139qmb 72cc big bore kit

[scooternub]

I believe I know what I am going to do with my second 2009 sunny jinlun 49cc scooter that needs a cdi and cdi plugs.

I have a knowledgeable mechanic across the street from me that said he will definitely  help me with a big bore kit and the extra's.

I am guessing I need a new carb for a big bore kit.

Is this true?

Also, with this bbk, do I need to change anything else out, like crank, probably the exhaust, lifters, valves, clutch variator and rollers?

This is going to be a long project. As I am limited on money and time with the mechanic, like weekends. This is my first major project.

Another thing, do I have to worry about heat?
Yes, I am right excited .

[Silar]

Some of us are running our BBK's with an 18mm or 19mm carb. Just make sure you jet it properly and it works properly. You may have to adjust your airbox or go to an aftermarket air filter. From what I understand, stock exhaust (unless it's restricted in some way) should be fine. Crank doesn't have to be changed out unless you want to stroke it, or if your existing crank or bearings are having issues.

There are BBK kits come with a big bore head like the one from 02starrider on ebay, but from what I understand, you can actually use your stock head. His kit even comes with new rocker arms, gasket kit, new rollers, new big bore head with valves, etc.. Even a #90 jet which I'm running with now. Pretty much everything you need for around $55. I use his kit as does a few others here and it seems to be pretty good. 02starrider BBK kit

He does have other kits that include exhaust, CDI, etc also. This is for the 100cc (Really 83cc) kit so may not be what you want to do.

You don't have to change out the clutch/variator/rollers/belt, but you may find you need to depending on the current condition of those items, your weight, how fast you want to take off, etc.

Parts for these scooters are cheap, but do add up based on what you want to do and it does take some time tweaking to get everything tuned properly. Just make sure you take your time when installing everything.

[scooterpimp]

47mm bbk , stock head works fine ,best results ive had keep stock airbox , main jet will/may have to be increased in size , then dropping cvt roller/ slider weight down , then go onto heavier clutch & contra spring. Makes for good launch & acceleration. Most important dont do too many mods at 1 time to prevent tuning headaches. Dont forget to replace cvt belt if old with good quality belt. You will get the most bang for your buck from bbk & jetting (main jet) don't waste too much time/money on performance cdi's ,performance air filters or exaust. They produce little to no gains imo.most important have fun!

[Elektrey]

have fun take your time and like scooterpimp said, don't do too many mods at once, if something is wrong/off you will have no idea where to begin.

[Silar]

Like Scooterpimp and Elecktrey said. One thing at a time. I did the exact opposite of that and it took me forever to figure out what was actually going wrong on mine..

[humanshield]

You are justified to be excited.

When you feel the difference between a stock 49cc scooter and a 72cc scooter you'll love your scooter even more.

I do highly recommend an A9 cam while you're installing the BBK. You can get them for $20 and well worth it imo.