Carb Problems

[fabio]

Hi

I've recently purchased a Kymco Agility 50 (in the UK) and i'm having some problems with it, namely the rpm at idle is erratic......

To explain what I mean....sometimes it will idle sometimes it wont.....sometimes it idles at 1800 rpm, sometimes at 4000rpm, at other times less than 1000 and then it dies. The idle can move up and down as if its "hunting" but always ends up dying.

To try to sort the problem.... I've taken the carb apart, disassembled and thoroughly cleaned it, I've soaked the jets overnight and blown them out till they're clear, I've cleaned the air filter, I've adjusted the idle screw, I've adjusted the fuel/air mixture screw, I've checked for good fuel delivery, I've checked that the throttle cable isn't hanging up, I've tested that the Auto-choke works properly, and I've changed the CDI just in case.

The Agility starts first time every time (with the throttle half open) and then there is very little acceleration to it (its de-restricted both at the boss, the CDI and it has a 85 MJ, however the problem was no different with the stock 80MJ that it previously had installed)

Help!!!!!!!!!!!!!!

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[fabio]

A bit more info...I've just taken it around the block and it will hit 45-50 downhill and about 25-30 uphill, on the flat it approaches 40ish. It takes a great deal to time to get up to any of these speeds though    so perhaps I need to look at replacing the clutch springs and the contra spring once I've got the idling problem sorted.

I must admist then when it was running just around the block it ran well, so i think my carb problem is perhaps isolated to the idle circuit, as the choke circuit and the MJ circuit seem to be running well.

Another quick question...when you start your Agility from cold does anyone know what the idle speed should be (i.e. the idle rpm until the choke turns off and the engine revs drop a touch)

Thanks

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[mono]

Does the idle rpm also go up and down when you don't touch the throttle after a successful start ?
Or does the "hunting" only begin after "blipping" the throttle one or more times ?

I've had problems like these because of the carb slide sticking, took me a while to find out...

I was lucky to see that the slide was still open when I disconnected the air hose after stalling the engine one time, but it spontaneously "unstuck" as soon as I noticed, and the engine was running fine again... So I might as well have never found out that there were a few grains of sand in the air hose, making the slide stick every now and then...

[blue]

as far as your spped try changeing your rollers try 5.5 or 6 gram rollers.mine starts with out turning the throttle.but on cold days I need to let it worm up good befor I take off. what size carb do you have try a 19 or even a 20 works great. also check your manfold bolts to see if they are tight the smallest amount of air comeing from there well bong the scoot down.

[fabio]

Does the idle rpm also go up and down when you don't touch the throttle after a successful start ?
Or does the "hunting" only begin after "blipping" the throttle one or more times ?

I've had problems like these because of the carb slide sticking, took me a while to find out...

I was lucky to see that the slide was still open when I disconnected the air hose after stalling the engine one time, but it spontaneously "unstuck" as soon as I noticed, and the engine was running fine again... So I might as well have never found out that there were a few grains of sand in the air hose, making the slide stick every now and then...

Hi

It goes up and down on its own and then dies.. touching the throttle makes no difference and also after a run it makes no difference....that's why I think that its got something to do with the idle circuit of the carb, I had a close look at the slide when I took the carb apart and it looked very "free" with no drag at all....a couple of thoughts that I've just had are to check that the needle isn't bent (but I'm sure that it isn't) and to re-check that the diaphragm at the top of the carb isn't holed or compromised in any way

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[fabio]

as far as your speed try changing your rollers try 5.5 or 6 gram rollers.mine starts with out turning the throttle.

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Its got 6.5gr rollers so I think that I'll take it down to 6.0 and try it and then 5.5 and try it

Mine starts from cold without throttle, but when warm it need the throttle....

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What size carb do you have try a 19 or even a 20 works great.

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Its the standard CV carb, I have got a Dellorto 17.5 PHVA carb that i was thinking of trying but I wasn't too sure if this will work with the Kymco's set up?

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Also check your manifold bolts to see if they are tight the smallest amount of air coming from there well bong the scoot down.

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Yep they're tight and I've used WD40 around them and the rest of thew carb and associated pipes to test for air-leaks all to no avail

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[streido]

Sounds like an airleak on the carb manifold. Check the hard right angled rubber manifold that comes from the carb and bolts onto to the engine, if it has a loose clamp or bolts it'll let air in kr the same happens if they split. Revs and idle goes all over the place. It may have split at the clamp that holds it onto the carb if you overtightened it. Best to remove the manifold completely and check it properly, mine split underneath before and i couldnt work out the problem for a week or so till i found it.

[fabio]

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Just popped into the garage to double check - unbolted and removed the manifold and checked it - no crazing or cracks, the o ring looks good too and it was tightened down well.

More head-scratching!

Any thoughts anyone?

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[fabio]

...and, I've removed the top of the carb again to check the needle (that is not bent) and the diaphragm (that is not holed), I've re-seated it with a bit of grease to make sure that is sealed well too.

Still no joy though....

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[blue]

try to recap the plug to 06. to o7. and see if the plug is showing good spark. this might be a sign of your coil going bad to if so I would get a nkg coil they are more trusting........

[mono]

His Agility starts first time every time, so I guess there's nothing wrong with the ignition itself. It might need a new plug though, it's possible that it has an insulation fault that doesn't show when cold, but my money is still on a carb/air leak issue...

@fabio : did you have a look at the plug right after the engine dies ? If you clean it before starting (preferably when the engine is warmed up, so the choke is off) and check after it died, it can tell whether you have to look again for an air leak or blocked passage in the idle circuit (clean plug), or whether it's running way too rich from e.g. a damaged idle mixture screw seat (black soot on the nose and/or top of the threads)...

Also, have you checked the float level and reliability of the float valve ?

[blue]

If you have a few extra dollars I would just throw a new carb in the scoot and by pass the other issues.

[fabio]

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Aaaaargh!!!

Just took the carb to bits and cleaned it all out again - the sodding thing wont start at all now !!!!

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[blue]

New carb. but calm down you well be ok new is better,try a 20 mm carb you well love it. the take off is great.

[fabio]

New carb. but calm down you well be ok new is better,try a 20 mm carb you well love it. the take off is great.

Took it apart and got it going again, the idle jet was loose - but still the same idle problem - its got me thinking...I wonder whether the idle jet is tatered - it was blocked when I first took it apart and I've cleaned it that many times I'm wondering if I've enlarged the bore and its now too rich and that's why its stalling??

Thoughts?

(Also - do you have a link for a 20mm carb that would do the job?....or ideas for sourcing one? - thanks !!)

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