Motorcycle sounds/acts strange

JTerra · L Plate Warrior Joined: 03 Nov 2015 Karma :

Hi,

First let me apologise for creating a thread that might have already been created by someone else, I'm a motorcycle beginner but my mechanic is forcing me to learn about mechanics as I no longer trust him with my bike.

I bought a Leonart Daytona 125, yes It's Chinese (the parts), some might consider it junk but its my junk. First month after I bought the bike i had take it to the mechanic every weekend, because at first the bike was good and after the first revision the sound changed and I notice, mechanic says its my mind and because I'm a beginner, I'm panicking.

The first problem,
In the morning when I start the engine I always open the air until she warms up, but for a warm up she revs too high or at least that's the feeling I have and I unscrew idle speed screw until i sense its a good rev, this is ok until i close the air and the bike won't turn on until i screw the idle speed screw again.

The second problem,
After the warm up whenever i do a 1/4 turn on the throttle, looks like the bike gags for a couple seconds and then starts to rev up. I've adjust the mixture screws but the sound is best at 3 1/4 turns (which according to the internet it means there's something wrong with it because the factory default is about 2 - 2 1/2 turns on the screw).

I still need to check the spark plug, but I'd appreciate some insight from more experienced people as I'm learning as I go.

P. · Red Rocket Joined: 14 Feb 2008 Karma :

In the morning it's supposed to rev a little higher on the choke. Just put it on, put gloves on and ride gently. Then knock choke off after a mile. It should idle around 1200-1300rpm warm

Nobby the Bastard · Harley Gaydar Joined: 16 Aug 2013 Karma :

It's sounds like it's revving up when the choke is used (like it's supposed to) and so you mess with the tickover speed screw or maybe the air mixture screw(which you aren't supposed to do.)

And then you wonder why it bogs down afterwards....
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JTerra · L Plate Warrior Joined: 03 Nov 2015 Karma :

Nobby the Bastard · Harley Gaydar Joined: 16 Aug 2013 Karma :

B0ndy · Spanner Monkey Joined: 25 May 2015 Karma :

What RPM do you get when you use the choke?

Stating the obvious, the choke is progressive so if the RPMs are too high, you just lay off the choke abit until the RPM drops down to say 4k RPM to let the bike warm up.

Don't start fiddling around with the idle screw as this will change the idle speed that was previously set once warm, if you start adjusting it when it's cold, the idle won't be correct when warm and you will then have to readjust. My advice in regards to this is just set it once the bike is warm and don't touch it again.

Moving onto your second problem, it sounds like the bike is running rich if you have some throttle delay. Would I be correct in assuming there's only a delay once it warms up; the bike runs better cold than when warm? If so, the bike is most likely running rich.

Aside from the million different "symptoms" which a bike displays when running rich, I always find the best way to determine the mixture is correct is by checking the colour of the spark plugs. Note that you will need to check the colour of the spark plugs after a ride (doesn't have to be straight after the ride of course), this is because the plugs need to get up to "self cleaning", the temperature when the carbon fouling is cleaned from the plug's insulator and you can get a true representation of the mixture from the carbs. From memory a NGK spark plug's self cleaning temperature is 450 degrees, don't worry too much about the temperature, just make sure you take the bike out for a long ride before checking the colour of the plugs.

Here's a chart to compare your plugs to: https://kereta.info/wp-content/uploads/2009/07/spark-plug-colour.jpg

Right, so you've verified whether whether the engine is getting the correct air/fuel mixture, next step is adjusting the mixture screw as recommended in your service manual (2 1/2 turns out as you say). I've found this to be a good video to watch if you haven't got much experience on making adjustments to a mixture screw, it explains what to listen out for etc: https://www.youtube.com/watch?v=YxpQjDQzX7g

I hope that helps

JTerra · L Plate Warrior Joined: 03 Nov 2015 Karma :

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

Had to look it up and Leonart are a bunch of Spanish hombres
Knocking out a range of small cruisers from their Barcelona worshops
The engine's a 125 single cylinder, water cooled, carbed device sourced from Piaggio.
Not Chinese OK? habla espanol?
here's a pic of one:
(this info would have been better coming from the OP not me)

https://www.leonartmotors.com/assets/img/daytona1.jpg

Advice:
As its a simple machine a so called 'mechanic' cant sort out
and who's possibly buggered up, take it elsewhere.
Dont just twiddle and hope, it's not good technique.

If you're determined to do it yourself using forum advice
the better the info you give with added pics and vids too,
the better the quality of advice you'll get in return.
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P. · Red Rocket Joined: 14 Feb 2008 Karma :

Where abouts are you based? If you are local it's probably a minute or two to get it how it should be.

arry · Super Spammer Joined: 03 Jan 2009 Karma :

Rogerborg · nimbA Joined: 26 Oct 2010 Karma :

chris-red · Have you considered a TDM? Joined: 21 Sep 2005 Karma :

Set both the idle and mixture when the bike is warmed up and at idle then DO NOT touch them. You are not meant to play with them every time you start the bike. You do know the choke is not an on/off switch right? You can set it in the middle.

Stop being precious sweetheart you are supposed to be a roughty toughty biker Laughing

No one was being mean, it all been good advice.

It sounds like you are inventing problems that do not exist to me, stop messing with bits. Eventually you will get to know you bike and know it need x amount of choke for x amount of time before you can ride off on it.
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JTerra · L Plate Warrior Joined: 03 Nov 2015 Karma :

Here's the sound: https://soundcloud.com/terramoto-1/voz0002

Don't know if you can notice at the end when i rev the bike drops then gets goes up again.

WD Forte, motorcycle is chinese, the brand is Spanish if you check AJS Daytona its the same.

Paddy, you wouldn't be by chance in Portugal, Algarve? :p

RogerBorg, i was thinking about warming up the bike, check the spark plug, disable one of the sparks at a time and adjust the mix screw of each carb.

Ariel Badger · Super Spammer Joined: 02 Dec 2006 Karma :

Have you tried starting the bike with no choke?
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JTerra · L Plate Warrior Joined: 03 Nov 2015 Karma :

B0ndy · Spanner Monkey Joined: 25 May 2015 Karma :

Ariel Badger · Super Spammer Joined: 02 Dec 2006 Karma :

Why on earth do you think an iridium plug is going to sort out the fact that your mechanic/you have ballsed up the carb settings? Save your money your bike does not need an iridium plug and take it to someone who knows what they are doing..
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chris-red · Have you considered a TDM? Joined: 21 Sep 2005 Karma :

JTerra · L Plate Warrior Joined: 03 Nov 2015 Karma :

Yes! I finally got it to work properly, its working between 2 and 2 1/2 turns now and the sound is linear slow. Apparantly it looks like the idle was too low and the mix was too high, i had to adjust one carb at a time.

According to the spark plug chart one plug seems to be normal:
https://s9.postimg.org/dtuwpbx7z/IMAG0151.jpg

The other plug is slightly burned on the ceramic, which i cant find in the chart. But IMHO i would say its because this one was on heavy duty while the other one was working on low performance?:

https://s29.postimg.org/em71d1odz/IMAG0152.jpg

Both carbs seem to have different mix settings but only by a 1/4 of turn.