Author Topic: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE - NOW COMPLETE  (Read 48416 times)

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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #105 on: October 10, 2017, 02:27:40 PM »
MrDavo,  I've no problems with opposing views. I feel that anything I write on here should be up for scrutiny,  if it won't stand up to your enquiring mind or any others with experience in different areas to me then it can't be seen as truly valid.

Slightly wary about trampling over Julie's thread as it originally started but I guess the subject is relevant as the motor looks such a mess. For anyone coming to this thread later on if they find themselves with something similar,  then it's thoroughness will be of interest. It's something that I think is worthwhile in that it should shake out the real problem,  threads on other forum when it starts well but never really concludes what went wrong I find frustrating. Especially if I'm looking to gain from that problem and how those poster's split it down to find what failed and how.

Your observations about air leaks are entirely valid as well,  guess that's why everyone on here all shouts "airleak" when a new poster comes on with a running inconsistency,  they can be so minor and frustrating or really significant.

I'll post on what I understand how detonation happens to see if that adds to the overall view.

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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #106 on: October 10, 2017, 03:19:36 PM »
Were the pipes blued?

No they weren't into porn, these were good little pipes as befitting a ladies bike.
No blued pipes chaps, double skinned original Honda downpipes fitted.
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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #107 on: October 10, 2017, 04:34:20 PM »
Positive steps forward today. Split the crank cases and no damage evident at this stage. All cogs have their teeth, the gearbox looks good, measured the dogs and they are well within spec at 5.79-5.91mm with a service limit of 5.5mm.

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The cam chain tensioner horseshoe is in one piece although the pivot pin was a little tight. The cam chain is the original. The primary chain is the original and is knackered.

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Have taken all the bearings out of the cases and off of the con rods. These actually look in really good condition considering the amount of swarf that could have been going around the engine but, won’t know for sure until measured.
I have cleaned all the parts and have been given a corner of a shelf in the Engine building room to start storing everything when it's cleaned until the engine is ready to be rebuilt.

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Graham has another slot booked at the acid dippers in about 3 weeks time, so I have put all the casings etc in a crate and they can go in with his next lot of engines that need the acid treatment.

The measuring of the shells will happen when I get the cases back so they are all nice and clean to work with, but I’m sure there can be some bits I can measure in the meantime, like the camshaft. Also all the machine work will be done after acid stripping. I can also start cleaning the nuts and bolts prior to sending for zinc plating. The outer casings had a lot of Allen bolts fitted but I am going to go back to what was fitted as standard.

What I have learnt today, 1) My cleaning of parts standards fall well short of Triggers exacting requirements. I would wash a load of bits in the parts wash and put them on the drying racks and he would look at them and give them back to me to do again, some parts came back twice !!! >:( >:( But, I suppose that is one of the reasons why his engine building is so excellent. 2) Don't turn gear shafts with cogs, bearings, circlips, spacers etc on their ends in the parts wash, all the cogs etc fall off and I have no idea where they came from or in what order. Trig made me get the workshop manual out and work out where all these bits belong and made me re assemble them  ::) ::). 3)Don't get the cleaning solution from the parts wash all over the floor when transferring the parts to the drying racks. It was like an ice rink and I had to scrub that part of the workshop floor :'( :'(
« Last Edit: October 30, 2017, 10:23:34 AM by Nurse Julie »
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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #108 on: October 10, 2017, 04:39:50 PM »
What I have learnt today, 1) My cleaning of parts standards fall well short of Triggers exacting requirements. I would wash a load of bits in the parts wash and put them on the drying racks and he would look at them and give them back to me to do again, some parts came back twice !!! >:( >:( But, I suppose that is one of the reasons why his engine building is so excellent. 2) Don't turn gear shafts with cogs, bearings, circlips, spacers etc on their ends in the parts wash, all the cogs etc fall off and I have no idea where they came from or in what order. Trig made me get the workshop manual out and work out where all these bits belong and made me re assemble them  ::) ::). 3)Don't get the cleaning solution from the parts wash all over the floor when transferring the parts to the drying racks. It was like an ice rink and I had to scrub that part of the workshop floor :'( :'(

God he sounds worse than my old english teacher  ;D ;D ;D ;D ;)
Glad the rest of it looks OK
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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #109 on: October 10, 2017, 05:30:43 PM »
I think oil filters are about 10 to 15 micron filtration so not much in the way of bits will go through them.

Different for the oil pump though as it's only got a sieve to stop the chunky bits getting in there.

Most of the rings usually go out the exhaust valve and don't generally go down past the piston if it remains intact so the rest of the engine doesn't see much of the broken parts.

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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #110 on: October 10, 2017, 06:39:31 PM »
Mr Davo, Oddjob, Hairy, K2-6, Bryan and everyone else who have given their theories' and insights, I think your input is invaluable to this thread and please do carry on. This is a huge learning curve for me but maybe also of interest to other current members of this forum and future members' also. It would have been alot easier me doing this in 'private' ie, not sharing with anyone else but, what's the point in that......no one learns by my mistakes or enhances their knowledge base by something I get right. I still think the diagnostics are the most important part of this process as a means of hopefully preventing it in the future.
Thanks all for your interest.
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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #111 on: October 10, 2017, 08:14:58 PM »
I'm very much inclined to think the rings gaining a bit of rust in a prolonged lay up theory is why the rings would break up like that. On my 550 it had a indicated milsge that was not that high, - I cannot remember the figures exactly but around 30k, I doubt that bike had been around the clock given the wear elsewhere on it, but it had doubtless been stood a long while given the rust that had been painted over.
I suspect the rising values of Sohc bikes will see more bikes dragged out, forced to turn over then thrashed and flogged quick so if the theory is right we can look foreward to more of these threads. I've seen a few pistons where the rings have picked up on the cylinder, they do melt rather readily. I've also had a few where the piston have pre ignited and holed the piston, to me this looks like the damage from the bits chewing the head up. - the melting to me is as likely to be friction from repeatedly hammering those bits of ring til they exit and running temperatures combined. I did blacksmithing in collage and it was a trick of the old hands to take a bit of cold 10mm diameter steel, and hammer it so fast they could light a cigarette  off it, so I reacon the melting might just be that. Rings are really brittle and easy to shatter so I can well imagine a bit of rust in the bores causing them to fail. Worst case of this kind of abuse I've seen was a dumper engine I bought a few years ago, probably easy start causing the top of the piston to fail ( they have a small pocket in the top of the piston with a spike inside it and a washer fixed around that to aid cold starting ) the washer had come loose off the piston, similar damage to the head  to look at although the rings survived ok I think. It had obviously been run that way for a long, long time as the valves were bent and stuck plus the exhaust port was almost closed up with soot, crank though free turning was down to copper on the main and big end bearings. Con rod was a bit bent too. Just the impact seemed to leave the head and piston crown in that condition.
Got a 500/4 with rust and a sidecar and loadsa bits. nice and original and been round the clock

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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #112 on: October 10, 2017, 08:40:44 PM »
If it makes you feel any better Julie my 45k restoration project was equally mullered when I stripped it down and funnily enough mine also had 3 pistons and crowns damaged.







Mine had sat since 1997 and wasn't run for 9 years, promptly broke and sat for another 9 years before I bought it, just proves these things need to be ridden to be in good shape

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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #113 on: October 10, 2017, 08:47:46 PM »
That's really interesting Craig, also good to see another wrecked engine  ;D Can you remember if #4 piston was ok or was it one of the others?
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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #114 on: October 10, 2017, 09:05:26 PM »
Craig, you are right, these bikes are far better off being used, my cb500 got to 250,000 miles and the engines in better  shape, just needs new rings and one selector fork plus gear it runs in.
Julie, you need to see the contents of my shed - plenty of wrecked engines in there, thanks to my buying at the very bottom of the market.
Got a 500/4 with rust and a sidecar and loadsa bits. nice and original and been round the clock

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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #115 on: October 10, 2017, 09:15:29 PM »
That's really interesting Craig, also good to see another wrecked engine  ;D Can you remember if #4 piston was ok or was it one of the others?

It was an end one on mine too, also had the same damage to the rings and sides of the pistons. My research on the cause was not definitive but best guess was the carbs running very lean and judging by the state of them when I checked them it may be right

« Last Edit: October 10, 2017, 09:21:36 PM by Craig CB400 »

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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #116 on: October 10, 2017, 09:23:19 PM »
Craig, you are right, these bikes are far better off being used, my cb500 got to 250,000 miles and the engines in better  shape, just needs new rings and one selector fork plus gear it runs in.
Julie, you need to see the contents of my shed - plenty of wrecked engines in there, thanks to my buying at the very bottom of the market.
I would love to look in your shed Matt ;D. I think the consensus from the experts on here is that this damage had occurred prior to me owning the bike and yes, it was definitely off the road for 9 years before I got her. So this brings up another learning point which is that if a bike has been sitting for however long not being ridden, it may be years (nearly 4 in my case) and miles (almost 5000 in my case) before a pre existing problem worsens and presents itself. I am now beginning to understand why with every bike that Trigger buys, (and i mean every bike !!!) regardless of condition or if the PO says it has had an engine rebuild or the bike has undergone restoration, he strips that bike right down to the frame, including the engine because he wants to check every part for himself, just to make sure it's ok.
« Last Edit: October 10, 2017, 09:44:50 PM by Nurse Julie »
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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #117 on: October 10, 2017, 09:39:10 PM »
That's really interesting Craig, also good to see another wrecked engine  ;D Can you remember if #4 piston was ok or was it one of the others?

It was an end one on mine too, also had the same damage to the rings and sides of the pistons. My research on the cause was not definitive but best guess was the carbs running very lean and judging by the state of them when I checked them it may be right



A matching set Craig !!!
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And the back side
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« Last Edit: October 10, 2017, 09:42:32 PM by Nurse Julie »
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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #118 on: October 10, 2017, 09:45:17 PM »
Did you mention chains Oddjob  ;D I empty this bloody box every six months, get through a few  ;)


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Re: CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE
« Reply #119 on: October 11, 2017, 06:06:47 AM »
That grey sludge in the bottom was probably not grinding type paste but well chewed up bits of alloy from anywhere, those chains and gears mush alloy up really well, ask Trigger about the 175 and 250 centrifugal oil filters! On looking the shells I would use again as long as you know which rod/hole they came from, same with horseshoe, looks in really good knick---just make sure it pivots extremely freely and locktite the two special retaining bolts in---I have seen those come loose. New tensioner springs would be nice but I don't think they exist any more, sure a similar size but maybe a bit stronger can be found

 

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