Cold morning, blocked carbs and whoops unscrewed idle!

[Juniper]

Hey so I had an interesting morning yesterday so thought I would post it. Maybe get some ideas.

Yesterday morning I went to go start my bike and it had totally frozen over (Left it outside as was at a mates place...she usually sleeps inside) and obviously it wouldn't start.

Used choke and wound the idle right up (or so I thought) and would start and then rev off to a stall. Figured it was cold and after some phone calls a mate thought that maybe one of the jets had frozen, so there I was heating my bike up with the hairdryer on the battery, in the engine as much as I could see without taking the tank off and down my air intake pipes (which actually lead nowhere) but I figured it would heat up the airbox and whatever else down there.

Got it going with the choke still in, and it heated up so much the fan kicked in. But it still wouldn't run without the choke and every time I even slightly twisted the throttle the revs would drop and it would either stall or when I let it off it would rev higher and then settle down to its fluctuating 3-5k. My bike idles at 1-2k depending on the weather, I ride at between 6-10 commuting and eco mode motorway (6th) and it redlines at 19. Open road is usually 11-14k.
I figured applying gas was flooding it so it would stall or when I let off it was revving higher to burn it off.

By then I had accidentally unscrewed my idle. Called George MD and he said I would need to take the carbs out to put it back in. Now bear in mind I'm at my mates house, no tools and typical girl knowing fuck-all about fixing it (or so I thought)

Made a few posts on Facebook and phone calls, everyone said carb problems. Mate came round and another guy from Facebook turned up with some tools. (Thank you biker community you ROCK!)

We took the fairings off and the tank (full tank of 98!!) the airbox and the thingy under the airbox that connects to the carbs. Started it up and watched the throttle turn open the float thingies (when looking down at the carbs in the bike the things that move up and down/open close by suction) and watched the bike drop revs and die.

• When we choked the carbs (thats what FB Friend called it) by putting hand over each one so it sucked against our palm creating pressure it worked when the throttle was turned, the bike reved up and not down. Figured we'd fixed it so put it all back together and then it stopped working and went back to first paragraph problems. Took it all apart again and when extra fuel was dumped into the carbs by either choking them or blowing down the intake pipe to push fuel up it worked. Now this is the part we don't quite know how we fixed. The seals need replacing as each of them have been cut to make them fit and some silicone was applied to a couple of them which I think caused a problem in the first place by fouling them. We decided that it was a loss because the carbs weren't sucking fuel.
• Mate figured out where the idle screw was meant to go in (without removing the carbs!!) and suddenly that fixed everything. We could take the bike off choke and now when the throttle was turned the bike reved up instead of down.

Other than coming to the conclusion that carbs are run on black magic and pixie dust. I want to know why and how they fouled and how/why we fixed it by flodding them with our hands over each one at a time.

I think that I understand that you can't run the bike with choke on when its warm..... but why? And that the idle is needed so that you can take the choke off and turn the throttle. Without the idle its got nothing from stopping it from stalling.


Ideas?

Cheers,

[f2dz]

I'm a complete rookie when it comes to mechanical things, but to my understanding the bike will die with choke on at normal running temperatures because the air/fuel mixture is off. By choking the carbs you're blocking air thereby increasing the fuel in the mixture. Incoming fuel and air have gotta be at the right ratio for the sparks to ignite the mixture.

As for diagnosing the problems I wouldn't really want to comment because carbs confuse the crap outta me too. I took apart the one on my old car once and I told myself never again.

I'm glad I no longer have any carbed vehicles for this exact reason.

[unstuck]

Maybe there was something stuck in there that got forced through when you choked them. Carbs can be so much fun.

[Juniper]

Yeah I'm thinking maybe that Sicilian crap?

But what would cause it to happen because it froze over?

[Big Dog]

Could be water. Droplets sink. Without significant pressure they don't fit through carb needles.
There are treatments you can buy. In the nineties I used to use a tablespoon of diesel or a teaspoon of white spirits, paraffin or some other thinners to about 17 litres ( or a tank).


Stupid phone / Tapatalk, apologies in advance.

[Big Dog]

Or if already caught out, shaking the bike side to side by turning the bars whilst stood astride. If that did not work get a mate to steady the back while jumping up and down in the pegs.

Others have since told me but only done once, tried draining the float. Warm your carb. Turn off the fuel tap. Drain carb via little screw. Do up screw. Check it does not leak when you open the tap. Should work.


Stupid phone / Tapatalk, apologies in advance.

[Ribit]

Juniper

Used choke and wound the idle right up (or so I thought) and would start and then rev off to a stall.

Is it possible the idle screw was unscrewed at this point? therefore all the problems stemmed from this?

[Juniper]

Is it possible the idle screw was unscrewed at this point? therefore all the problems stemmed from this?

I thought that, but Nah. the screw came out after I had pushed it to the end of the driveway. Which was after about an hr of trying.

[Ribit]

I thought that, but Nah. the screw came out after I had pushed it to the end of the driveway. Which was after about an hr of trying.

It would explain why it went wrong and everything came right after reinstalling it, but anyway....

and would start and then rev off to a stall

This would indicate a partial fuel blockage. as the fuel in the float chambers are used the mixture leans out (runs out of petrol) and the motor stops. ya crank it back over and because your not using fuel as quickly the floats can refill. 'Choking' the carbs may have cleared the blockage by the extra suction put on the carb, sucking the blockage through.

[ducatilover]

Not enough skids.

[pete376403]

water (wouldn't take much) freezing would block the passages, and even after the engine heated enough to thaw, the water would still remain blocking the passages. Bear in mind that the only thing normally pushing fuel through the jets is the difference between atmospheric pressure above the fuel in the float bowl, and the less-than-atmospheric pressure in the carb venturi - i.e. not much.

When you blocked the carb inlet, all the vacuum in the carb throat was applied to the jets and passages, which would have sucked the obstruction through.

[Juniper]

water (wouldn't take much) freezing would block the passages, and even after the engine heated enough to thaw, the water would still remain blocking the passages. Bear in mind that the only thing normally pushing fuel through the jets is the difference between atmospheric pressure above the fuel in the float bowl, and the less-than-atmospheric pressure in the carb venturi - i.e. not much.

When you blocked the carb inlet, all the vacuum in the carb throat was applied to the jets and passages, which would have sucked the obstruction through.

Yeah thats kinda what I was thinking!!

What do you think of this: http://litetek.co/Carb_Kit_Kawasaki_ZXR250.html

I've got my old carbs at home so am going to check to see the seals are in good condition. The ones in there atm have been cut to make them fit.

[ducatilover]

I doubt you'll get it cheaper anywhere else that's around $65nz?

[Juniper]

I doubt you'll get it cheaper anywhere else that's around $65nz?

Yeah about that. But I'll try my old ones first though. And for some reason first time we took it apart I cleaned out a lot of dirt from them. When we put it back together and took it apart again it was dirty again. Not as bad as the first time but still had git and stuff in there.

Is my air box not working properly? Or dirt in my tank? Or the seals letting it through?

Mate said my air filter wasent any dirtier than it should be.

[unstuck]

Fuel filter clogged or you do not have one installed.