Help, Zuma 2008 unstable

[Ronin]

Hello, I need help with my scooter that I just upgraded. It is a Zuma 2008, and I upgraded it to have 70cc and Yasuni R exhaust, but still has a "stock carb" (it's a Chinese knock-off carb). The electric start doesn't work... But the electric starter does, I tested it myself, it will spin perfectly fine until I install it and it just stops. I noticed that the electric clutch is super rusty (the pins didn't even fall out, so I'm getting a new one), could that be the problem? Now, here is the big thing. It kick starts, but only when warm (might have to do with the cold weather outside, I don't know) to kick start it cold I have to remove the air filter and block the air intake, why is that? And when it does start, the revs go really high and start to go down and then boggs to a silence. HELP! What do I do? I have an 86 main jet set in there, and I don't know how to tune the air-fuel mixture. 

Please feel free to ask any more info on the scooter itself, I'm sorry if I didn't give a lot of technical info, I am a newb with all of this if you haven't noticed by now.   This is my first vehicle I have ever owned, so yeah... not very technical yet.

Thanks in advance for the help!

[benji]

First thing I would do is get a good carb. Those Chinese carbs are full of problems. A stock carb w a 86 jet should work ok, I'd start at a 88 or 90 mj tho. I would also get a new air filter for fun, and I'm guessing it will run pretty good at that point.

[aeroxbud]

Welcome to the forum.
Brent has a good help section for tuning carbs here www.49ccscoot.com/faq/carbtune.html

[pinkscoot]

Having to cover the intake to get it to start is the sign of a lean condition. I agree with Benji, you spent a lot of money on the BBK and exhaust spend a little more and get a good 19mm carb. You probably need look for leaks before you tune you new carb.

[jackrides]

Really sounds like a vacuum leak (airleak).

[spaz12]

Sounds like a lean condition to me as well. Remember, bogging is lean and sputtering is rich.

You didn't say what clone carb you have. If it's a clone of the phbg then you can make them work good by replacing a few of the parts. Not sure which parts but I'm sure someone will chime in if you confirm the carb.

[Ronin]

Thank you so much for all the replies! I wasn't expecting so many!

I'll get a new carb when I can, but thank you so much for the carb tuning faq. What kind of carb would you guys recommend getting?

I can give you the link to where I got the Chinese carb because I don't really know what model it is: www.ebay.com/itm/Yamaha-Zuma-YW50-Carburetor-Carb-2008-2011-2008-2009-2010-2011-NEW/122887884375?hash=item1c9cb04e57:g:CtEAAOSwqu9VNmw3&vxp=mtr

To what jackrides said: I don't think it could be a vacuum leak as the gas runs fine, and I made sure it was all sealed. Though I am a newb, so how else could I make sure it is not a leak?

What kind of air filter should I get? I heard it was harder to tune a carb with a new one.

['O'Verse]

As soon as you cover the intake. Your forcing the carb to suck more gas into it. As soon as you get it started your choke should do its job and yes that comes with higher revs. When it starts settling is when your choke is tapering off. You might need to turn your rpms up so it doesn't die. Maybe even an adjustment of your air/fuel mixture screw. You have two screws on one side of your carb. One protruding out with a spring on it. That is your idle rpm screw. There should be another screw nearby. That's your air or fuel mixture screw. In your case air mixture. Both screws are a flat head design. Idle usually being the bigger of the two. I'd try and turn your idle rpm screw clockwise as soon as you get it started by atleast a half a turn. Even more if needed. If that keeps it running then back off the rpms until it runs smooth and continuously. youtu.be/A1vRMERs4RQ

[pinkscoot]

Ronin , I've bought these carbs before with pretty good luck. You should then get one of these for a choke or this or just a cable. If you want to go with a safer vendor get this carb from treatland. The only difference I saw between that and the Bay carb was the Ebay carb had better bowl screws. To tune it in get yourself some Jets from Treatland. Whatever carb you get be sure to clean it out, they ship with bits of metal and stuff in them and just need to be blown out. Once you get all of this Brent has a great thread on tuning them: www.49ccscoot.com/faq/carbtune.html. That should get you on the road to a great running scoot.

You do need to solve your vacuum leak as well. Start with Brents thread here: 49ccscoot.proboards.com/thread/1889?page=1. If that doesn't find it one place to check is that the boot where the throttle cable goes into the carb needs to be a tight seal, it can be a source thats overlooked. Once you have all of this together then please feel free to ask other advice.

[ryan_ott]

On the Zuma it’s almost mandatory to use a cable choke with non factory carbs unless your cutting the seat bottom out or not using the battery cover panel. It’s extremely difficult to reach the carb when it’s all together.

[benji]

I have a mikuni vm24 with a choke knob on the side of it, and it's hard as hell to get to. I'm gonna end up cutting out the bottom of the seat bucket and doing a 'false floor' to cover it I think.

[ryan_ott]

Jan 5, 2018 17:24:42 GMT -5 benji said:

I have a mikuni vm24 with a choke knob on the side of it, and it's hard as hell to get to. I'm gonna end up cutting out the bottom of the seat bucket and doing a 'false floor' to cover it I think.

A sheet of kydex is perfect for the job. Cheap and easy to work with. I’ll add a pic of mine when I make it out to the garage.

Edit:

[ThaiGyro]

Ronin, as usual there is good advise from the guys. One method we use...on clone carbs especially, but also old PBHG, Mikuni and others, is to use a non permanent thread lock goo, such as Loc-Tite Blue. If you apply a thin band all the way around, you can usually resolve any air leaks.




Here is a shot with a strip, usually applied for anti vibration. Most often, before I do that, I use teflon (PTFE) tape to see where the leak is...and only use blue goo where it is needed.

Some of the problems with thin cast carb bodies is that they can distort easily and threads can gall or shred from over tightening. The bolts, even if aluminum, will nearly always be a harder alloy than the cast pieces. The harder material will always win.

[pinkscoot]

The nice thing about the Dellorto PHGB carbs is the bolt on the bottom of the bowl, it makes main jet running a breeze. No fighting the 4 screws on the bottom and opening the float bowl. on a couple of my scoots I just loosen the clamps and spin it to get at the Jet.

['O'Verse]

Even better is the VHST model. Flatside, and the bottom screw not only gives you access to the main jet but also holds the bowl on just with the one screw. Not to mention the floats are on glides.