new bbk  By  pgs (Read 1,130 times)

Air Sal is a great brand and I have heard several who have bought from RacingPlanetUSA and was happy . Now with a 2T BBK you will need to have a jet kit as they are more picky than a 4T . Many use an iron cylinder since it is cheaper and more forgiving in a soft seize where aluminum can damage the cylinder and not be reusable . This is a HP kit and you would want to get a HP full circle crank that is matched to it so it will have more compression over stock and be able to handle higher RPMS .

Note the 2Ts , also called Minarelli and JOG can come in 10mm and 12mm wristpins so measure yours with a caliper before buying .

To get the most of out that kit you will need a 19mm to a 21mm carb , as many have a 17.5mm or smaller carb stock . Exhaust plays a more important role in performance on a 2T and will require tuning the carb to work with it . I have a pipe from www.pmtuning.co.uk/ I bought used . Well first thing its loud in between a chainsaw and Yamaha YZ 80 . Take off was less since its unrestricted and does not build up back pressure on bottom end but the power band kicks in when the RPMs get up around 6k and I have hit 10,500 RPMs with peak around 9k . I had a wristpin come out and eat up the head , piston and cylinder which was iron . Aluminum parts are so soft you can scratch them with a finger nail , so be gentle handling them .

I had a MODCycles 47mm BBK and I like it . I have been looking at Stage6 and Polini kits like here scootertuning.ca/en/26-cylinders . Here is another place that sells Air Sal kits www.mhr-usa.com/airsal

I removed my body as a single part and after removing the fan shroud it was very simple to remove the stock and install the BBK . You will need ring pliers to get the wristpins in and I could get to one side but the other not so . I Installed a wristpin on the side with less clearance and made darn sure the clip was in snug . Should have an arrow on top of the piston and be pointed to the exhaust pipe . Cover the piston , rings and cylinder with plenty of 2T oil or engine assembly grease . Compress the rings by hand while making sure the ring gaps are in place and gently get it started in the cylinder . Do not force it in and it is a tight fit . Once the second ring ( street and sport are dual ring and racing a single ring ) I used a soft mallet and gave it a couple of tabs to get going down the studs . The head easily slides on and torque the 4 head nuts . At this point I installed the exhaust and gave it a test start up for a few seconds and revved it up a hair for 30 seconds . Recheck the head nuts then put the fan shroud back on .

I have a 19mm TK carb that had a 40IJ and 68 main jet that I replaced with a 75 and a with small Uni when it was 49cc . With 47mm BBK , Uni and unrestricted exhaust a 120 works and a 105 was a lil lean . I run it rich since 2Ts are known for soft seizing after mods and the jetting is not perfect . Im ordering a jet kit since I want to go back with stock exhaust since it is too darn loud and has made my ears ring and go with airbox with holes drilled since I can not ride in the rain with a Uni . It started instantly but would stall while idling . A 45 idle jet and tada it idles perfect . With the 40 I had to give it a sip of throttle to start and with 45 no need to .

You may want to try lighter or heavier weights than you had with the stock engine . I would for sure get a new belt since a BBK has more power and why risk it on a used belt ?

I think RacingPlanetUSA sells a Stage6 replica pipe for around 150 but if you have the cash a LeoVince Hand Made 70 is a great pipe and not so loud . My scooter dealer has one on a Yamaha Zuma hot rod . Here is a great article on 2T exhaust 49ccscoot.proboards.com/thread/1391

Start with a synthetic blend 2T oil like Maxxima that says its ok to use with injector unless you will be premixing . Depending on break in method you may go full synthetic next time or at the 3rd time you buy oil . Do not get Lucas 2T oil it sucks and does not stay mixed . Bel Ray is a great brand as I used it when I had motorcross bikes but I really like Motul 710 full synthetic but hate paying 17 a quart instead of 10 . For a sparkplug I use NGKBRP8HIX which is the iridium . Some use the 7 which is hotter temp , like I did but the 8 ran better for me