Honda-SOHC

Remember the article in Motor cycle Mechanics in 1978 ??.  Well heres a quick reminder.

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and .....

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Not my cup-of-tea back then either

Hi, I stopped using my old K3 back in 1995 when it started burning loads of oil and poor performance.   Fast forward some 25 years later and I finally decided to restore the bike.

I pulled the top end off and was surprised to find there was no lip on the bores at all.  The rings and oil scrapers were well tired.  So I thought a very light hone and a new set of rings would be ok.  I also put some paraffin down the valve intakes to check for leaks.  They were still in good(ish) shape.

So it was all resembled and after much effort to get the carbs to stop leaking it finally was ready for the road.   The bike actually starts and runs ok.  It could do with the carbs being setup better but it does rev ok and pulls through the gears.
Unfortunately the speed does not match the engine revs.  So I thought it might be the clutch (42k) miles and purchased a new cllutch kit and cable from DSS.  I fitted these and it made no difference at all.

So next I checked the timing - looks almost spot on.  So finally I checked the compression.......
With COLD cylinders and no oil down bores and all plugs out and throttle fully open I tested each in turn.

I found the pressures to all be about 155-165/cylinder.  I think the manual says they should be 177psi.

So after some 200 miles the engine has improved a little but the engine still needs to rev too hard.  I was expecting about 5200k revs for 60mph.

I have been trying to keep the revs down to start with to run-in the engine after the rebuild.

My question is ...... is 155-165/cylinder too low?? when cold.  I should really try the test with a hot engine I guess.

Other than this issue it seems to run ok.

Ta
Nairb

The only thing I can really add to all this is......

I have owned the bike from new and ridden almost all of its 42k miles.  A chunk of that must have been with both plugs and caps having resistance and the bike seemed to work fine.
Its only now after a long restoration/rebuild that I thought to check and change the plugs/caps.  The plugs all checked out at 5k ohms and were probable little used .  The plug caps varied between 5k-12k ohms.

I may not notice any difference with the new parts - except new is usually best for a while.

Interesting info about plugs/caps and resistance tho.

The plug caps on my cb550k3 are as old as the Dinosaurs..... But the engine starts ok and does idle.

I thought I would check if they needed replacing, and maybe the plugs too(DR7ES).
I checked the resistance of each plug cap(NGK).  Some are 5k and both outer caps are 10K+ (ohms).

Now 2 questions.....
1. Should the caps all be the same resistance?  5k ohms.
2. If the caps have resistance then the plugs should NOT be .

My current set up is resistor in both caps & plugs.  Not good I suspect.

So a set of new NGK plug caps with 5k ohms and a new set of d7ea plugs(non resistor).

Ta
Nairb

Nearly 5 weeks and counting........ Dare I hope for success?.  It might be here this month.

I have not heard of a 1976 K3. K3 was from 1977 on.

Mmmm, I thought it was a 76 model.  Or I thought I purchased it in 76.  So I managed to dig out its invoice from that time. See below.

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And it plainly says 20-01-78.  So there we go.  And it does say New CB550K3.  Funny how the new clutch cable is to long and the K3 throttle cables dont fit.  Maybe I dident get the right ones.  The frame/engine numbers are correct for a k3.

The European type wiring diagram seems to be the one. 

Thanks
Nairb

After a recent topic on here about tyres I am seriously considering changing the TT100's on my 750F1, they were fitted when I rebuilt the bike in 2007 and with the amount of miles I do they will probably last another ten years but they will probably be as hard as a rock by then.

Its why I asked the question about 10 years old tyres.  My cl450 does 300/400 miles a year on good quality tyres.  They could last 15/18 years.... Is "could" the right way?.  If the 10 year rule from the dvla is passed on to all vehicles then my bike would fail an MOT.  I know I dont need an MOT for an historic vehicle but it would still be illegally on the road!.

I chucked out a set of TT100's a couple of years ago.... they had set like rock.

Just checked a bike I've had (in bits) for 26 years - a CB77. It was classed as not taxed, so I sorned it. At least it is now on their radar as currently cared for.  It was an old blue V5c , so I suppose It could appear forgotten about.

The other bike I was worried about is already classed as  sorned and I could'nt find a way of updating that.

Regards, Terry.

An interesting bit of info.  I just went on line and managed to sorn my cb550k3 which has been in bits for years and has/is being restored.  It was last taxed before the sorn system was implemented.  I now expect a letter from the dvla wanting an explanation why its not been on a sorn before......

When did this all change.  Several years ago they would not let me put the machine on a sorn.  Now I can so it seems.

Nairb