt.

r6100mph · « **Reply #6 on:** April 09, 2009, 08:47:56 AM »

and yes the cam chain blades are out, cylinder heads removed, pistons removed from rods, etc, stripped down to cases, but left on rotor for the alternator, clutch is still on along with all the shifting mechanisms.

I'll take some pics tonight and post tomorrow.....stupid Job, too bad i didn't win the powerball last night, or else i would be at home right now rebuilding the engine!

mattcb350f · « **Reply #7 on:** April 09, 2009, 08:51:59 AM »

Quote from: r6100mph on April 09, 2009, 08:47:56 AM

...clutch is still on along with all the shifting mechanisms.

That's where she's hung up, the clutch side needs some disassembly in order to pull the main shaft out. It's kind of an awkward process and If I remember right, the manual doesn't help alot either

It's one of those...you'll understand how it works once it's apart things

Matt.

r6100mph · « **Reply #8 on:** April 09, 2009, 08:58:15 AM »

Thanks for the pics, i see what you are saying about removing the main shaft where the drive chain is attached to the crankshaft(upper case) and the main shaft(lower case).

Matt, can you please provide me with some details on removing the main shaft? How do i get the drive chain released from the main shaft, while the cases are still together? Do i need a shaft puller to remove the shaft?

Thanks again for all the help, this is my first engine rebuild, so i'm a little hesistant about things.

r6100mph · « **Reply #9 on:** April 09, 2009, 09:06:12 AM »

regarding the clutch removal, the pressure plate has a round nut on it with 4 gaps on it.

Basically like a spanner bolt, do i need to modify a socket to fit that nut in order to remove it?

Sorry for the lack of pics, i have them just forgot to bring them to work

mattcb350f · « **Reply #10 on:** April 09, 2009, 09:08:10 AM »

It's been a while since I did mine but here it goes:

The main shaft (I think) goes out the oil pump side (that has to come off too). The large bolt on the clutch side needs to be removed and I think the clutch has to come off to do this too.

There isn't anything holding in the shaft, it should 'slide' out without much effort once the bolt and gear are removed (I belive there is a flange on the other side of the shaft which presses up against a bearing which holds it in place). The large gear set up that is driven by the main chain stays in place but will come lose once the shaft is out.

Once the shaft is out the case should lift up, but be careful to hang on to the large gear setup and main chain because they are no longer attached to anything. There are a lot of wee parts within this gear set up and (again, if I remember right) there is nothing that holds it together.

In the second pic, the gear assembly is left out, but when you take it appart, it will be sitting there inside the main chain and the same for reasembly.

Hope that helps, Matt.

mattcb350f · « **Reply #11 on:** April 09, 2009, 09:09:47 AM »

Not sure about the clutch, I think the 400F is diferent than the 350F...nut wise.

You have to back off and remove the bolts that hold the spring loaded plate down and there should be a nut or C-clip or like you say, a wierd nut that holds the clutch assembly onto the shaft.

Matt.

r6100mph · « **Reply #12 on:** April 09, 2009, 09:16:17 AM »

Matt, that help is enormous! Thank you!

I'm sure I'll have more questions once i get back to it tonight. All of this for a stupid broken cam chain bolt that I didn't even break,

r6100mph · « **Reply #13 on:** April 09, 2009, 09:19:46 AM »

regarding the clutch:

I have removed the pressure plate and springs, and behind it is the nut i'm talking about, no cir-clip, just the odd nut and a washer with tabs that bend around the nut.

The awful clymers manuals says the same thing you did, with the cir-clip, but it's obviously different.

mattcb350f · « **Reply #14 on:** April 09, 2009, 05:40:03 PM »

Ok, 400F guys will know this one, but what you're describing is a tabbed lock washer and a regular nut. Bend the tabs back to allow the nut to spin and take off the nut.

I would like a second opinion on this first though...I've heard of some wierd styles of clutch retainment hardware....but it does sound like a locking tab/nut combo to me.

Matt.

mattcb350f · « **Reply #15 on:** April 09, 2009, 06:23:38 PM »

Quote from: mattcb350f on April 09, 2009, 05:40:03 PM

I would like a second opinion on this first though..but it does sound like a locking tab/nut combo to me.

Matt.

Can I quote myself?

I just looked at the parts fiche and it calls them a lock nut and washer. Go ahead and pry back the tabs and undo the nut mate.

Matt.

r6100mph · « **Reply #16 on:** April 10, 2009, 10:03:59 AM »

matt, thanks for the primary chain help and the primary shaft! That did the trick, i was hesitant about pulling the guts out, but once you do it no big deal, so i stripped the cases and will get them ready to strip and paint once the broken cam chain bolt is fixed.

here are some pics:

r6100mph · « **Reply #17 on:** April 10, 2009, 10:07:22 AM »

i have some questions regarding valve build up removal, different height of cylinder head studs, worn cam chain pivot, and crank case.....etc etc.

But will ask specifics later, due to leaving work for the day.

Stay tuned! thanks to everyone for helping me get this far, hopefully you'll be there when i try to get this thing back together

Jason

mattcb350f · « **Reply #18 on:** April 10, 2009, 06:15:07 PM »

Those pics sure take me back

I dug up this old thread for ya :http://forums.sohc4.net/index.php?topic=38903.0

Tim in Ohio logged his entire 350F build very well here and it's a good read. Some of the questions you have are probably answered in there already. The 350F engine is very similar to the 400F and the fundamentals are the same.

I also had a broken cam chain adjuster lock bolt in my case, and I had to get a machinist to repair it. Luckily he's a friend of mine

. He said it was a difficult job, and I recommend you do the same. The problem is to properly drill out the old bolt, it has to be rigged up in a mill or something. Otherwise it makes a mess to do it freehand.

As for the wear on the U shaped adjuster....It's junk. I got one through Westernhillshondayamaha.com....but I hear they may be running low on those parts...they're a common problem on these wee fours.

Two of the cyl. head studs are a different length; the two near the inner cylinder spark plugs. All the others are the same height.

You've done well so far, It took me a lot longer than you to get mine torn down like that...good work.

Matt.

bryanj · « **Reply #19 on:** April 11, 2009, 01:06:38 AM »

With the amount of case wear by the chain i would say a new cam chain is in order and the horseshoe is very difficult to get now from Honda. As long as it pivots freely and holds the tensioner blade lockating rubber securely it will be OK but i'm sure i read on here somwhere that ttr400(I think thats the name) was making replacements.

r6100mph · « **Reply #20 on:** April 14, 2009, 01:46:46 PM »

regarding the cam chain, the bikes only got 16K miles on it, is there a way to check the stretch on it?

I finally got the broken cam chain tensioner bolt out of the case, but drilling it out, and re-tapping it for a 6mm bolt, but in doing so i actually drilled right through the "plunger" tensioner. It's still in one piece but has a hole right through the middle of it.

had a piece of the old bolt floating around in the shaft so i had a heck of a time getting that piece out, by drilling it a couple of times to get it small enough to pull out through one of the holes.

I was thinking about getting someone to fill the hole with a weld or jb weld it. any thoughts?

r6100mph · « **Reply #21 on:** April 14, 2009, 01:52:03 PM »

i'm in the process of getting the cases and cover, heads, etc ready to strip and paint....

as far as gasket sets go, i have seen many Vesrah made sets, and have good things about them, but have read to stay away from the cheaply made Athena.

another question is, should I replace all the oil seals? for example the seals on the crankshaft that seal to the crankcase. There were no oil leaks before, but i wonder if they have been compressed when the original cases were put together. I'd really hate to get this thing back together and have oil leaking out all over the place.

Tim2005 · « **Reply #22 on:** April 14, 2009, 03:01:13 PM »

I'd certainly replace the oil seals on the crankshaft, they are pretty cheap and can get distorted when you remove the crank. The other one, behind the rear sprocket, is very tempting to do while you are there too.

As for your camchain plunger, I wouldn't JB weld that hole, either replace it or get someone much better than me with a welder to weld it.

bryanj · « **Reply #23 on:** April 14, 2009, 11:24:49 PM »

Its in bits, the camchain tensioner was not working right and the chain has been eating alluminium.

Sorry its a no brainer CHANGE IT

mattcb350f · « **Reply #24 on:** April 15, 2009, 04:39:39 AM »

Yeah, replace the chain...they're cheap too; +/- $50.

It's a good idea to replace all the parts that are suspect while in there. Replacing all the seals is also another cardinal rule of rebuilding. You're right about them being pressed in place.....once they're disturbed from being taken appart there's no guarantee that they'll do the job again.

...but seals are cheap too

That cam chain bolt hole is a funny set up. It's like a 6mm threaded hole, sunk in a bigger 8mm hole...or something like that. This is because the bolt has two different threads on it; one for the bolt, the other for the lock nut.

My machinist guy put a metal thread insert in mine...but I know little of the kind of wizardry he performed to do so.

...maybe take it to a shop

Cheers, Matt.

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Author Topic: 75 CB400F Splitting Cases loose but not apart (Read 5893 times)