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Discussion Starter · #1 ·
Rebuilt 1978 Honda CB 400 A motor from the ground up. Honed the cylinders and the ring end gap was a little large but within tolerance. plenty of oil on piston install and upon completion the motor ran fine. The cylinder temp was only a few degrees form each other and the right oil was used. 385 miles later the motor got so noisy I shut it down I thought it was going to fly apart.

I tore the motor down and found the right or #1 sleeve had broken off it the ring area at the top of the cylinder. The sleeve had dropped down to the crankshaft and the top piston had caught on the break and folded up the side of the piston. I havent split the lower end yet so may be more.

Any ideas of what caused this .

Thanks

Bill
 

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Was the cylinder dropped when the engine was apart? I would really like to see some pictures.
TOOLS
 

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The only sleeve failures similar to this I've seen are from being over bored which obviously isn't the case. Very strange.
 

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Could it have had a tiny crack in it? I had a sleeve that was cracked during shipping and didn't even notice it until it went to the machine shop
 

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Discussion Starter · #5 ·
Im not able to down load any photos. There in the computer but wont transfer to this site?? I dont know any thing about computers.

When I bought this bike I found the #2 sleeve was bad so I replaced it . Honed the sleeves and installed new rings. Could the #1 sleeve have been a few .000 loose from the replacement of the #2 sleeve and maybe set up some kind of vibration because it looks like metal failure all the way around and not in one spot. May never know. At this time I think Ill try to part it out dont want to tie up any more money in it.


Tools . If Im not able to part it out there are cylinders on the net and CMS has oversize pistons. If I sent the parts to you could you bore the sleeves for the oversize pistons?


Thanks fellows.

Bill
 

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A tangential comment on sleeves-

Sleeves can develop "hot spots", where something has happened to the metal's structure in localized areas.
Even after boring and honing you can sometimes actually see them in a raking light.
They have to be discarded at that point, it's happened to me twice.
My machinist pointed this out to me.
 

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I had a sleeve turn in a bore before. I dropped the cylinders off the sleeves in an oven. When I reinstalled the hot and cold parts I'd rigged a wood block under a press of a few tons. I read in a book that the bottom of the sleeve cools and grips first, leaving the top flange high. Immersing the top in cold water was also a recommended option. After it cooled the sleeves sat quite low and the block had to be milled. I would bet something happened when you resleeved.
 

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Discussion Starter · #12 ·
Thanks tools may take you up on that with info from LDR. Its a nice looking bike and would be a shame to part it out.

Hi Jim. I dont look at David Silvers Spares any more they never had what I needed in the past. Thanks for the heads up. Will still need a set of pistons and rings. Will look at the cost of parts and see where I end up before doing any thing.


Lefty You are correct, when I replaced the #2 sleeve I had the head lightly skimmed for a flat gasket surface.

Thanks fellows.

Bill
 

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DSS is worth checking, sometimes they've picked up some obscure parts that have been out of production for 40 years. They had NEW stator assy's for the 1978 400's last year for $250, all gone now.
 

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Discussion Starter · #14 ·
Split the cases and checked the rest of the motor and all seems ok. Found a cylinder on fleabay very rough looking but cheap. It cleaned up well and after honing the sleeves a bore check shows it is well within specs. Found a seller in Japan that has stock pistons with wrist pins,rings and keepers so Im good to go. Have a seal cracked on a front fork so will rebuild the forks, touch up the frame and paint the motor. Thought of building another bobber out of it but its in pretty good shape so will put it back stock.

Thanks for the help and info.

Bill
 
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