SA50P - To BBK or Not to BBK

[Raharu]

I purchased a bunch of performance parts about 6 years ago for my '98 SA50P and am finally getting around to putting 'em in. I'm not a wheelie-popping speed demon or anything, but there's a couple stretches of road around me at 55MPH that I'd like to be able to match speed with a little better.

The BBK is some Taiwanese one I got off eBay, 80cc. Looks to be decent quality. I also have a Keli variator, YMS exhaust, stiffer clutch springs, and a 9.2:1 gearing kit to install. My understanding is that the gearing is more important than raw HP for better top speeds, but unfortunately, I don't have the equipment to re-gear this bike right now so I'm looking to install everything else first.

So my question is... should I install the BBK? The bike is totally de-restricted now with the exception of still running the 68 main jet. If I just up-jet, run the YMS exhaust, and install the new variator, what kind of speeds should I expect? I took the bike for a quick test run with just the new exhaust and hit an underwhelming 34MPH without re-jetting.

I'm looking to be able to cruise at 40-45 - would a Keli variator and a re-jet get me there? Or should I bite the bullet and put the BBK on? I'm a bit apprehensive on installing the BBK as I've heard there's quality concerns with these Taiwanese kits and I'd hate to damage an otherwise functional machine.

Thanks in advance for taking the time to read/reply!

[IvyOperator]

If you already have the BBK, it would never hurt to give yourself a bump in power assuming it's good quality and fitment. With BBK's, you will need to rejet anyways. I don't know enough about SA50P variators, so I can't help you out there.

Jetting alone should help you out though, not sure what numbers you can hit but it can only go up with a proper jet size. Especially when you have a high flow exhaust.

[Meatball]

Skip the Taiwan bore and get a Polini Sport Kit. Follow the build that Wheelman did and you wont regret it.

[Raharu]

If you already have the BBK, it would never hurt to give yourself a bump in power assuming it's good quality and fitment. With BBK's, you will need to rejet anyways.

Thanks for the feedback. To be honest I was a bit gun-shy about putting the BBK on as I've never done a head swap before. But since I already have the new jet for the BBK I went ahead and threw it on and re-jetted to 105. It seems to be working!

Will throw the exhaust back on tomorrow and report back. The heat shroud isn't fitting perfect anymore, though - is that to be expected? I've got no problem cutting it to size but want to make sure before I go hacking off plastic

After doing a bit of research, this kit is identical to the NCY 82cc BBK so I think that's what it is. It doesn't look like the ChiCom stuff they have on Amazon/eBay nowadays, at least.

Skip the Taiwan bore and get a Polini Sport Kit. Follow the build that Wheelman did and you wont regret it.

I'd love a nice Polini kit but I already own the NCY If I ever upgrade, it'd be a Polini all the way. This scooter has sat collecting dust (alongside a Honda Grom that I don't have a license for) for the past 6 years and I'd just like to get it running well enough for trips into town to save on gas.

Since it's a money-saving endeavor I'm just going to use the gear I already own. Maybe after Great Recession 2.0 is through I can throw some Italian cast iron on it!

[Wheelman-111]

Greetings:

I never had much luck with the Taiwanese kits. For sure it's a good idea to get in there with a stone and chamfer the Knife-Edged ports in the cylinder before you install. If you don't, or do it poorly, it won't last long. Save your pennies and soon you'll be able to afford the Polini Contesta. With 9:1 gears and a ZX variator, mine does 55 all day long, on a stock intake, carb and pipe. Jetted to 90. Surprisingly a 92 caused it to run like dog *, but it likes the 90. Your mileage may vary. Wheel-boy rides it mostly now, and the frame has 6000 miles. About 4000 as Flash 9. Meatball was the original stock AF16 engine donor, and I am very grateful.

[Raharu]

Greetings:

I never had much luck with the Taiwanese kits. For sure it's a good idea to get in there with a stone and chamfer the Knife-Edged ports in the cylinder before you install. If you don't, or do it poorly, it won't last long. Save your pennies and soon you'll be able to afford the Polini Contesta. With 9:1 gears and a ZX variator, mine does 55 all day long, on a stock intake, carb and pipe. Jetted to 90. Surprisingly a 92 caused it to run like dog *, but it likes the 90. Your mileage may vary. Wheel-boy rides it mostly now, and the frame has 6000 miles. About 4000 as Flash 9. Meatball was the original stock AF16 engine donor, and I am very grateful.

Thanks for the reply, Wheelman! Love your bikes. I did pop the NCY kit on and it runs well, so I'm just gonna run it into the ground and pick up an Italian top end once that happens I'm sure a Polini or Malossi is much nicer, but I bought all these parts at 25-50% lower than today's prices ~7 years ago and I'm ruthlessly frugal by default. Went from 34 to 42 top speed with just the new head and V8 exhaust!

I also went ahead and got a shop press to re-gear her to 9.1:1. It was easy enough. I'm still waiting on my tubeless wheels and 39MM socket to arrive to swap out the clutch springs, but I wanted to test the new gearing, so I slapped on a Keli variator with 7g weights, the stock clutch, and a new drive belt.

Now it runs like crap We're talkin' 5MPH WOT crap. She revs well but then kinda bogs out after 5-10 seconds.

Could this be the result of re-gearing the bike and running a BBK without doing any clutch tuning? She ran like a dream for a week with just the BBK and V8 exhaust before I started monkeying with the CVT and final drive. I'm going to put all the OEM gear back in except the gears and see if that fixes things. I don't have a compression tester but I did spray carb cleaner around the head gaskests and didn't get any RPM spikes so I don't think it's an air leak.

[Meatball]

Your bore makes it’s peak torque/hp somewhere in the upper rpm band. No precise way to know exactly where without dyno pulls. The key is to tune the cvt to do its “shifting” at the top end of your bore’s peak power range where it starts to run out breath. Well, as close as you can. This uses your bore’s full potential.

I think your cvt is shifting too soon as a result of roller weights too heavy, a contra spring too weak or possibly both. You should try lighter rollers to get the revs up higher before its starts shifting. If you go TOO light then top speed will suffer. Keep in mind that cvt tuning is probably the most crucial part of getting your scoot dialed aside from carb. Play with it and report back.