Author Topic: Engine disassembly problem (Read 3558 times)

billdramp · « **on:** August 03, 2007, 11:39:48 AM »

I was tearing into my first engine rebuild last night, and everything was going smoothly... Until I reached the point of removing the cylinder block from the cases. The thing seems to be glued down. The clymers manual simply says to tap on the fins gently with a rubber mallot. Well... let me tell ya. It did not budge. I banged on them for about an hour with absolutely no progress other than a few broken fins

. Is there a secret for this process that I am unawared of.

Engine guros...any advice for me?

Oh yeah... The bike is a 75 400four.

Cheers from Portland

Billy

spitfire · « **Reply #1 on:** August 03, 2007, 12:18:11 PM »

Don't know much about the 400, but check for hidden bolts, in the cam tunnel maybe.
Has the bike been sitting for a while, when I stripped my 76 CB750F1 which had sat fro 12 years I had the same problem, the head came off great, but the cylinder barrels would not move, after a lot of prying I did get them off. The problem in my case was rusty head studs and dowels, took quite a lot of beating to loosen them off.

Cheers

Den

billdramp · « **Reply #2 on:** August 03, 2007, 01:11:44 PM »

Well... it has been sitting for god knows how long. I'm pretty sure I did not leave any bolts intact. I will check again.

This thing will not budge.

Anyone else ever had a similar problem? If so, how did you fix it?

Billy

scunny · « **Reply #3 on:** August 03, 2007, 03:03:11 PM »

if all bolts are out. turn the motor over at the crank, this can sometimes shift the jugs

billdramp · « **Reply #4 on:** August 03, 2007, 03:40:59 PM »

Quote from: scunny on August 03, 2007, 03:03:11 PM

if all bolts are out. turn the motor over at the crank, this can sometimes shift the jugs

Scunny, thanks for the tip... unfortunately we tried that last night... pistons move freely. The thing still won't budge.

This is frustrating.

edbikerii · « **Reply #5 on:** August 03, 2007, 04:01:35 PM »

If it is a problem with rust buildup on the studs, maybe a good soaking with penetrating oil down the stud holes might help free it up? Maybe let it soak that way for a couple of days.

Perhaps heating up the barrels might help, too. Use a propane torch with one of those wide-angle tips, maybe. I've never done this before, but it seems like it might work.

scondon · « **Reply #6 on:** August 03, 2007, 04:21:30 PM »

I'm not sure about the cb400's, but on the cb750 cylinders there is a rectangular casting at the bottom front of the cylinders with "736cc" stamped on it. It provides a sturdy enough shelf to put a large screwdriver to, not for prying but you can hit the back of the driver with a mallet and drive the cylinder upward just enough to break the seal on the base gasket or rusty dowels.

Also, when hitting the fins with a rubber mallet i've found that the direction of impact can make a difference. Take a side(cylinder one or four) and use a horizontal stroke to hit the front, then rear, of the block. Switch to the other side and do the same. Moderate taps, changing location frequently. The idea is to "twist" the block back and forth in order to break the seal. Very little room for twisting, I know, but often it is enough to break a stubborn seal.Upward strokes are OK once the cylinder starts to budge, but if applied before the seal is broken then bent and broken fins tend to be the result.

paulages · « **Reply #7 on:** August 03, 2007, 05:49:30 PM »

i was "supervising" this operation (didn't want to be responsible for broken fins), and i can tell you, these mother#$%*ers are stuck. i think someone used a good gasket sealer and it's being really stubborn. we did tap on the 406cc stamp, and on the back side where there is also a pretty solid spot. i know from pulling a clean set off of nothing but the locating pins that it can be tricky finagling it off against the pressure of those pins and the studs, but this won't even crack loose in the slightest. oh well, we'll get it.

mlinder · « **Reply #8 on:** August 03, 2007, 06:30:48 PM »

Stick it in your powdercoat oven at 500 for a while, then bang it?

HondaMan · « **Reply #9 on:** August 03, 2007, 07:36:28 PM »

Quote from: billdramp on August 03, 2007, 01:11:44 PM

Well... it has been sitting for god knows how long. I'm pretty sure I did not leave any bolts intact. I will check again.

This thing will not budge.

Anyone else ever had a similar problem? If so, how did you fix it?

Billy

Here's what I do:
1. Apply Liquid Wrench all the way around the base of the cylinders where that gasket lives.
2. Let it soak an hour or so.
3. Do it again, let it sit overnight.
4. Using a razor blade or Xacto knife, cut in around the edges where you can see the gasket: this starts the separation by cutting the gasket into thinner section. Soak in some more LW as you go.
5. Patience: when you get to the point where it's been cut all around, try again with the mallet. Normally, this combination breaks it loose.
6. Get the fins heliarced back on, thin them back down with a file. They will look and work fine for many years afterward: just check out mine sometime.

mrbreeze · « **Reply #10 on:** August 03, 2007, 09:07:53 PM »

Heed Hondaman's rule #5.......patience!!!!!! Don't get in a rush & break fins.

Bodain · « **Reply #11 on:** August 04, 2007, 06:19:04 AM »

I really have no experience with Honda cylinders that won't budge. They have all come off fairly easily... If they didn't I finally figured out I overlooked a nut...

The problem you describe is very very common one 70's Kawasaki H1 and H2... I've done that battle several times. It's are real bear. The problem is the studs become rusted to the cylinders.

I took long wood clamps.. The type that screw... I would locate a place at the base of the cylinders and the upper part of the frame. The goal is to get some constant upward force on the cylinders. This in itself will not get them off. Screw those clamp tight. The cylinders will still probably not budge and thats fine. Now take a plastic mallet and start gently wacking it. The constant upward pressure and the jarring of the mallet always gets them loose for me. Once I see just slightest upward movement. I re tighten the screw clamps to maintain the pressure and continue with the mallet....

I did this once on cylinders on a H1... It took several rounds of bang and tighten, but slowly they came off with no damage.

I use long screw type wood clamps on a alot of my bikes. If you have those hardened rubber carb intake boots and can't push or pull the carbs on or off. I use the screw clamps to pull them on an off...

billdramp · « **Reply #12 on:** August 04, 2007, 02:48:50 PM »

Thanks everyone... I am going to try Hondaman's suggestion tonight when I get off work... If that does not work, I may have to admit defeat and take it to a machine shop.

Bodain, I do not have any long wood clamps at the moment.

So I won't be able to try your suggestion just yet.

Mark,

I tried fitting it into the oven... it would not fit with the cylinder studs attached, so I tried to take them out... guess what. ONE WAS STUCK!

I'll cuss some more at it this evening.

Thanks again folks. Keep your ideas coming.

HondaMan · « **Reply #13 on:** August 04, 2007, 07:23:49 PM »

Quote from: mlinder on August 03, 2007, 06:30:48 PM

Stick it in your powdercoat oven at 500 for a while, then bang it?

You have a powdercoat oven?

I'm thinking of doin' some resto to mine this winter, got it running so nicely now. Putting in a new(er) tranny, clutch, crank & rod bearings...time to pretty it up some. I want a blue (maybe sapphire, maybe Honda's "blue-green", a little teeny metalflake and/or silver undercoat, transparent overcoat, embedded wing logo...and better-looking frame paint. Will your oven fit my swingarm? Chainguard? Top triple tree clamp? (What else is black.....).

paulages · « **Reply #14 on:** August 04, 2007, 08:44:12 PM »

Quote from: HondaMan on August 04, 2007, 07:23:49 PM

Quote from: mlinder on August 03, 2007, 06:30:48 PM
Stick it in your powdercoat oven at 500 for a while, then bang it?

You have a powdercoat oven?
I'm thinking of doin' some resto to mine this winter, got it running so nicely now. Putting in a new(er) tranny, clutch, crank & rod bearings...time to pretty it up some. I want a blue (maybe sapphire, maybe Honda's "blue-green", a little teeny metalflake and/or silver undercoat, transparent overcoat, embedded wing logo...and better-looking frame paint. Will your oven fit my swingarm? Chainguard? Top triple tree clamp? (What else is black.....).

it's nothing but a kitchen range we use to cure powdercoat and paint, etc., but a swingarm would certainly fit. i believe a rim just barely fits in there. small parts-- no problem.

billdramp · « **Reply #15 on:** August 05, 2007, 11:41:42 AM »

Well... I went down there last night with the determination of not leaving until I get that cylinder removed... One way or another.

I tried Hondaman's method first. As I had obviously been spraying tons of penetrating oil on it for the last few days, I decided to go ahead and spray it one more time and go at it.

I had a very thin paint scraper that had been ground down to a razor sharp end. I inserted it into the center of the base gasket on the corner of the cylinder. And just started working into the gasket. Next I went to the opposite corner and did the same. Then went back to the other corner and applied just a little pressure and then it went all the way through the gasket... went around the entire cylinder and then it broke free!

Man:1 Machine:0 (at least for the evening)

Too bad about the broken fins in this process though. I hope I can get them fixed somehow. Was it here I read you can use JB Weld to fix broken fins?

Cheers!

Billy

I took some pictures but they really are not very exciting. I will post them If I have time today.

billdramp · « **Reply #16 on:** August 05, 2007, 12:44:52 PM »

Behold, the worst photos ever taken in the history of mankind.
But you get the idea. I know how much we like photos on this forum.

Bob Wessner · « **Reply #17 on:** August 05, 2007, 03:14:41 PM »

Congrats on the separation.

Quote

Too bad about the broken fins in this process though. I hope I can get them fixed somehow. Was it here I read you can use JB Weld to fix broken fins?

I repaired a broken fin on my heads this past winter using something called FIXIT, an epoxy/clay mix. So far it has held up well through many heating/cooling cycles and vibration of quite a few miles. Might be worth considering.

http://www.sohc4.us/forums/index.php?topic=19402.msg202306#msg202306

oldbiker · « **Reply #18 on:** August 06, 2007, 01:04:24 AM »

I recently used 'Lumiweld' alum rod to repair a broken alloy bracket on the handle of a mower. The repair has stood up to the abuse which broke the original bracket. It can be done using only a butane torch and I have been very impressed with its strength. I think a broken fin could be re-fixed with this or a small piece could be built up.

Bob Wessner · « **Reply #19 on:** August 06, 2007, 03:54:33 AM »

After posting the FIXIT approach, it seemed to me you should try a more perm/better fix as suggested since you now have the engine apart. I was trying methods to avoid parting the engine just to fix a broken fin.

paulages · « **Reply #20 on:** August 06, 2007, 11:21:44 AM »

think he's picking up a spare, so i'll probably try tig welding them back.

HondaMan · « **Reply #21 on:** August 20, 2007, 08:19:09 PM »

Quote from: billdramp on August 05, 2007, 12:44:52 PM

Behold, the worst photos ever taken in the history of mankind.
But you get the idea. I know how much we like photos on this forum.

I think you needed some more beer to steady your nerves before those shots.

mark · « **Reply #22 on:** August 20, 2007, 08:38:35 PM »

I just bought a head and cylinder from a guy on ebay. Even fedex couldn't knock that head off the jugs! The box looks like they had fun trying. 1 broken exhaust stud and another bent but no broken fins. The chain guide sticking out got lunched but I expected that.

UPS would have gotten them apart for sure!

Happy trails.

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Author Topic: Engine disassembly problem (Read 3558 times)