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

[jon stead]

Hi

When I bought my bike teh carbs were flooding. I sent the carbs off for professional overhaul. They were set up on the bench. I got the bike running only to find oil leaks that weren't evident when it was stopped. The bike has been away and had the leaks fixed but the lad doing it couldn't get the engine to run correctly. Below are some of the comments from the emails he was sending me:

"Engine running no leaks. All the electrics are good with no issues. However, the engine hunts badly, revs to 3k when warm and when I adjust the throttle stop to set a tick over the engine dies. It won't idle at all unless I hold it on the throttle but if bring the throttle stop up to hold the throttle the rev climb to 3k again.
 
Ignition is spot on at static and full advance.
 
When I started the bike before I started work it did similar and commented that the carbs were miles out. Anyway I have removed and stripped and balanced the throttles, all of the floats are set to the same height, and all of the jets are (were) all matching across the carbs and the throttle slides are matching too.  Need to do some research on these carbs are they correct for year etc.
 
For your records
 slow running jet = 40
main jet = 100
Float height 23mm (should be 22mm but the springs in the float needles are very weak, they should hold the float a little but do not so 22mm turns into more like 20mm in use). 
Air jets turned out 1 1/2 turns.
NEVER LEAVE THE FUEL ON, the float valves fitted are brass type not Viton tipped so they will pass a little fuel over time and eventually will overflow. As the bike is used the valves will seat a little better.
 
It runs horrible, those carbs are not at all nice. Both 1 and 2 flood intermittently, the whole bank is rich and doesn't want to idle at all again. I will have a go later.
I have worked on just about every type of carb but these things are doing my head in. The float needles will not seal, the needle springs have various tensions and the carbs slowly flood. I had them in a bath, they have been blown through, I have adjust the floats between 22 and 25mm height and the running is no better. I have altered the emulsion tube needles to run at 4 standard, 3 and 2. And the air screws have been everywhere from 1 to 2.5 turns out in 1/8 th turn stages. Again no better.
 
When cold the bike tries to run ok but when hot it doesn't want to know which screams "rich mixtures". The bike won't idle but I can hold it on the throttle at say 1500rpm but if I bring the throttle stop screw up and let this hold the throttle then the engine speed rises and hunts between 2500 and 3000 rpm, if I back off the throttle stop the engine does. I have had the carbs on and off, stripped and put back together more times than can remember. All the jets are correct size assuming the numbers stamped are a true reflection. I have even fitted a harder platinum evx  plug set. "

I am now at a loss as to whether the problem is with teh carbs or somewhere else. How can I tell if the carbs are "worn out"? Any advice gratefully accepted.

Thanks in advance.

Chris
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[Trigger]

Hi Chris, I feel your pain, after 7 months in storage i got my 500 out today and i am having the same problems even after it was running spot on when it went in to storage. I will have a look tomorrow to see what i can find. I will start with the carbs as they are flooding after a while and it is sitting at 2500 rpm and will not drop.

[JamesH]

I swear the bloody fuel in the Uk is getting worse and worse. Somehow I think the ethanol (in addition to knackering the rubber components) affects the float valves on our vintage carbs...

[Johnwebley]

mine has become more sensitive to slow running and temp,at present it runs at about 1,100 rpm quite well,

same jets as stated,BUT the air screws are only 1 turn out,the extra 1/2 turn does upset the slow running,

also check plug gaps,no more than 27 thou,

[matthewmosse]

Had similar issues when I laid the bike up a few years ago, but with 550k3 carbs fitted. I am reverting to original ones for the rebuild, really hope I don't get this. Redex is worth a shot, might have additives that help the petrol behave better from some reafing I have done on other forums. I did find my rebel 125 started behaving a bit like this on Tesco fuel, ran the tank near empty and filled up at tesco, bike was running badly until run near empty again, filled up at my regular Texaco stop, bike returned to good form, only problem in the list I didn't get wss overflowing carb on the rebel. Makes fuel quality a possibility to try, just in case.

[Bitsa (Ralph Wright - RIP)]

I stay well away from any ethanol petrol its shite and absolutley NO GOOD for our classics.
Cheers
Bitsa

[florence]

If your carbs are flooding you have no chance of getting it to run correctly.  Check the brass tube in the float chamber.  They are prone to cracking, then they will flood whatever the float valve is doing.  I had this problem and cured it with a thin smear of epoxy resin adhesive.

[Bryanj]

New float needles and seats are worth fitting if the tiny springs are week

[Tiny Tim]

I swear the bloody fuel in the Uk is getting worse and worse. Somehow I think the ethanol (in addition to knackering the rubber components) affects the float valves on our vintage carbs...

This is quite interesting info regarding ethanol in petrol.
http://www.groups.tr-register.co.uk/wessex/ethanol-update.html

[jon stead]

Thanks everybody for the responses and some good tips there to be getting on with. Much appreciated. I will let you all know how I get on. 

[jon stead]

Long shot, I know, but are there any other carbs available that would fit? MOre modern and more relaible ones?

[matthewmosse]

If fixed they are perfectly reliable. Got 180,000 + out of my originals with no more work than the odd redex treatement if thd carbs started leaking, which was not that often, and genrally only when the fuel tap was left on when standing, only had it overflow when on the move a few times, redex in the fuel for a tankfull and running the last half mile with the fuel off always cured mine, for at least the next year. They genrally only gave issues if the bike was stood for a few weeks or more, used daily they were better, my 550k3 carbs gave better economy but more issues.

[Trigger]

New float needles and seats are worth fitting if the tiny springs are week

I am going with Bryan on this one and will fit a new carb kit. Worked before on a 550F.

[jon stead]

If fixed they are perfectly reliable. Got 180,000 + out of my originals with no more work than the odd redex treatement if thd carbs started leaking, which was not that often, and genrally only when the fuel tap was left on when standing, only had it overflow when on the move a few times, redex in the fuel for a tankfull and running the last half mile with the fuel off always cured mine, for at least the next year. They genrally only gave issues if the bike was stood for a few weeks or more, used daily they were better, my 550k3 carbs gave better economy but more issues.

Matthew, that's answered my next question then, "Would I be better off with a set of 550 carbs on it?". I guess not from your experience.
The switching fuel off before you get home I've heard of before, never put it into practice, but I can see the merit in it. Just got to persevere with these ones then :-(

[matthewmosse]

I am not at all sure about if the 550f carbs would be any better, the k3 ones are leaner jetted and rather different I think. I never had a 550f bike to know the differences. Does sound like the new needles and float seats will be a good next step. Deffinately helped on a 6 foot cut knife mower I helped my dad fix recently, though due to it's total obscureity the options open to us were brand new carb from bing direct for £400 or search ebay for anything used, which eventually paid off after over a year of searching ebay.