1973 k2 Honda 500 carb problems (Sorted now, was coil wiring issue, not carbs)

[Trigger]

You checked the throttle stop screw on the butterfly? it's an eccentric cam arrangement and if it's out it will hold the throttle open even with no cables attached.

Will go through it again tomorrow. I can get it to tick over at 800 rpm but, twist the throttle to 7,000 rpm and it will only return to 3,000 rpm and after a while will return to 800 rpm or drop off completely.

[deltarider]

Possible air leaks between carbs and head? O-rings between head and intake manifold are always suspect.

[jon stead]

^^^thanks Delt Rider.

Got the bike running today but it will not tick over. Rides ok ish, apart from a horrendous front wheel wobble and once warmed up is a pig to restart.

When I get more time I will check for air leaks as suggested. At the moment I'm just glad I actually got a rude out if it. Gears work, brakes work, no engine oil leaks, so just this wheel wobble and tick over and jobs a good'un.

Thanks everybody for your support and suggestions, much appreciated.

[mike the bike]

Have you checked the idle jets/emulsion tubes?

[matthewmosse]

Outside chance here, but the bit about being a pig to restart once hot reminded me of my first cb550, it had most of the same symptoms as I recall, it was down on compression thanks to the rings being mia on top of pistons.... If you don't know the history of the inside of the engine, it might be worth just checking compression. Mine still pulled a ton with the engine like that, pretty well inpossible to start once hot, tickover a pain to get anywhere near right. Valve clearences were often needing adjustment too. Worth a quick check in my books.

[jon stead]

^^^ Thanks Matthewhouse. Compression has been checked and confirmed good, but I agree it could of been the cause.

[jon stead]

Hello all, my poor running engine saga continues. Because I work away a lot I don't get much time to work on it. Since last posting, the head has been off, cylinders rebored, new pistons and rings fitted. The carbs have been back once more to the original overhauler but still the same symptoms. Won't tick over and runs hot so must be rich. I will pass the suggestions from this thread to the guy that's got my bike now. I'm close to deciding to bin these carbs, despite the amount of money spent on spares for them, and getting another set. It would be great if I had a set if carbs that I know work correctly so I could try them and know for sure.

[jon stead]

Hello All. Changed the old carbs for a newly refurbished set from the USA. Bike is running as good as it's ever done whilst I've owned it. New swinging arm bushes fitted, new battery, new MOT and I've been out n it today. Taking it easy considering the rebore and hopeful of the bike improving all the time now.

Tickover still erratic, nice when first started, but rises the 2,500 rpm when warmed up. I can live with that. I think the tank is rusty and cruddy so next job is to clean the tank out with some drain cleaner and get some miles on the engine.

Typical that I get to this stage at the end of the summer!

[jon stead]

Hello once more. Yet again I am away for some months and have had to interrupt my bike's progress. Before I left though, I managed to clean the tank out and refilled with new fuel. I am struggling to get more than 6,000 rpm out of the engine. I'm thinking that the mixture is too rich and possibly needs more air. Also maybe some of the tank crap had got through to the carbs so I'll check the jets when I get home. SO frustrating not having the time to get to it. It's slowly getting better as I do more to it and I feel that it's something relatively simple now.

[Johnwebley]

check your plugs,running HOT tends to be to lean,

 rich will mean sooty plugs,

  how soft are the carb to head rubbers?as they age,they get hard and can leak air

[jon stead]

HI johnwebley, thanks for the reply. Since the second set of carbs the engine isn't running hot anymore and the plugs aren't sooty but the engine is down in power and won't rev over 6,000 rpm.

[jon stead]

What a momentous day, today, has been in the saga of my 500/4. I feel a huge corner has been turned, a momentous mile stone reached and many more similar metaphors you can think of.

The bad running of my bike continued, so bad it was unridable. I didn't have the time it needed to sort it properly, but whilst working away, I continued researching my symptoms, and found an article about powering the coils straight off the battery, bypassing the ignition switch and the cut off switch. I also downloaded a copy of the electronic ignition system that had been installed on the bike a few years ago, shortly after I'd bought it.

I set to this morning and made up my bypass lead. As I looked at the coils and the wiring diagram to work out where to connect to, I noticed that my coils were wired in parallel and they should be in series. I rewired them, as per the manufacturer of the electronic ignition systems diagram, and hey presto, a transformation occurred. The engine fires first time, every time on the button. The engine ticks over smoothly now and revs freely. I am over the moon.

It still needs some fine tuning but for the first time in three years I am out and about on it with a huge degree of enjoyment.

Thank you to all who have commented and offered advice along the way, much appreciated.

[Bryanj]

Boyer ignition?

[Johnwebley]

What a momentous day, today, has been in the saga of my 500/4. I feel a huge corner has been turned, a momentous mile stone reached and many more similar metaphors you can think of.

The bad running of my bike continued, so bad it was unridable. I didn't have the time it needed to sort it properly, but whilst working away, I continued researching my symptoms, and found an article about powering the coils straight off the battery, bypassing the ignition switch and the cut off switch. I also downloaded a copy of the electronic ignition system that had been installed on the bike a few years ago, shortly after I'd bought it.

I set to this morning and made up my bypass lead. As I looked at the coils and the wiring diagram to work out where to connect to, I noticed that my coils were wired in parallel and they should be in series. I rewired them, as per the manufacturer of the electronic ignition systems diagram, and hey presto, a transformation occurred. The engine fires first time, every time on the button. The engine ticks over smoothly now and revs freely. I am over the moon.

It still needs some fine tuning but for the first time in three years I am out and about on it with a huge degree of enjoyment.

Thank you to all who have commented and offered advice along the way, much appreciated.

 great news,and still lots of warm weather to enjoy it
now its running ,use it,they love being used

[jon stead]

Boyer ignition?

Yes, Boyer Brandon, Micro Power system.