Honda-SOHC

The hanging seems to be fixed now; somehow. I started and ran the bike this morning; allowing it to warm up before I used a strobe light to set the timing. Timing was out by a few degrees - in front of the F mark so retarded? Since I posted I had a hanging problem I have stripped and cleaned the carbs; replaced the old idle jets with 'new' Honda ones, re-set the float heights to 22mm; 2 were way out and re-synched the carbs on the bench so the slides are just opening. Before I bench-synched with a small gap using a drill bit as a gap tool. I have also fitted 2 in-line Aeroline fuel filters. Idle air screw is out 1.5 turns on all 4 carbs.

Another thing I noticed when starting the bike this morning was that when I turned the fuel tap on there was an audible release of air pressure. I also got this when I opened the fuel cap to check the fuel level in the tank. I have an aftermarket fuel cap from DS and when I checked the vent hole I found that a piece of cotton wool or similar was pushed into the little vent hole; presumably to prevent ingress of dirt. However, it was so tightly pushed in that it was preventing the air from getting in the tank so I removed it.

I don't seem to have any hanging issues now and the plugs which were super sooty are now a nice tan colour with no oil or soot.

The remaining issue is that the bike is not eager to pull away from standstill and needs more revs than I think it should. Im going to be investigating this next but if anyone has any pointers for this issue please point!

Lovely sunny day on the Ridgeway

Thanks all for the help. I stripped and cleaned the carbs paying particular attention to the idle circuits giving it a good squirt through with carb cleaner, blowing out the residue and leaving overnight to evaporate away thoroughly. I rebuilt the carbs this morning with the new idle jets (thanks Julie, I forgot I had bought them but not fitted them!) and checked and adjusted the float heights - a couple were out by 1.5 - 2.0 mm. I re-synched the carbs; this time I set all sliders at the just opening position; previously I had set at a bigger gap. I fitted 2 of the in-line Aeroline filters (thanks Ted for the photos).

The bike ran much better and I have just got back from a blast up and down the road - about 5 or 6 miles; flipping cold but very satisfying :-)

There is still a slight hang now and then but nothing like it was; the bike hesitates when pulling away from a standstill and needs quite a lot of revs. Its been years since I rode a 4 cylinder bike so partly the 'hesitation' might be that I am more used to big twins with low-end torque? The bike still smells as if it running rich.

All in all a pretty good mornings work though

069a carbs are for a CB550F not a CB500K Ted, as I'm sure you know. a 500K made for the UK should be wearing 627B carbs. The 069a carbs have 4 slots on their needles and it runs at 2nd from top as standard IIRC, the problems here sound like flooding to me, if you can smell petrol there's something wrong. Flooding will cause it to run really rich, hence the black plugs, it's like the engine is running on fast idle setting on a car with auto choke.

As these bikes get older we don't know what's been done to them before we bought it, it may no longer have the same brassware it was made with, a lot of people tended to think they'd be better replacing it with stuff like Keysters etc thinking it was wearing etc, worst thing they could have done IMO. The next owner then has to suffer that mistake and a lot move the bike on because it's not running as it should and they don't know why.

All 4 carbs on my bike are stamped 087A - its a US import 1976 K2 CB550

Does this PDF file help at all?

Thanks Ted, it all helps. Incidentally mine is. ‘76 K2 and I also have the hollow tip cross drilled air screw in my carbs.

I have a pair of new aero line filters and spare fuel line tubing so when I put the carbs back on I’ll do as suggested.

I thought I would check the mixture screw settings were correct this afternoon as it’s easy to do and doesn’t require removing anything significant. Something possessed me to remove the mixture screws and check they didn’t have any muck in them - they didn’t. I put them back setting them at 1 turn out. The bike won’t run now. It fired on a couple of cylinders and then decided not to fire on any at all. Spark at all plugs but only cylinder 3 plug was ‘wet’ with fuel. I’m guessing I have dislodged some crud and bunged up the carbs so yet again I’ll remove them and give a good clean and re-synch. Plugs were very sooty too.

I don’t have a vacuum gauge

https://www.ebay.co.uk/itm/167269669258

you beat me to it Julie :-)