Porting/Polishing a New BBK as a Beginner

[zumanoob]

Hey all, I have just received my new BBK (Malossi Sport 70cc) and I have a Yasuni R to go with it. I heard porting and polishing is a way to make a little more power but I have no clue how to go forward with it, nor do I know if its even worth the risk. I am mechanically inclined but are the gains on a sport BBK even worth it? I thought maybe I port the exhaust to match the Yasuni R if it is different but other then that I am seeking other peoples knowledge and opinions. Also where do people polish to gain power, never fully understood that.
Bike : 08 Yamaha Zuma 2t
Thanks everyone!

[bigmatthew86]

You polish the exhaust port. If you port it wrong you can mess it up. For a sport build I vote for just installing it.

[Lucass2T]

Apr 21, 2024 6:21:58 GMT -5 bigmatthew86 said:

You polish the exhaust port. If you port it wrong you can mess it up. For a sport build I vote for just installing it.

Like you said, just install it.
Polishing does nothing really. It's not an old lumpy cast iron v8 with tons of casting imperfections. These minarelli engines and malossi aftermarket parts are very high quality and don't need any porting or polishing really. You can gain some power from raising the exhaust port. Widening any more will greatly increase the possibility of a ring snagging.
Raising the port will increase but also narrow the powerband. So tuning will become way more important, otherwise you'll end up with a complete dog of a bike for 99% of the time.
You'll be better off perfecting your cvt setup and carb jetting.
Brent has done some really extensive cvt tuning on his T2 bike. I'd suggest watching all his youtube vids.

[zumanoob]

Apr 21, 2024 13:19:58 GMT -5 Lucass2T said:

Apr 21, 2024 6:21:58 GMT -5 bigmatthew86 said:

You polish the exhaust port. If you port it wrong you can mess it up. For a sport build I vote for just installing it.

Like you said, just install it.
Polishing does nothing really. It's not an old lumpy cast iron v8 with tons of casting imperfections. These minarelli engines and malossi aftermarket parts are very high quality and don't need any porting or polishing really. You can gain some power from raising the exhaust port. Widening any more will greatly increase the possibility of a ring snagging.
Raising the port will increase but also narrow the powerband. So tuning will become way more important, otherwise you'll end up with a complete dog of a bike for 99% of the time.
You'll be better off perfecting your cvt setup and carb jetting.
Brent has done some really extensive cvt tuning on his T2 bike. I'd suggest watching all his youtube vids.

OK I will head over to youtube. I am probably not going to do anything for porting.  Just ride it as it is.

[aeroxbud]

I would just run it as is.
Just take the sharp edges off the ports. And check the squish band and transfer ports are okay.
Pedparts did a good blog on basic porting. www.pedparts.co.uk/blog/tuning-a-polini-70cc-sport-cylinder-basic-porting
But I would definitely get it running good as it is before deciding if you want extra.