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

[Nurse Julie]

Julie

Is that a new O ring on the starter motor spigot?
I doubt they ever leak ? .... just looks a bit flat in its groove.

I think it's my dodgy photo Clem, it is a new one, it is just sitting proud, not by much..... but just.

[Clem2112]

I was paranoid about all the seals being renewed when I rebuilt mine....no leaks to date.

Now I just want it running right....  I suspect the cylinder head work that I offloaded, through lack of  confidence in my skills,  might not have been done quite thoroughly enough. This year's challenge.

[Nurse Julie]

I was paranoid about all the seals being renewed when I rebuilt mine....no leaks to date.

Now I just want it running right....  I suspect the cylinder head work that I offloaded, through lack of  confidence in my skills,  might not have been done quite thoroughly enough. This year's challenge.

I'm finding it's not difficult to get paranoid when building an engine and I'm definitely not the paranoid type!!!.
I will have replaced all the seals, O rings etc on this build, no point in not replacing them in my mind. Thinking that all the rubber bits are almost 40 years old, except the gear change lever seal that I changed last year, they are all due for a change.

[Nurse Julie]

Just a tantalising glimpse....full update tomorrow 

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[paul G]

WHOOOoooo Looking good

[Integra99]

Nice work... looking lovely! on the homebound stretch now!

[taysidedragon]

Looking good. There might be a problem with that camshaft though! 

[Nurse Julie]

Looking good. There might be a problem with that camshaft though! 

Yep, it will never work 

[Nurse Julie]

Going back 2 days.

The barrels have been rebored to +.50. The rebore was done to a physical piston and the barrels were cross hatched. The tolerance is about 1 thou.
I fitted the rings to the pistons. The bottom ring or oil ring has 3 parts to it. With these 3 parts you fit the spacer ring on the piston first and then 1 rail on top and one underneath making a spacer sandwich. The second ring goes in the middle groove of the piston and has a very square cut face to it. The top ring has a little sort of chamfer on the top and bottom edge.  Any markings on the second and top rings have to face upwards. Luckily, Trig just happened to pick up one of the pistons and although I thought I had checked to make sure I put the rings in with the writing facing upwards, there was one top ring facing downwards……how pleased am I that he noticed my cock up.
All the rings were staggered around the pistons at approx. 120°.
The circlip was then fitted to the farthest side of the pistons from the side I was working and the pistons put on top of the con rods with the arrow on the piston facing the front of the engine and ‘IN’ facing the rear and the gudgeon pin pushed through from my side. Then the other circlip was inserted with the little tail pointing downwards. I actually found the circlips quite difficult to get in, not because they were particularly tight but I just couldn’t seem to get the angle right with the thin nose pliers so I got Trig to do them for me as I was worried about bending them out of shape.

I put the dowels in and as these dowels have oil coming up through them, Trig said that he always fits an ‘O’ ring around the dowel, just in case. This ‘O’ ring is not mentioned anywhere in the service manual and does not come in the gasket set. Trig punched out the hole in the gasket just a little larger to accommodate the seal. I then fitted the gasket, trying it both ways round to make sure I had ‘the best fit’. In fact this pattern gasket set has been very good for sizes, shape, holes in the exact right place etc. I then dropped in the cam blades making sure they located correctly.


The 3 part oil rings

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The top ring

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The second ring

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Big 'O'rings around the bottom of the barrels

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The extra 'O' ring Trig fitted

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[Nurse Julie]

The gasket and the pistons fitted to the con rods

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The positioning of the circlip holding the gudgeon pin in situ

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We then fitted the barrels over the pistons. I was quite concerned about this and was not even going to try and do it without Trig helping me. It was actually very straight forward. We lowered the barrels down over the studs to just resting very gently on the top rings, we compressed the top rings using our fingers and by just applying gentle pressure, the barrels slipped over a treat. We did the same with the second rings and then the same with the bottom oil control rings. Once all the pistons were in the barrels, it was just a case of smacking the barrels down with your hand until they sat on top of the bottom casing.

The pistons / bores then had a good squirt of oil applied and we manually turned the engine over quite a few times to get lubrication down the side of the pistons. Then some Graphogen was applied and again, the engine turned over manually to get the pistons moving up and down.


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I then put in the oil jets with their new seals and the stud dowels with their new stud gaskets.

The oil restrictor jet and stud dowel with gasket.

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[Nurse Julie]

Whilst assembling the engine, any dowel that has oil going up it, especially the stud dowels, was thoroughly cleaned again with a small brush to make sure they hadn't picked up any contamination.

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One thing I would mention here is that although it is easier re assembling the top end of the engine with the bottom end in the frame, I did find other bits, like frame, wiring, coils, cables etc getting in the way at times. I think if it were at all possible, I would have found the whole process much easier with the engine out of the frame. But then, you have to get the whole engine back in the frame. Not a problem if you have the bike stripped 100% as you can lay it on it’s side and do it.

 I then fitted the cylinder head gasket and the cylinder head which I had re assembled previously. I used the new Dowty washers under the special 8mm nuts and the original copper covered steel washers under the 8mm cap nuts. The head was then torqued down in sequence and left for 24 hours before re torquing again in sequence the next day.

Head bolts

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Whilst all this had been going on the cam chain had been held aloft on a piece of wire and fed through to the top.
I fitted the points plate with everything still attached from before but Trig pointed out that the covering and indeed the wire from the points had seen better days so I removed it and he un soldered the flags and soldered them back on to some new wire, I fitted a new white covering on it and put the bullets on and I must admit it looks a lot better. I refitted the points plate and found TDC 1.4 . I then fitted the cam sprocket on the camshaft and inserted in from the right of the engine and lined up the marks on the sprocket with the upper surface of the cylinder head. Now here’s a strange thing, nowhere in the Shop Manual or Haynes did it tell me which way up to have the camshaft, ie lobes facing up or down, I had to look at videos on line to in which position the lobes needed to be facing, bloody weird, unless I missed something obvious. Also, I seem to have got a ‘plate’ on the sprocket, where the two bolts go through, which does not show on any fiche or in any books, so I don’t know what that is all about either. The cam chain fitted over to sprocket with no problem at all and we then undid the cam chain adjuster, which had been in the locked position with no tension, and the little bit of slack came out of the cam chain and we locked the adjust again. We turned the engine manually again, to make sure everything was turning and going up and down as it was meant to be, just for my piece of mind really.

Points and wiring before

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And after a quick refurb

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You can just see the lines on the cam sprocket in line with the upper surface of the cylinder head and the strange metal plate that seems to not be shown in any books or on any fiche

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[Nurse Julie]

Elastic bands were fitted to hold the tappets and rockers up out of the way whilst fitting the rocker cover to the engine. One thing I had not noticed previously was that one of the tappets had a small chip and one had quite bad pitting, so I found some replacements in the workshop and fitted them. Trig then applied a little Graphogen to the rocker pads.
I fitted the cam shaft oil spray pipes with their nice new grommets and fitted the rocker cover and bolted it all down and removed the elastic bands.
I adjusted one of the tappets and Trig did the rest. He re checked them all again this morning. This is where I found it all very awkward with the engine in the frame as it really was awkward getting the feeler gauge in the tappets with everything else in the way.

Pitted tappet

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Elastic bands holding tappets and rockers up out of the way

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A dab of Graphogen on the rocker pads



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And this is the stage that I am at now. Engine all bolted in now with crash bars fitted. Exhaust system back on. Drive chain on plus a few other bits fitted.




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[Johnwebley]

Elastic bands were fitted to hold the tappets and rockers up out of the way whilst fitting the rocker cover to the engine. One thing I had not noticed previously was that one of the tappets had a small chip and one had quite bad pitting, so I found some replacements in the workshop and fitted them. Trig then applied a little Graphogen to the rocker pads.
I fitted the cam shaft oil spray pipes with their nice new grommets and fitted the rocker cover and bolted it all down and removed the elastic bands.
I adjusted one of the tappets and Trig did the rest. He re checked them all again this morning. This is where I found it all very awkward with the engine in the frame as it really was awkward getting the feeler gauge in the tappets with everything else in the way.

Pitted tappet

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Doing great. Not long to go
Just all the fiddly jobs looking forward to the start up

Sent from my SM-G361F using Tapatalk

[K2-K6]

Very good clear pictures of the build Julie, getting close to firing it now.

The camshaft positioning (up or down lobes) is not important. With the crank set at T for cylinders 1 and 4, both of these are at tdc. Camshaft one way will give firing on one cylinder and exhaust on the other,  then flip the cam 180 degrees without moving the crank, and the sequence just flips cylinders with it. As they are both sparked at the same point it makes no difference which way you build it.

Nigel.

[Rob62]

Its all looking very 👍 roll on spring