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Discussion Starter · #1 · (Edited)
Hi all, this is my first post. I've started to strip my engine after a nasty sounding breakdown took it off the road. My CB400T has a CB400N engine. This is my first time stripping an engine and I'm planning on doing a full break down and clean. so will likely be posting questions often.

I'm following the Haynes manual for the CB400N. I've got as far at removing the cylinder block and pistons. It looks like the RH Piston was knocking against the cylinder head as there are some impact marks on both and the RH connecting rod has a lot of slop on the crack shaft. It also has some crazy looking thin metal flakes coming on one side of the connecting rod. I noticed that there are no cross hatching on the bore (see photos). And finally I've been and idiot and managed to get the cam chain trapped. I guess I'm asking for some good advise, will the RH piston need replacing? will the cylinder head be warped out of shape due to the impacts? Are there so-posed to be cross hatchings on the bore, will it need re honing? and what is the best way to get that cam chain out.

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James
 

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Welcome - you should post an introduction in the appropriate area to get the 400 crowd familiarized with you and your bike. One of them will be along with a proper FSM (factory shop manual)
 

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Thank you. Okay, is that Just the general member introduction thread or is there one specific for 400s?
General member introduction. BTW, you'll be able to create a signature after 10 posts... done that way to reduce spammers. Sorry to see the engine issues... I'm not versed in the 400 series engine, but there are many here who are and you'll get all the help and good advice you'll need
 

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The cross hatch is normally gone on a used engine.

Given the damage you describe, you might want to look into the possibility of acquiring a used engine. The connecting rod/crank shaft damage is particularly concerning, quite possibly beyond economical repair.

PM sent regarding factory service manual.
 

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Discussion Starter · #6 ·
Thanks J-T

Is it possible that replacing the connecting rod/ crank shaft would be the end of my worries or does the level of damage to them make you think it would have caused more damage elsewhere?

Thanks for the manuals and advice, Its definitely something I'm considering now
 

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The damage repair will entail fresh crank, at least one rod plus all of the bearings. It'll need to be stripped down and inspected closely to see what else is needed. This failure is usually associated with the left rod and due to loss of oil pressure. Most of the time the loss of oil pressure is due to very low oil level.
 

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From my experience rebuilding these engines and the cost associated.. go with a used engine. Sure that may have its own issues but you will need a new crank and bears and more which is more costly and a pita
 

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+1 on replacing the engine vs a rebuild. You should be able to find a good used engine for around $200. -$250 which will barely touch a rebuild cost; especially if you are not a person who is familiar with engine rebuilding. A machine shop would be required the access the damage and viability of the parts in your current engine if you are not able to do the measurements and damage assessment yourself and that will just be the start of the wallet lightening.
 

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A buddy of mine has a lower end from a 1981 cb400T that dropped a number one valve so head and piston are shot. I used the #2 sleeve and piston on another project.

You can reach Doc at, [email protected], if interested.

Bill
 

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Discussion Starter · #12 ·
I've had a pretty good dig for a used CB400N engine around the UK this week but not had much luck.

Im wandering does anyone know of any other Honda engines that would be compatible and wouldn't spoil the original styling?

or any tips for sites/ market places to look at.

Thanks

James
 

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Discussion Starter · #13 ·
A buddy of mine has a lower end from a 1981 cb400T that dropped a number one valve so head and piston are shot. I used the #2 sleeve and piston on another project.

You can reach Doc at, [email protected], if interested.

Bill
Not sure how much it would be to ship it to the UK but I'm assuming it wont be worth it.
sounds a real good match otherwise
 

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Any of the sohc 400/450 (except the sc) should drop right in. The sc model need a small mod to the drive sprocket spacing, otherwise another 'drop in'.
 
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