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Engine dying at idle (in wet?)

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louis_sutton
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Solved Engine dying at idle (in wet?)

Post by louis_sutton on Fri 13 Feb 2015, 8:01 pm

Aaaargggh!  Help!  Bought my 2000 CB500S a couple of weeks back (about 21k on the clock).  Seems in fairly good nick, so all good.

I've put about 500 miles on it, and all has been well thus far.  It needs a carb balance, and the idle is a little high (sitting about 1800 revs), but nothing too major, and I'm in the process of dropping the oil/changing the air filter, lubing the cables and stuff this weekend.

I've just ridden home in an utter deluge, and for the last part (admittedly, it was very wet), the bike wouldn't hold revs at idle.  As I came to a stop, the revs would drop and the engine would die and stall.  Fine if I kept the throttle partly open, and fine to ride, but at stop, with the throttle released, it wouldn't maintain revs.

Just trying to figure out the most likely culprit - the fact it ran ok with the throttle even partly open confuses me.

Any chance someone has any ideas?
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Flyingbrick
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Solved Re: Engine dying at idle (in wet?)

Post by Flyingbrick on Fri 13 Feb 2015, 8:39 pm

Hi,

most likely one or two idle jets are plugged. While opening the throttle, the main jet is active so the bike runs well. In many cases, the previous owner adjusted the mixture "rich" to compensate for the dirt, leading to an high idle when the engine warms up.

So, i would recommend an ultrasonic cleaning for the carbs.
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skyrider
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Solved Re: Engine dying at idle (in wet?)

Post by skyrider on Fri 13 Feb 2015, 9:04 pm

you might want to check the air filter as well it could be soaking wet through
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louis_sutton
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Solved Re: Engine dying at idle (in wet?)

Post by louis_sutton on Fri 13 Feb 2015, 9:06 pm

Many thanks Michael - guess I was a little confused because the idle has been solid once warm, no variation, so I assumed (guessed) that the idle had been lifted to help starting as the carbs needed balancing.

If it's the idle jet blocked, then it literally came on in the space of ten minutes ride tonight out of nowhere.  Might pull the carbs this weekend for a quick check and a blast with carb cleaner to check the jets.

I'll definitely have a look at the air filter (was going to replace it this weekend anyway) to see if it's drenched.

Really appreciate the help.

Louis
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Flyingbrick
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Solved Re: Engine dying at idle (in wet?)

Post by Flyingbrick on Fri 13 Feb 2015, 9:14 pm

Hi Louis,

did you checked the fuel tank for rust? I remember some cases where the carbs have been cleaned (so everything seems to be okay) but the tank was rusty. If this happens, it won't take long until the problem occurs again. This could happen very suddenly, indeed.

I don't think that someone would increase the idle to 1800 rpm which is quite fast. But sometimes the owner thinks that a simple turn of a screwdriver would be a good replacement for a proper repair Wink
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louis_sutton
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Solved Re: Engine dying at idle (in wet?)

Post by louis_sutton on Fri 13 Feb 2015, 9:18 pm

That was one of the main things I checked when I bought it fortunately - and the tank is lovely and clean inside.  That doesn't of course mean there isn't a bit of rubbish blocking the pilot jet.  And I know what you mean about previous owners - I had a bandit that had been bodged in every single way.  Fortunately this CB is less tinkered with - I'd been holding off playing with the carbs until I'd done some basic service work, at which point I was going to balance them and sort the idle (I'd been hoping I didn't need to play with the idle mix screws).  Now it looks as if that's going to have to move up the to do list quickly!

I think I'll do the oil and filter, then when it's all dry I'll see if it starts/runs as previously.  If not, then off the carbs come...
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louis_sutton
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Solved Re: Engine dying at idle (in wet?)

Post by louis_sutton on Fri 13 Feb 2015, 9:48 pm

And the air filter is lovely and dry.  Bit nasty, but nothing out of the ordinary.  Dammit.

Fresh oil in tomorrow and I'll see if it runs once it's dried out (after cadging a quick weld of the indicator bracket off the place doing the MoT on my other bike tomorrow).  Once I've won the battle with the oil filter, obviously.  

I can see myself having to pull the carbs tomorrow afternoon.  The long haired general will love me demanding an afternoon working on the bike...
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Beresford
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Solved Re: Engine dying at idle (in wet?)

Post by Beresford on Fri 13 Feb 2015, 9:58 pm

Check for leakage in the manifold rubbers and the vacuum line to the fuel tap.
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louis_sutton
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Solved Re: Engine dying at idle (in wet?)

Post by louis_sutton on Fri 13 Feb 2015, 10:00 pm

Hmmm, good call.  I'll have a close look at that.  Could that potentially explain the higher idle in the dry and non running when wet?
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Celt500
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Solved Re: Engine dying at idle (in wet?)

Post by Celt500 on Fri 13 Feb 2015, 10:01 pm

Pulling the carbs on mine was a right PITA.
Before doing that I would try WD40 in the spark plug leads and make sure they're seated down fully, and take the air filter out and spray some carb cleaner in the airbox with the engine running. 
(At least that's roughly what it says to do on the can of carb cleaner stuff I have.)
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louis_sutton
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Solved Re: Engine dying at idle (in wet?)

Post by louis_sutton on Fri 13 Feb 2015, 10:03 pm

Got to admit I've not pulled the carbs on this yet - but on my nasty old bandit it got to be such a regular occurrence that I could get the tank, airbox and carbs off in under ten minutes.  Familiarity breeding contempt I think...

If I can get it running at idle, I'm tempted to give that a try, and then if it runs in the dry, stick some redex through it.  Beresford might have a really good point on the leakage though. 

All good ideas, and all appreciated! Very Happy
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eternally_troubled
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Solved Re: Engine dying at idle (in wet?)

Post by eternally_troubled on Sun 15 Feb 2015, 12:19 pm

@louis_sutton wrote:

All good ideas, and all appreciated! :D

What you were planning sounded pretty good to me.

If the jets are blocked with old petrol 'varnish' (gunk) then the redex might help; if they are blocked with
'actual' dirt then it won't help!
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skyrider
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Solved Re: Engine dying at idle (in wet?)

Post by skyrider on Sun 15 Feb 2015, 4:45 pm

or failing that take the carbs off and put them in a tub of coka-cola  and leave them for day I have seen my mate do that (bike mechanic)before you put them back soak them in new petrol to get rid of the coke
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Solved Re: Engine dying at idle (in wet?)

Post by Flyingbrick on Sun 15 Feb 2015, 5:13 pm

You surely mean "joke" instead of "coke"? Laughing 
Why should i put a carburettor (of course, a complete one) in a tub with liquid sugar???

Thats what a proper cleaning looks like Wink

These 100 parts are disassembled and cleaned by ultrasonic. The diameter of an idle jet, for example, ist 0.38 millimeters. You won't be able to clean it with such a voodoo trick -less than ever if it is inside of a closed float chamber...

If the carbs are only dirty, you may clean the jets with brake cleaner and compressed air, but in many cases even that is not sufficant.
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skyrider
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Solved Re: Engine dying at idle (in wet?)

Post by skyrider on Mon 16 Feb 2015, 2:03 am

well that's what my mate does and it seems to work gets all the crud out of the carbs never tried it my self but he does it all the time
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Solved Re: Engine dying at idle (in wet?)

Post by skyrider on Mon 16 Feb 2015, 2:13 am

but  again if you have money coins and you put them in a tub of coke watch how clean  they come up Smile
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Solved Re: Engine dying at idle (in wet?)

Post by Flyingbrick on Mon 16 Feb 2015, 8:25 am

...and for a lean mixture, try Diet Pepsi Smile

I don't want to be inpolite, but i guess he must be kidding. I am cleaning my carburettors since a couple of years in a professional manner as shown above. This is one of the most complicated maintenance jobs and there are many things that can go wrong -this is why an ultrasonic cleaner doesn't make sense if you don't know what you're doing. For example, every part that was cleaned has to be conserved with oil in order to avoid oxydation. In addition, the ultrasonic cleaner and the fluids are quite expensive and a proper cleaning procedure takes about three hours -warm up the bath, disassembling, pre-washing, cleaning, flushing with water, drying, a soaking bath with conservation oil, drying, assembling and so on. I would be VERY happy if a simple dipping in a 50 Pence-Coke would have the same effect.

So don't be cross with me, but this tip isn't serious and might even harm the parts caused by the sugar.


Last edited by Flyingbrick on Mon 16 Feb 2015, 1:47 pm; edited 1 time in total

sullivj
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Solved Re: Engine dying at idle (in wet?)

Post by sullivj on Mon 16 Feb 2015, 8:30 am


That's impressive...

I would be VERY reluctant to soak my carbs in coke too!
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louis_sutton
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Solved Re: Engine dying at idle (in wet?)

Post by louis_sutton on Mon 16 Feb 2015, 9:41 pm

Ha.  I've been enjoying this threat.

It's water.  Same thing happened on the way home tonight, so I'm off to deploy WD-40.
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Solved Re: Engine dying at idle (in wet?)

Post by Flyingbrick on Mon 16 Feb 2015, 10:07 pm

Okay -if you're sure about that, one of the possible items to check is the side stand switch -at least if the problem occurs only when a gear is engaged.



It cuts the ignition if a gear is engaged and the side stand is swinged out. I once had that problem as well on a rainy day.

So, check this: detach the left hand frame cover. The regulator/rectifier is fixed with two screws. The right one has a ground wire. This is the ground connection for the ignition. Is the connection (and the part of the frame where the regulator is mounted to) tight and free of rust and dirt? Fine. On the left hand side, there is a green multiple connector.



from left to right:
green: ground (to the side stand switch)
green-white: to ignition
yellow/brown: to the side stand control light


All wires are (-). The switch connects ground either to the ignition box or to the control light.

Take a paper clip and shorten the two outer green wires. Don't worry -as mentioned, they are both ground connections, so it isn't necessary to isolate them. Just be aware that now the side stand switch is shortened, so don't ride until you're sure that the side stand is in an upright position!

Now you're ready to check if the problem still occurs. If not, the switch may be the problem.Should the problem still occur, take a short wire and shorten the green/white wire to the regulator/rectifier screw. This could be necessary if the ground wire from the wire harness is faulty.

If this doesn't solve the issue, we'll try other possibilities.

On any other bike i would suggest to check the spark plug connectors, but those on our bikes are so durable that i hadn't any problem with them during the years.
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louis_sutton
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Solved Re: Engine dying at idle (in wet?)

Post by louis_sutton on Mon 16 Feb 2015, 10:28 pm

That's a great call - really appreciate that.  What I can't figure out is why it's just at idle, when I'm at a halt after a burn home (my daily commute is 28 miles each way, takes about 90 minutes).

To be honest, that kind of instructable is the sort of thing I'll do as soon as I find out about it, as it sounds like a useful thing to have checked.

Muchas gracias - I think I'll hold off doing it right now though, it's raining, it's dark and my two year old has left the house a pit...
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Solved Re: Engine dying at idle (in wet?)

Post by stormbringer on Tue 17 Feb 2015, 7:05 am

@skyrider wrote:but  again if you have money coins and you put them in a tub of coke watch how clean  they come up Smile

I'm really tempted to join ranks with flyingbrick and sullivj on this one. But, on the other hand; coke is corrisive/caustic - children's teeth as well as eg coins undergo changes when exposed to it.

So, bathing your carburettor innards in coke (just for the sake of it I'd go for 'the real thing', not that light-stuff) might actually cause - well, something. Similar to applying descaler to your bathroom tiles.

Doing it properly, like flyingbrick suggests (the german way) seems logical. You get visual confirmation and no corrosive agents are involved. But! It takes time. Furthermore, prodding and poking these delicate components is a risk-factor in itself. Yes, adding even more time and going all scientific about it may alleviate some of the risk, but still; not poking anything would pose no risk.
De-gunking your carbs the chemical way has its advantages. My personal favourite is Redex; it gets properly flushed through internal waterways and requires no disassembly. Downside is that it requires proactive usage; You can't flush a clogged pipe, now can you?
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eternally_troubled
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Solved Re: Engine dying at idle (in wet?)

Post by eternally_troubled on Tue 17 Feb 2015, 1:08 pm

Coke has phosphoric acid in it *and* carbonic acid (from the carbon-dioxide dissolved in the water), both of which will help a bit in cleaning things.

The sugar shouldn't actually be a problem if you wash it out again afterwards, but personally I couldn't be bothered with that much cleaning, so if I was doing this I would use diet-coke (which still has the phosphoric and carbonic acids in it but not the sugar).

Mind you, if you were using any water-based cleaning product on your carbs, you would want to use some compressed air to blow the water out of the passageways afterwards - if you haven't got a compressor then one of those 'air duster' aerosol cans would be OK.

Coke also has the advantage of being fairly 'clean' i.e. the water in it has been softened and shouldn't leave the water marks and calcium deposits that tap water would it should also be relatively free of other foreign bodies/dust/crud etc.

To be honest, given that your carb will mainly be blocked by dried petrol scum/varnish then I would prefer to soak it in some kind of solvent-type cleaner which might stand a chance of dissolving the stuff.

Having said all of this as flyingbrick says, there is no real substitute for ultrasonic cleaning - it cleans even the parts you cannot see, it is fairly quick and does not harm the carb.

Ultrasonic cleaners are also not as expensive as they used to be.

So, I'm not saying you shouldn't use coke to clean your carb, but your results may vary Smile

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Solved Re: Engine dying at idle (in wet?)

Post by Guest on Tue 17 Feb 2015, 3:09 pm

Just a quick question while you're at it. Would 'Wynn's Carburettor Cleaner' (additive to fuel - comes in a can with pull-tab to open) be OK to use on bikes and cars alike?
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Flyingbrick
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Solved Re: Engine dying at idle (in wet?)

Post by Flyingbrick on Tue 17 Feb 2015, 3:54 pm

Yes, Coke contains phosphoric acid -in a small amount.
Not enough to take any remarkable effort for technical purposes, but it does.
But even if coke would be useful: it is no magic potion to soak a complete carb; magic enough to save yourself the complete disassembling. A carburettor is made of a hundred parts -brass, aluminium, rubber, plastic and steel. All those parts have to be cleaned in a different manner, and, worst of all, you have to remove them and clean them separately from the body.

But if you do so, because you're a mechanic and not just someone owning a coke bottle: why should you use your drink instead of proper cleaning substances? For instance, citric acid is available for less money, it is supposed to clean brass parts and may be, mixed with water, disposed in the kitchen sink. This is why citric acid, in addition to tensides, is a content of carburettor cleaning substances such as Tickopur. Just be sure that you do not exceed the recommended exposure time. For example, zinc plated steel gets black after a couple of minutes, but brass will be furbished.

So, again, why should someone recommend coke instead?
The reason may be that coke is meaningless. It does not clean, it does not destroy, it is just a miracle fluid that could do, according to some urban legends, fantastic things. So, if you are very unsure about the cleaning procedure and how to dismantle this complicate piece of craftsmanship, take coke. Voice something under your breath, pivot the carbs around at midnight and swear that the master has told you so. Thereafter, take unleaded fuel to wash away the coke, hoping that it will wash away the dirt as well, and try to restart the engine.

But if, for some reason, you don't believe in miracles and don't want to waste your time with such an annoying ultrasonic cleaning procedure, there is another way of proper cleaning. Use brake cleaner. Although you have to take apart the floater chamber, you could spray the cleaner in every available hole without harming anything. The can pressure and the chemistry will do their job as long as the dirt is not to old.

Very Happy


@Werner: you may use such a cleaner, but it is more preventive. A light pollution will be eliminated as well.


Last edited by Flyingbrick on Tue 17 Feb 2015, 3:59 pm; edited 1 time in total

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