CB400/4 ENGINE STRIP, ASSESSMENT AND REBUILD BY JULIE - NOW COMPLETE

[Bryanj]

Thats the problem with the Honda workshop manuals---they were written for Honda workshops!

[haynes66]

i also want to say how inspirational this thread has been. i have two 750-4 hondas which will be stripped and rebuilt side by side but i've been waylaid by a number of major issues which have knocked me for six since the beginning of 2016. and to be honest, i've been struggling with a lack of confidence generally, and lacking the courage to tackle the engine strip. i've stripped and rebuilt two TL125 hondas, a couple of fordson major tractors and a number of machines over the years. but for some reason i've been putting this off all the time, focusing instead on calipers and brackets etc.  but i'm determined to make a start in the new year after seeing this engine coming together. thank you, nurse!!

[K2-K6]

Agree with above posts, very well illustrated too with your photos too Julie.

Something it also illustrates,  it's often given that conventionally when you drain old oil from engines which is often sludgy,  then it contains a lot of metal that's been worn away from the inside components. Your example here ( excluding the obvious missing bits of piston)  proves really that's not the case.
At the mileage it's covered most of it is still there!
Most of the parts you've assessed still have virtually all of their original materials in place,  this view aided by your cleaning and recording of the parts with photos for us to see.

It's more the case that with oil changes completed,  then very little wear actually takes place.

It's obvious problems accepted,  it appears that this one has been looked after, service wise, right from the outset.

[Nurse Julie]

I think it has been well maintained in the past Nigel and certainly has since I purchased it. We all go on about oil, what it's got in it, or hasn't got in it or how expensive or cheap it is but I still think it is the frequency that the oil is changed that is more important than the chemical make up of the oil. I will carry on with my 1000 mile oil / filter change (after the initial 500 mile running in oil change) in the hope the engine lasts longer than I do 

[K2-K6]

Yes,  agree, oil condition trumps most other things in general use with these engines.

[Nurse Julie]

Re assembled the gear shift mechanism yesterday.

There are 4 parts. Only 3 show in this photo as even though I thought I had taken a pic of the gear shift spindle, I hadn't !!!
Left to right  Neutral stopper arm, Positive stopper and gear shift drum stopper.

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The gear selector drum needs to be in neutral as identified by seeing the brass point through the hole on the opposite side of the casing

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First, the neutral stopper arm is fitted, with one end of  the spring in the notch on the lever and the other end of the spring hooked on the crankcase. You can just about see the 2 ends of the spring in this photo.

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Then fit the gear shift drum stopper, once again locating the ends of the spring in the notch and the other hooked on the crankcase

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Then fit the positive stopper assembly with the two hairpins either side of the pivot post of the neutral stopper arm.

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[Nurse Julie]

Then the gear shift spindle was pushed through to the other side and through the new seal

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This photo shows everything in its correct place with all bolts tightened up

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Finally, all gears were found and I have marked them on the drum stopper plate

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I will tell the truth here. I couldn't remember how I took this lot apart during stripdown and I hadn't taken a photo either, which is strange as I seem to have taken photo's of the most ridiculous silly little parts. I first reassembled it, trying to remember how it all went and failed miserably. I had all the parts in the right place but it was all just sitting there and I just couldn't work out how it was meant to function or operate. I had to get Trig to have a look and, stupid me, I had not jammed the ends of the springs against the casing and therefore they were just sitting in thin air and there was no tension and nothing would work. Stupid of me really, I even kept looking at the pictures in the manual etc and reading what to do and every time I missed the line saying 'and hook their springs into the crankcase'............never mind, all sorted now.

[Nurse Julie]

And finally for yesterday a nice simple job, putting the 4 screws in the oil separation plate in the sump.........another little bit finished

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[Spitfire]

It's so satisfying sitting there with a pile of clean refurbished/new parts and put an engine back together, I used to love it, keep up the good work.

Cheers

Dennis

[Nurse Julie]

It's so satisfying sitting there with a pile of clean refurbished/new parts and put an engine back together, I used to love it, keep up the good work.

Cheers

Dennis

Yes Dennis, it is rather nice working with all clean bits, it makes this job a lot more civilised than it could have been.

[Nurse Julie]

I lapped in the valves this afternoon. Had never done it before so had to have a Tutorial from Trig. Took me ages to do but got there in the end.



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[paul G]

I hate doing that job especially when the poxy rubbers won't stay stuck to the valve 😡😡
Did get a good tip that does work tried it last time, self adhesive Velcro cut to the size of the rubber and the valve👍👍👍

[Johnwebley]

You could use a  small piece of fueltubing on the valve stem.to help twist.also pull the head on the seat.

Sent from my SM-G361F using Tapatalk

[Drew400]

Hi Julie,

Reading your update with interest (after a long lay-off the site).

I'm a big velcro fan (for all the right reasons!) and you've just given me a new right reason. Wish I'd read that before I struggled with my sink plunger-style lapper-in tool!

Keep up the good winter work.

D.

[Nurse Julie]

I actually just did it the 'normal' way, rubber on the valve. It took me a very, very long time to get them as perfect as I could. And yes, the bloody thing kept slipping off and my hands are quite sore now. Reminded me of trying to start a fire with a stick in a hole 😁😁😁