Honda CB400 engine disassembly struggles

[beth0509]

So I've been pulling apart the engine from my grandads old Honda CB400 today, aiming to find the source of a few rouge oil leaks. I've gotten as far as pulling the cylinder head off the block, but am finding it extremely difficult to remove the block from the crankcase. (yes I've tried hitting it with a hammer. Repeatedly)

The manual suggests "rotate to TDC then hit with a rawhide mallet or a block of wood & hammer (to loosen adhesive on the dowels I would imagine) then EASE (ha!) off pistons". After a couple hours of concerted effort I'm relatively convinced that no combination of hammering and levering (which i have hesitantly attempted despite the manual advising against it :/) is going to do it. I'm also still very uncomfortable about hammering wildly into the poor engine!

Any help/advice would be hugely muchly appreciated!!

Cheers,
Beth

[actungbaby]

So I've been pulling apart the engine from my grandads old Honda CB400 today, aiming to find the source of a few rouge oil leaks. I've gotten as far as pulling the cylinder head off the block, but am finding it extremely difficult to remove the block from the crankcase. (yes I've tried hitting it with a hammer. Repeatedly)

The manual suggests "rotate to TDC then hit with a rawhide mallet or a block of wood & hammer (to loosen adhesive on the dowels I would imagine) then EASE (ha!) off pistons". After a couple hours of concerted effort I'm relatively convinced that no combination of hammering and levering (which i have hesitantly attempted despite the manual advising against it :/) is going to do it. I'm also still very uncomfortable about hammering wildly into the poor engine!

Any help/advice would be hugely muchly appreciated!!

Cheers,
Beth

Id say double check theres not some bolt trough from head down holding the head down or even inside where the cams are
sounds to me that still got bolt holding it on there oh what about the cam chain tension guide does that cam out

the chain is of the sprocket at the top make sure you secure the cam chain with wire to stop it falling into the engine block also

[jellywrestler]

So I've been pulling apart the engine from my grandads old Honda CB400 today, aiming to find the source of a few rouge oil leaks. I've gotten as far as pulling the cylinder head off the block, but am finding it extremely difficult to remove the block from the crankcase. (yes I've tried hitting it with a hammer. Repeatedly)

The manual suggests "rotate to TDC then hit with a rawhide mallet or a block of wood & hammer (to loosen adhesive on the dowels I would imagine) then EASE (ha!) off pistons". After a couple hours of concerted effort I'm relatively convinced that no combination of hammering and levering (which i have hesitantly attempted despite the manual advising against it :/) is going to do it. I'm also still very uncomfortable about hammering wildly into the poor engine!

Any help/advice would be hugely muchly appreciated!!

Cheers,
Beth

yes, tell us what the bike is first so maybe someone who knows them knows any secrets for that bike.

[FJRider]

yes, tell us what the bike is first so maybe someone who knows them knows any secrets for that bike.

At the top of each of her post's she tells us she has a 1980's CB400 Nighthawk ... I assume it is the bike in question ...

[jellywrestler]

At the top of each of her post's she tells us she has a 1980's CB400 Nighthawk ... I assume it is the bike in question ...

In her posts she says she's working on her Grandads old CB400, nowhere does it say she's working on her own bike. I noted that but I'm a tradesman, I don't assume shit like that that could lead one up the garden path.
It could be an old Four Cylinder 400 Four for all I know.
My point is the more information the betterer.

[beth0509]

Yeah it's the nighthawk, inline 2, sorry for any confusion!

I have pulled the cams and cam chain sprocket out already, and the chain is looped around a twisted old clothes hanger, and not interfering at all. The cam chain tensioner is pulled up and locked into the upright position.

Thanks for your replies guys

[FJRider]

Yeah it's the nighthawk, inline 2, sorry for any confusion!

I have pulled the cams and cam chain sprocket out already, and the chain is looped around a twisted old clothes hanger, and not interfering at all. The cam chain tensioner is pulled up and locked into the upright position.

Thanks for your replies guys

I use a long piece of strong string on the chains, baling twine actually, and it seems to work. Easy to attach/tie off ...

Sounds like the pistons have a good grip on the cylinders (that's a good sign)... Where is/was it leaking from ... ???

[spanner spinner]

these motors are held together with dowls due to the head studs also holding the cams in. the dowls rust and expand in there locating holes and lock the motor together, heating the dowl points with gas is the best way to free them up but plenty of force will still be needed. If you go to http://www.hdlparts.com/default.asp you can get a parts listing for this bike in the listing for 1980 this will show you where the dowls are. I have had to use that much force on these motors to get the dowls to release that you end up damaging heads and barrels, hope you don't have to end doing the same. Best of luck.

[jellywrestler]

does the engine turn over? make sure when trying that the cam chain is well out of the way, i usually use a stretchy on loose setting as the last thing you want is while your attention is diverted the chain to pile up on the crankshaft and cause trouble.
if the pistons are stuck the first thing to do is get them loose, depending on how stuck will depend on how to loosen them ...