Stock carb jet size

[rafow]

How do I tell what size the jets are in my stock carb. I do not see any sort of marking on them. I am taking off the stock air box and putting on a pod filter directly to the carb. I assume a re-jet will be needed to compensate for the less restricted air.

[badpumpkin]

Ok,a stock 49cc. Did you watch the video at left of screen. The taotao carb air box one. Then buy jets. Main jets. Is it a stock carb? Then you have to drill out your screws. Or get a keihin.

[rafow]

Sorry for being unclear. Stock carb on 139QMB China Scooter. It is not sealed. Three screws hold the bowl on. There is no marking on the jets to identify. Need to buy some to tune but don't know what I am starting with. Only marking is on the carb itself. CVK

[dan50]

For a stock carb, I use a #31 pilot jet and a #78 or #80 main jet. With the pod air filter, you should go with a #85 main jet and a #35 pilot jet to start with and adjust jet size from there.

I suggest buying a selection of jets. Scrappydogs has sets in a plastic case to keep them sorted. Which one you go with depends on your budget (and how many scooters you own). Links;

10 piece kit: chinesescooterparts.com/product/10-piece-139qmb-carb-tuning-kit/

50 piece kit: chinesescooterparts.com/product/50-piece-139qmb-shop-jet-kit/

I hope this helps.

Dan50

[rafow]

Thanks Dan50. That sounds good. My first and only scoot. Rebuilding to learn more about them.

[humanshield]

Dan50 may have already mentioned this but don't overlook the needle position.

It can make a big difference in the transition from idle to higher speeds.

[dan50]

Thanks humanshield, I didn't mention that. Moving the needle is mostly for 2t carb tuning, but I watched a video by 90GTVert about moving the needle on a 4t carb.

Rejet first, then fine tune by adjusting the needle.

Videos in the Tech Section on tuning a carb.

[rafow]

Awesome info. Thanks guys. Putting the shopping list together.