Honda-SOHC

Looking good girly, make sure you get someone videoing you on the first startup (NO CHEATING!, by that I mean don't have it running the day before making the video!) and then watch you ride of happy and proud. Well done sticking with it and not losing your temper and "sort it next summer/year/ decade"  like a few I've seen (and bought from people) over the years.

Thanks Mr Hairy.I will get Trig to Video the start up and ride away. I will start giving him lessons now on how to use the Vid function on his phone, it may take some time !!!!

The engine is now all complete and the bike is back together, all but the carbs. I wanted to get the carbs fitted and fire her up as I am an impatient bitch but Trig said........ NO !!!. He wants me to wait so the first time I fire her up I can take her for a very long ride ie, 100 miles to start running her in. Now, I am a fair weather rider these days and just the thought of getting out on a bike this time of year for a couple of hours fills me with dread (and covers me in goose pimples !!!!). Therefore, as it's going to be some time before the first start up / ride of the year, I'm going to strip the carbs and give them a good clean, have all the necessary parts zinc plated, fit a new 'O' rings etc. Luckily, I have had these carbs apart a few times before and I know they function well just by being bench synced so will be no problem when I re fit them.

This engine strip and rebuild has been a MASSIVE learning curve for me. I knew my knowledge base was extremely limited when it comes to all things mechanical and engineering but I have always to be able to do basic routine maintenance on bikes and I though this would help but it was of no use to me at all.

It was my plan to do everything myself (except the machine work) and I suppose I did an awful lot of it but I had to keep asking questions like 'how do I do this?' or 'where does this go?' or 'why have I got this bit left over?', 'what tool do I use for this bit' and my favourite was 'no, your going to have to explain it again'. I just did not know enough of basic engineering / mechanics to do this job entirely alone. Using the Workshop Manual, the Haynes Manual and microfiches basically tells you diddly squat, they are books printed for people who know the basics of building an engine and no more.

I have learnt that building an engine is all about measurements, tolerances and individual components working together to perform a function, checking at every stage that something you have just re assembled actually works before you go on to the next component. I have also learnt that if you do it right, you do it once.

I was lucky this was a CB400/4 engine. They are compact, every component fits together really nicely and I can now understand why Ian (Orcadian) says they are like a Swiss watch, they are lovely to work on, everything is a manageable weight and size and feels 'just right'.

Would I do it again? Yes, of course I would if it were a CB400/4 engine. I feel I have learnt enough and gained an understanding of the basics of building a CB400/4 engine that I would probably enjoy it more next time.

More importantly, the damage this engine had sustained and ultimately the reason I did this strip and rebuild has been dealt with.
I have no doubts now that she will run and perform very well once run in and hopefully will be good for many more years.

Not only have I learnt the basics of the practical side of engine building but you guys have been so brilliant sharing your years of knowledge in the diagnostics of the initial problem and sharing your practical experiences, that to me has been totally invaluable. Thank you all so much for your input throughout, it has made it so interesting for me. And thanks for all the 'SOHC Banter' as well, I love it and it makes a job much nicer having a laugh. Thanks to all those that have sent me PM's, emails and texts as well, your encouragement has meant a lot to me.

Could I have done this without Trig, NO, most definitely not. I would probably still be trying to get the mullered nut off the head stud and getting nowhere fast. His theoretical knowledge and more importantly his practical experiences of engineering, engines and in particularly Honda SOHC engines never fails to amaze me. I know he is sick to the back teeth of me keeping on asking questions, wanting to queue jump for machine work and being in his workshops with all the tools out of the chests.

I will let you know when she is going on her first post rebuild run and let you know how it all goes.

Julie
 

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! Should that be £25 Julie? S/H previously enjoyed on ebay or brand new?

  Unfortunately not £25 but £250 but that is for new ones. I have just found some on teabay USA whilst looking for something else and they are $270 which is approx. £200 so I'm sue if you really looked around you could find them cheaper. They are very good quality though and luckily mine were fitted to the bike when I got her.

This is coming along really nicely, i guess you are itching to get the bike back on the road to harvest the fruits of your labour, i know i have when i doing this sort of work.

Yes, I want it all finished ASAP but still got quite a bit to do really just fitting all the bits back on. I'm on the homeward stretch though and as far as the engine is concerned basically it's all done which is a huge relief to me. It all came together really quickly in the end, it's just all the work leading up to the re assembly that takes time. I keep wanting to go and turn the engine over manually just to make sure it all still works as it should but that's my lack of confidence in what I have done that's causing that I think.

Did you have to gap the piston rings at all.

No gaping needed. Bored out to .50, fitted .50 rings to .50 pistons so everything fitted perfectly.

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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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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That is good news Roy. Sad that you are out of pocket but could have been a lot worse I suppose.