CB400 Project

[tom400f]

Crikey slow down!

http://www.cmsnl.com/products/piston-set-025_00000kit0506/#.Va5hHvkYFys

0.25 oversize kit (after market). Anyone know if these are good?

Packing washers - previous knob couldn't match the bolt lengths and got lazy? May be you'll find a short one elsewhere in the cases 

[Chris400F]

I agree with Tom, quite possibly just the wrong bolt in that hole and a lazy owner.
If you look at the parts list you will find all the bolt lengths are given in there so you can check what should be fitted (M8 x 114 I think).
(Personally I find a paper copy is useful to have as well as an electronic one and was a good investment; maybe that's just me!).
I suspect it is possible to buy a replacement set of bolts from somewhere, but that's more expense.

[beemsquar]

The crankcase has packing washers on every bolt too! I will definitely replace all the bolts with new and clean up all the internal threads, possibly buy a full stainless steel hex set or just ordinary bolt set.

At least that way I won't have any issues when I come to torque everything up and I know i've done the best I can.

I might try and print the parts list off at work tomorrow as I agree, it's much easier to thumb the pages then read on a laptop with oily hands.

Tom, that looks a reasonable price for a full set of pistons, I was looking at this on eBay.
http://www.ebay.co.uk/itm/391177502510?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Any ideas why the gudgeon pins would look like that and the piston ring disintegrated on removing the block?

I didn't test the cylinder pressure before I dismantled as I didn't have the tool to do it and  had already bought a shed load of specialist tools and hardly any parts for the bike at that point, wish I had now just to have some more info.

So how can I tell if it's already had a rebore? Someones clearly had the head off at some point and maybe the block, not sure what signs to look for, It looks pretty clean inside for its age and all things considered.

I've only tinkered on old cars in the past and they have always been a lot worse inside, especially the Triumph Spitfire I restored a few years back, but that turned out alright in the end, hopefully this will too, maybe just more money than I first anticipated.

[Bryanj]

Thats a normal looking pin and you can "Feel" wear with your finger that can not be measured with a Mic so as you are going oversize dont worry, piston rings do break, more on  some models than others, if you had a K4 250 and did not let it warm up before you rode hard it would shatter rinrs

[Chris400F]

I might try and print the parts list off at work tomorrow as I agree, it's much easier to thumb the pages then read on a laptop with oily hands.

If you have the time and facilities then by all means print the list, otherwise at £12 delivered this one seems good value:
http://www.ebay.co.uk/itm/Honda-Parts-List-Book-CB400F-400-4-400-Four-1970s-Reproduction-Original-Honda-/251407786645?pt=LH_DefaultDomain_3&hash=item3a89126295

[beemsquar]

Bryanj, thats good to know thats normal looking, I've never had to do this before to know the difference.

Chris, I have that part book in PDF so I may as well print it for now and save some pennies for engine parts! Its a good manual though and has helped me identify some of the parts I'm missing so far.

I just had a closer look at the cam and the cylinder head and the cam tolerances are just within the wear limits according to the clymer manual, but I might just replace it to be sure.

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It also looks like a new head might be in order as the cam bearings are very deeply scored as you can see in this picture.

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If I went down the acquiring a used head, would I have to get it skimmed to match the block face?

[Chris400F]

Chris, I have that part book in PDF so I may as well print it for now and save some pennies for engine parts! Its a good manual though and has helped me identify some of the parts I'm missing so far.

Take your point entirely, your rebuild is going to be an expensive business!
If you get some of those plastic ring-binder wallets and put the pages in you won't even get the pages oily.

With cost saving in mind I was curious and had a look to see how the exhaust prices compare.
Saisei headers and collector only are £327.60. Motad starting price is £129.99 (both + carriage).
You pays your money and you takes your choice, and to some extent maybe get what you pay for, but that's a lot of pennies difference.

[beemsquar]

Wow that's a massive difference in price! And a 10 year guarantee.  Where did you see that deal Chris? Motad's website shows no price and possibly out of stock.

[tom400f]

Motad is a member here and very friendly. Look up motad uk in the members list and pm Ian. They may be making more of the stainless ones if that's taking your fancy.

Broken rings: interesting what Bryan says. Member ManicGTI has the same problem and posted pics. Check his thread. Most likely the broken bits stayed in the groove.

Yes I thought your cam journals looked suspect in the pics  oh well.

These days it seems hex bolts are out of fashion. Back in the day it was the thing to do! Now originality is prized and anyway hex bolts (I mean allen bolts) retain water 

Keep it coming

[tom400f]

Do the pistons have any oversize markings? Would expect them to be on the crown but may be the recessed part of the skirt.

Crankcase bolts... Haynes chapter 1 section 44 for all your bolt order and position needs! If I could do it as a naive 19 y/o then it can't be that hard 

[Chris400F]

Wow that's a massive difference in price! And a 10 year guarantee.  Where did you see that deal Chris? Motad's website shows no price and possibly out of stock.

It's in their eBay shop: http://www.ebay.co.uk/itm/Honda-CB400-4-4-1-Stainless-steel-pipes-and-collector-by-Motad-/161768793224
Just over a day left on the auction as I write this, and it's a lot cheaper than their chrome version I bought from DSS last year.

For a silencer there are various ones available when you look around, such as this one at £105 delivered:
http://www.ebay.co.uk/itm/Honda-400-4-CB400-4-Four-Silencer-UK-Made-/371359425604?pt=LH_DefaultDomain_3&hash=item5676bf2444

[Saisei]

My bid is in on the S/S downpipes  . The silencer is Brituro has anyone used them?

[beemsquar]

Cheers for the replies guys.

I read ManicGTI's post, very interesting, possibly the same problem, maybe I should have checked the compression first? Tom I see your point about hex heads, I think a new bolt set might be more fitting to a classic build. I would like to keep the engine as original as possible, I think I might even shy away from painting it yet and just get it blasted, so many decisions!

I haven't checked the pistons for oversize markings yet, but I will do when I finish work later.

I'm going to try and split the crankcase later so I can make a full shopping list of parts.  I was reading Royhalls experience on here last night about getting the right colour main bearing shells, lets hope I don't need black ones!

You never know the bottom end could be fine, here's to hoping anyway.

As for the exhausts and mufflers, if anyone has either of these or others on there bikes I would love to see a video clip to hear the differences!

I think the sound is as important as the aesthetics.

I don't want anything too loud, but a bit of low growl would be nice!

[sweetpeauk]

I would use OEM bolts for the crankcase half's. Pistons "should" have their oversize marked on the flat next to the piston pin, but I have a set of Honda +25's with no markings. Ade at cga fabrications in Poole can do weld repairs on alloy cases 01202 747405.

[Saisei]

Crikey! Are there any cam bearings in there?