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General => General Discussion => Topic started by: Randu on April 07, 2023, 10:58:55 AM

Title: Kymco Downtown 350 revs while idle
Post by: Randu on April 07, 2023, 10:58:55 AM

Hello, I own a 2019 Dowtown 350 with 4000km on the odo but lately while engine is on idle it keeps reving up to 3000rpm on its own.. A friend of mine with same scooter has the same problem. Is this a fault from factory? Maybe someone had this problem and solved it. Thank you in advance. Location Malta.

Title: Re: Kymco Downtown 350 revs while idle
Post by: Neil955i on April 12, 2023, 03:01:59 PM

Hi Randu and welcome to the forum.  Haven't heard anyone else with a DT350 mention this, but I'm sure someone else will be along soon to put me straight.

By the way, as an ex-Siggiewi resident, I'm jealous of all the sunny weather that you get to ride in there - though in July & August from memory, it would be too hot!

Title: Re: Kymco Downtown 350 revs while idle
Post by: CROSSBOLT on April 12, 2023, 06:50:09 PM

I vote for fuel tank vent valve stuck shut. Next time it happens, open the gas cap with engine running to see what happens. Either restart quickly or take a spare key. You may hear a quiet "whoosh" when you open but it will definitely smooth/slow the idle if that is the problem.

Title: Re: Kymco Downtown 350 revs while idle
Post by: mousejunks on April 13, 2023, 02:24:01 AM

I've never encountered this problem at such low km, although it does happen sometimes with bad fuel.

It could also be the idle control valve. You can reset the idle control by following steps:

How to Do a Idle Speed Controller reset.

Put the bike on centre stand
Twist back the throttle
Turn the ignition on
Wait 8 seconds
Release the throttle
Turn the ignition off then on.

Also, the air box has a clear tube hanging off the bottom to drain oil mist from the crankcase vent tube. This clear tube can break off where it joins the air box, allowing air to leak behind the air filter and contaminate the ISC and MAF sensor.

Title: Re: Kymco Downtown 350 revs while idle
Post by: Iahawk on April 13, 2023, 02:47:32 AM

Quote from: mousejunks on April 13, 2023, 02:24:01 AM

I've never encountered this problem at such low km, although it does happen sometimes with bad fuel.

It could also be the idle control valve. You can reset the idle control by following steps:

How to Do a Idle Speed Controller reset.

Put the bike on centre stand
Twist back the throttle
Turn the ignition on
Wait 8 seconds
Release the throttle
Turn the ignition off then on.

Also, the air box has a clear tube hanging off the bottom to drain oil mist from the crankcase vent tube. This clear tube can break off where it joins the air box, allowing air to leak behind the air filter and contaminate the ISC and MAF sensor.

wow, very good stuff!!

Title: Re: Kymco Downtown 350 revs while idle
Post by: Neil955i on April 13, 2023, 09:54:47 AM

Quote from: Iahawk on April 13, 2023, 02:47:32 AM

wow, very good stuff!!

+1

Title: Re: Kymco Downtown 350 revs while idle
Post by: scootadventurer on December 19, 2023, 02:46:59 PM

Not sure if you've sold this. My DT X360 350cc version had the same problem. It would hang around 2500 rpm when letting off the throttle before settling down to idle. The solution was a throttle body cleaning. For some reason it was dirty at unit activation. Never really found out why it was dirty since it was brand new, it had what looked like burnt oil or soot that easily cleaned out with throttle body cleaner.