Hi guys, questions are coming thick and fast, it never rains but it pours eh?

Starting the bike from cold on full choke she fires up no problem, allow her to warm up a little, choke off and she still idles at around 1200rpm, so far so good.

However, when she has warmed up to full operating temp, the idle increases to 1800-1900rpm, so I then used the idle adjuster to reduce the idle to 1100rpm. All was then good and the bike rode normally.

The problem comes the next day when it's a cold start on full choke. She wont start unless I once again use the idle control to increase idle speed (before starting). Then I have to go through the whole process again.

Also when hot, the idle will slowly decrease until she stalls, I can blip the throttle before she dies and she'll idle again happily for a minute or two and then she'll slow down again and stall.

Are these symptoms related and any idea what is causing them?

Thanks again for your patience and help.

 

I think you have to look at how the choke works. Old carbs on cars had a butterfly valve that "choked" off the air making the mixture rich. Our constant velocity carbs don't work that way. The choke moves a valve in each carb that allows air pressure to raise the piston/needle out of the main jet. That makes it richer by adding more fuel.

The car choke blocked the air at every engine speed, not just idle. That's why you see some old cars with heavy black smoke. But on our bikes, raising the piston/needle at idle should only affect the engine at idle. At other speeds, the piston/needle should rise up normally, according to how much throttle is applied.

I think the piston and/or the piston bore is dirty and the piston/needle is hanging up on one or more of your carbs.

 

Looks like I might be stripping the carbs again

 

Maybe we need a UK 1000F Tech Day?

 

Don't you just love it when someone knows what they're talking about.
Thanks Slowpoke. I've never got my head around the workings of the choke on these carbs simply because I've never had to.
I'm sure your rides have done more than blow the cobwebs out Steve but perhaps there's still a few earwigs left in there from the winter hibernation.
Have you ever replaced the rubber boots between the head and carbs? Just a thought. You may have air getting in through them when cold which causes you to have to raise the tick over manually then the engine heats up and....blah blah......
I got a set from Wemoto when I did the head on the old bike and they were such a delight, despite the dosh factor. I strongly recommend changing yours if you haven't already done so. You'll be taking off what feels like lumps of granite and replacing them with the equivalent of silk underwear. A very good insurance policy to ensure your carbs are serving up the correct mixture. Old rubber sucks!

Ragimund. If a UK tech day means hanging onto a solid pewter bar and putting Honda to rights then yes, we need one, rapidly. Mines a long island DOHC!

 

(Pilot needles need attention) imo, having done this more times than I ever wanted to

Steve pull the pilot needles and clean them good - a little steel wool (brillo pad)
then put them back all the way to a very gentle stop then back then out a full
2 & 1/2 turns

Get the bike running to full hot then set your idle if she's still a little choppy sync
'em and adjust the idle again

 

Thanks for the advice guys. I'm away right now so it'll have to wait until I get home.

But I'm getting pretty good at whipping the carbs off and stripping em down. I may have to start doing 'em blindfolded and in the dark

Am I correct in thinking that carb cleaner should be kept well clear of the rubber diaphragms? Wouldn't want to dissolve them

 

Very correct in thinking that

 

A lot easier said than done though. How do you really guarantee that you're not dousing rubber & silicone when you unleash a can of that stuff on your carbs?
I absolutely crap myself using that pungent solvent and avoid it as often as possible. (Note to self " reason to be more lazy...... is that possible?")
I guess, not deliberately trying to destroy your diaphragms and O rings is the best you can hope for.
Just thought I'd add a little realism to the mix Hawk. What's your take?
Would you disassemble the carbs completely before feeling completely confident that you hadn't damaged any rubber with the evil solvent or would you compromise, offering up a vague whim and prayer, hoping to negate the effect of blasting powerful chemicals through tiny holes in a complex casting straight back into your own eyes?
Tough call isn't it.
I know you'll already have the answer in your mighty soul......

 

Managed to spend some time on the bike yesterday, stripped her down in record time, the Mrs hardly even knew I was out in the garage

Had just enough carb cleaner to clean the plastic part of the needle diaphragm. To answer HenryM I did spray, but pointing down with the spray nozzle below the delicate rubber. The plastic slider bits drop into the carb body with no resistance and with a satisfying 'thunk'.

Despite my best efforts, I could not find any traces of the 'Cow Snot', Henry so vividly described My breather pipes are as clean as the proverbial whistle.

As Mark recommended I cleaned up the pilot jets with some fine steel wool and re-installed as per the manual. However I did notice the little 'o' rings are missing! This may explain my dodgy idle perhaps?

However, I reassembled the bike, patience was never a strong point of mine, started her up, balanced the carbs, adjusted the idle and all was much improved.

I was quite proud of myself, from start to finish, total work time was only about two hours, including reinstalling plastics and a bit of tinkering with the exhaust shrouds as well.

She now idles much better and today she started from cold with the idle adjusted to about 1100rpm (this was set last night when she was warm), once warm she seemed to be quite happy.

Does anyone know what size the pilot screw 'o' rings are? Don't really want to buy the full kit as everything else is there and I don't like to pay a fortune for four tiny bits of rubber!

Thanks again for all the advice and support

P.S. Test ride today, she ran like a dream. Started on the button and never missed a beat the whole time, got back and she idled rock steady while I opened up the garage to put her away. I'm in love again