Modern Buddy

Hi all,
I have a 2013 that I just finished installing the Malossi 70cc kit on. It rides pretty smooth and I'm happy with the extra power I'm getting especially between 20-30 mph, the one problem is that it dies when idle. I tried adjusting the idle screw (with the black knob) but that didn't help. I thought about the adjusting the fuel mixture but I don't think I know where the screw is. I found a screw that's flush with carb body towards the bottom, but it's not turning easily which make me think it's not the right screw.
Is this a fuel mixture issue? If so, can someone tell me how that's adjusted? a picture of the screw would be great. IF that's not the issue, can you tell me what might be the problem?

Thank you,
Akeel.

When you put a bigger cylinder on you need to increase the amount of fuel as well, you do this by increasing the size of your Main Jet. The general rule of thumb is to increase by 10% but your scoot may need more. Not doing this will cause the scooter to run lean and probably soft seize on you. You'll only know by playing with it. You will also need to adjust the Fuel/Air mixture screw as well and possibly up jet the pilot jet and adjust the needle on the throttle to allow more fuel. A picture of your carb will help with the location of the A/F screw, the factory carb has them plugged and you should replace the screw with one that isn't. Theres more to installing a BBK then just a new piston and cylinder.

This will give you a clue, at the bottom he talks about carbs. http://49ccscoot.proboards.com/thread/5 ... it-1e40qmb

Thank you for the link Pinkscooter, I'll take a look and see what adjustments I will need to make.

Here is a pic of the screw and a cut and paste of some instructions that may help

PostPosted: Wed Mar 16, 2016 1:56 pm Post subject: Reply with quote Edit/Delete this post Delete this post Report post
It sounds to me like the idle mixture is not adjusted correctly. On my roughhouse I had to remove a welch plug to uncover the screw so I could adjust it. At least thats what I think I remember. First find the screw, you may need to remove the seat bucket. Don't bother bolting it down between adjustments. I hardly ever bolt them in actually. Next locate the mixture screw I'm pointing at with the pencil. The picture is taken standing on the kick stand side. If there is a welch plug( brass plug cover) you'll have to remove it using: try a dental pic and spin it. I was able to work mine out by rocking back and forth. If that doesn't work try a dremel or small drill bit. Drill a whole and using a hook pic or something like it pull it out. Discard it because you don't need it. Now turn the newly exposed screw clockwise until it seats, gentle pressure only. Count the number of turns in and write down the factory setting. Return the screw to factory setting. Now start the bike and warm it up and or ride it around. You cannot adjust the mixture until the bike is at full operating temperature. We want to adjust the mixture screw till you have the fastest idle speed possible. There will be a spot in the middle of the adjustment where its near optimal, you will notice a slight movement in either direction that doesn't have any effect. The rule of thumb is you locate the middle of this "zone" and then set the screw and additional 1/8 to 1/4 richer.

Okay I assume your bike is set lean because mine was as well. Start by turning the screw 1/4 turn counterclockwise at time (this richens the mixture). The idle should increase in speed. Find the maximum idle speed add an additional 1/8 turn richer and go for a test ride.

This is good video on the theory of adjustment allthough he's adjusting an air screw in this video and not a fuel screw which means the settings are inverted. But the process of listening for response is the same.
https://www.youtube.com/watch?v=A1vRMERs4RQ

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161cc big bore kit, NCY big valve head Hand ported, NCY transmission kit, jetted and tuned. I can port your cylinder head.

On my stock Carb the mixture screw had no head so I had to cut a slot in it to get it out. I eventually replaced it with this http://www.epfguzzi.com/scooterpunks/parts/buddy.html Look almost at the bottom..