Time for an engine overhaul

Thanks  BritPete, I shall look into that at some point in time

This is my alternative to a work mate.












The bottom case had some oily muck as expected, the gearset bearing journals were okay.  Con rods are marked with a 3.  I did remove the barrels before to have a look at the piston skirts 

and the ring sets.  Surprisingly clean all round.

 If I cannot find a good bottom case , I might use mine, as the load area . ie, upwards is undamaged . This bike will not be a showroom jobbie, but certainly

as clean as I can within a reasonable budget.

Now.... if this was a CB 360 , then it would be a different matter.  I spent many happy hours drooling over the reviews ( 101.6MPH) when I was younger.  I bought one (green) and loved it

before moving up to a T140V bonneville.. Happy days. There was something so special looking at the green side panel  with the Letters CB 360 on it. I still have those feelings for that 

bike in green.




















Thanks for all the help.

Bob

I've got quite an old impact driver which I think came from halfords. I bought a set of jis bits for it from amazon and that got mine out as I wasn't aware they didn't need to come out. The jis bits fit the screws so well I had to prise them apart afterwards. I did have to hit the impact driver quite hard with a lump hammer to get them out though.

The left big end shell is brown, not sure why . Over heating?



I will check clearances with plasti gauge.

Ring gaps will be measured tomorrow, I will list what I find as the bike is showing 43k, with seemingly good compression, although not accurately tested prior to strip down.

The bores have lost their honing marks, so that needs doing.

Have taken pictures of which big end caps go on which rod , plus any other reminders like the gearbox bearing with the locating dimple to stop it rotating. Balance weight timing settings. 

Do the cam and balancer shaft chain guides ever wear? I know it is normal to replace them. 

I have not yet split the balance weights, do the rubbers need replacing?

Any thing else , other than gaskets, o rings ,seals etc.

Bob

Thanks buster , I will renew the big end shells anyway. 

I measured the ring gaps today, and you could drive a bus through both top and middle rings on both pistons, but both oil rings were better.

Top and middle ring gaps were 0.029 - 0.030 inches , at the outer limit, so new rings .

Should have compression tested the bike before stripping her.



I need to take the barrels and pistons to an engineering shop to have them measured.

My pick up had a small piece of plastic on it, I will put photos of the tensioners for you to look at.

I have not looked at the cush rubbers yet , but will change if necessary.

Will have to make a list of what the bike needs, and  budget for it, with out going over board.

Bob

I was astonished to see the ring gaps, perhaps if I had run the bike up to temperature, I might have seen some blue smoke.  The price was too good to miss, and I needed a project .

 The DVLA check mot history page will not show any thing once it becomes historic, so I could not verify its mileage.  If it needs a rebore, then its pretty poor, unless it has been abused.

  My measuring stuff is basic, ie, do not read 10ths of a thou, so either get it to an engineering shop for measuring,  or invest in an electronic micrometer and a bore gauge with a run out dial.

These are expensive but I do like to have the proper tools though.   I can start checking  big end and mains clearances before that .

This bike will probably take at least a year, due to other things needing money.

I wonder what is the average life of the bores on bikes of that era.  Did the mighty CB750 achieve high miles before a strip down.  I remember having to buy a new ford pinto

engine for my Cortina which had done 80k, I thought that was impressive at the time. 

  Imagine modern bike engines only lasting 80k, they would go out of business.

Thanks buster for the offer, I will take mine apart soon and have a look.

My photo shows two punch marks on both rods caps,  I believe they are number coding , is that correct?



Bob

the numbers can be a real pain to read, the paint fades (or wasnt brilliant in the first place, who knows?) a gentle clean of the flat surface (circled) and sunlight (what in february? in britain?) will hopefully reveal them.

Thanks buster, will look again.

John, thanks, I took photos of the rods in situ to keep them the right way round.

Not sure whether the springs were upside down, just took them off.

I am happy with the balance shaft timing, as long as Haynes are correct.....

Found and understood all the bearing colour codes . I will plasti gauge the lot, so I need to clean the threads in the crank case.

Do I need to apply gasket goo to the cases  while I check the clearances on the main bearings?  

Part of me says get it rebored and honed anyway, can anyone give me an idea of the cost. 

Oversize piston and ring sets at David Silver spares are quite reasonable.  

What are the pit falls with the head bolts, I know my bike is an early build, so, no seals on the inner bolts, which are shorter than the outer four.

If I have the rebore done, then I will do the frame and cycle parts first, I do not want to have new pistons sitting in new bores doing nothing for a long period of time.

Bob