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 Newb looking for bore kit advice! 
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Joined: Thu Sep 06, 2018 2:00 pm
Posts: 2
Post Newb looking for bore kit advice!
Hey! First time posting to this forum. So first off, glad to be a part of this community!

Now to my question.....I have a 2012 Yamaha Zuma 50 4 stroke, or Yamaha BWS 50 where I'm from and to be honest its just not kicking it like it used to.
To be fair I have not been all that kind to it but have done the regular oil changes along with spark plug and air filters. I have about 8800 km on it at the moment and it's just sluggish. I know this is most likely from poor upkeep, but I have been interested in increasing the bore size for years now but havn't had a good reason to till now.

So what I'm asking is would anyone recommend a big bore kit that i could order online to install myself? nothing crazy, even 70cc would suffice, as well as what I would need to do in order to get the proper performance out of it? ( i know about the restricted CDI but dont know to much about it, etc.)

Also, the belt has never been changed before, would this help with performance at all if i put in a new one???

Thanks to anyone that has a reply to any of these questions!!

Thu Sep 06, 2018 4:11 pm

Joined: Wed Sep 05, 2018 9:39 pm
Posts: 5
Post Re: Newb looking for bore kit advice!
Welcome to both of us. ;)

Thu Sep 06, 2018 8:17 pm
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Joined: Fri Aug 31, 2018 5:18 pm
Posts: 602
Location: Fox Valley Wisconsin
scooters and mods: 2 2004 Vinos 2004 Zuma
Post Re: Newb looking for bore kit advice!
I can speak for the belt on both bikes ,A end of life belt would hurt performance use a oem yamaha belt it is as good or better than anything else.
On the 2 stroke if you are looking for biggest bang for buck you can grab a cast iron sport bbk polini or malossi around $150 bucks if you want to step up a notch in price and performance from there the sport verions bbk top trophy or the street race pro are still very reliable and forgiving and are in the $200 range .
I prefer cast iron over aluminum .
You have to be prepared to upjet the carburetor on all of these you also may have to adjust the cvt variator weights .
If you decided to add a pipe you may have to upjet the carb further and dial in the cvt for the new power band .
Very important to use the same brand jets .
I had to use mikuni jets since I could not find TK jets and i had to buy a set 6 sizes higher to find the right range .
The 4stroke upgrade kits are spendy .

2004 Vinos Derestricted exhaust and variator stock carb with mikuni 70 main jet needle down 1 clip 40 mph
Athena Sport BBK waiting to go on

2004 Vino Malossi sport 70cc Malossi Wild Lion pipe malossi multivar 6.5 sliders green polini clutch springs stock carb 75 mikuni main one clip rich 47.5 mph Michelin S1 90/90/10 rear tire Michelin S1 3" x 10 up front

2004 Zuma Malossi sport 70 cc Technigas next r 2008 zuma torque driver polini high speed variator 5.5 grams sliders malossi delta clutch yellow contra yellow clutch springs Stock Carb 84 main jet 46 pilot jet needle 1 clip rich stock athena 14/42 gears 11 to 1 final ratio 56 mph

2005 Eton Beamer (Taiwan Zuma Clone) Airsal sport 70cc 9200 peak rpm top speed 42 77.5 mikuni jet needle 1 clip rich (sold)

Sat Sep 15, 2018 8:26 pm
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