OK so as the title says.

Symptoms :-

So I adjust the idle control when she's nice and hot so she ticks over at about 1100 rpm, she idles fine and starts fine when hot.

However, next day, when it's cold start time she wont start. But if I adjust the idle control to a faster tick-over she'll start fine when cold, but then when she's warmed up, she ticks over at about 1800 rpm.

Right now I've got her so she'll just about start after 2/3 attempts and ticks over at about 1500 rpm.

There are no vacuum leaks I can find, carbs are clean (done about 500miles ago), choke mechanism works fine, was thinking maybe the pilot screws need adjusting?

Any suggestions from the wise ones will be greatly appreciated.

 

Hey:

Pilots maybe but check your petcock filter/strainer inside your tank for build up.
I had one than was partially blocked that leaned out the bike after it was running making the rpms increase, and was hard to start without starting fluid every morning. It ran ok but always seemed down on power, cleaned it out and all was good. Good Luck

Dub

 

Thanks for the reply Dub. I'll check the filters as you suggested, though I think if anything she runs rich.

 

This is how I think the choke works. Opening the choke lever lets air pressure into all four of the vacuum chambers of the carbs. That raises the piston/needles which lets in more fuel. The richer mixture lets the bike start.

Why not just twist the grip when starting? That can raise the needles and let in more fuel. But twisting the grip also opens the throttles which lets in a bunch more air. That leans the mixture too much. Using the choke and not twisting the grip keeps the throttle closed, making a rich mixture.

Adjusting the idle speed richens the mixture. I assume it does it by raising the piston/needles manually.

If the choke doesn't work, what's wrong? Either the choke cable is sticking or broke, or the piston/needles are sticking and not rising. The air pressure difference is slight, so if the piston/needles are only a little bit dirty, one or all may not rise at all. Stickiness of the piston/needles can be checked. I have it in another thread.

 

My bike runs around 2000 RPM on the choke - still a bugger to start when she's cold- always has been. When the bike starts to warm up the idle increases to around 3000 (!) and then I dump the choke and she's good to go - Idles at 1250RPM......

I ran some injector cleaner through the bike to sort any idle problems, it's a possible solution and a lot less work than removing the carbs....again

Why not just twist the grip when starting?
If you do that you'll flood the bike and she won't start (at least with mine)

 

I hate to keep saying it but, that ethanol is not helping matters. If this is a new problem, I would say that you got a bad batch of fuel. That's what you would expect to happen with that crap. Cold starting problems. It is hot, slow burning stuff that won't light off when cold. In Brazil where they use ethanol, they have a pony tank of gas on their firewall that they switch to for cold starting. Once warmed up the ethanol works better in the warm engine and rpm picks up. You are at the mercy of that crap. I myself have to richen the mix as mine falls on her face off the line.

I am away for work for one month starting next week. After that I plan on lifting the needles and will report back. I hope to stop this stumbling she has (like a 2-stroke loading up and then running like a raped ape).

 

Don't know if they add ethanol here in the UK Tim. But the last couple of days have been warmer here and she's starting on the choke just fine now

Maybe tomorrow I'll back off the idle speed a couple hundred rpm and see if she'll still start when cold. If so I'll leave her alone, after all you can't fix it if it aint broke. But if she still plays up, I'll pull the carbs and have a play around.

 

^ You can smell it.

From what I have heard, the E-85 hear has 15% gas so people won't drink it.

 

My owners manual says to not use fuel with any ethanol at all. It does say if fuel with ethanol is used, never higher than10%

I'm lucky enough to live where 93 premium is still available and it is ethanol free.

Btw, owners manual says to use the "choke" (enrichment) to start at temperatures 10-35c (50-95f) then back the choke off to an idle of 1500-2500 rpm

Wild eh? I never use it except for cold start.